You searched for subject:(Damage mechanics).
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KTH
1.
Uustalu, Martin.
Crush simulation of carbon/epoxy NCF composites -Development of a validation test for material models.
Degree: Lightweight Structures, 2015, KTH
URL: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185274 
► The high specific stiffness and strength of composites makes it advantageous for load carrying structures in the automotive industry. By successfully be able to…
(more)
▼ The high specific stiffness and strength of composites makes it advantageous for load carrying structures in the automotive industry. By successfully be able to numerically simulate the crush behaviour of composites, structure with high specific energy absorption can be implemented in the automotive industry. The purpose of this thesis is to verify the predictive capabilities of a crush model developed at SICOMP. Initially currently available material models are investigated. Puck’s criterion is deeper studied. An improvement of the criterion is suggested and the model is updated to be able to output fracture angles in Abaqus.The material model developed by SICOMP is a three-dimensional physically based damage model where failure initiation is estimated with proven failure criteria and damage growth is combined with friction to account for the right energy absorption. The crush damage model has been implemented in Abaqus/Explicit as a VUMAT subroutine. Numerical predictions are compared with experimental results. Specimens with different fibre layups and crash triggers are tested.
Subjects/Keywords: Damage mechanics; NCF; Automotive
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APA (6th Edition):
Uustalu, M. (2015). Crush simulation of carbon/epoxy NCF composites -Development of a validation test for material models. (Thesis). KTH. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185274
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):
Uustalu, Martin. “Crush simulation of carbon/epoxy NCF composites -Development of a validation test for material models.” 2015. Thesis, KTH. Accessed April 17, 2021.
http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185274.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Uustalu, Martin. “Crush simulation of carbon/epoxy NCF composites -Development of a validation test for material models.” 2015. Web. 17 Apr 2021.
Vancouver:
Uustalu M. Crush simulation of carbon/epoxy NCF composites -Development of a validation test for material models. [Internet] [Thesis]. KTH; 2015. [cited 2021 Apr 17].
Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185274.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Uustalu M. Crush simulation of carbon/epoxy NCF composites -Development of a validation test for material models. [Thesis]. KTH; 2015. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185274
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Texas – Austin
2.
Karki, Pravat.
An integrated approach to measure and model fatigue damage and healing in asphalt composites.
Degree: PhD, Civil Engineering, 2014, University of Texas – Austin
URL: http://hdl.handle.net/2152/31322
► This study presents a test and analysis method to determine both damage and healing characteristics of asphalt composites using the same test specimen. The test…
(more)
▼ This study presents a test and analysis method to determine both
damage and healing characteristics of asphalt composites using the same test specimen. The test involves applying multiple stretches of load cycles, each separated by a period of zero load introduced at several different levels of reduced stiffness. The analytical procedure involves (1) using modified correspondence principles to transform the time-dependent physical quantities (stress, strain and energy density) into time-independent pseudo-elastic quantities, and then (2) using viscoelastic continuum
damage mechanics to quantify
damage and healing properties of the material based on the transformed quantities. The results obtained using two different asphalt mortars subjected to uniaxial and shear load cycles confirmed the findings from the previous researchers that the characteristic pseudo stiffness versus
damage relationship for a given material is independent of testing conditions. More importantly, this study demonstrated that the aforementioned relationship was also independent of the rest periods introduced intermittently during the cyclic tests. Results also show that healing defined in terms of the change in the internal state variable for
damage represents the true healing potential of a material. Furthermore, healing properties obtained using the proposed test method (a) agreed with the properties obtained using a more rigorous protocol with multiple test specimens, and (b) were independent of the loading conditions used to induce fatigue
damage. These observations strongly suggest that the proposed method can be used to predict
damage and healing properties for any arbitrary loading condition from properties determined using the proposed protocol.
Advisors/Committee Members: Bhasin, Amit (advisor), Machemehl, Randy (committee member), Prozzi, Jorge A. (committee member), Zhang, Zhanmin (committee member), Li, Wei (committee member).
Subjects/Keywords: Fatigue; Continuum Damage Mechanics; Healing
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APA (6th Edition):
Karki, P. (2014). An integrated approach to measure and model fatigue damage and healing in asphalt composites. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/31322
Chicago Manual of Style (16th Edition):
Karki, Pravat. “An integrated approach to measure and model fatigue damage and healing in asphalt composites.” 2014. Doctoral Dissertation, University of Texas – Austin. Accessed April 17, 2021.
http://hdl.handle.net/2152/31322.
MLA Handbook (7th Edition):
Karki, Pravat. “An integrated approach to measure and model fatigue damage and healing in asphalt composites.” 2014. Web. 17 Apr 2021.
Vancouver:
Karki P. An integrated approach to measure and model fatigue damage and healing in asphalt composites. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2014. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/2152/31322.
Council of Science Editors:
Karki P. An integrated approach to measure and model fatigue damage and healing in asphalt composites. [Doctoral Dissertation]. University of Texas – Austin; 2014. Available from: http://hdl.handle.net/2152/31322
3.
Reberg, Andrew Steven.
An Anisotropic Damage Mechanics Model for Concrete with Applications for Fatigue Loading and Freeze-Thaw Effects.
Degree: 2013, North Dakota State University
URL: http://hdl.handle.net/10365/26994
► It is well known that the formation and propagation of microcracks within concrete is anisotropic in nature, and has a degrading effect on its mechanical…
(more)
▼ It is well known that the formation and propagation of microcracks within concrete is anisotropic in nature, and has a degrading effect on its mechanical performance. In this thesis an anisotropic damage mechanics model is formulated for concrete which can predict the behavior of the material subjected to monotonic loading, fatigue loading, and freeze-thaw cycles. The constitutive model is formulated using the general framework of the internal variable theory of thermodynamics. Kinetic relations are used to describe the directionality of damage accumulation and the associated softening of mechanical properties. The rate independent model is then extended to cover fatigue loading cycles and freeze-thaw cycles. Two simple softening functions are used to predict the mechanical properties of concrete as the number of cyclic loads as well as freeze-thaw cycles increases. The model is compared with experimental data for fatigue and freeze-thaw performance of plain concrete.
Subjects/Keywords: Anisotropy; Continuum damage mechanics; Concrete – Fatigue
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APA (6th Edition):
Reberg, A. S. (2013). An Anisotropic Damage Mechanics Model for Concrete with Applications for Fatigue Loading and Freeze-Thaw Effects. (Thesis). North Dakota State University. Retrieved from http://hdl.handle.net/10365/26994
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):
Reberg, Andrew Steven. “An Anisotropic Damage Mechanics Model for Concrete with Applications for Fatigue Loading and Freeze-Thaw Effects.” 2013. Thesis, North Dakota State University. Accessed April 17, 2021.
http://hdl.handle.net/10365/26994.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Reberg, Andrew Steven. “An Anisotropic Damage Mechanics Model for Concrete with Applications for Fatigue Loading and Freeze-Thaw Effects.” 2013. Web. 17 Apr 2021.
Vancouver:
Reberg AS. An Anisotropic Damage Mechanics Model for Concrete with Applications for Fatigue Loading and Freeze-Thaw Effects. [Internet] [Thesis]. North Dakota State University; 2013. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10365/26994.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Reberg AS. An Anisotropic Damage Mechanics Model for Concrete with Applications for Fatigue Loading and Freeze-Thaw Effects. [Thesis]. North Dakota State University; 2013. Available from: http://hdl.handle.net/10365/26994
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Delft University of Technology
4.
Maravalalu Suresh, R.S. (author).
Nonlocal Damage Models for Concrete.
