You searched for subject:(granular materials).
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University of Hong Kong
1.
黃暉然; Wong, Vivian.
A 3-parameter particle packing model for spherical and
non-spherical particles.
Degree: PhD, 2015, University of Hong Kong
URL: Wong,
V.
[黃暉然].
(2015).
A
3-parameter
particle
packing
model
for
spherical
and
non-spherical
particles.
(Thesis).
University
of
Hong
Kong,
Pokfulam,
Hong
Kong
SAR.
Retrieved
from
http://dx.doi.org/10.5353/th_b5610976 
;
http://hdl.handle.net/10722/221161
► In many fields of industries, it has been found that the properties of granular materials are intimately related to their packing densities. To find the…
(more)
▼ In many fields of industries, it has been found
that the properties of granular materials are intimately related to
their packing densities. To find the particle size distribution for
optimum packing density rendering the best performance of granular
materials, it is useful to have a particle packing model which can
accurately predict the packing density of granular materials.
Nevertheless, the development of particle packing model is
difficult and complex as there are many factors affecting packing
density including particle shape, packing method and formation of
agglomerates between cohesive fine particles.
Even for binary
mixes of particles, the existing 2-parameter model which takes into
account the loosening effect and the wall effect and assumes a
linear relationship between specific volume (reciprocal of packing
density) and volumetric fractions of particles, does not give
satisfactory prediction. Through comprehensive experimental study,
the author has found that the deviations from experimental results
are caused by the wedging effect of the fine particles situating at
the gaps between the coarse particles producing extra voids. The
newly identified wedging effect was incorporated into the
3-parameter model, in which the specific volume is no longer a
linear function of the volumetric fractions. This thesis presents
the further development of the 3-parameter model, which is extended
to ternary mixes and multi-component mixes of spherical and
non-spherical particles with various factors affecting packing
density taken into account.
In extending the 3-parameter model
to ternary mixes and multi-component mixes of particles, an
approach was adopted so that the final packing density of the
mixture consisting of several size classes was taken as the minimum
of those determined from a set of equations, each corresponding to
one dominant size class. The extended model was verified using the
experimental results of spherical particles obtained from this
study and cylindrical particles obtained from the literature. The
accuracy of the model was also compared to other existing models
for multi-component mixes, such as the 2-parameter model and the
compressible packing model.
For more general applications to
angular aggregate particles, the 3-parameter model was modified by
a number of adjustments which include the re-derivation of the
interaction functions of the three parameters accounting for the
loosening, wall and wedging effects under both uncompacted and
compacted packing conditions. However, it was demonstrated that
without the consideration of the formation of agglomerates between
cohesive fine particles, which would produce extra voids known as
the agglomeration effect, would result in interaction functions
giving unreasonable interpretation of the various interaction
effects. Consequently, the 3-parameter model was also modified to
account for the agglomeration effect. Finally, for application in
concrete industry, the 3-parameter model was also modified for
continuous grading of aggregate particles,…
Subjects/Keywords: Granular materials
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APA (6th Edition):
黃暉然; Wong, V. (2015). A 3-parameter particle packing model for spherical and
non-spherical particles. (Doctoral Dissertation). University of Hong Kong. Retrieved from Wong, V. [黃暉然]. (2015). A 3-parameter particle packing model for spherical and non-spherical particles. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5610976 ; http://hdl.handle.net/10722/221161
Chicago Manual of Style (16th Edition):
黃暉然; Wong, Vivian. “A 3-parameter particle packing model for spherical and
non-spherical particles.” 2015. Doctoral Dissertation, University of Hong Kong. Accessed December 14, 2019.
Wong, V. [黃暉然]. (2015). A 3-parameter particle packing model for spherical and non-spherical particles. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5610976 ; http://hdl.handle.net/10722/221161.
MLA Handbook (7th Edition):
黃暉然; Wong, Vivian. “A 3-parameter particle packing model for spherical and
non-spherical particles.” 2015. Web. 14 Dec 2019.
Vancouver:
黃暉然; Wong V. A 3-parameter particle packing model for spherical and
non-spherical particles. [Internet] [Doctoral dissertation]. University of Hong Kong; 2015. [cited 2019 Dec 14].
Available from: Wong, V. [黃暉然]. (2015). A 3-parameter particle packing model for spherical and non-spherical particles. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5610976 ; http://hdl.handle.net/10722/221161.
Council of Science Editors:
黃暉然; Wong V. A 3-parameter particle packing model for spherical and
non-spherical particles. [Doctoral Dissertation]. University of Hong Kong; 2015. Available from: Wong, V. [黃暉然]. (2015). A 3-parameter particle packing model for spherical and non-spherical particles. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5610976 ; http://hdl.handle.net/10722/221161
University of Hong Kong
2.
Gu, Xiaoqiang.
Dynamic properties of granular materials at the macro and
microscales.
Degree: PhD, 2012, University of Hong Kong
URL: Gu,
X.
[顾晓强].
(2012).
Dynamic
properties
of
granular
materials
at
the
macro
and
micro
scales.
(Thesis).
University
of
Hong
Kong,
Pokfulam,
Hong
Kong
SAR.
Retrieved
from
http://dx.doi.org/10.5353/th_b4775262
;
http://dx.doi.org/10.5353/th_b4775262
;
http://hdl.handle.net/10722/181472
► Dynamic properties of soil, including modulus and damping, play essential roles in evaluating the response of the soil deposit and its supporting structures when subjected…
(more)
▼ Dynamic properties of soil, including modulus and
damping, play essential roles in evaluating the response of the
soil deposit and its supporting structures when subjected to
dynamic loads induced by earthquakes, traffic, explosions, machine
foundations, and so on. It is well recognized that the dynamic
properties of soil are affected by many factors, such as strain
amplitude, stress condition, void ratio, saturation and gradation.
Despite tremendous works have been done, the macroscopic effects of
several key factors on the dynamic properties of granular material
are not yet fully understood, due primarily to its particulate and
multiphase nature. Furthermore, the understanding of how the
influencing factors affect the dynamic properties of granular
material or the underlying fundamental mechanism is inadequate.
This study thus is carried out to investigate the effects and the
underlying mechanisms of these important factors, including strain
amplitude, stress condition, void ratio, particle size, saturation,
and initial fabric, by means of advanced laboratory tests and
numerical simulations. To study the dynamic properties at the macro
scale, a series of laboratory tests are carried out in a
state-of-art resonant column (RC) apparatus incorporating bender
element (BE) and torsional shear (TS). Test materials include
artificial glass beads with different sizes, commercially available
standard sands and natural completely decomposed granite (CDG). The
specimens are prepared at various densities, confined at different
pressures, tested both in dry and saturated conditions, and
reconstituted by different preparation methods. In particular, the
characteristics of wave signals (both S-wave and P-wave) at various
conditions and the associated interpretation methods in BE tests
are investigated in detail. The results obtained from BE, RC and TS
are compared to clarify the potential effect of test method.
Moreover, attempts are made to explain the test results from the
viewpoint of micromechanics. Numerical simulations using discrete
element method (DEM) are performed to study the dynamic properties
of granular materials and explore the underlying fundamental
mechanism at the micro scale. The simulations indicate that the
elastic properties are closely related to the coordination number
and the distribution of normal contact forces in the specimen. The
effects of initial fabric and induced fabric, which are
respectively achieved by different specimen generation methods and
the application of anisotropic stress states, are investigated. The
anisotropy of the specimen and its evolution during shearing are
also studied. The results indicate that the anisotropy is resulted
from the spatial distributions of contact force and contact number.
The modulus reduction curve and damping curve obtained from the
simulations are compared with those from laboratory
tests.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
Subjects/Keywords: Granular materials.
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APA ·
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APA (6th Edition):
Gu, X. (2012). Dynamic properties of granular materials at the macro and
microscales. (Doctoral Dissertation). University of Hong Kong. Retrieved from Gu, X. [顾晓强]. (2012). Dynamic properties of granular materials at the macro and micro scales. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4775262 ; http://dx.doi.org/10.5353/th_b4775262 ; http://hdl.handle.net/10722/181472
Chicago Manual of Style (16th Edition):
Gu, Xiaoqiang. “Dynamic properties of granular materials at the macro and
microscales.” 2012. Doctoral Dissertation, University of Hong Kong. Accessed December 14, 2019.
Gu, X. [顾晓强]. (2012). Dynamic properties of granular materials at the macro and micro scales. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4775262 ; http://dx.doi.org/10.5353/th_b4775262 ; http://hdl.handle.net/10722/181472.
MLA Handbook (7th Edition):
Gu, Xiaoqiang. “Dynamic properties of granular materials at the macro and
microscales.” 2012. Web. 14 Dec 2019.
Vancouver:
Gu X. Dynamic properties of granular materials at the macro and
microscales. [Internet] [Doctoral dissertation]. University of Hong Kong; 2012. [cited 2019 Dec 14].
Available from: Gu, X. [顾晓强]. (2012). Dynamic properties of granular materials at the macro and micro scales. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4775262 ; http://dx.doi.org/10.5353/th_b4775262 ; http://hdl.handle.net/10722/181472.
Council of Science Editors:
Gu X. Dynamic properties of granular materials at the macro and
microscales. [Doctoral Dissertation]. University of Hong Kong; 2012. Available from: Gu, X. [顾晓强]. (2012). Dynamic properties of granular materials at the macro and micro scales. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4775262 ; http://dx.doi.org/10.5353/th_b4775262 ; http://hdl.handle.net/10722/181472
Rutgers University
3.
Siu, Theodore Lordin, 1988-.
Non-linear phenomena in granular materials.
Degree: PhD, Physics and Astronomy, 2016, Rutgers University
URL: https://rucore.libraries.rutgers.edu/rutgers-lib/51468/
► Granular materials are quite common in our everyday lives in both nature and industry. Yet much of the phenomena that they exhibit is not well…
(more)
▼ Granular materials are quite common in our everyday lives in both nature and industry. Yet much of the phenomena that they exhibit is not well understood and in fact quite complex and non-linear. For example, it has been known since Faraday‘s time that swirling sandstorms are able to generate electric charge that manifest as multi-million volt lightning discharges. Poured glass beads have been demonstrated to also charge electrically, causing random ejections of grains and creating interesting raised clump structures known as razorbacks. Lastly, granular materials are known to exhibit self- segregation based on size. An example of this phenomenon is the landscape observed on the asteroid 25143/Itokawa, which has spatially separated boulder fields and sand seas. In this work, we discuss three projects that examine non-linear behavior in granu- lar materials. In our first chapter, we discuss a computational electrostatic model of vibrated identical granular particles. We show in our model that granular materials are able to exponentially generate charge and polarization through 1/r2 electric field interactions. By adding neutralization between neighboring particles, we find complex phenomena such as charge and polarization waves that propagate through the particles. In closing, we reproduce a polarized state experimentally using vibrated glass beads which represents one of the phenomena that we observe in our model phase diagram; we also discuss our experimental efforts to image charge and polarization waves. In the second chapter, we examine the dynamical behavior of charged granular par- ticles. We find that by experimentally exposing grains to simple electric fields, a number of novel behaviors appear including dust clouds, dust columns and tendrils. In addi- tion, in our experiments and simulations we find evidence for non-linear electrostatic interactions between particles including asymmetries and particle trajectories that do not adhere to naive electric field lines. In our final chapter, we deal with granular segregation found on the asteroid known as 25143/Itokawa. On the asteroid there exists segregation between smaller sized dust and rocks on the centimeter size, from large boulders with diameters on the order of meters. While current explanations attribute the segregation to the phenomenon known as the Brazil Nut Effect, we show that "ballistic segregation" or a difference of collision types on the asteroid surface can be responsible for the separation between different sized particles. We show that the surface area growth of particles can be modeled using the non-linear Hill Equation, which shows that increasing amounts of dust accumulation promotes further dust accumulation.
Advisors/Committee Members: Shinbrot, Troy (chair), Bhanot, Gyan (internal member), Yuzbashyan, Emil (internal member), Tse, Stephen (outside member).
Subjects/Keywords: Granular materials
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APA ·
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APA (6th Edition):
Siu, Theodore Lordin, 1. (2016). Non-linear phenomena in granular materials. (Doctoral Dissertation). Rutgers University. Retrieved from https://rucore.libraries.rutgers.edu/rutgers-lib/51468/
Chicago Manual of Style (16th Edition):
Siu, Theodore Lordin, 1988-. “Non-linear phenomena in granular materials.” 2016. Doctoral Dissertation, Rutgers University. Accessed December 14, 2019.
https://rucore.libraries.rutgers.edu/rutgers-lib/51468/.
MLA Handbook (7th Edition):
Siu, Theodore Lordin, 1988-. “Non-linear phenomena in granular materials.” 2016. Web. 14 Dec 2019.
Vancouver:
Siu, Theodore Lordin 1. Non-linear phenomena in granular materials. [Internet] [Doctoral dissertation]. Rutgers University; 2016. [cited 2019 Dec 14].
Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/51468/.