Degree: 2013, Delft University of Technology
URL: http://resolver.tudelft.nl/uuid:39a672a4-a554-4a1e-97da-7bc613b40cf1
► An understanding of response of concrete structures to impact loading is of interest to the Explosions, Ballistics and Protection department of TNO. Numerical simulations conducted…
(more)
▼ An understanding of response of concrete structures to impact loading is of interest to the Explosions, Ballistics and Protection department of TNO. Numerical simulations conducted to study this response require very small elements to capture the shockwave propagation and the material response which were found to be mesh dependent. The goal of the thesis is to implement and investigate a nonlocal model to obtain mesh independent results when simulating concrete failure under dynamic loads. The nonlocal models are implemented in LS-DYNA by modifying the user subroutines. The original nonlocal model has certain drawbacks which are investigated by means of certain benchmark tests. The use of the constant length scale and the isotropic weight function is found to be the cause of the drawbacks of the nonlocal model. A modified nonlocal model, the Stress based nonlocal model which resolves the issues of the original nonlocal model is implemented. The stress based nonlocal model is investigated to understand its behavior which leads to the resolution of the drawbacks of the nonlocal model. The stress based nonlocal model provides physically relevant fracture processes. The behavior of the model in a dynamic loading at various loading rates is investigated in comparison to the quasi-static loading. It is found that the model cannot capture the varying fracture processes zone widths as expected with the varying loading rates. The stress based nonlocal model is finally validated with experimental results and mesh independent results are obtained. The model cannot capture the varying fracture processes with different loading rates as seen in experiments. This is due to the use of the rate independent material model in combination with the stress based nonlocal model behavior.
Structural Mechanics
Structural Engineering
Civil Engineering and Geosciences
Advisors/Committee Members: Sluys, L.J. (mentor), Weerheijm, J. (mentor), Khoe, Y.S. (mentor).
Subjects/Keywords: damage mechanics; nonlocal; concrete; mesh sensitivity
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APA (6th Edition):
Maravalalu Suresh, R. S. (. (2013). Nonlocal Damage Models for Concrete. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:39a672a4-a554-4a1e-97da-7bc613b40cf1
Chicago Manual of Style (16th Edition):
Maravalalu Suresh, R S (author). “Nonlocal Damage Models for Concrete.” 2013. Masters Thesis, Delft University of Technology. Accessed April 17, 2021.
http://resolver.tudelft.nl/uuid:39a672a4-a554-4a1e-97da-7bc613b40cf1.
MLA Handbook (7th Edition):
Maravalalu Suresh, R S (author). “Nonlocal Damage Models for Concrete.” 2013. Web. 17 Apr 2021.
Vancouver:
Maravalalu Suresh RS(. Nonlocal Damage Models for Concrete. [Internet] [Masters thesis]. Delft University of Technology; 2013. [cited 2021 Apr 17].
Available from: http://resolver.tudelft.nl/uuid:39a672a4-a554-4a1e-97da-7bc613b40cf1.
Council of Science Editors:
Maravalalu Suresh RS(. Nonlocal Damage Models for Concrete. [Masters Thesis]. Delft University of Technology; 2013. Available from: http://resolver.tudelft.nl/uuid:39a672a4-a554-4a1e-97da-7bc613b40cf1
Colorado School of Mines
5.
Butt, Awais.
Ultrasonic velocity tomography method for damage evaluation in rocks.
Degree: MS(M.S.), Civil and Environmental Engineering, 2019, Colorado School of Mines
URL: http://hdl.handle.net/11124/173289
► The naturally occurring fractures and discontinuities have a significant influence on the mechanical and hydraulic properties of rocks and various engineering problems such as reservoir…
(more)
▼ The naturally occurring fractures and discontinuities have a significant influence on the mechanical and hydraulic properties of rocks and various engineering problems such as reservoir development, hydraulic fracturing, slope stability, underground construction, and earthquake prediction require an accurate characterization of such natural discontinuities and their progression. Therefore, it is very important to understand several
damage processes associated with the loading of rock materials, including the closure of existing micro-cracks and the initiation of cracks and their propagation. The Ultrasonic Velocity Tomography (UVT) technique is one of the full-field measurement technique that can be used, independently or in combination with other techniques, to study the changes in mechanical properties in the material, by mapping the ultrasonic wave velocity in the entire specimen. UVT is capable of identifying the heterogeneous changes (e.g. strain localization) occurring inside a material due to external loading. The main objective of this thesis was to develop and implement UVT techniques for characterizing the
damage in prismatic brittle rocks subjected to uniaxial loads. By comparing the generated velocity field tomograms at different stages of loading, this thesis aimed to identify the formation of
damage zones (e.g. strain localization zones) in a laboratory specimen, which are often a precursor to crack initiation, propagation and ultimately material failure. To achieve the research objectives, the following tasks were undertaken: (a) Evaluation of the applicability/suitability of the UVT technique in identifying the velocity field in prismatic brittle rock specimens; (b) Validation of the UVT technique: first, by using synthetic data and second, by using material with a known response; (c) Sensitivity analysis to determine the influential parameters for velocity tomograms; (d) Determination and comparison of the velocity field in prismatic brittle rock specimens with the flaws at different stages of loading to infer the changes occurring inside the specimen; and (e) Determination of the full-field strain profile, using the Digital Image Correlation (DIC) technique for better interpretation of the relationship between the mechanical changes and the geophysical response. Piezoelectric ultrasonic sensors were used to generate and receive elastic waves across the specimen and a fast LabView-based data acquisition system was used to record the waveforms that provided a great spatial resolution. The three major steps involved in the UVT procedure included Arrival time picking, Double Beamforming (DBF) for low Signal-to-noise ratio waveforms, and the inversion. Arrival times of the received compressional waves were used as the input to the MATLAB implemented tomographic inversion method and sectional velocity field tomograms were generated, during different stages of the uniaxial loading. By analyzing and comparing the changes in generated velocity tomograms, the initiation and growth of cracking and
damage in…
Advisors/Committee Members: Hedayat, Ahmadreza (advisor), Rostami, Jamal (committee member), Kim, Eunhye (committee member).
Subjects/Keywords: damage characterization; rock mechanics; geophysics; brittle rocks
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APA (6th Edition):
Butt, A. (2019). Ultrasonic velocity tomography method for damage evaluation in rocks. (Masters Thesis). Colorado School of Mines. Retrieved from http://hdl.handle.net/11124/173289
Chicago Manual of Style (16th Edition):
Butt, Awais. “Ultrasonic velocity tomography method for damage evaluation in rocks.” 2019. Masters Thesis, Colorado School of Mines. Accessed April 17, 2021.
http://hdl.handle.net/11124/173289.
MLA Handbook (7th Edition):
Butt, Awais. “Ultrasonic velocity tomography method for damage evaluation in rocks.” 2019. Web. 17 Apr 2021.
Vancouver:
Butt A. Ultrasonic velocity tomography method for damage evaluation in rocks. [Internet] [Masters thesis]. Colorado School of Mines; 2019. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/11124/173289.
Council of Science Editors:
Butt A. Ultrasonic velocity tomography method for damage evaluation in rocks. [Masters Thesis]. Colorado School of Mines; 2019. Available from: http://hdl.handle.net/11124/173289
Texas A&M University
6.
McLendon, Wesley R.
Prediction of Damage Zone Growth in Composites Using Continuum Damage Mechanics.
Degree: MS, Aerospace Engineering, 2010, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7509
► The continuum damage mechanics (CDM) approach is widely used to model damage in polymer matrix composite materials which are represented using the homogenized properties of…
(more)
▼ The continuum
damage mechanics (CDM) approach is widely used to model
damage in polymer matrix composite materials which are represented using the homogenized properties of the fiber and matrix constituents. CDM simplifies the problem of accounting for a large number of defects in a material by considering the homogenized effect of the defects as a change in constitutive properties of the material. However, recent investigations of textile composites have shown that CDM inaccurately predicts the direction of
damage zone growth for some composite architectures which fail under shear load, tending to predict failure transverse to the fibers. This behavior is fundamentally attributable to the fact that shear failure in textiles results in large (tow-scale) matrix cracks, while CDM is intended to model distributed micro-cracks. It is shown that when CDM is used to model shear failure in anisotropic continua, material anisotropy tends to cause CDM to predict failure contrary to what is expected for these structures. An approach is presented that may allow CDM to better predict
damage growth for shear failure in composites by encouraging the creation of an intial
damage zone with sufficient directional bias to overcome the effect of material anisotropy.
Advisors/Committee Members: Whitcomb, John D. (advisor), Talreja, Ramesh (committee member), Gao, Xin-Lin (committee member).
Subjects/Keywords: composite; damage; continuum damage mechanics
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APA (6th Edition):
McLendon, W. R. (2010). Prediction of Damage Zone Growth in Composites Using Continuum Damage Mechanics. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7509
Chicago Manual of Style (16th Edition):
McLendon, Wesley R. “Prediction of Damage Zone Growth in Composites Using Continuum Damage Mechanics.” 2010. Masters Thesis, Texas A&M University. Accessed April 17, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7509.
MLA Handbook (7th Edition):
McLendon, Wesley R. “Prediction of Damage Zone Growth in Composites Using Continuum Damage Mechanics.” 2010. Web. 17 Apr 2021.
Vancouver:
McLendon WR. Prediction of Damage Zone Growth in Composites Using Continuum Damage Mechanics. [Internet] [Masters thesis]. Texas A&M University; 2010. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7509.
Council of Science Editors:
McLendon WR. Prediction of Damage Zone Growth in Composites Using Continuum Damage Mechanics. [Masters Thesis]. Texas A&M University; 2010. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7509
Delft University of Technology
7.
Coppejans, Okko (author).
Investigating the size effect in SENB specimens with a triaxiality and Lode angle based damage model.
Degree: 2017, Delft University of Technology
URL: http://resolver.tudelft.nl/uuid:db08aa87-eaa4-414f-8eca-5a2174356301
► This master thesis is built up around two questions. First: Is it possible to calibrate a ductile failure model, where the strain at failure is…
(more)
▼ This master thesis is built up around two questions. First: Is it possible to calibrate a ductile failure model, where the strain at failure is a function of stress triaxiality and Lode angle, using only a single SENB specimen? The failure model that is referred to describes local failure in a finite element model to simulate ductile fracture. In this thesis, an orthotropic
damage constitutive material model is constructed to accommodate the most realistic fictitious crack growth. Simple isotropic element erosion or deletion was found to have severe effects on the stress states of neighbouring elements due to a major loss of constraint. The
damage model is based on the stress triaxiality and Lode angle, derived from the invariants of the stress tensor. For any combination of stress triaxiality and Lode angle, an equivalent plastic strain to failure is required in the form of a three-dimensional failure surface. Typically, multiple experiments with varying dominant stress states are needed to accurately calibrate such a failure surface or model. This research project shows that one can not only calibrate a failure surface from a single three-point bending specimen, but also obtains more calibration points than other approaches that are typically used for this purpose along the way. These calibration points are collected during a fully automated iterative procedure, where points are added every time the force in the simulation exceeds the force found in the experiment by more than 1%. As soon as enough calibration points with distinct stress states were found, the Hosford-Coulomb model was fitted using the least squares method. Finally, the obtained failure model was verified by using it to simulate the specimen on which it was calibrated. From these results, it can be concluded that it is possible to calibrate a failure model using only a single SENB specimen. In addition to this thesis, this procedure is outlined in a paper (Coppejans & Walters, 2017). The second part of the thesis revolves around whether a ductile failure model obtained from the procedure presented in this thesis can be successfully used to predict failure in different geometries. To verify this, the differences in stress states that occur in specimens with different dimensions and aspect ratios is researched both theoretically and numerically. From that study, it is found that indeed the geometry has an influence on the stress states that are present and where they are present. This influence is great enough that simple fracture
mechanics approaches such as the J-Integral and CTOD are only transferable if strict requirements are met between SENB specimen from the same material but with different dimensions. Standards such as BS7448 and ASTM E1820 describe the validity of the experimentally obtained fracture toughness parameters with respect to the specimen size to deal with these requirements. Where the global approach (fracture
mechanics) fails, the local approach (
damage mechanics) finds a natural application due to its revolving around…
Advisors/Committee Members: Sluijs, Lambertus J. (mentor), Kassapoglou, Christos (graduation committee), Popovich, Vera (graduation committee), Walters, C. L. (graduation committee), Delft University of Technology (degree granting institution).
Subjects/Keywords: Continuum Damage Model; Fracture mechanics; Damage mechanics; SENB; Calibration; Crack growth; Ductile fracture; Steel; Plasticity; Lode angle; Stress triaxiality; orthotropic damage
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APA ·
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APA (6th Edition):
Coppejans, O. (. (2017). Investigating the size effect in SENB specimens with a triaxiality and Lode angle based damage model. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:db08aa87-eaa4-414f-8eca-5a2174356301
Chicago Manual of Style (16th Edition):
Coppejans, Okko (author). “Investigating the size effect in SENB specimens with a triaxiality and Lode angle based damage model.” 2017. Masters Thesis, Delft University of Technology. Accessed April 17, 2021.
http://resolver.tudelft.nl/uuid:db08aa87-eaa4-414f-8eca-5a2174356301.
MLA Handbook (7th Edition):
Coppejans, Okko (author). “Investigating the size effect in SENB specimens with a triaxiality and Lode angle based damage model.” 2017. Web. 17 Apr 2021.
Vancouver:
Coppejans O(. Investigating the size effect in SENB specimens with a triaxiality and Lode angle based damage model. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2021 Apr 17].
Available from: http://resolver.tudelft.nl/uuid:db08aa87-eaa4-414f-8eca-5a2174356301.
Council of Science Editors:
Coppejans O(. Investigating the size effect in SENB specimens with a triaxiality and Lode angle based damage model. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:db08aa87-eaa4-414f-8eca-5a2174356301
Vanderbilt University
8.
Jimenez, Stephen Keith.
Damage Mechanics Approaches for Sharp and Diffuse Fracture Propagation: Application to Ice Sheet Fracture and Composite Delamination.
Degree: PhD, Civil Engineering, 2017, Vanderbilt University
URL: http://hdl.handle.net/1803/15084
► Damage mechanics approaches are developed for the numerical modeling of fracture evolution along sharp (i.e., zero-thickness) and diffuse (i.e., finite-thickness) interfaces and applied to investigate…
(more)
▼ Damage mechanics approaches are developed for the numerical modeling of fracture evolution along sharp (i.e., zero-thickness) and diffuse (i.e., finite-thickness) interfaces and applied to investigate ice sheet fracture and fatigue delamination of composites. Throughout this work, three computational
damage mechanics models, namely the cohesive zone model (CZM), creep
damage model (CDM), and phase field model (PFM) for brittle fracture, are implemented using the finite element method. The models are extended to incorporate time- and rate- dependent
damage mechanisms, thus incorporating the multi-physics nature of fracture. The CZM is a robust methodology for simulating sharp crack growth under non-monotonic mixed-mode loading conditions where the potential crack path is known a priori. The gradient and nonlocal CDM and PFM approaches are suited for modeling the evolution of diffuse crack interfaces for quasi-brittle fracture where the crack paths are not known a priori. The selection of the CZM is motivated by the need to simulate interface degradation in laminate composites subjected to high-cycle fatigue loading, and parametric sensitivity studies are conducted in order to establish a reliable fatigue
damage criterion. The creep
damage approach is employed to model time-dependent crevasse propagation in polar ice sheets undergoing large creep deformations. The cohesive zone and phase field models are also deployed to model the time-independent, brittle fracture of polar ice sheets by simulating the evolution of water-filled crevasses. The
damage mechanics approach is shown to be consistent with theoretical fracture
mechanics models for predicting the penetration of crevasses through ice.