Council of Science Editors:
Siu, Theodore Lordin 1. Non-linear phenomena in granular materials. [Doctoral Dissertation]. Rutgers University; 2016. Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/51468/
Rutgers University
4.
Barrasso, Dana.
Multi-scale modeling of wet granulation processes.
Degree: PhD, Chemical and Biochemical Engineering, 2015, Rutgers University
URL: https://rucore.libraries.rutgers.edu/rutgers-lib/48388/
► Wet granulation is a particle design process used to create larger granules from fine powder, improving flowability, compactibility, and homogeneity. Although it is widely used…
(more)
▼ Wet granulation is a particle design process used to create larger granules from fine powder, improving flowability, compactibility, and homogeneity. Although it is widely used in the food, pharmaceutical, detergent, and fertilizer industries, it is often operated inefficiently, with high recycle ratios in continuous processes and high rejection rates in batch processes. In pharmaceutical applications, wet granulation is a critical step in tablet manufacturing that affects the uniformity and compactibility of the final dosage form. A model-based approach can be used to understand the effects of process parameters and material properties on critical quality attributes, developing a knowledge space for Quality by Design. Population balance modeling (PBM) provides a fundamental framework for tracking changes in particle properties over time, though it requires rate expressions and empirical parameters that cannot easily be measured. Discrete element modeling (DEM) is more mechanistic, tracking particles as they move through space and collide, but does not consider the complex mechanisms involved in wet granulation. Through this thesis, a multi-dimensional PBM for a continuous wet granulation process is presented. Model calibration and validation are performed using experimental data. A multi-scale PBM-DEM framework is developed and demonstrated using mechanistic rate expressions to enhance predictive capabilities. The multi-scale model is applied to realistic systems using computationally efficient techniques.
Advisors/Committee Members: Ramachandran, Rohit (chair), Dutt, Meenakshi (internal member), Ierapetritou, Marianthi (internal member), Litster, James D. (outside member).
Subjects/Keywords: Wetting; Granular materials
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APA ·
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APA (6th Edition):
Barrasso, D. (2015). Multi-scale modeling of wet granulation processes. (Doctoral Dissertation). Rutgers University. Retrieved from https://rucore.libraries.rutgers.edu/rutgers-lib/48388/
Chicago Manual of Style (16th Edition):
Barrasso, Dana. “Multi-scale modeling of wet granulation processes.” 2015. Doctoral Dissertation, Rutgers University. Accessed December 14, 2019.
https://rucore.libraries.rutgers.edu/rutgers-lib/48388/.
MLA Handbook (7th Edition):
Barrasso, Dana. “Multi-scale modeling of wet granulation processes.” 2015. Web. 14 Dec 2019.
Vancouver:
Barrasso D. Multi-scale modeling of wet granulation processes. [Internet] [Doctoral dissertation]. Rutgers University; 2015. [cited 2019 Dec 14].
Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/48388/.
Council of Science Editors:
Barrasso D. Multi-scale modeling of wet granulation processes. [Doctoral Dissertation]. Rutgers University; 2015. Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/48388/
Rutgers University
5.
Chen, Sheng-Wen, 1988-.
Apply DEM to study wet binder addition and dry binder addition wet granulation in a high shear granulator.
Degree: MS, Chemical and Biochemical Engineering, 2017, Rutgers University
URL: https://rucore.libraries.rutgers.edu/rutgers-lib/53467/
► Wet granulation is widely used in many industries especially in the pharmaceutical industry for its capability to improve flowability and handling of powder substances. A…
(more)
▼ Wet granulation is widely used in many industries especially in the pharmaceutical industry for its capability to improve flowability and handling of powder substances. A discrete element model (DEM) was developed to study two kinds of liquid addition methods in wet granulation in high shear granulator: wet binder addition (WBA) and dry binder addition (DBA). To define the complex interaction in the systems, liquid bridge model and powder penetration theory are applied to develop the contact model. The DBA system possesses ten times higher viscosity particles than the WBA system. The results of two systems were compared and differences in viscosity profile were identified. Viscous regions are found to move when time progressing. The relationship between impeller and viscosity profile are studied. The great difference in viscosity is related to strong liquid bridge force and average bridge number in the DBA system. The strong liquid bridge force results in larger granules in the DBA system.
Advisors/Committee Members: Ramachandran, Rohit (chair), Glasser, Benjamin (internal member), Singh, Ravendra (internal member).
Subjects/Keywords: Granular materials; Binders (Materials)
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APA ·
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APA (6th Edition):
Chen, Sheng-Wen, 1. (2017). Apply DEM to study wet binder addition and dry binder addition wet granulation in a high shear granulator. (Masters Thesis). Rutgers University. Retrieved from https://rucore.libraries.rutgers.edu/rutgers-lib/53467/
Chicago Manual of Style (16th Edition):
Chen, Sheng-Wen, 1988-. “Apply DEM to study wet binder addition and dry binder addition wet granulation in a high shear granulator.” 2017. Masters Thesis, Rutgers University. Accessed December 14, 2019.
https://rucore.libraries.rutgers.edu/rutgers-lib/53467/.
MLA Handbook (7th Edition):
Chen, Sheng-Wen, 1988-. “Apply DEM to study wet binder addition and dry binder addition wet granulation in a high shear granulator.” 2017. Web. 14 Dec 2019.
Vancouver:
Chen, Sheng-Wen 1. Apply DEM to study wet binder addition and dry binder addition wet granulation in a high shear granulator. [Internet] [Masters thesis]. Rutgers University; 2017. [cited 2019 Dec 14].
Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/53467/.
Council of Science Editors:
Chen, Sheng-Wen 1. Apply DEM to study wet binder addition and dry binder addition wet granulation in a high shear granulator. [Masters Thesis]. Rutgers University; 2017. Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/53467/
University of Hong Kong
6.
Liu, Yuanyuan.
Arching in granular materials.
Degree: PhD, 2011, University of Hong Kong
URL: Liu,
Y.
[刘媛媛].
(2011).
Arching
in
granular
materials.
(Thesis).
University
of
Hong
Kong,
Pokfulam,
Hong
Kong
SAR.
Retrieved
from
http://dx.doi.org/10.5353/th_b4658719
;
http://dx.doi.org/10.5353/th_b4658719
;
http://hdl.handle.net/10722/143211
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
Advisors/Committee Members: Tham, LG, Yeung, ATC.Subjects/Keywords: Granular materials.
Record Details
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Liu, Y. (2011). Arching in granular materials. (Doctoral Dissertation). University of Hong Kong. Retrieved from Liu, Y. [刘媛媛]. (2011). Arching in granular materials. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4658719 ; http://dx.doi.org/10.5353/th_b4658719 ; http://hdl.handle.net/10722/143211
Chicago Manual of Style (16th Edition):
Liu, Yuanyuan. “Arching in granular materials.” 2011. Doctoral Dissertation, University of Hong Kong. Accessed December 14, 2019.
Liu, Y. [刘媛媛]. (2011). Arching in granular materials. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4658719 ; http://dx.doi.org/10.5353/th_b4658719 ; http://hdl.handle.net/10722/143211.
MLA Handbook (7th Edition):
Liu, Yuanyuan. “Arching in granular materials.” 2011. Web. 14 Dec 2019.
Vancouver:
Liu Y. Arching in granular materials. [Internet] [Doctoral dissertation]. University of Hong Kong; 2011. [cited 2019 Dec 14].
Available from: Liu, Y. [刘媛媛]. (2011). Arching in granular materials. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4658719 ; http://dx.doi.org/10.5353/th_b4658719 ; http://hdl.handle.net/10722/143211.
Council of Science Editors:
Liu Y. Arching in granular materials. [Doctoral Dissertation]. University of Hong Kong; 2011. Available from: Liu, Y. [刘媛媛]. (2011). Arching in granular materials. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4658719 ; http://dx.doi.org/10.5353/th_b4658719 ; http://hdl.handle.net/10722/143211
Montana State University
7.
Shertzer, Richard Hayden.
Fabric tensors and effective properties of granular materials with application to snow.
Degree: College of Engineering, 2011, Montana State University
URL: https://scholarworks.montana.edu/xmlui/handle/1/2264
► Granular materials e.g., gravel, sand, snow, and metallic powders are important to many engineering analysis and design problems. Such materials are not always randomly arranged,…
(more)
▼ Granular materials e.g., gravel, sand, snow, and metallic powders are important to many engineering analysis and design problems. Such
materials are not always randomly arranged, even in a natural environment. For example, applied strain can transform a randomly distributed assembly into a more regular arrangement. Deviations from random arrangements are described via material symmetry. A random collection exhibits textural isotropy whereas regular patterns are anisotropic. Among natural
materials, snow is perhaps unique because thermal factors commonly induce microstructural changes, including material symmetry. This process temperature gradient metamorphism produces snow layers that can exhibit anisotropy. To adequately describe the behavior of such layers, mathematical models must account for potential anisotropy. This feature is absent from models specifically developed for snow, and, in most
granular models in general. Material symmetry is quantified with fabric tensors in the constitutive models proposed here. Fabric tensors statistically characterize directional features in the microstructure. For example, the collective orientation of intergranular bonds impacts processes like conduction and loading. Anisotropic, microstructural models are analytically developed here for the conductivity, diffusivity, permeability, and stiffness of
granular materials. The methodology utilizes homogenization an algorithm linking microscopic and macroscopic scales. Idealized geometries and constitutive assumptions are also applied at the microscopic scale. Fabric tensors tying the
granular arrangement to affected material properties are a natural analysis outcome. The proposed conductivity model is compared to measured data. Dry dense snow underwent temperature gradient metamorphism in a lab. Both the measured heat transfer coefficient and a developing ice structure favored the direction of the applied gradient. Periodic tomography was used to calculate microstructural variables required by the conductivity model. Through the fabric tensor, model evolution coincides with measured changes in the heat transfer coefficient. The model also predicts a different conductivity in directions orthogonal to the gradient due to developing anisotropy. Models that do not consider directional microstructural features cannot predict such behavior because they are strictly valid for isotropic
materials. The conclusions are that anisotropy in snow can be significant, fabric tensors can characterize such symmetry, and constitutive models incorporating fabric tensors offer a more complete description of material behavior.
Advisors/Committee Members: Chairperson, Graduate Committee: Edward E. Adams. (advisor).
Subjects/Keywords: Anisotropy.; Granular materials.; Microstructure.; Snow.
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Shertzer, R. H. (2011). Fabric tensors and effective properties of granular materials with application to snow. (Thesis). Montana State University. Retrieved from https://scholarworks.montana.edu/xmlui/handle/1/2264
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Shertzer, Richard Hayden. “Fabric tensors and effective properties of granular materials with application to snow.” 2011. Thesis, Montana State University. Accessed December 14, 2019.
https://scholarworks.montana.edu/xmlui/handle/1/2264.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Shertzer, Richard Hayden. “Fabric tensors and effective properties of granular materials with application to snow.” 2011. Web. 14 Dec 2019.
Vancouver:
Shertzer RH. Fabric tensors and effective properties of granular materials with application to snow. [Internet] [Thesis]. Montana State University; 2011. [cited 2019 Dec 14].
Available from: https://scholarworks.montana.edu/xmlui/handle/1/2264.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Shertzer RH. Fabric tensors and effective properties of granular materials with application to snow. [Thesis]. Montana State University; 2011. Available from: https://scholarworks.montana.edu/xmlui/handle/1/2264
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Sydney
8.
Li, Shuoqi.
The Distribution of Saturated Clusters in Wetted Granular Materials
.
Degree: 2017, University of Sydney
URL: http://hdl.handle.net/2123/17619
► As a typical multiphase fluid flow process, drainage in porous media, also called as fluid displacement, is of fundamental interest in nature and various industrial…
(more)
▼ As a typical multiphase fluid flow process, drainage in porous media, also called as fluid displacement, is of fundamental interest in nature and various industrial applications. During this drainage process occurs in porous media, saturated clusters, which formed when liquid phases fully occupy the pore space between solid grains, affect the relative permeability and the effective stress of unsaturated soils and rocks. In this study, we studied the drainage process in unsaturated granular media experimentally. The distribution of saturated clusters is analysed by an optical imaging method under different drainage conditions, in which the pore-scale information from the Voronoi and Delaunay tessellation was used to characterize the crystallisation effect on saturated cluster distributions. By employing a method of statistical analyses, the observed spatial and temporal information of multiphase flow in granular media are described. The results indicated that the distributions of both the crystallised cell size and pore size are positively correlated to the spatial and temporal distribution of saturated cluster sizes. The saturated cluster size was found to follow a lognormal distribution, in which the negative and positive correlation with the generalised Bond number (〖"Bo" 〗^*) have found for the scale parameter (𝜇) and shape parameter (𝜎), respectively. With further consideration of the total surface energy obtained based on liquid-air interfaces, we were able to include additional grain-scale information in the constitutive modelling of unsaturated soils using both the saturation degree and generalised Bond number. These findings have successfully bridged the pore-scale behaviours with the overall hydro-mechanical characteristics in partially saturated soils.