Advisors/Committee Members: Prodyot K. Basu (committee member), Caglar Oskay (committee member), Haoxiang Luo (committee member), Ravindra Duddu (Committee Chair).
Subjects/Keywords: Damage mechanics; Ice dynamics; fracture mechanics; finite element analysis
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APA (6th Edition):
Jimenez, S. K. (2017). Damage Mechanics Approaches for Sharp and Diffuse Fracture Propagation: Application to Ice Sheet Fracture and Composite Delamination. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/15084
Chicago Manual of Style (16th Edition):
Jimenez, Stephen Keith. “Damage Mechanics Approaches for Sharp and Diffuse Fracture Propagation: Application to Ice Sheet Fracture and Composite Delamination.” 2017. Doctoral Dissertation, Vanderbilt University. Accessed April 17, 2021.
http://hdl.handle.net/1803/15084.
MLA Handbook (7th Edition):
Jimenez, Stephen Keith. “Damage Mechanics Approaches for Sharp and Diffuse Fracture Propagation: Application to Ice Sheet Fracture and Composite Delamination.” 2017. Web. 17 Apr 2021.
Vancouver:
Jimenez SK. Damage Mechanics Approaches for Sharp and Diffuse Fracture Propagation: Application to Ice Sheet Fracture and Composite Delamination. [Internet] [Doctoral dissertation]. Vanderbilt University; 2017. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1803/15084.
Council of Science Editors:
Jimenez SK. Damage Mechanics Approaches for Sharp and Diffuse Fracture Propagation: Application to Ice Sheet Fracture and Composite Delamination. [Doctoral Dissertation]. Vanderbilt University; 2017. Available from: http://hdl.handle.net/1803/15084
Columbia University
9.
Mobasher, Mostafa.
Enhanced continuum damage modeling of mechanical failure in ice and rocks.
Degree: 2017, Columbia University
URL: https://doi.org/10.7916/D85D94B8
► Modeling fracture in geomaterials is essential to the understanding of many physical phenomenon which may posses natural hazards e.g. landslides, faults and iceberg calving or…
(more)
▼ Modeling fracture in geomaterials is essential to the understanding of many physical phenomenon which may posses natural hazards e.g. landslides, faults and iceberg calving or man-made processes e.g. hydraulic fracture and excavations. Continuum Damage Mechanics (CDM) models the crack as a solid region with a degraded stiffness. This continuum definition of cracks in CDM allows more feasible coupling with other forms of material non-linearity and eliminates the need to track complicated crack geometry. Using CDM to analyze fracture for the modeling of fracture in geomaterials encounters several challenges e.g.: 1) the need to model the multiple physical processes occurring in geomaterials, typically: coupled fluid flow and solid deformation, 2) the need to consider non-local damage and transport in order to capture the underlying long range interactions and achieve mesh-independent finite element solutions and 3) the elevated computational cost associated with non-linear mixed finite element formulations.
The research presented in this thesis aims at improving the CDM formulations for modeling fracture geomaterials. This research can be divided into three main parts. The first is the introduction of a novel non-local damage transport formulation for modeling fracture in poroelastic media. The mathematical basis of the formulation are derived from thermodynamic equilibrium that considers non-local processes and homogenization principles. The non-local damage transport model leads to two additional regularization equations, one for non-local damage and the other for non-local transport which is reduced to non-local permeability. We consider two options for the implementation of the derived non-local transport damage model. The first option is the four-field formulation which extends the (u/P) formulation widely used in poroelasticity to include the non-local damage and transport phenomena. The second option is the three-field formulation, which is based on the coupling of the regularization equations under the assumptions of similar damage and permeability length scales and similar driving local stress/strain for the evolution of the damage and permeability. The three-field formulation is computationally cheaper but it degrades the physical modeling capabilities of the model. For each of these formulations, a non-linear mixed-finite element solution is developed and the Jacobian matrix is derived analytically. The developed formulations are used in the analysis of hydraulic fracture and consolidation examples.
In the second part, a novel approach for CDM modeling of hydraulic fracture of glaciers is pretended. The presence of water-filled crevasses is known to increase the penetration depth of crevasses and this has been hypothesized to play an important role controlling iceberg calving rate. Here, we develop a continuum damage-based poro-mechanics formulation that enables the simulation of water-filled basal and/or surface crevasse propagation. The formulation incorporates a scalar isotropic damage…
Subjects/Keywords: Continuum damage mechanics – Mathematical models; Fracture mechanics; Rocks – Fracture
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APA (6th Edition):
Mobasher, M. (2017). Enhanced continuum damage modeling of mechanical failure in ice and rocks. (Doctoral Dissertation). Columbia University. Retrieved from https://doi.org/10.7916/D85D94B8
Chicago Manual of Style (16th Edition):
Mobasher, Mostafa. “Enhanced continuum damage modeling of mechanical failure in ice and rocks.” 2017. Doctoral Dissertation, Columbia University. Accessed April 17, 2021.
https://doi.org/10.7916/D85D94B8.
MLA Handbook (7th Edition):
Mobasher, Mostafa. “Enhanced continuum damage modeling of mechanical failure in ice and rocks.” 2017. Web. 17 Apr 2021.
Vancouver:
Mobasher M. Enhanced continuum damage modeling of mechanical failure in ice and rocks. [Internet] [Doctoral dissertation]. Columbia University; 2017. [cited 2021 Apr 17].
Available from: https://doi.org/10.7916/D85D94B8.
Council of Science Editors:
Mobasher M. Enhanced continuum damage modeling of mechanical failure in ice and rocks. [Doctoral Dissertation]. Columbia University; 2017. Available from: https://doi.org/10.7916/D85D94B8
10.
Xu, Hao.
Theoretical and numerical modeling of anisotropic damage in rock for energy geomechanics.
Degree: PhD, Civil and Environmental Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/53035
► At present, most of the energy power consumed in the world is produced by fossil fuel combustion, which has raised increasing interest in renewable energy…
(more)
▼ At present, most of the energy power consumed in the world is produced by fossil fuel combustion, which has raised increasing interest in renewable energy technologies, non-conventional oil and gas reservoirs, and nuclear power. Innovative nuclear fuels and reactors depend on the economical and environmental impacts of waste management. Disposals in mined geological formations are viewed as potential consolidated storage facilities before final disposition. Different stress paths during construction result in different kinds of failure mechanisms, which alter rock strength and induce anisotropy of rock elastic properties. Crack propagation in rock can be originated by these engineering activities (excavation, drilling, mining, building overburden), or by changes of the natural environment (tectonic processes, erosion or weathering).
Damage is a mathematical variable that can represent a variety of microstructure changes, such as crack density, length, aspect ratio and orientation. The framework of Continuum
Damage Mechanics allows modeling the resulting reduction in strength and stiffness, as well as the associated stress-induced anisotropy and irreversible deformation.
This work presents a modeling framework for anisotropic crack propagation in rock, in conditions of stress typical of geological storage and oil and gas extraction. Emphasis is put on the prediction of the
damage zone around cavities and ahead of pressurized fracture tips. An original model of anisotropic
damage, the Differential Stress Induced
Damage (DSID) model, is explained. The Drucker-Prager yield function is adapted to make the
damage threshold depend on
damage energy release rate and to distinguish between tension and compression strength. Flow rules are derived with the energy release rate conjugate to
damage, which is thermodynamically consistent. The positivity of dissipation is ensured by using a non-associate flow rule for
damage, while nonelastic deformation due to
damage is computed by an associate flow rule. Stress paths simulated at the material point illustrate damaged stiffness and deformation variations in classical rock
mechanics tests. The maximum likelihood method was employed to calibrate and verify the DSID model against stress-strain curves obtained during triaxial compression tests and uniaxial compression tests performed on clay rock and shale. Logarithmic transformation, normalization and forward deletion allowed optimizing the formulation of the DSID model, and reduce the number of
damage constitutive parameters from seven to two for clay rock. The DSID model was implemented in ABAQUS Finite Element (FE) software. The iterative scheme was adapted in order to account for the non-linearities induce both by
damage and
damage-induced deformation. FE simulations of laboratory tests capture size an intrinsic anisotropy effects on the propagation of
damage in rock. Smeared DSID zones representing shale delamination planes avoid some convergence problems encountered when modeling discontinuities with debonded contact…
Advisors/Committee Members: Arson, Chloé (advisor), Santamarina, Juan Carlos (committee member), Frost, James David (committee member), Huber, Christian (committee member), Busetti, Seth (committee member), Chester, Frederick M. (committee member).
Subjects/Keywords: Damage mechanics; Rock mechanics; Numerical modeling; Energy geomechanics; Anisotropy
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APA (6th Edition):
Xu, H. (2014). Theoretical and numerical modeling of anisotropic damage in rock for energy geomechanics. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53035
Chicago Manual of Style (16th Edition):
Xu, Hao. “Theoretical and numerical modeling of anisotropic damage in rock for energy geomechanics.” 2014. Doctoral Dissertation, Georgia Tech. Accessed April 17, 2021.
http://hdl.handle.net/1853/53035.
MLA Handbook (7th Edition):
Xu, Hao. “Theoretical and numerical modeling of anisotropic damage in rock for energy geomechanics.” 2014. Web. 17 Apr 2021.
Vancouver:
Xu H. Theoretical and numerical modeling of anisotropic damage in rock for energy geomechanics. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1853/53035.
Council of Science Editors:
Xu H. Theoretical and numerical modeling of anisotropic damage in rock for energy geomechanics. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/53035
University of Hong Kong
11.
Wang, Chun.
Development of an
anisotropic damage mechanics model in ductile fracture.
Degree: 1987, University of Hong Kong
URL: http://hdl.handle.net/10722/34506
Subjects/Keywords: Fracture mechanics.;
Continuum damage mechanics.
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APA (6th Edition):
Wang, C. (1987). Development of an
anisotropic damage mechanics model in ductile fracture. (Thesis). University of Hong Kong. Retrieved from http://hdl.handle.net/10722/34506
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):
Wang, Chun. “Development of an
anisotropic damage mechanics model in ductile fracture.” 1987. Thesis, University of Hong Kong. Accessed April 17, 2021.
http://hdl.handle.net/10722/34506.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Wang, Chun. “Development of an
anisotropic damage mechanics model in ductile fracture.” 1987. Web. 17 Apr 2021.
Vancouver:
Wang C. Development of an
anisotropic damage mechanics model in ductile fracture. [Internet] [Thesis]. University of Hong Kong; 1987. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10722/34506.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Wang C. Development of an
anisotropic damage mechanics model in ductile fracture. [Thesis]. University of Hong Kong; 1987. Available from: http://hdl.handle.net/10722/34506
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Delft University of Technology
12.
Sluijs, J. (author).
A stiffness independent Interfacial Thick Level Set method: A modified approach for crack analysis.
Degree: 2020, Delft University of Technology
URL: http://resolver.tudelft.nl/uuid:7408e962-afb8-4c83-9f46-302db0b3bddf
► Crack growth is an important failure mechanism in many engineering materials. Numerical models for crack growth have been developed within the framework of damage mechanics.…
(more)
▼ Crack growth is an important failure mechanism in many engineering materials. Numerical models for crack growth have been developed within the framework of
damage mechanics. All these models aim for the same goal, obtaining accurate results for crack growth under various loading conditions. Many
damage models are based upon the cohesive crack approach. However, level set based models provide advantages compared to the cohesive crack models with regard to fatigue analysis. An alternative method to the existing thick level set (TLS) method was proposed, the interfacial thick level set (ITLS) model. The use of interface elements made the model more suitable to simulate several failure processes. In this thesis it is demonstrated that this method suffers from a dependency on the initial interfacial stiffness for the global response of a system by conducting a parameter study under quasi-static loading conditions. This parameter study proves that for a varying value of the initial interfacial stiffness parameter K the global response varies as well. This gives motivation to conduct further research on the removal of the initial interfacial stiffness from the current ITLS model. Two methods are developed to overcome the initial interfacial stiffness dependency. The first method assumes that the initial interfacial stiffness dependency is caused by the current formulation of the constitutive law of the interface. A new expression for the interfacial stiffness is adapted after which all constitutive relations are updated. The new method shows a perfect agreement with the current ITLS model, which validates the method as an accurate alternative. Compared to the current ITLS model, method 1 allows for the control of the initial stiffness of the undamaged part of the interface by changing the lower bound
damage without affecting the global response. However, when executing simulations for a varying initial interfacial stiffness K the same problem as for the current ITLS is observed. It can be concluded that in a way this method removes the dependency on the initial interfacial stiffness but the initial interfacial stiffness parameter K should then remain constant. Furthermore, the calibration process is not simplified compared to the current ITLS model. For this reason method 1 is rejected as the final solution to the problem and a second method is proposed. The second method assumes a direct relation between the
damage parameter c1 and the initial interfacial stiffness parameter K. This
damage parameter is responsible for the steepness of the
damage profile. The results from the parameter study showed that an increase of one of these parameters results in opposite behaviour for the initial stiffness of the global response. The leading hypothesis becomes that an increase in the stiffness parameter K can be neutralized by an increase in the
damage parameter c1. Proportionality between both parameters is assumed. By trial and error the proportionality is found to be one to one. When using this proportionality condition,…
Advisors/Committee Members: van der Meer, F.P. (mentor), Dekker, R. (mentor), Pavlovic, M. (graduation committee), Delft University of Technology (degree granting institution).
Subjects/Keywords: FEM; Damage mechanics; ITLS model; Fatigue; Crack growth; Fracture mechanics
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APA ·
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APA (6th Edition):
Sluijs, J. (. (2020). A stiffness independent Interfacial Thick Level Set method: A modified approach for crack analysis. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:7408e962-afb8-4c83-9f46-302db0b3bddf
Chicago Manual of Style (16th Edition):
Sluijs, J (author). “A stiffness independent Interfacial Thick Level Set method: A modified approach for crack analysis.” 2020. Masters Thesis, Delft University of Technology. Accessed April 17, 2021.
http://resolver.tudelft.nl/uuid:7408e962-afb8-4c83-9f46-302db0b3bddf.
MLA Handbook (7th Edition):
Sluijs, J (author). “A stiffness independent Interfacial Thick Level Set method: A modified approach for crack analysis.” 2020. Web. 17 Apr 2021.
Vancouver:
Sluijs J(. A stiffness independent Interfacial Thick Level Set method: A modified approach for crack analysis. [Internet] [Masters thesis]. Delft University of Technology; 2020. [cited 2021 Apr 17].
Available from: http://resolver.tudelft.nl/uuid:7408e962-afb8-4c83-9f46-302db0b3bddf.
Council of Science Editors:
Sluijs J(. A stiffness independent Interfacial Thick Level Set method: A modified approach for crack analysis. [Masters Thesis]. Delft University of Technology; 2020. Available from: http://resolver.tudelft.nl/uuid:7408e962-afb8-4c83-9f46-302db0b3bddf
13.
Klimczak, Christian.
Processes of Progressive Deformation with Applications to Jointing, Faulting and Fluid Flow.