Subjects/Keywords: unsaturated soil;
granular materials
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APA (6th Edition):
Li, S. (2017). The Distribution of Saturated Clusters in Wetted Granular Materials
. (Thesis). University of Sydney. Retrieved from http://hdl.handle.net/2123/17619
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Li, Shuoqi. “The Distribution of Saturated Clusters in Wetted Granular Materials
.” 2017. Thesis, University of Sydney. Accessed December 14, 2019.
http://hdl.handle.net/2123/17619.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Li, Shuoqi. “The Distribution of Saturated Clusters in Wetted Granular Materials
.” 2017. Web. 14 Dec 2019.
Vancouver:
Li S. The Distribution of Saturated Clusters in Wetted Granular Materials
. [Internet] [Thesis]. University of Sydney; 2017. [cited 2019 Dec 14].
Available from: http://hdl.handle.net/2123/17619.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Li S. The Distribution of Saturated Clusters in Wetted Granular Materials
. [Thesis]. University of Sydney; 2017. Available from: http://hdl.handle.net/2123/17619
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
McGill University
9.
Huang, Zhi Jie.
Computer Modelling and Simulations of Mechanics of Granular Materials.
Degree: PhD, Department of Civil Engineering and Applied Mechanics, 1993, McGill University
URL: http://digitool.library.mcgill.ca/thesisfile156757.pdf
► Note:
The present study considers the stresses in ice rubble mounds. A dynamic relaxation method has been developed to simulate the quasi-static equilibrium problems in…
(more)
▼ Note:
The present study considers the stresses in ice rubble mounds. A dynamic relaxation method has been developed to simulate the quasi-static equilibrium problems in cohesionless and cohesive granular media. Analyses and computer models are described that predict the stress distribution in ice rubble accumulations. A linear and a nonlinear force-displacement relation with the possibility of tension cutoff is used to determine the contact forces. The equations governing the motion of particles resulting from the contact forces and gravity forces are discussed. Because the calculation cycle is realized by an explicit numerical scheme, in which the contact forces and motion of the particles are separately determined one by one, the present computational approach is very flexible in dealing with various boundary conditions. […]
Cette étude a pour sujet les pressions présentes dans l'amoncellement de glace fracturée. Une méthode de relaxation dynamique a été développée afin de simuler les problèmes d'équilibre statique présents chez les matériaux granulaires cohésifs et non-cohésifs. Les différents programmes d'ordinateur et méthodes utilises pour évaluer les distributions de pressions dans l'accumulation de glace fracturée sont décrites. Des relations linéaires et non-linéaires entre les déplacements et les forces, pouvant inclure ou non les tensions, ont été utilisées pour déterminer les forces de contact. Les équations gouvernant les mouvements des particules, causes par les forces de contact et de gravite, sont présentées. Le cycle de calcul a été réalisé par un schéma numérique explicite. Dans ce schéma les forces de contact et les mouvements des particules sont détermines séparément et un après l'autre. Ainsi, cette approche est très flexible lorsqu'il s'agit des conditions aux frontières. […]
Advisors/Committee Members: Savage, S. B. (Supervisor).
Subjects/Keywords: Granular Materials
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10.
Nguyen, Sinh Khoa.
Faisabilité de la définition d'une loi de comportement pour les matériaux granulaires par changement d'échelle mésoscopique-macroscopique : Broyage du silicium et particules fines : génération et comportement de particules fines de silicium métallurgique au cours du broyage pour l'industrie des silicones.
Degree: Docteur es, Mécanique, Energétique, Génie Civil et Acoustique, 2014, Ecully, Ecole centrale de Lyon
URL: http://www.theses.fr/2014ECDL0051
► Les modèles de comportement phénoménologiques développés pour les sols peinent à traduire la complexité du comportement des matériaux granulaires, essentiellement du fait de leur nature…
(more)
▼ Les modèles de comportement phénoménologiques développés pour les sols peinent à traduire la complexité du comportement des matériaux granulaires, essentiellement du fait de leur nature discrète. Il est usuel d’avoir recours aux analyses multi-échelle, afin de proposer des comportements macroscopiques prenant finement en compte les propriétés locales du milieu. La question de l’échelle locale a été largement étudiée et il ressort qu’une méso-échelle, définie au niveau d’arrangements locaux de particules, semble plus appropriée que l’échelle du contact entre particules pour comprendre la texture et le comportement de ce type de milieux. Dans ce cadre, ce travail de thèse se propose d’étudier la faisabilité de la définition d’une loi de comportement pour les matériaux granulaires par changement d’échelle mésoscopique-macroscopique. Un échantillon granulaire est analysé par simulation DEM (Méthode aux Eléments Discrets) d’un essai biaxial de charge et de décharge. A l’échelle mésoscopique, le milieu granulaire est subdivisé en méso-domaines dont la texture est caractérisée par deux variables : degré d’allongement et orientation par rapport à la direction de compression. Les méso-domaines ayant des caractéristiques de texture communes sont regroupés en six phases, afin de mieux discriminer leur comportement. Les variables locales sont définies : méso-texture, méso-contrainte et méso-déformation, et leurs évolutions sont analysées. Les simulations montrent que le matériau s’appuie sur les phases orientées dans la direction de compression, d’autant plus qu’elles sont allongées, pour supporter la sollicitation. Ces dernières sont capables de développer une forte dilatance et une forte anisotropie, leur permettant de récupérer une forte valeur de rapport de contraintes. A contrario les phases allongées et perpendiculaires à la direction de compression constituent des maillons faibles pour le système. Sur la base des résultats DEM, un processus de changement d’échelles -dont l’ingrédient est l’évolution des pourcentages volumiques des phases au cours de l’essai- a permis de retrouver le comportement macroscopique. Un modèle élasto-plastique à élasticité linéaire, mécanisme plastique déviatoire et écrouissage cinématique a été proposé pour modéliser le comportement de chaque phase à l’échelle mésoscopique. L’essai de charge a permis d’identifier les 8 paramètres du modèle. L’essai de décharge a permis la validation du modèle proposé. Similairement, un modèle à un paramètre est proposé, et validé, pour l’évolution du pourcentage volumique de chaque phase. Sur la base de ces modélisations, le comportement macroscopique de l’échantillon a pu être retrouvé par changement d’échelle mésoscopique-macroscopique. Cette étude ouvre la voie à la définition d’un nouveau type de modèle de comportement des matériaux granulaires basé sur l’existence de phases à l’échelle mésoscopique.
Most of the developed constitutive models for granular materials cannot capture the complexity of their behavior, due to the discrete nature of the…
Advisors/Committee Members: Vincens, Eric (thesis director), Cambou, Bernard (thesis director), Magoariec, Hélène [Martine Francine] (thesis director).
Subjects/Keywords: Matériaux granulaires; Granular materials
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APA (6th Edition):
Nguyen, S. K. (2014). Faisabilité de la définition d'une loi de comportement pour les matériaux granulaires par changement d'échelle mésoscopique-macroscopique : Broyage du silicium et particules fines : génération et comportement de particules fines de silicium métallurgique au cours du broyage pour l'industrie des silicones. (Doctoral Dissertation). Ecully, Ecole centrale de Lyon. Retrieved from http://www.theses.fr/2014ECDL0051
Chicago Manual of Style (16th Edition):
Nguyen, Sinh Khoa. “Faisabilité de la définition d'une loi de comportement pour les matériaux granulaires par changement d'échelle mésoscopique-macroscopique : Broyage du silicium et particules fines : génération et comportement de particules fines de silicium métallurgique au cours du broyage pour l'industrie des silicones.” 2014. Doctoral Dissertation, Ecully, Ecole centrale de Lyon. Accessed December 14, 2019.
http://www.theses.fr/2014ECDL0051.
MLA Handbook (7th Edition):
Nguyen, Sinh Khoa. “Faisabilité de la définition d'une loi de comportement pour les matériaux granulaires par changement d'échelle mésoscopique-macroscopique : Broyage du silicium et particules fines : génération et comportement de particules fines de silicium métallurgique au cours du broyage pour l'industrie des silicones.” 2014. Web. 14 Dec 2019.
Vancouver:
Nguyen SK. Faisabilité de la définition d'une loi de comportement pour les matériaux granulaires par changement d'échelle mésoscopique-macroscopique : Broyage du silicium et particules fines : génération et comportement de particules fines de silicium métallurgique au cours du broyage pour l'industrie des silicones. [Internet] [Doctoral dissertation]. Ecully, Ecole centrale de Lyon; 2014. [cited 2019 Dec 14].
Available from: http://www.theses.fr/2014ECDL0051.
Council of Science Editors:
Nguyen SK. Faisabilité de la définition d'une loi de comportement pour les matériaux granulaires par changement d'échelle mésoscopique-macroscopique : Broyage du silicium et particules fines : génération et comportement de particules fines de silicium métallurgique au cours du broyage pour l'industrie des silicones. [Doctoral Dissertation]. Ecully, Ecole centrale de Lyon; 2014. Available from: http://www.theses.fr/2014ECDL0051
Delft University of Technology
11.
Ashruf, T.N.
Surface Wave Analysis for the characterization of granular material deposits :.
Degree: 2015, Delft University of Technology
URL: http://resolver.tudelft.nl/uuid:33d07a9e-2e76-40c1-af10-9fecba12eb8d
► Knowledge of near-surface seismic-wave velocity of granular materials plays a valuable role in seismic exploration data processing. I will use the surface-wave analysis method for…
(more)
▼ Knowledge of near-surface seismic-wave velocity of
granular materials plays a valuable role in seismic exploration data processing. I will use the surface-wave analysis method for estimation of shear-wave velocity profile and P-wave refraction for estimation of pressure-wave velocity on a data set acquired over a sand dune in The Netherlands, a dune area part of The Holland coast. For surface-wave analysis I exploit the fact that in these
materials the velocity profile follows a power-law and I invert for the power-law coefficients using a Monte Carlo inversion. A second power-law is introduced into the Monte Carlo inversion to recover vertically varying structures. The P-wave refraction is applied for estimation of the groundwater depth and P-wave velocity. After the seismic data were acquired, several analyses were made on the extracted dispersion curves from different sources, windowing in space domain indicate the presence of lateral variation. The estimated shear-wave velocity profiles demonstrates the usefulness of imposing a power-law trend to the velocity.
Although the inverted power-law coefficients results into small differences with the literature and theoretical values, these can be explained by the varying shapes of the grains. Furthermore, the implementation of the second power-law results into velocities that are lower than the first layer. The depth of the shear-wave velocity profiles is limited by the shallow position of the water-table around 3 m. For the best practice in field work the vibroseis source is advised due to the advantage of the continuous sweep covering the whole frequency band in one signal.
Advisors/Committee Members: Socco, V., Ghose, R., Garofalo, F..
Subjects/Keywords: surface waves; granular materials; characterization
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APA (6th Edition):
Ashruf, T. N. (2015). Surface Wave Analysis for the characterization of granular material deposits :. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:33d07a9e-2e76-40c1-af10-9fecba12eb8d
Chicago Manual of Style (16th Edition):
Ashruf, T N. “Surface Wave Analysis for the characterization of granular material deposits :.” 2015. Masters Thesis, Delft University of Technology. Accessed December 14, 2019.
http://resolver.tudelft.nl/uuid:33d07a9e-2e76-40c1-af10-9fecba12eb8d.
MLA Handbook (7th Edition):
Ashruf, T N. “Surface Wave Analysis for the characterization of granular material deposits :.” 2015. Web. 14 Dec 2019.
Vancouver:
Ashruf TN. Surface Wave Analysis for the characterization of granular material deposits :. [Internet] [Masters thesis]. Delft University of Technology; 2015. [cited 2019 Dec 14].
Available from: http://resolver.tudelft.nl/uuid:33d07a9e-2e76-40c1-af10-9fecba12eb8d.
Council of Science Editors:
Ashruf TN. Surface Wave Analysis for the characterization of granular material deposits :. [Masters Thesis]. Delft University of Technology; 2015. Available from: http://resolver.tudelft.nl/uuid:33d07a9e-2e76-40c1-af10-9fecba12eb8d
University of Minnesota
12.
Fan, Yi.
Shear-induced segregation in dense granular mixtures.
Degree: PhD, Civil Engineering, 2011, University of Minnesota
URL: http://purl.umn.edu/110149
► Granular mixtures such as sand and powders tend to segregate or unmix by particle property. The details are important for many natural and industrial applications.…
(more)
▼ Granular mixtures such as sand and powders tend to segregate or unmix by particle property. The details are important for many natural and industrial applications. While kinetic theory provides a mechanistic framework for modeling segregation in energetically agitated granular mixtures, there is no analogous framework for dense sheared granular mixtures. A number of segregation mechanisms have been identified as important, including those associated with pressure gradients, gravity, gradients in shear rates, and gradients in granular temperature – the kinetic energy of velocity fluctuations. All likely contribute to segregation in densely sheared systems, though there is no constitutive relationship for mixtures, and the details are difficult to determine. Further, in typical experimental systems designed to study segregation in dense granular flow (such as chutes and rotated drums), gravity, velocity gradients, and porosity gradients coexist in the direction of segregation.
The research in this thesis uses physical and computational experiments to elucidate particular segregation mechanisms in dense granular flow and develop a theoretical model incorporating these segregation mechanisms. Experiments are conducted in a relatively new geometric configuration called split-bottom cell which can isolate shear rate and porosity gradients from gravity. Distinct Element Method (DEM) simulations of experiments in this geometry and in a chute flow provide details inaccessible experimentally including particle concentrations and velocities at every point in space and interparticle forces. These simulations reveal unique dynamics associated with shear-induced segregation in dense systems. Based on the results, a theoretical framework is developed to model segregation associated with shear gradients in dense sheared granular mixtures.
Subjects/Keywords: Granular materials; Segregation; Civil Engineering
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APA (6th Edition):
Fan, Y. (2011). Shear-induced segregation in dense granular mixtures. (Doctoral Dissertation). University of Minnesota. Retrieved from http://purl.umn.edu/110149
Chicago Manual of Style (16th Edition):
Fan, Yi. “Shear-induced segregation in dense granular mixtures.” 2011. Doctoral Dissertation, University of Minnesota. Accessed December 14, 2019.
http://purl.umn.edu/110149.
MLA Handbook (7th Edition):
Fan, Yi. “Shear-induced segregation in dense granular mixtures.” 2011. Web. 14 Dec 2019.
Vancouver:
Fan Y. Shear-induced segregation in dense granular mixtures. [Internet] [Doctoral dissertation]. University of Minnesota; 2011. [cited 2019 Dec 14].
Available from: http://purl.umn.edu/110149.
Council of Science Editors:
Fan Y. Shear-induced segregation in dense granular mixtures. [Doctoral Dissertation]. University of Minnesota; 2011. Available from: http://purl.umn.edu/110149
Rutgers University
13.
Remy, Brenda, 1978-.
Granular flow, segregation and agglomeration in bladed mixers.
Degree: PhD, Chemical and Biochemical Engineering, 2010, Rutgers University
URL: http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000056730
► A large number of industrial processes involve the transport, mixing and storage of particulate systems. While prevalent in industry, particulate processes are commonly plagued by…
(more)
▼ A large number of industrial processes involve the transport, mixing and storage of particulate systems. While prevalent in industry, particulate processes are commonly plagued by problems due to the complex rheology of these systems. In this work, the behavior of granular materials in a bladed mixer, an industrially relevant geometry, was investigated using computational and experimental techniques. Experimental flows were characterized via Particle Image Velocimetry and image analysis. Discrete element simulations were carried out to examine the effect of a wide range of system parameters. Particulate flows in bladed mixers were found to be periodic with complex flow patterns developing throughout the particle bed. Cohesionless flows were initially studied. For monodisperse flows, two distinct flow regimes were observed: a quasi-static regime where blade speed provides the time scale for momentum transfer and an intermediate regime where stresses scale linearly with blade speed. Particle and wall roughness were found to significantly affect bladed mixer flows. Systems with higher roughness are characterized by enhanced particle motion and mixing. Simple scaling relationships were observed for monodisperse flows in the quasi-static regime. Particle velocities and diffusivities were found to scale linearly with mixer size and blade speed, while stresses scaled linearly with particle bed weight. In polydisperse flows, size segregation was found to occur due to sieving. However, it was found that the extent of segregation can be reduced by introducing intermediate particle sizes in between the smallest and largest particles. Finally, wet particle flows were examined. At low moisture contents, enhanced particle velocities and mixing kinetics were observed in comparison to dry flows. However, at higher moisture contents, particle velocities and mixing rates were observed to decrease. Wet particle flows were characterized by the formation of particle agglomerates. Agglomerate formation led to an increase in particle bed roughness which significantly influenced macroscopic and microscopic flow properties. These findings contribute to the understanding of granular behavior in complex systems. Improved understanding of granular flows will enable the development of first-principles based models which can assist in the design and scale-up of bladed mixer operations and the identification of critical processes parameters.
Advisors/Committee Members: Remy, Brenda, 1978- (author), Glasser, Benjamin J (chair), Pedersen, Henrik (internal member), Shapley, Nina (internal member), Gilchrist, James F (outside member).
Subjects/Keywords: Granular materials – Mixing; Mixing machinery
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APA (6th Edition):
Remy, Brenda, 1. (2010). Granular flow, segregation and agglomeration in bladed mixers. (Doctoral Dissertation). Rutgers University. Retrieved from http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000056730
Chicago Manual of Style (16th Edition):
Remy, Brenda, 1978-. “Granular flow, segregation and agglomeration in bladed mixers.” 2010. Doctoral Dissertation, Rutgers University. Accessed December 14, 2019.
http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000056730.
MLA Handbook (7th Edition):
Remy, Brenda, 1978-. “Granular flow, segregation and agglomeration in bladed mixers.” 2010. Web. 14 Dec 2019.
Vancouver:
Remy, Brenda 1. Granular flow, segregation and agglomeration in bladed mixers. [Internet] [Doctoral dissertation]. Rutgers University; 2010. [cited 2019 Dec 14].
Available from: http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000056730.
Council of Science Editors:
Remy, Brenda 1. Granular flow, segregation and agglomeration in bladed mixers. [Doctoral Dissertation]. Rutgers University; 2010. Available from: http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000056730
Rutgers University
14.
Chaudhury, Anwesha.
Mechanistic modeling, simulation and optimization of wet granulation processes.
Degree: PhD, Chemical and Biochemical Engineering, 2015, Rutgers University
URL: https://rucore.libraries.rutgers.edu/rutgers-lib/46319/
► Particulate processes involving handling of solids are ubiquitous in various industries and are typically operated inefficiently due to a lack of adequate mechanistic process understanding.…
(more)
▼ Particulate processes involving handling of solids are ubiquitous in various industries and are typically operated inefficiently due to a lack of adequate mechanistic process understanding. A primary application of such processes is found in the pharmaceutical industry that involve manufacturing of solid dosage forms (e.g. tablets). Granulation is a critical particulate process that plays an important role in the overall manufacture of pharmaceutical drugs. This work focuses on improved mathematical modeling of granulation processes using the population balance framework. One of the primary objectives deals with model development for granulation followed by development of improved numerical techniques for reduced computational overheads associated with the solution techniques for solving population balance models. This study is also aimed at identifying the influence of various operating parameters on the final granule properties through the development of a novel semi-mechanistic kernel and an integrated mesoscale model framework that can effectively capture key granulation dynamics. A compartmentalized model has also been formulated for a high-shear wet granulator that can capture the inhomogeneities (with respect to liquid and particle velocity) within the vessel. This integrated, compartment-based model can be further extended for open loop optimization and control of the granulation process, which can aid at obtaining an optimal recipe for the operation of the granulation process. This work will make a significant contribution towards improved understanding of the granulation process and is aimed at mitigating the current inefficient operation of the process.
Advisors/Committee Members: Ramachandran, Rohit (chair), Ierapetritou, Marianthi (internal member), Shapley, Nina (internal member), Dutt, Meenakshi (internal member), Pandey, Preetanshu (outside member).
Subjects/Keywords: Granular materials; Wetting; Granulation
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APA (6th Edition):
Chaudhury, A. (2015). Mechanistic modeling, simulation and optimization of wet granulation processes. (Doctoral Dissertation). Rutgers University. Retrieved from https://rucore.libraries.rutgers.edu/rutgers-lib/46319/
Chicago Manual of Style (16th Edition):
Chaudhury, Anwesha. “Mechanistic modeling, simulation and optimization of wet granulation processes.” 2015. Doctoral Dissertation, Rutgers University. Accessed December 14, 2019.
https://rucore.libraries.rutgers.edu/rutgers-lib/46319/.
MLA Handbook (7th Edition):
Chaudhury, Anwesha. “Mechanistic modeling, simulation and optimization of wet granulation processes.” 2015. Web. 14 Dec 2019.
Vancouver:
Chaudhury A. Mechanistic modeling, simulation and optimization of wet granulation processes. [Internet] [Doctoral dissertation]. Rutgers University; 2015. [cited 2019 Dec 14].
Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/46319/.
Council of Science Editors:
Chaudhury A. Mechanistic modeling, simulation and optimization of wet granulation processes. [Doctoral Dissertation]. Rutgers University; 2015. Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/46319/
Rutgers University
15.
Engisch, William E.
Loss-in-weight feeding in continuous powder manufacturing.
Degree: PhD, Chemical and Biochemical Engineering, 2014, Rutgers University
URL: https://rucore.libraries.rutgers.edu/rutgers-lib/45245/
► Processes involving granular material handling are found in many industries, such as pharmaceutical, chemical, catalyst, and food. Significant differences are observed, both between materials as…
(more)
▼ Processes involving granular material handling are found in many industries, such as pharmaceutical, chemical, catalyst, and food. Significant differences are observed, both between materials as well as between handling methods. Often, special equipment has been developed to monitor, control, and feed these widely varied materials in order to enable the end user to continuously feed or dose the raw powder material so that it can be continuously processed, which has many advantages over batch processing. To address the difficulties of feeding granular materials, powder feeders are equipped with a variety of tooling that can be used for various rates and powders. Unfortunately most of the sizing and performance knowledge is internal to the feeding equipment manufacturers and is not generally available to the end-user. In this work, a method for evaluating feeding performance was developed, which allowed for testing that was independent of the type of feeder being evaluated. This method was applied to various feeders to characterize the feeders for the feeding of various powders. In addition, the effects of hopper refilling were quantified and investigated. Finally, the downstream effects were simulated. iii For each powder, the fluctuations caused during normal steady state feeding were minimized through tooling and feeder selection. The effects of refill were found to be considerably more significant than the fluctuations associated with steady state feeding. However, optimized refill schedules, easily reduced the deviations to more manageable levels. In continuous manufacturing systems, the feeders are a potential high risk to content uniformity. The implications of this are investigated from a overarching view of a pharmaceutical direct compression system with a specific focus on regulatory compliance and product quality. Regulatory compliance requires batch definition and raw material traceability, and solutions to both were investigated. The presented options for batch definition are based on the residence time distribution (RTD) of the system, which describes the dispersion of material across the interface between "batches". Raw material traceability was similarly investigated utilizing residence time distribution as a tool.
Advisors/Committee Members: Muzzio, Fernando J (chair), Ierapetritou, Marianthi (internal member), Ramachandran, Rohit (internal member), Kiang, San (outside member).
Subjects/Keywords: Granular materials; Manufacturing processes
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APA (6th Edition):
Engisch, W. E. (2014). Loss-in-weight feeding in continuous powder manufacturing. (Doctoral Dissertation). Rutgers University. Retrieved from https://rucore.libraries.rutgers.edu/rutgers-lib/45245/
Chicago Manual of Style (16th Edition):
Engisch, William E. “Loss-in-weight feeding in continuous powder manufacturing.” 2014. Doctoral Dissertation, Rutgers University. Accessed December 14, 2019.
https://rucore.libraries.rutgers.edu/rutgers-lib/45245/.
MLA Handbook (7th Edition):
Engisch, William E. “Loss-in-weight feeding in continuous powder manufacturing.” 2014. Web. 14 Dec 2019.
Vancouver:
Engisch WE. Loss-in-weight feeding in continuous powder manufacturing. [Internet] [Doctoral dissertation]. Rutgers University; 2014. [cited 2019 Dec 14].
Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/45245/.
Council of Science Editors:
Engisch WE. Loss-in-weight feeding in continuous powder manufacturing. [Doctoral Dissertation]. Rutgers University; 2014. Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/45245/
University of Illinois – Urbana-Champaign
16.
Kothari, Konik Ramesh.
Localization and instability in sheared granular materials: role of friction and vibration.
Degree: MS, Mechanical Engineering, 2017, University of Illinois – Urbana-Champaign
URL: http://hdl.handle.net/2142/97789
► Shear banding and stick-slip instabilities have been long observed in sheared granular materials. Yet, their microscopic underpinnings, interdependencies and variability under different loading conditions have…
(more)
▼ Shear banding and stick-slip instabilities have been long observed in sheared
granular materials. Yet, their microscopic underpinnings, interdependencies and variability under different loading conditions have not been fully explored. Here, we use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in sheared, dry,
granular materials. We consider frictional and frictionless grains as well as presence and absence of acoustic vibrations. Our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the
granular network and de-localize slip at these rates. Stick-slip is only observed for frictional grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of application alters the system response and may cause long-lasting rheological changes. We analyse these observations in terms of possible transitions between rate strengthening and rate weakening response facilitated by a competition between shear induced dilation and vibration induced compaction. We discuss the implications of our results on dynamic triggering, quiescence and strength evolution in gouge filled fault zones.
Advisors/Committee Members: Hu, Yuhang (advisor), Elbanna, Ahmed (advisor).