Degree: 2011, University of Nevada – Reno
URL: http://hdl.handle.net/11714/3795
► The study of progressive deformation of fracture mechanical processes in earth and planetary sciences is applicable to all fracturing modes (opening-, sliding-, tearing-, and closing…
(more)
▼ The study of progressive deformation of fracture mechanical processes in earth and planetary sciences is applicable to all fracturing modes (opening-, sliding-, tearing-, and closing modes) and provides insight into evolution and behavior of fracturing on all scales. Hence, studying such processes helps to better characterizing fracture geometries and their temporal and spatial development. Understanding the processes is then crucial for evaluating the deformed rocks as media for fluid flow or reservoir. Knowledge about development and evolution of specific fractures and fluid flow through them can then be applied to deformation processes in general in order to help improving our understanding of, as well as highlighting connections between, the different processes and, thus, finds a wide applicability in the geosciences.Processes of progressive deformation were studied by characterizing the origin of a radial array of graben on the planet Mercury, the development of faulting in porous rock with formation of surrounding deformation band
damage zones, fracturing micro-mechanisms, and fracture-governed fluid flow. Fracture geometries, development, and mechanisms were analyzed by field- and spacecraft imagery mapping, conceptual- and numerical modeling using finite element and discrete fracture network methods, and optical- and scanning electron microscopy. When this variety of techniques and methods is utilized it highlights the diversity of progressive deformation as found on all scales and for all fracturing modes. Studying deformation bands in two sandstone basins in south-central Europe yield new insights on the controls of deformation band growth and geometry development, quartz-cementation mechanisms associated with structural diagenesis, and evolution of deformation banding into fault
damage zones. Evaluation of the hypotheses for the origin of the radial graben array on Mercury highlights the importance of testing data against the proposed formation mechanisms. Displacement-to-length scaling of opening mode fracturing was used to derive an improved flow law through such fractures, which is found to yield geologically more representative results. The results of this dissertation have important implications for fracture-, rock-, soil-, and fluid
mechanics on terrestrial and planetary tectonophysical settings.
Advisors/Committee Members: Schultz, Richard A. (advisor), Taranik, James V. (committee member), Carr, James R. (committee member), Reeves, Donald M. (committee member), Lange, Horst (committee member).
Subjects/Keywords: Fault damage zone formation; Faulting; Fracture mechanics; Planetary tectonics; Rock mechanics
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APA (6th Edition):
Klimczak, C. (2011). Processes of Progressive Deformation with Applications to Jointing, Faulting and Fluid Flow. (Thesis). University of Nevada – Reno. Retrieved from http://hdl.handle.net/11714/3795
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):
Klimczak, Christian. “Processes of Progressive Deformation with Applications to Jointing, Faulting and Fluid Flow.” 2011. Thesis, University of Nevada – Reno. Accessed April 17, 2021.
http://hdl.handle.net/11714/3795.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Klimczak, Christian. “Processes of Progressive Deformation with Applications to Jointing, Faulting and Fluid Flow.” 2011. Web. 17 Apr 2021.
Vancouver:
Klimczak C. Processes of Progressive Deformation with Applications to Jointing, Faulting and Fluid Flow. [Internet] [Thesis]. University of Nevada – Reno; 2011. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/11714/3795.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Klimczak C. Processes of Progressive Deformation with Applications to Jointing, Faulting and Fluid Flow. [Thesis]. University of Nevada – Reno; 2011. Available from: http://hdl.handle.net/11714/3795
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Michigan State University
14.
Zhou, Wu (Scientist).
Peridynamic modeling and impact testing of dynamic damage, fracture, and failure process in fiber-reinforced composite materials.
Degree: 2018, Michigan State University
URL: http://etd.lib.msu.edu/islandora/object/etd:19407
► Thesis Ph. D. Michigan State University. Mechanical Engineering 2018
"This study focuses on developing a peridynamics (PD) theory based model for the prediction of impact-induced…
(more)
▼ Thesis Ph. D. Michigan State University. Mechanical Engineering 2018
"This study focuses on developing a peridynamics (PD) theory based model for the prediction of impact-induced fracture and failure process in laminated composites, and the impact testing of damage evolution in composites." – Abstract.
Online resource;
Advisors/Committee Members: Liu, Dahsin, Xiao, Xinran, Averill, Ronald, Zhou, Zhengfang.
Subjects/Keywords: Mechanics, Applied; Continuum damage mechanics; Fracture mechanics – Mathematical models; Fibrous composites – Fracture – Analysis; Mechanics; Computational physics; Mechanical engineering
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APA (6th Edition):
Zhou, W. (. (2018). Peridynamic modeling and impact testing of dynamic damage, fracture, and failure process in fiber-reinforced composite materials. (Thesis). Michigan State University. Retrieved from http://etd.lib.msu.edu/islandora/object/etd:19407
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):
Zhou, Wu (Scientist). “Peridynamic modeling and impact testing of dynamic damage, fracture, and failure process in fiber-reinforced composite materials.” 2018. Thesis, Michigan State University. Accessed April 17, 2021.
http://etd.lib.msu.edu/islandora/object/etd:19407.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Zhou, Wu (Scientist). “Peridynamic modeling and impact testing of dynamic damage, fracture, and failure process in fiber-reinforced composite materials.” 2018. Web. 17 Apr 2021.
Vancouver:
Zhou W(. Peridynamic modeling and impact testing of dynamic damage, fracture, and failure process in fiber-reinforced composite materials. [Internet] [Thesis]. Michigan State University; 2018. [cited 2021 Apr 17].
Available from: http://etd.lib.msu.edu/islandora/object/etd:19407.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Zhou W(. Peridynamic modeling and impact testing of dynamic damage, fracture, and failure process in fiber-reinforced composite materials. [Thesis]. Michigan State University; 2018. Available from: http://etd.lib.msu.edu/islandora/object/etd:19407
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
15.
Khan, Shehzad Saleem.
Low cycle lifetime assessment of
Al2024 alloys.
Degree: 2011, Technische Universität Dortmund
URL: http://hdl.handle.net/2003/29297
► Summary and Conclusions Many research groups around the globe take a direct route from failure undermonotonic loading to high cycle fatigue. Surprisingly, low cycle fatigue…
(more)
▼ Summary and Conclusions Many
research groups around the globe take a direct route from failure
undermonotonic loading to high cycle fatigue. Surprisingly, low
cycle fatigue being a border phenomenon between the aforementioned
failure phenomena, is often not considered. In the present thesis,
the gap between failure under monotonic loading and HCF was closed
by thorough LCF analyses. As a practically relevant material, the
high-strength aluminium alloy Al2024 has been chosen. The SRµCT
investigations have made it evident that micro-
mechanics based
porous plasticity
damage models are not suitable for this
particular alloy due to a high number of dense particles. The
particles are arranged in continuous layers throughout the
micro-structure. Studying the microstructure and fracture
mechanisms, it can be safely stated that bigger inclusions in
Al2024 sheets and plates are responsible for
damage initiation in
the LCF regime. Al2024 thick plate, due to its underlying
manufacturing process develops precipitates in the middle of the
plate, creating layers within. A transition of fracture mode, from
surface to internal fracture, was observed with increasing plastic
range in cyclic experiments. In an ordinary low cycle regime
(40-200 cycles), a fatal crack is generated by the propagation and
frequent coalescence of small surface cracks. Eventually, a
mesocrack initiates from the surface of the specimen due to the
presence of bigger intermetallics. For a 100 mm thick plate the
S-direction has been found to be very brittle when compared to L
and T-directions (rolling directions) respectively. Although there
is a ductility observed, the resulting failure occurs without
macroscopic softening. An identical response was also observed in 4
mm thin sheets. For allowing symmetric strain amplitudes (R = -1)
in such sheets, a oating antibuckling guide has been proposed which
successfully prevents buckling at high compressive loading without
affecting adversely the mechanical behaviour of the specimen. In
summary, the material behaviour in S-direction can be characterised
as neither completely brittle nor completely ductile. More
precisely, plastic strain accumulation as
damage driving process as
well as small fatigue crack growth as brittle
damage mechanism can
be seen for LCF. This led to a conclusion that for modelling low
cycle fatigue for these materials, a material model which
incorporates both these effects (coupled ductile and brittle) was
required. For that purpose, a phenomenological CDM approach was
considered in the present thesis. In our earlier analyses in the
past, only ductile
damage was taken into account. However, since
the microstructural arrangement of Al2024, as observed in our
experiments favour also brittle failure modes, a fully coupled
ductile-brittle model has been proposed. While ductile
damage has
been modelled in a similar fashion as advocated formerly by other
authors (see, e.g. Lemaitre & Desmorat (2005)), a novel
approach was elaborated for brittle
damage. In sharp contrast to
the ductile
damage model,…
Advisors/Committee Members: Mosler, Jörn.