Subjects/Keywords: Granular materials; Shear localization
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APA (6th Edition):
Kothari, K. R. (2017). Localization and instability in sheared granular materials: role of friction and vibration. (Thesis). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/97789
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Kothari, Konik Ramesh. “Localization and instability in sheared granular materials: role of friction and vibration.” 2017. Thesis, University of Illinois – Urbana-Champaign. Accessed December 14, 2019.
http://hdl.handle.net/2142/97789.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Kothari, Konik Ramesh. “Localization and instability in sheared granular materials: role of friction and vibration.” 2017. Web. 14 Dec 2019.
Vancouver:
Kothari KR. Localization and instability in sheared granular materials: role of friction and vibration. [Internet] [Thesis]. University of Illinois – Urbana-Champaign; 2017. [cited 2019 Dec 14].
Available from: http://hdl.handle.net/2142/97789.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Kothari KR. Localization and instability in sheared granular materials: role of friction and vibration. [Thesis]. University of Illinois – Urbana-Champaign; 2017. Available from: http://hdl.handle.net/2142/97789
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Rutgers University
17.
Meng, Wei, 1988-.
Parametric analysis of continuous high shear wet granulation.
Degree: MS, Chemical and Biochemical Engineering, 2015, Rutgers University
URL: https://rucore.libraries.rutgers.edu/rutgers-lib/46392/
► The main focus of this research is to investigate the continuous high shear wet granulation process. Wet granulation is used broadly in the pharmaceutical industry.…
(more)
▼ The main focus of this research is to investigate the continuous high shear wet granulation process. Wet granulation is used broadly in the pharmaceutical industry. This technology has many advantages such as enhancing compression and powder handling, decreasing ingredient segregation and ensuring the content uniformity through binding of ingredients to each other. A high level of interest exists at the present time in the continuous version of this technology, both by the US FDA, and by large pharmaceutical manufacturers. Continuous manufacturing methods can provide significant technical and business advantages relative to batch methods. As has been demonstrated in other process industries, continuous manufacturing methods are more robust and controllable. They achieve the same production rates as batch processes in much smaller and thus less capital-intensive equipment. However, despite these advantages, the pharmaceutical industry still relies almost exclusively on traditional batch methods to produce tablets and capsules. In recent years, different continuous WG techniques have been investigated, such as fluid bed agglomeration and twin-screw extrusion. However, integration of these unit operations into a complete continuous tablet manufacturing line is still a bottleneck due to high production cost and poor understanding of impact of granule properties. In this work, a continuous high-shear wet granulation process is examined based on a placebo formulation comprising of 70% ∂-lactose monohydrate and 30% microcrystalline cellulose (Avicel PH101). The process includes two stages. As the powders are fed into the granulator, the blades mounted on the shaft will push the dry powders forward and promote both dispersive axial mixing and convective cross-sectional mixing. This is the mixing stage. The granulation stage occurs once the mixtures reach the nozzle location where a binding liquid (water) is fed via a pump. Then the granule size grows and decays due to nucleation, coalescence, consolidation and attrition or breakage. In this study, two process variables (rotation speed, L/S ratio) and two design parameters (blade configuration and nozzle position) are selected for the I-optimal design. The collected granules are dried in a hot-air convection oven to a desirable LOD (~ 3%). Granule properties, such as particle size distribution, flow properties, density, compaction and are measured. Batches with desirable particle size distribution are selected for further characterization. The rotation speed and L/S ratio have the most significant effects on the granule properties. The optimum operations of this granulation are 0.3 L/S ratio with the rotation speed of 275RPM or 660RPM.
Advisors/Committee Members: Muzzio, Fernando J (chair), Ramachandran, Rohit (internal member), LIU, XUE (internal member).
Subjects/Keywords: Granular materials; Wetting; Drugs – Granulation
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APA ·
Chicago ·
MLA ·
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Export
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APA (6th Edition):
Meng, Wei, 1. (2015). Parametric analysis of continuous high shear wet granulation. (Masters Thesis). Rutgers University. Retrieved from https://rucore.libraries.rutgers.edu/rutgers-lib/46392/
Chicago Manual of Style (16th Edition):
Meng, Wei, 1988-. “Parametric analysis of continuous high shear wet granulation.” 2015. Masters Thesis, Rutgers University. Accessed December 14, 2019.
https://rucore.libraries.rutgers.edu/rutgers-lib/46392/.
MLA Handbook (7th Edition):
Meng, Wei, 1988-. “Parametric analysis of continuous high shear wet granulation.” 2015. Web. 14 Dec 2019.
Vancouver:
Meng, Wei 1. Parametric analysis of continuous high shear wet granulation. [Internet] [Masters thesis]. Rutgers University; 2015. [cited 2019 Dec 14].
Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/46392/.
Council of Science Editors:
Meng, Wei 1. Parametric analysis of continuous high shear wet granulation. [Masters Thesis]. Rutgers University; 2015. Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/46392/
University of Johannesburg
18.
Theyse, Hechter Luciën.
A mechanistic-empirical design model for unbound granular pavement layers.
Degree: 2010, University of Johannesburg
URL: http://hdl.handle.net/10210/3095
► D.Ing.
Unbound granular material has and is still being used with great success in the construction of road pavements in South Africa and many other…
(more)
▼ D.Ing.
Unbound granular material has and is still being used with great success in the construction of road pavements in South Africa and many other countries around the world. Often this material is used in the main structural layers of the pavement with very little protection provided against high traffic induced stresses by way of a surface treatment or thin asphalt concrete layer. The performance of unbound granular pavement layers depend mainly on the level of densification and degree of saturation of the material in addition to the stress levels to which the layers are subjected. The main form of distress of unbound granular layers is the permanent deformation of the layer, either through the gradual deformation or rapid shear failure of the layer. Design engineers need accurate and appropriate design procedures to safeguard the road against such rapid shear failure and to ensure that the road has sufficient structural capacity to support the traffic loading over the structural design period. The recent trend in pavement design has been to move away from empirical design methods towards rational mechanistic-empirical design methods that attempt to relate cause and effect. Although a mechanistic-empirical pavement design method has been available in South Africa since the midseventies, increasing criticism has been levelled against the method recently. The models for characterising the resilient response and shear strength and estimating the structural capacity of unbound material have been of particular concern. The purpose of the research reported in this thesis was therefore to develop an improved mechanistic-empirical design model, reflecting the characteristics and behaviour of unbound granular material. The new design model consists of three components namely a resilient modulus, yield strength and plastic deformation damage model with each model including the effects of the density and moisture content of the material unbound granular where appropriate. The models were calibrated for a range of unbound materials from fine-grained sand and calcrete mixture to commercial crushed stone products using the results from static and dynamic tri-axial tests. An approximation of the suction pressure of partially saturated unbound material was introduced in the yield strength model and was validated with independent matric suction measurements on the sand and calcrete mixture. The yield strength model which is a function of the density and moisture conditions as well as the confinement pressure was calibrated for the individual materials with a high accuracy. A single plastic strain damage model was calibrated for the combined plastic strain data from all the crushed stone materials but a single model could not be calibrated for the plastic strain data of the natural gravels as these materials vary too much in terms of particle size distribution and the properties of the fines found in these materials. The formulation of the plastic strain damage model includes the density and degree of saturation of the…
Subjects/Keywords: Pavements design and construction; Granular materials mechanical properties; Granular materials testing
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Theyse, H. L. (2010). A mechanistic-empirical design model for unbound granular pavement layers. (Thesis). University of Johannesburg. Retrieved from http://hdl.handle.net/10210/3095
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Theyse, Hechter Luciën. “A mechanistic-empirical design model for unbound granular pavement layers.” 2010. Thesis, University of Johannesburg. Accessed December 14, 2019.
http://hdl.handle.net/10210/3095.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Theyse, Hechter Luciën. “A mechanistic-empirical design model for unbound granular pavement layers.” 2010. Web. 14 Dec 2019.
Vancouver:
Theyse HL. A mechanistic-empirical design model for unbound granular pavement layers. [Internet] [Thesis]. University of Johannesburg; 2010. [cited 2019 Dec 14].
Available from: http://hdl.handle.net/10210/3095.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Theyse HL. A mechanistic-empirical design model for unbound granular pavement layers. [Thesis]. University of Johannesburg; 2010. Available from: http://hdl.handle.net/10210/3095
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Cambridge
19.
Tsang, Jonathan Michael Foonlan.
Modelling dry granular flows over topography
.
Degree: 2019, University of Cambridge
URL: https://www.repository.cam.ac.uk/handle/1810/294574
► Dry granular flows are common and important in the environment and industry, and yet their behaviour is very poorly understood. The dynamics of individual grains…
(more)
▼ Dry granular flows are common and important in the environment and industry, and yet their behaviour is very poorly understood. The dynamics of individual grains are governed by the simple and well-known laws of Newtonian mechanics, but how do these 'microscopic' particle-level laws translate into the 'macroscopic' collective motion of thousands or millions of grains, which flow like a liquid?
Various rheological models of granular flows have been developed to facilitate a continuum approach, but hitherto they have only been applied to flows in very simple geometries such as parallel shear flow. In these applications, the flows are assumed to be quasi-steady and to vary only over very long distances in the streamwise direction. This approximation, related to the 'shallow water' model of hydraulics, greatly simplifies the equations of motion. However, the assumption is inappropriate for modelling flows interacting with basal features that vary over lengthscales comparable to the depth of the current, or for flows with abrupt time-dependence that cannot be assumed to be quasi-steady. We refer to these spatial and temporal inhomogeneities collectively as topography.
In this thesis, we apply a common rheological model to problems involving various types of spatial or temporal topography. One problem that we shall particularly study concerns a flow down a chute that experiences a sudden increase in basal roughness, either spatially or in time. This change induces an evolution of the depthwise velocity profile that begins near the base but eventually spreads throughout the current. We introduce an adaptation of the μ(I) rheology and find the velocity profile that this rheological model predicts, using a technique similar to the Blasius boundary layer theory for Newtonian fluids flowing past an aerofoil.
We validate the predictions of the rheological model by comparing them against the results of discrete particle model (DPM) simulations. We review existing techniques for DPM, and present a number of novel ways of employing these techniques. These methods allow us to reduce the computational cost of simulations while maintaining their realism.
The internal profile of a granular flow, and its response to a change in basal conditions, are difficult to observe in experiments or in real life, since grains are opaque. However, the models studied here can help to make predictions about the depth and speed of the flows, or conversely to make inferences about the nature of the base, given measurements on the surface of the flow.
Subjects/Keywords: granular flows;
granular materials;
rheology;
boundary layers;
fluid dynamics;
fluid mechanics;
granular mechanics;
mathematical physics
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Tsang, J. M. F. (2019). Modelling dry granular flows over topography
. (Thesis). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/294574
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Tsang, Jonathan Michael Foonlan. “Modelling dry granular flows over topography
.” 2019. Thesis, University of Cambridge. Accessed December 14, 2019.
https://www.repository.cam.ac.uk/handle/1810/294574.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Tsang, Jonathan Michael Foonlan. “Modelling dry granular flows over topography
.” 2019. Web. 14 Dec 2019.
Vancouver:
Tsang JMF. Modelling dry granular flows over topography
. [Internet] [Thesis]. University of Cambridge; 2019. [cited 2019 Dec 14].
Available from: https://www.repository.cam.ac.uk/handle/1810/294574.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Tsang JMF. Modelling dry granular flows over topography
. [Thesis]. University of Cambridge; 2019. Available from: https://www.repository.cam.ac.uk/handle/1810/294574
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Cambridge
20.
Tsang, Jonathan Michael Foonlan.
Modelling dry granular flows over topography.
Degree: PhD, 2019, University of Cambridge
URL: https://www.repository.cam.ac.uk/handle/1810/294574
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782944
► Dry granular flows are common and important in the environment and industry, and yet their behaviour is very poorly understood. The dynamics of individual grains…
(more)
▼ Dry granular flows are common and important in the environment and industry, and yet their behaviour is very poorly understood. The dynamics of individual grains are governed by the simple and well-known laws of Newtonian mechanics, but how do these 'microscopic' particle-level laws translate into the 'macroscopic' collective motion of thousands or millions of grains, which flow like a liquid? Various rheological models of granular flows have been developed to facilitate a continuum approach, but hitherto they have only been applied to flows in very simple geometries such as parallel shear flow. In these applications, the flows are assumed to be quasi-steady and to vary only over very long distances in the streamwise direction. This approximation, related to the 'shallow water' model of hydraulics, greatly simplifies the equations of motion. However, the assumption is inappropriate for modelling flows interacting with basal features that vary over lengthscales comparable to the depth of the current, or for flows with abrupt time-dependence that cannot be assumed to be quasi-steady. We refer to these spatial and temporal inhomogeneities collectively as topography. In this thesis, we apply a common rheological model to problems involving various types of spatial or temporal topography. One problem that we shall particularly study concerns a flow down a chute that experiences a sudden increase in basal roughness, either spatially or in time. This change induces an evolution of the depthwise velocity profile that begins near the base but eventually spreads throughout the current. We introduce an adaptation of the μ(I) rheology and find the velocity profile that this rheological model predicts, using a technique similar to the Blasius boundary layer theory for Newtonian fluids flowing past an aerofoil. We validate the predictions of the rheological model by comparing them against the results of discrete particle model (DPM) simulations. We review existing techniques for DPM, and present a number of novel ways of employing these techniques. These methods allow us to reduce the computational cost of simulations while maintaining their realism. The internal profile of a granular flow, and its response to a change in basal conditions, are difficult to observe in experiments or in real life, since grains are opaque. However, the models studied here can help to make predictions about the depth and speed of the flows, or conversely to make inferences about the nature of the base, given measurements on the surface of the flow.
Subjects/Keywords: granular flows; granular materials; rheology; boundary layers; fluid dynamics; fluid mechanics; granular mechanics; mathematical physics
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Tsang, J. M. F. (2019). Modelling dry granular flows over topography. (Doctoral Dissertation). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/294574 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782944
Chicago Manual of Style (16th Edition):
Tsang, Jonathan Michael Foonlan. “Modelling dry granular flows over topography.” 2019. Doctoral Dissertation, University of Cambridge. Accessed December 14, 2019.
https://www.repository.cam.ac.uk/handle/1810/294574 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782944.
MLA Handbook (7th Edition):
Tsang, Jonathan Michael Foonlan. “Modelling dry granular flows over topography.” 2019. Web. 14 Dec 2019.
Vancouver:
Tsang JMF. Modelling dry granular flows over topography. [Internet] [Doctoral dissertation]. University of Cambridge; 2019. [cited 2019 Dec 14].
Available from: https://www.repository.cam.ac.uk/handle/1810/294574 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782944.
Council of Science Editors:
Tsang JMF. Modelling dry granular flows over topography. [Doctoral Dissertation]. University of Cambridge; 2019. Available from: https://www.repository.cam.ac.uk/handle/1810/294574 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.782944
University of Manchester
21.
Gajjar, Parmesh.
Modelling size-segregation in dense granular
flows.
Degree: 2016, University of Manchester
URL: http://www.manchester.ac.uk/escholar/uk-ac-man-scw:301379
► Dense flows of grains are commonplace throughout natural and industrial environments, from snow-avalanches down the sides of mountains to flows of cereal down chutes as…
(more)
▼ Dense flows of grains are commonplace throughout
natural and industrial environments, from snow-avalanches down the
sides of mountains to flows of cereal down chutes as it is
transported from one part of a factory to another. A ubiquitous
feature in all of these flows is their ability to separate the
different grain types when shaken, stirred, sheared or vibrated.
Many flows are sheared through gravity and these flows are
particularly efficient at segregating particles based on their
size, with small particles percolating to the bottom of the flow
and large particles collecting at the top. Within this mechanism,
an asymmetry between the large and small particles has been
observed, with small particles percolating downwards through many
large particles at a faster rate than large particles rise upwards
through many small particles. This alternative format thesis
presents a revised continuum model for segregation of a bidisperse
mixture that can account for this asymmetry. A general class of
asymmetric segregation flux functions is introduced that gives rise
to asymmetric velocities between the large and small grains. Exact
solutions for segregation down an inclined chute, with homogenous
and normally graded inflow conditions, show that the asymmetry can
significantly enhance the distance for complete segregation.
Experiments performed using a classical shear-box with refractive
index matched scanning are able to quantify the asymmetry between
large and small particles on both bulk and particle scales. The
dynamics of a single small particle indicate that it not only falls
down faster than a single large particle rises, but that it also
exhibits a step-like motion compared to the smooth ascent of the
large grain. This points towards an underlying asymmetry between
the different sized constituents. The relationship between the
segregation-time and the volume fraction of small grains is
analysed, and solutions presented for the steady-state balance
between segregation and diffusive remixing. These help to show the
good agreement between the asymmetric model and experimental data.
Segregation at the front of natural avalanches produces a
recirculation zone, known as a `breaking size-segregation wave', in
which large particles are initially segregated upwards, sheared
towards the front of the flow, and overrun before being
resegregated again. Solutions for the structure of this
recirculation zone are derived using the asymmetric flux model,
revealing a novel `lens-tail' structure. Critically, it is seen
that a few large particles starting close to the bottom of the flow
are swept a long way upstream and take a very long time to
recirculate.The breaking size-segregation waves highlight the
important interplay between segregation and the bulk velocity
field. The properties of flowing monodisperse grains are explored
through experiments on a cone that produce a beautiful radial
fingering pattern. Equations developed in a conical coordinate
system reproduce the measured linear relationship between fingering
radius and initial…
Advisors/Committee Members: JOHNSON, CHRISTOPHER CG, Gray, Nico, Johnson, Christopher.
Subjects/Keywords: granular materials; particle-size segregation; mathematical modelling; dense granular flows; avalanches
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Gajjar, P. (2016). Modelling size-segregation in dense granular
flows. (Doctoral Dissertation). University of Manchester. Retrieved from http://www.manchester.ac.uk/escholar/uk-ac-man-scw:301379
Chicago Manual of Style (16th Edition):
Gajjar, Parmesh. “Modelling size-segregation in dense granular
flows.” 2016. Doctoral Dissertation, University of Manchester. Accessed December 14, 2019.
http://www.manchester.ac.uk/escholar/uk-ac-man-scw:301379.
MLA Handbook (7th Edition):
Gajjar, Parmesh. “Modelling size-segregation in dense granular
flows.” 2016. Web. 14 Dec 2019.
Vancouver:
Gajjar P. Modelling size-segregation in dense granular
flows. [Internet] [Doctoral dissertation]. University of Manchester; 2016. [cited 2019 Dec 14].
Available from: http://www.manchester.ac.uk/escholar/uk-ac-man-scw:301379.
Council of Science Editors:
Gajjar P. Modelling size-segregation in dense granular
flows. [Doctoral Dissertation]. University of Manchester; 2016. Available from: http://www.manchester.ac.uk/escholar/uk-ac-man-scw:301379
University of Sydney
22.
Athani, Shivakumar.
Granular drag forces under dynamic loadings
.
Degree: 2019, University of Sydney
URL: https://ses.library.usyd.edu.au/handle/2123/21247
► This Thesis examines the mechanical response of large objects -called intruders or anchors that are embedded into a granular packing and subjected to dynamic loadings.…
(more)
▼ This Thesis examines the mechanical response of large objects -called intruders or anchors that are embedded into a granular packing and subjected to dynamic loadings. By using a numerical approach based on a discrete element method, the study focuses on a canonical test comprising a plate-shaped intruder, placed horizontally and being uplifted vertically. The research is articulated into three projects.
The first project considers steady and quasi-static loading conditions, whereby the intruder is uplifted at a constant velocity. Its purpose is to validate the numerical method against previously established models for the maximum drag force, also known as uplift capacity. Incidentally, this project establishes to what extent it is possible to downscale/upscale the size of the intruder relative to the grain size. This result is important as most laboratory and numerical tests, starting from those presented in this study, are performed with object-to-grain size ratios much smaller than real applications.
The second project considers the mobility response under cyclic loading, whereby the object is subjected to a cyclic uplift force. A series of numerical tests exploring a range of loading frequency and magnitude reveals the existence of three possible mobility responses. The object can either move up steadily, not move up at all or exhibit a creep trajectory. Furthermore, this study points out a phenomena of elasto-inertial resonance inducing a fluidisation of the packing even at low loading magnitudes.
The third project considers loading patterns including some acceleration of the object. This reveals a new contribution to the drag force, which we named “inertial drag”. We show that this contribution results from gradual mobilisation and acceleration of grains in the packing above the object. We further find that achieving a complete grain mobilisation takes a finite period of time, controlled by the elasto-inertial stress propagation from the object to the free surface.
These three projects highlight fundamental differences between the drag force in quasi-static loading and dynamic loading conditions. A number of analytical models, built from identified micro-mechanical processes, are proposed to rationalise these effects
Subjects/Keywords: Anchors;
Cyclic loadings;
Granular drag;
Granular materials;
Inertia;
Mobility
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APA ·
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MLA ·
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Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Athani, S. (2019). Granular drag forces under dynamic loadings
. (Thesis). University of Sydney. Retrieved from https://ses.library.usyd.edu.au/handle/2123/21247
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Athani, Shivakumar. “Granular drag forces under dynamic loadings
.” 2019. Thesis, University of Sydney. Accessed December 14, 2019.
https://ses.library.usyd.edu.au/handle/2123/21247.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Athani, Shivakumar. “Granular drag forces under dynamic loadings
.” 2019. Web. 14 Dec 2019.
Vancouver:
Athani S. Granular drag forces under dynamic loadings
. [Internet] [Thesis]. University of Sydney; 2019. [cited 2019 Dec 14].
Available from: https://ses.library.usyd.edu.au/handle/2123/21247.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Athani S. Granular drag forces under dynamic loadings
. [Thesis]. University of Sydney; 2019. Available from: https://ses.library.usyd.edu.au/handle/2123/21247
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
23.
Alonso Campoi Trípodi.
Resposta magnética de supercondutores estruturados: dependência com a granulometria.
Degree: 2010, Universidade Federal de São Carlos
URL: http://www.bdtd.ufscar.br/htdocs/tedeSimplificado//tde_busca/arquivo.php?codArquivo=3040
► A máxima corrente crítica que pode ser transportada através de um supercondutor granular é, em geral, limitada pela corrente crítica dos elos fracos (EFRs) que…
(more)
▼ A máxima corrente crítica que pode ser transportada através de um supercondutor
granular é, em geral, limitada pela corrente crítica dos elos fracos (EFRs) que acoplam grãos vizinhos. Para amostras cuja distribuição de correntes críticas intergranulares é suficientemente estreita, a dependência da suscetibilidade-AC com a temperatura, ( ) ( ) ( ) ACχ T=χT+iχ T, exibe uma estrutura característica, com dois patamares em χ e dois picos em χ . A ocorrência de um pico intergranular estreito evidencia um bom controle da distribuição dos EFRs no que se refere à sua capacidade de transporte, o quê, em geral, depende de parâmetros que podem ser controlados durante a produção de amostras granulares. Para estudar a retenção de fluxo magnético em amostras supercondutoras é preciso entender o comportamento dos elos fracos. A capacidade de blindagem e aprisionamento de uma amostra supercondutora reflete-se diretamente em seu ciclo de histerese que, devidamente tratado, revela a máxima capacidade de transporte de corrente da amostra. Neste trabalho de mestrado, utilizamos pó de nióbio para estudar a resposta magnética das regiões intergranulares de pastilhas formadas a partir da compactação do pó, tratando de compreender o papel de três parâmetros empregados na preparação da pastilha: a pressão de compactação do pó, o tamanho dos grãos e a sua dispersão. Estudamos a dependência da resposta magnética (magnetização e suscetibilidade AC) com tais parâmetros controláveis. Dissertação de Mestrado Alonso Campoi Trípodi Constatamos que amostras preparadas com maiores pressões têm maior capacidade de aprisionamento de fluxo magnético na região intergranular e EFRs mais fortes. Por outro lado, amostras com partículas maiores têm EFRs com temperaturas críticas mais altas, ou seja, pastilhas fabricadas com partículas maiores exibem uma supercondutividade mais robusta. Observamos o Efeito Meissner Paramagnético, na forma de reentrâncias em curvas de Magnetização em função da Temperatura. Comparando pastilhas com diferentes tamanhos de grãos, o ancoramento dos fluxo foi mais eficaz em amostras com partículas grandes e pequena dispersão de tamanho. Verificamos também o caráter metaestável de estados preparados de modo que houvesse fluxo aprisionado, comparando medidas de magnetização antes e depois da aplicação de um campo AC, que causa desprendimento parcial do fluxo magnético aprisionado em regiões intergranulares, efeito similar ao chamado Vortex Shaking. Realizamos também experimentos em função do campo magnético aplicado - os chamados laços de histerese - com vistas à obtenção da dependência da corrente crítica com o campo magnético aplicado, empregando para isso um modelo de estado crítico. Verificamos que para temperaturas mais baixas a densidade de corrente crítica é maior para pastilhas com partículas maiores e pequena dispersão de tamanho. Em resumo, nossos resultados indicam claramente que, para uma mesma granulometria, maiores pressões de compactação propiciam respostas mais diamagnéticas, bem como EFRs com…
Advisors/Committee Members: Wilson Aires Ortiz.
Subjects/Keywords: Granular materials; Nióbio; Supercondutividade; FISICA; Corrente crítica
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APA (6th Edition):
Trípodi, A. C. (2010). Resposta magnética de supercondutores estruturados: dependência com a granulometria. (Thesis). Universidade Federal de São Carlos. Retrieved from http://www.bdtd.ufscar.br/htdocs/tedeSimplificado//tde_busca/arquivo.php?codArquivo=3040
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Trípodi, Alonso Campoi. “Resposta magnética de supercondutores estruturados: dependência com a granulometria.” 2010. Thesis, Universidade Federal de São Carlos. Accessed December 14, 2019.
http://www.bdtd.ufscar.br/htdocs/tedeSimplificado//tde_busca/arquivo.php?codArquivo=3040.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Trípodi, Alonso Campoi. “Resposta magnética de supercondutores estruturados: dependência com a granulometria.” 2010. Web. 14 Dec 2019.