Subjects/Keywords: Aluminium alloys; Continuum
damage mechanics (CDM); Low cycle fatigue; Quasi-brittle damage;
620; 670
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APA (6th Edition):
Khan, S. S. (2011). Low cycle lifetime assessment of
Al2024 alloys. (Thesis). Technische Universität Dortmund. Retrieved from http://hdl.handle.net/2003/29297
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):
Khan, Shehzad Saleem. “Low cycle lifetime assessment of
Al2024 alloys.” 2011. Thesis, Technische Universität Dortmund. Accessed April 17, 2021.
http://hdl.handle.net/2003/29297.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Khan, Shehzad Saleem. “Low cycle lifetime assessment of
Al2024 alloys.” 2011. Web. 17 Apr 2021.
Vancouver:
Khan SS. Low cycle lifetime assessment of
Al2024 alloys. [Internet] [Thesis]. Technische Universität Dortmund; 2011. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/2003/29297.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Khan SS. Low cycle lifetime assessment of
Al2024 alloys. [Thesis]. Technische Universität Dortmund; 2011. Available from: http://hdl.handle.net/2003/29297
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Texas A&M University
16.
Rahmani, Eisa.
Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete.
Degree: PhD, Civil Engineering, 2015, Texas A&M University
URL: http://hdl.handle.net/1969.1/155201
► Oxidative aging is known to be one of the main contributors to reducing the service life of asphalt pavements. Asphalt concrete becomes stiffer and more…
(more)
▼ Oxidative aging is known to be one of the main contributors to reducing the service life of asphalt pavements. Asphalt concrete becomes stiffer and more brittle when it reacts with oxygen. The aged asphalt pavement is more susceptible to crack development and damages when subjected to repeated traffic loading. The aim of this dissertation is to develop and validate a mechanistic-based aging constitutive relationship based on an aging state variable.
Oxidative aging of asphalt concrete involves a thermodynamic process between reactive molecules of asphalt and oxygen. The repercussion of such a process is a change in mechanical, macroscopic properties of the material. This phenomenon is accounted for in this study by formulating an aging constitutive equation, based on continuum theory, in which the aging state variable is correlated with oxygen content via an evolution function. In this aging constitutive equation, the rate of change of the aging variable and oxygen content are formulated as conjugate variables. In other words, oxygen content is considered as the driving force for the rate of change of the aging variable. The rate of change of the aging state variable is expressed as a function of oxygen content, temperature, and level of aging at any given time.
The behavior of asphalt concrete is modeled using the PANDA (Pavement Analysis Using a Nonlinear
Damage Approach) framework, which accounts for the viscoelastic, viscodamage, and viscoplastic behavior of the materials. The time-dependent response of aged asphalt concrete is investigated by introducing the aging state variable to Schapery’s viscoelastic model. The aging state variable causes an increase in the stiffness and viscosity of the aged material by decreasing the compliance terms and the retardation times. Because the viscoelastic, viscodamage, and viscoplastic components of PANDA are coupled or interrelated, the change in the viscoelastic properties, because of aging, affects the overall mechanical behavior of asphalt concrete.
The aging constitutive equation is calibrated using data obtained from laboratory experiments, and then its predictions are validated against independent experimental data. It is shown that the proposed model is capable of predicting mechanical response of aged asphalt concrete specimens subjected to different loading conditions.
Advisors/Committee Members: Little, Dallas N (advisor), Masad, Eyad A (advisor), Hueste, Mary Beth D (committee member), Glover, Charles J (committee member), Allen, David H (committee member), Darabi, Masoud K (committee member).
Subjects/Keywords: Oxidative aging; Asphalt concrete; Continuum Damage Mechanics; Constitutive modeling; Viscoelasticity; Viscoplasticity; Viscodamage; Fatigue damage
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APA (6th Edition):
Rahmani, E. (2015). Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/155201
Chicago Manual of Style (16th Edition):
Rahmani, Eisa. “Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete.” 2015. Doctoral Dissertation, Texas A&M University. Accessed April 17, 2021.
http://hdl.handle.net/1969.1/155201.
MLA Handbook (7th Edition):
Rahmani, Eisa. “Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete.” 2015. Web. 17 Apr 2021.
Vancouver:
Rahmani E. Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete. [Internet] [Doctoral dissertation]. Texas A&M University; 2015. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1969.1/155201.
Council of Science Editors:
Rahmani E. Continuum-Based Constitutive Modeling of Coupled Oxidative Aging-Mechanical Response of Asphalt Concrete. [Doctoral Dissertation]. Texas A&M University; 2015. Available from: http://hdl.handle.net/1969.1/155201
17.
Khan, Shehzad Saleem.
Low cycle lifetime assessment of Al2024 alloys.
Degree: 2011, Technische Universität Dortmund
URL: http://dx.doi.org/10.17877/DE290R-3389
► Summary and Conclusions Many research groups around the globe take a direct route from failure undermonotonic loading to high cycle fatigue. Surprisingly, low cycle fatigue…
(more)
▼ Summary and Conclusions Many research groups around the globe take a direct route from failure undermonotonic loading to high cycle fatigue. Surprisingly, low cycle fatigue being a border phenomenon between the aforementioned failure phenomena, is often not considered. In the present thesis, the gap between failure under monotonic loading and HCF was closed by thorough LCF analyses. As a practically relevant material, the high-strength aluminium alloy Al2024 has been chosen. The SRµCT investigations have made it evident that micro-
mechanics based porous plasticity
damage models are not suitable for this particular alloy due to a high number of dense particles. The particles are arranged in continuous layers throughout the micro-structure. Studying the microstructure and fracture mechanisms, it can be safely stated that bigger inclusions in Al2024 sheets and plates are responsible for
damage initiation in the LCF regime. Al2024 thick plate, due to
its underlying manufacturing process develops precipitates in the middle of the plate, creating layers within. A transition of fracture mode, from surface to internal fracture, was observed with increasing plastic range in cyclic experiments. In an ordinary low cycle regime (40-200 cycles), a fatal crack is generated by the propagation and frequent coalescence of small surface cracks. Eventually, a mesocrack initiates from the surface of the specimen due to the presence of bigger intermetallics. For a 100 mm thick plate the S-direction has been found to be very brittle when compared to L and T-directions (rolling directions) respectively. Although there is a ductility observed, the resulting failure occurs without macroscopic softening. An identical response was also observed in 4 mm thin sheets. For allowing symmetric strain amplitudes (R = -1) in such sheets, a oating antibuckling guide has been proposed which successfully prevents buckling at high compressive loading without
affecting adversely the mechanical behaviour of the specimen. In summary, the material behaviour in S-direction can be characterised as neither completely brittle nor completely ductile. More precisely, plastic strain accumulation as
damage driving process as well as small fatigue crack growth as brittle
damage mechanism can be seen for LCF. This led to a conclusion that for modelling low cycle fatigue for these materials, a material model which incorporates both these effects (coupled ductile and brittle) was required. For that purpose, a phenomenological CDM approach was considered in the present thesis. In our earlier analyses in the past, only ductile
damage was taken into account. However, since the microstructural arrangement of Al2024, as observed in our experiments favour also brittle failure modes, a fully coupled ductile-brittle model has been proposed. While ductile
damage has been modelled in a similar fashion as advocated formerly by other authors (see, e.g. Lemaitre
& Desmorat (2005)), a novel approach was elaborated for brittle
damage. In sharp…
Advisors/Committee Members: Mosler, Jörn (advisor), Schmauder, Siegfried (referee).