Vancouver:
Trípodi AC. Resposta magnética de supercondutores estruturados: dependência com a granulometria. [Internet] [Thesis]. Universidade Federal de São Carlos; 2010. [cited 2019 Dec 14].
Available from: http://www.bdtd.ufscar.br/htdocs/tedeSimplificado//tde_busca/arquivo.php?codArquivo=3040.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Trípodi AC. Resposta magnética de supercondutores estruturados: dependência com a granulometria. [Thesis]. Universidade Federal de São Carlos; 2010. Available from: http://www.bdtd.ufscar.br/htdocs/tedeSimplificado//tde_busca/arquivo.php?codArquivo=3040
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
24.
Salerno, Kenneth Michael.
Inertia and the Critical Scaling of Avalanches in Sheared Disordered Solids.
Degree: 2013, Johns Hopkins University
URL: http://jhir.library.jhu.edu/handle/1774.2/37080
► This thesis presents results from molecular dynamic (MD) studies of disordered materials undergoing quasi-static shear at zero temperature. Simulations are performed in both two and…
(more)
▼ This thesis presents results from molecular dynamic (MD) studies of disordered
materials undergoing quasi-static shear at zero temperature. Simulations are performed in both two and three dimensions and with a variety of different damping dynamics. During shear, periods of linearly increasing stress and strain alternate with rapid releases of potential energy and stress, termed avalanches. These avalanches have been found in the past to follow power-law statistics. Avalanches in our simulations are observed to exhibit power-law statistics and obey finite-size scaling relations, indicating critical behavior. In contrast with past studies of the nonequilibrium critical depinning transition at the onset of motion, where inertia was observed to destroy critical behavior, we find that inertia qualitatively changes but does not destroy the observed critical behavior. We can characterize three damping regimes, termed overdamped, underdamped and crossover regimes, by measuring
scaling and critical exponents in each regime. During each avalanche, potential energy is transformed to atomic motion, with some particles undergoing large displacements. The distribution of particle displacements during avalanche events is quantified, leading to a relationship between local plasticity and stress release. Over larger strain intervals particle displacements allow us to quantify an effective strain-dependent diffusion and define a diffusion constant. Avalanche events demonstrate notable spatial correlations over strain intervals large compared with the typical inter-event interval. These correlations are measured using the power-spectrum of measures of the local strain field. The correlations are found to be angle dependent and long range in nature, independent of damping rate.
Advisors/Committee Members: Robbins, Mark O (advisor).
Subjects/Keywords: granular materials;
disordered solids;
nonequilibrium critical phenomena
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APA (6th Edition):
Salerno, K. M. (2013). Inertia and the Critical Scaling of Avalanches in Sheared Disordered Solids. (Thesis). Johns Hopkins University. Retrieved from http://jhir.library.jhu.edu/handle/1774.2/37080
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Salerno, Kenneth Michael. “Inertia and the Critical Scaling of Avalanches in Sheared Disordered Solids.” 2013. Thesis, Johns Hopkins University. Accessed December 14, 2019.
http://jhir.library.jhu.edu/handle/1774.2/37080.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Salerno, Kenneth Michael. “Inertia and the Critical Scaling of Avalanches in Sheared Disordered Solids.” 2013. Web. 14 Dec 2019.
Vancouver:
Salerno KM. Inertia and the Critical Scaling of Avalanches in Sheared Disordered Solids. [Internet] [Thesis]. Johns Hopkins University; 2013. [cited 2019 Dec 14].
Available from: http://jhir.library.jhu.edu/handle/1774.2/37080.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Salerno KM. Inertia and the Critical Scaling of Avalanches in Sheared Disordered Solids. [Thesis]. Johns Hopkins University; 2013. Available from: http://jhir.library.jhu.edu/handle/1774.2/37080
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Hong Kong University of Science and Technology
25.
Liu, Zhaochen.
Micromechanical study of mechanical behavior of granular media accounting for the role of particle shape.
Degree: 2015, Hong Kong University of Science and Technology
URL: https://doi.org/10.14711/thesis-b1450648
;
http://repository.ust.hk/ir/bitstream/1783.1-74352/1/th_redirect.html
► The behavior of granular media is challenging to understand and the study has been a focus of research for decades. The complexity of granular media…
(more)
▼ The behavior of granular media is challenging to understand and the study has been a focus of research for decades. The complexity of granular media originates from their heterogeneous and discrete nature. The properties of the constituent individual particles intrinsically control the macroscopic response of a granular material. In particular, the shape of particles underpins many facets of the mechanical behavior of the material, including packing, strength, deformation, failure, flow and breakage and others, while the micromechanics of the is still lack of deep understanding due to the limitation on the shape characterization and modelling. This thesis presents a micromechanical investigation of the influence of complex particle shape on the shear behavior of granular material based on 2D DEM simulations. A series of Fourier shape descriptors were used to quantify the shape of particles, which allows us to construct particles with quantitatively controlled shape properties, including irregularity, elongation and roughness. Packings of granular particles generated with controlled shape properties were subjected to monotonic biaxial shear tests and both their macroscopic and microscopic responses were carefully examined. At the macroscopic scale, the packing density, shear strength and volumetric responses were found to correlate closely with the shape properties in different ways. At the microscopic level, two new methods were introduced to quantify the micromechanical response, one intending to recognize the force chain network from both mechanical and geometrical perspectives and the other considering rolling resistance as an alternative to particle shape. Based on these methods, the anisotropy and force transmission mechanisms were analyzed. We found irregularity, elongation and roughness all enhance the packing strength by increasing the fabric anisotropy and mobilized friction. Irregularity and elongation are found to have significantly different influences on the material behavior due to different contact features. Roughness influences the micromechanics in a similar way with irregularity, but it is less dominant when irregularity is present. We concluded the particle shapes influences the micromechanical behaviors of granular media from at least two aspects: the micromechanics, for which particle shapes induce rolling resistance effect, and the micro-geometries, for which contact features influences the contact distributions and particle arrangement. The quantitative consideration of shape properties in this study enables us to attribute physical explanations to shape-induced rolling resistance which has long been considered in most DEM simulations in a phenomenological manner. It was found irregularity/roughness or elongation dominant particles offer rolling resistance at the grain scale in rather different manners due to different contact features, which cannot be fully explained by conventional rolling resistance models. The thesis was also devoted to the study of energy flows in granular media for better…
Subjects/Keywords: Granular materials; Mathematical models; Fluid dynamics; Micromechanics
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APA (6th Edition):
Liu, Z. (2015). Micromechanical study of mechanical behavior of granular media accounting for the role of particle shape. (Thesis). Hong Kong University of Science and Technology. Retrieved from https://doi.org/10.14711/thesis-b1450648 ; http://repository.ust.hk/ir/bitstream/1783.1-74352/1/th_redirect.html
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Liu, Zhaochen. “Micromechanical study of mechanical behavior of granular media accounting for the role of particle shape.” 2015. Thesis, Hong Kong University of Science and Technology. Accessed December 14, 2019.
https://doi.org/10.14711/thesis-b1450648 ; http://repository.ust.hk/ir/bitstream/1783.1-74352/1/th_redirect.html.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Liu, Zhaochen. “Micromechanical study of mechanical behavior of granular media accounting for the role of particle shape.” 2015. Web. 14 Dec 2019.
Vancouver:
Liu Z. Micromechanical study of mechanical behavior of granular media accounting for the role of particle shape. [Internet] [Thesis]. Hong Kong University of Science and Technology; 2015. [cited 2019 Dec 14].
Available from: https://doi.org/10.14711/thesis-b1450648 ; http://repository.ust.hk/ir/bitstream/1783.1-74352/1/th_redirect.html.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Liu Z. Micromechanical study of mechanical behavior of granular media accounting for the role of particle shape. [Thesis]. Hong Kong University of Science and Technology; 2015. Available from: https://doi.org/10.14711/thesis-b1450648 ; http://repository.ust.hk/ir/bitstream/1783.1-74352/1/th_redirect.html
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Hong Kong University of Science and Technology
26.
Guo, Ning.
Multiscale characterization of the shear behavior of granular media.
Degree: 2014, Hong Kong University of Science and Technology
URL: https://doi.org/10.14711/thesis-b1334193
;
http://repository.ust.hk/ir/bitstream/1783.1-70882/1/th_redirect.html
► Granular media are ubiquitous and important to a wide range of engineering applications and industries. A granular material under shear may exhibit exceedingly complicated behavior…
(more)
▼ Granular media are ubiquitous and important to a wide range of engineering applications and industries. A granular material under shear may exhibit exceedingly complicated behavior which is notoriously difficult to characterize and model, including anisotropy, dilatancy, plasticity, non-coaxiality, critical state and fluid-solid-phase transition. The macroscopic shear responses of a granular material reflect non-trivial micromechanical mechanisms originated from the grain scale of the material. The thesis aims to examine the behavior of granular media subjected to quasi-static shear from a multiscale perspective, based on two complementary approaches: a micromechanics approach based on the discrete element method (DEM) and a hierarchical multiscale approach based on coupled finite element method (FEM) and DEM. The micromechanical study is endeavored to develop an improved cross-scale understanding of key continuum concepts and phenomena in constitutive modeling of granular media, such as granular anisotropy and granular plasticity. The second approach aims to abandon the phenomenological nature of conventional constitutive modeling and to remove the scale limitation of the micromechanics approach in modeling practical boundary value problems (BVPs), by developing a novel hierarchical coupling between FEM and DEM. With a computational bridging scheme in this hierarchical framework, the macro observations and micro mechanisms in granular media can be linked intimately, which is exemplified with simulations of strain localization in various BVPs. Major findings from this thesis are summarized as follows: (i) Signature characteristics of shear-induced anisotropy at liquefaction, phase transformation, and critical states are identified based on micromechanical study. Static liquefaction is found to occur when the geometrical anisotropy dominates the mechanical anisotropy and the weak force network features an exceptionally high proportion of sliding contacts and develops certain degree of anisotropy. Phase transformation corresponds to a transitional, unstable state associated with a dramatic change in both coordination number and sliding contacts. The critical state in a granular material is always associated with a highly anisotropic fabric structure wherein both the critical void ratio and critical fabric anisotropy depends on the mean effective stress. (ii) The concept of the critical state in granular soils needs to make proper reference to the fabric structure. A unique relationship between the mean effective stress and a fabric anisotropy parameter, K, defined by the first joint invariant of the deviatoric stress tensor and the deviatoric fabric tensor, is found following power-law at critical state, and is path-independent based on DEM simulations under different loading conditions and intermediate principal stress ratios. Based on the findings, a new definition of critical state for granular media is proposed. In addition to the constant stress and volume required by the conventional critical state concept, an…
Subjects/Keywords: Granular materials; Mathematical models; Shear (Mechanics)
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APA ·
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APA (6th Edition):
Guo, N. (2014). Multiscale characterization of the shear behavior of granular media. (Thesis). Hong Kong University of Science and Technology. Retrieved from https://doi.org/10.14711/thesis-b1334193 ; http://repository.ust.hk/ir/bitstream/1783.1-70882/1/th_redirect.html
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Guo, Ning. “Multiscale characterization of the shear behavior of granular media.” 2014. Thesis, Hong Kong University of Science and Technology. Accessed December 14, 2019.
https://doi.org/10.14711/thesis-b1334193 ; http://repository.ust.hk/ir/bitstream/1783.1-70882/1/th_redirect.html.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Guo, Ning. “Multiscale characterization of the shear behavior of granular media.” 2014. Web. 14 Dec 2019.
Vancouver:
Guo N. Multiscale characterization of the shear behavior of granular media. [Internet] [Thesis]. Hong Kong University of Science and Technology; 2014. [cited 2019 Dec 14].
Available from: https://doi.org/10.14711/thesis-b1334193 ; http://repository.ust.hk/ir/bitstream/1783.1-70882/1/th_redirect.html.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Guo N. Multiscale characterization of the shear behavior of granular media. [Thesis]. Hong Kong University of Science and Technology; 2014. Available from: https://doi.org/10.14711/thesis-b1334193 ; http://repository.ust.hk/ir/bitstream/1783.1-70882/1/th_redirect.html
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Hong Kong
27.
Lopera Perez, Juan Camilo.
Micro-mechanical investigation of the instability of pure
sand and sand-rubber mixtures.
Degree: PhD, 2016, University of Hong Kong
URL: http://hdl.handle.net/10722/235910
► Soil instabilities caused by either increase of pore water pressure in undrained loading conditions or water infiltration in drained loading conditions, can lead to natural…
(more)
▼ Soil instabilities caused by either increase of
pore water pressure in undrained loading conditions or water
infiltration in drained loading conditions, can lead to natural
hazards such as landslides. New geo-materials, for instance,
mixtures of sand with rubber have become a popular approach in
ground improvement acting as a remedial against unstable soil
behaviour. The Discrete Element Method (DEM), which offers
particle-scale information, was employed to model granular systems
comprised of sand (stiff) and rubber (soft) particles under
different loading conditions and to provide fundamental
explanations to the failure mechanisms within granular systems.
The conditions required for quasi-static shearing in DEM
simulations were explored. The inertial number (𝐼) was used to
ensure that the shearing rate applied to simulated samples was
quasi-static. Clear trends were observed in macro and
micro-mechanical quantities at the critical state as 𝐼 varied. A
value of 𝐼 that divided the quasi-steady from a dynamic state was
identified.
A study of the influence of the initial void ratio
(𝑒0) on the coefficient of lateral pressure at rest (𝐾0) for sand
samples was carried out. It was found that higher density resulted
in lower values of 𝐾0. Denser states presented a bias towards
vertically-oriented contacts, resulting in lower stresses
transmitted in the horizontal direction. Contrastingly, contacts
were oriented more isotropically in looser states, allowing for a
more isotropic stress transmission, inducing more critical
conditions for geotechnical structures such as retaining walls.
Sand samples were prepared under different consolidation paths to
explore stress-induced anisotropy. The small strain stiffness was
affected by different degrees of induced anisotropy. However, when
sheared to larger strains, the influence of induced anisotropy
diminished, and unique macro and micro-scale critical state
relationships were attained. Higher degrees of induced anisotropy
on loose specimens helped increase the liquefaction resistance.
The instability of granular materials under drained conditions was
simulated by conducting Constant Shear Drained (CSD) tests.
Regardless of the initial packing, all samples attained an onset of
instability that coincided with fluctuations in the particle-scale
second-order work. Macro and micro quantities experienced drastic
changes, showing either a sharp increase or decrease. It was shown
how constant shear drained loading conditions may result in more
unfavourable situations than undrained shearing conditions.
A
series of DEM simulations, consisting of mixtures of sand and
rubber particles, were conducted under different loading
conditions. The content and size of rubber particles had a direct
impact on the peak strength and shear modulus of the mixtures.
Micro-scale information was obtained for all tests, and the
contribution of each type of contact in the overall response was
analysed and quantified. Different internal structures were
encountered at different test stages and linked to…
Subjects/Keywords: Discrete element method; Granular materials - Mathematical models
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APA (6th Edition):
Lopera Perez, J. C. (2016). Micro-mechanical investigation of the instability of pure
sand and sand-rubber mixtures. (Doctoral Dissertation). University of Hong Kong. Retrieved from http://hdl.handle.net/10722/235910
Chicago Manual of Style (16th Edition):
Lopera Perez, Juan Camilo. “Micro-mechanical investigation of the instability of pure
sand and sand-rubber mixtures.” 2016. Doctoral Dissertation, University of Hong Kong. Accessed December 14, 2019.
http://hdl.handle.net/10722/235910.
MLA Handbook (7th Edition):
Lopera Perez, Juan Camilo. “Micro-mechanical investigation of the instability of pure
sand and sand-rubber mixtures.” 2016. Web. 14 Dec 2019.
Vancouver:
Lopera Perez JC. Micro-mechanical investigation of the instability of pure
sand and sand-rubber mixtures. [Internet] [Doctoral dissertation]. University of Hong Kong; 2016. [cited 2019 Dec 14].
Available from: http://hdl.handle.net/10722/235910.
Council of Science Editors:
Lopera Perez JC. Micro-mechanical investigation of the instability of pure
sand and sand-rubber mixtures. [Doctoral Dissertation]. University of Hong Kong; 2016. Available from: http://hdl.handle.net/10722/235910
Stellenbosch University
28.
Els, Daniel Nicolaas Johannes.
The effectiveness of particle dampers under centrifugal loads.
Degree: Mechanical and Mechatronic Engineering, 2009, Stellenbosch University
URL: http://hdl.handle.net/10019.1/1429
► Thesis (PhD (Mechanical and Mechatronic Engineering)) – University of Stellenbosch, 2009.
The main research objective of this dissertation was to determine the performance parameters of particle…
(more)
▼ Thesis (PhD (Mechanical and Mechatronic Engineering)) – University of Stellenbosch, 2009.
The main research objective of this dissertation was to determine the performance
parameters of particle dampers (PDs) under centrifugal loads.
A test bench was developed consisting of a rotating cantilever beam with a PD at
the tip. Equal mass containers with di erent depths, filled with a range of uniform
sized steel ball bearings, were used as PDs. For all the tests, the total PD mass was
identical. During operation the tip of the beam was displaced, and after release, the
beam could vibrate freely. The decay in the vibratory motion of the tip of the beam
was measured over a range of centrifugal loads.
The experiments were duplicated numerically with a discrete element method
(DEM) model, calibrated against the experimental data. This model could then be
used for a more in-depth investigation of phenomena occurring when PDs are under
centrifugal loads.
From the data analysis, it can be concluded that there are two zones of damping,
one with a high and one with a low damping factor. These damping zones depend on
the ratio between the peak vibration acceleration and the centrifugal loading. Each
zone has a limit in terms of the centrifugal loading beyond which the PD cannot
function if the vibration amplitude is fixed. In the high damping zone, it was found
that the excitation state of the particles was high enough for the system vibration
frequency to change. In the low damping zone, there is only limited motion between
the particles.
The main parameters that influence the performance of the PDs are the friction
between the particles themselves and with the container, the PD length/diameter
aspect ratio, and the particle size. An important finding is that a PD with less layers
(increase in particle size) will still function at a higher centrifugal load compared to
one with a smaller number number of layers.
Advisors/Committee Members: Van Niekerk, J. L., University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering..
Subjects/Keywords: Mechanical engineering; Vibration; Centrifugal force; Granular materials
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APA (6th Edition):
Els, D. N. J. (2009). The effectiveness of particle dampers under centrifugal loads. (Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/1429
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Els, Daniel Nicolaas Johannes. “The effectiveness of particle dampers under centrifugal loads.” 2009. Thesis, Stellenbosch University. Accessed December 14, 2019.
http://hdl.handle.net/10019.1/1429.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Els, Daniel Nicolaas Johannes. “The effectiveness of particle dampers under centrifugal loads.” 2009. Web. 14 Dec 2019.
Vancouver:
Els DNJ. The effectiveness of particle dampers under centrifugal loads. [Internet] [Thesis]. Stellenbosch University; 2009. [cited 2019 Dec 14].
Available from: http://hdl.handle.net/10019.1/1429.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Els DNJ. The effectiveness of particle dampers under centrifugal loads. [Thesis]. Stellenbosch University; 2009. Available from: http://hdl.handle.net/10019.1/1429
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Rutgers University
29.
Karkala, Subhodh Kumar, 1984-.
Analyzing the mixing dynamics of a tumbling bin blender using discrete element modeling.
Degree: MS, Chemical and Biochemical Engineering, 2015, Rutgers University
URL: https://rucore.libraries.rutgers.edu/rutgers-lib/47455/
► Powder mixing is a critical step in pharmaceutical processes as it determines the final tablet composition. In this study a discrete element model (DEM) has…
(more)
▼ Powder mixing is a critical step in pharmaceutical processes as it determines the final tablet composition. In this study a discrete element model (DEM) has been developed for an industrial scale tumbling bin blender in which three different
materials are blended together. The dynamics of the mixing have been evaluated with the analysis of critical quality attributes (CQAs) such as relative standard deviation (RSD) and segregation intensity. This model has been developed and calibrated using an experimental setup in which the blend composition is monitored through a near-infrared range (NIR) probe mounted on the blender lid. The final blend quality is judged on the basis of measurements only at the lid in the experimental setup. However, the model has been used to study the quality of mixing in different locations inside the blender. The model is able identify poorly mixed zones and can be used to investigate other potential locations for the NIR probe. The effect of key process parameters (i.e. blender RPM and loading order of
materials) on the quality of mixing has also been studied.
Advisors/Committee Members: Ramachandran, Rohit (chair), Ierapetritou, Marianthi G. (internal member), Glasser, Benjamin J. (internal member).
Subjects/Keywords: Granular materials – Mathematical models; Finite element method
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APA (6th Edition):
Karkala, Subhodh Kumar, 1. (2015). Analyzing the mixing dynamics of a tumbling bin blender using discrete element modeling. (Masters Thesis). Rutgers University. Retrieved from https://rucore.libraries.rutgers.edu/rutgers-lib/47455/
Chicago Manual of Style (16th Edition):
Karkala, Subhodh Kumar, 1984-. “Analyzing the mixing dynamics of a tumbling bin blender using discrete element modeling.” 2015. Masters Thesis, Rutgers University. Accessed December 14, 2019.
https://rucore.libraries.rutgers.edu/rutgers-lib/47455/.
MLA Handbook (7th Edition):
Karkala, Subhodh Kumar, 1984-. “Analyzing the mixing dynamics of a tumbling bin blender using discrete element modeling.” 2015. Web. 14 Dec 2019.
Vancouver:
Karkala, Subhodh Kumar 1. Analyzing the mixing dynamics of a tumbling bin blender using discrete element modeling. [Internet] [Masters thesis]. Rutgers University; 2015. [cited 2019 Dec 14].
Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/47455/.
Council of Science Editors:
Karkala, Subhodh Kumar 1. Analyzing the mixing dynamics of a tumbling bin blender using discrete element modeling. [Masters Thesis]. Rutgers University; 2015. Available from: https://rucore.libraries.rutgers.edu/rutgers-lib/47455/
Rutgers University
30.
LaMarche, Keirnan R.
Electrostatic instabilities, charging and agglomeration in flowing granular materials.
Degree: PhD, Chemical and Biochemical Engineering, 2008, Rutgers University
URL: http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17342
► The unpredictable behavior of granular materials is one of the largest stumbling blocks on the way to satisfactory design and control of many manufacturing processes.…
(more)
▼ The unpredictable behavior of granular materials is one of the largest stumbling blocks on the way to satisfactory design and control of many manufacturing processes. There are many factors which contribute to the complex behavior of granular materials, however, the effect of electrostatic forces is both one of the least studied aspects of granular materials as well as one of the most important. Electrostatics can cause agglomeration of otherwise free flowing powders, the adhesion of grains to equipment surfaces, and particles of differing composition or size to segregate. In addition, electrostatic discharges can ignite dangerous dust explosions. With a better understanding of the effects of electrostatics, as well as the processes at work during the charging of particulate flows, some of these issues can begin to be addressed. To these ends, we examine the charge and agglomeration of grains and investigate how flows of particles charge, and in turn, how they are affected by those charges.
In this work, we show that the behavior of flows of uncharged grains through chutes can be approximated by simple models, but when charging takes place the behaviors change dramatically, replacing fluid-like flow instabilities with significant agglomeration, making the flow much more difficult to model. To understand and predict these transitions from relatively simple flow to a more complex/agglomerated state requires that the distribution of charge amongst the particles, as well as the effect of large electric fields, produced by either charged surfaces or particles, be investigated.
It was found that highly nonuniform distributions of charge could be generated by flowing particles. This distribution can result in significantly different forces acting on charged and uncharged grains and suggests that many of the problems commonly encountered during powder handling may be due to a small fraction of the particles.
Lastly, significant agglomeration was observed when particles were subjected to nonuniform electric fields. Nonuniform electric fields, which are produced as particles charge, cause polarization of the particles and attraction between grains. The resulting forces acting on the particles (referred to as dielectrophoretic forces) were large enough to produce both large agglomerates of powder, as well as adhesion to equipment surfaces. These forces may also be utilized to control particle behavior as this adhesion depends on the presence of an easily controlled external electric field.
Advisors/Committee Members: LaMarche, Keirnan R. (author), Cuitino, Alberto (chair), Pedersen, Henrik (internal member), Glasser, Benjamin (internal member), Michniak-Kohn, Bozena (outside member).
Subjects/Keywords: Electrostatics; Granular materials
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APA (6th Edition):
LaMarche, K. R. (2008). Electrostatic instabilities, charging and agglomeration in flowing granular materials. (Doctoral Dissertation). Rutgers University. Retrieved from http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17342
Chicago Manual of Style (16th Edition):
LaMarche, Keirnan R. “Electrostatic instabilities, charging and agglomeration in flowing granular materials.” 2008. Doctoral Dissertation, Rutgers University. Accessed December 14, 2019.
http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17342.
MLA Handbook (7th Edition):
LaMarche, Keirnan R. “Electrostatic instabilities, charging and agglomeration in flowing granular materials.” 2008. Web. 14 Dec 2019.
Vancouver:
LaMarche KR. Electrostatic instabilities, charging and agglomeration in flowing granular materials. [Internet] [Doctoral dissertation]. Rutgers University; 2008. [cited 2019 Dec 14].
Available from: http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17342.
Council of Science Editors:
LaMarche KR. Electrostatic instabilities, charging and agglomeration in flowing granular materials. [Doctoral Dissertation]. Rutgers University; 2008. Available from: http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17342
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