Subjects/Keywords: Aluminium alloys; Continuum damage mechanics (CDM); Low cycle fatigue; Quasi-brittle damage; 620; 670
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APA (6th Edition):
Khan, S. S. (2011). Low cycle lifetime assessment of Al2024 alloys. (Doctoral Dissertation). Technische Universität Dortmund. Retrieved from http://dx.doi.org/10.17877/DE290R-3389
Chicago Manual of Style (16th Edition):
Khan, Shehzad Saleem. “Low cycle lifetime assessment of Al2024 alloys.” 2011. Doctoral Dissertation, Technische Universität Dortmund. Accessed April 17, 2021.
http://dx.doi.org/10.17877/DE290R-3389.
MLA Handbook (7th Edition):
Khan, Shehzad Saleem. “Low cycle lifetime assessment of Al2024 alloys.” 2011. Web. 17 Apr 2021.
Vancouver:
Khan SS. Low cycle lifetime assessment of Al2024 alloys. [Internet] [Doctoral dissertation]. Technische Universität Dortmund; 2011. [cited 2021 Apr 17].
Available from: http://dx.doi.org/10.17877/DE290R-3389.
Council of Science Editors:
Khan SS. Low cycle lifetime assessment of Al2024 alloys. [Doctoral Dissertation]. Technische Universität Dortmund; 2011. Available from: http://dx.doi.org/10.17877/DE290R-3389
Delft University of Technology
18.
van Oostrum, Alexander (author).
Application of fracture mechanics in a blended numerical framework for progressive damage analysis of CFRPs in FEM.
Degree: 2017, Delft University of Technology
URL: http://resolver.tudelft.nl/uuid:f4c776d1-079c-49bd-ae60-e26450997c1a
► Composite structures are increasingly applied for their unique set of properties. However, their behavior is not yet fully understood, amongst others, due to complex interactions…
(more)
▼ Composite structures are increasingly applied for their unique set of properties. However, their behavior is not yet fully understood, amongst others, due to complex interactions of failure modes. This research implemented a blended stress-strain and fracture
mechanics based progressive
damage analysis model, based on a Continuum
Damage Model (CDM) for fibre failure, cohesive zones for delaminations and XFEM with cohesive zones for matrix cracks. The model was verified on a set of sub-laminate scaled open hole tensile specimens from literature and validated in an additional in-house experimental campaign. Failure loads are within the experimental scatter and failure patterns are in line with experimental X-ray CT scans, but underestimate matrix failure. The model is able to capture the interactions better than full CDM implementations, specifically those between matrix cracks and delaminations. However, work remains as the framework in Abaqus is unstable and cannot provide the full failure patterns for matrix cracks.
Advisors/Committee Members: Zarouchas, Dimitrios (mentor), Delft University of Technology (degree granting institution).
Subjects/Keywords: Progressive Damage Analysis; CFRP; Cohesive Zone Model; Fracture mechanics; Continuum Damage Model; ABAQUS
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APA (6th Edition):
van Oostrum, A. (. (2017). Application of fracture mechanics in a blended numerical framework for progressive damage analysis of CFRPs in FEM. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:f4c776d1-079c-49bd-ae60-e26450997c1a
Chicago Manual of Style (16th Edition):
van Oostrum, Alexander (author). “Application of fracture mechanics in a blended numerical framework for progressive damage analysis of CFRPs in FEM.” 2017. Masters Thesis, Delft University of Technology. Accessed April 17, 2021.
http://resolver.tudelft.nl/uuid:f4c776d1-079c-49bd-ae60-e26450997c1a.
MLA Handbook (7th Edition):
van Oostrum, Alexander (author). “Application of fracture mechanics in a blended numerical framework for progressive damage analysis of CFRPs in FEM.” 2017. Web. 17 Apr 2021.
Vancouver:
van Oostrum A(. Application of fracture mechanics in a blended numerical framework for progressive damage analysis of CFRPs in FEM. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2021 Apr 17].
Available from: http://resolver.tudelft.nl/uuid:f4c776d1-079c-49bd-ae60-e26450997c1a.
Council of Science Editors:
van Oostrum A(. Application of fracture mechanics in a blended numerical framework for progressive damage analysis of CFRPs in FEM. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:f4c776d1-079c-49bd-ae60-e26450997c1a
University of Arizona
19.
Kabiri Rahani, Ehsan.
Modeling of Ultrasonic and Terahertz Radiations in Defective Tiles for Condition Monitoring of Thermal Protection Systems
.
Degree: 2011, University of Arizona
URL: http://hdl.handle.net/10150/203011
► Condition based monitoring of Thermal Protection Systems (TPS) is necessary for safe operations of space shuttles. In the current research Terahertz radiation (T-ray) has been…
(more)
▼ Condition based monitoring of Thermal Protection Systems (TPS) is necessary for safe operations of space shuttles. In the current research Terahertz radiation (T-ray) has been used to detect mechanical and heat induced damages in TPS tiles. Voids and cracks inside the foam tile are denoted as mechanical
damage while property changes due to long and short term exposures of tiles to high heat are denoted as heat induced
damage.Ultrasonic waves cannot detect cracks and voids inside the tile because the tile material (silica foam) has high attenuation for ultrasonic energy. Instead, electromagnetic terahertz radiation can easily penetrate into the foam material and detect the internal voids although this electromagnetic radiation finds it difficult to detect delaminations between the foam tile and the substrate plate. Thus these two technologies are complementary to each other for TPS inspection.Ultrasonic and T-ray field modeling in free and mounted tiles with different types of mechanical and thermal damages has been the focus of this research. Shortcomings and limitations of FEM method in modeling 3D problems especially at high-frequencies has been discussed and a newly developed semi-analytical technique called Distributed Point Source Method (DPSM) has been used for this purpose.A FORTRAN code called DPSM3D has been developed to model both ultrasonic and electromagnetic problems using the conventional DPSM method. DPSM has been extended from ultrasonic applications to electromagnetic to model THz Gaussian beams, multilayered dielectrics and Gaussian beam-scatterer interaction problems. Since the conventional DPSM has some drawbacks, to overcome it two modification methods called G-DPSM and ESM have been proposed.The conventional DPSM in the past was only capable of solving time harmonic (frequency domain) problems. In this research DPSM has been extended to model DPSM transient problems. This modified technique has been denoted as t-DPSM.Using DPSM, scattering of focused ultrasonic fields by single and multiple cavities in fluid&solid media is studied. A comparison between the radiation forces generated by the ultrasonic energies reflected from two small cavities versus a single big cavity is also carried out.
Advisors/Committee Members: Kundu, Tribikram (advisor), Frantziskonis, George (committeemember), Zhang, Lianyang (committeemember), Kundu, Tribikram (committeemember).
Subjects/Keywords: Mechanical damage;
Terahertz technology;
TPS;
Ultrasonics;
Engineering Mechanics;
DPSM modeling;
Heat induced damage
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APA (6th Edition):
Kabiri Rahani, E. (2011). Modeling of Ultrasonic and Terahertz Radiations in Defective Tiles for Condition Monitoring of Thermal Protection Systems
. (Doctoral Dissertation). University of Arizona. Retrieved from http://hdl.handle.net/10150/203011
Chicago Manual of Style (16th Edition):
Kabiri Rahani, Ehsan. “Modeling of Ultrasonic and Terahertz Radiations in Defective Tiles for Condition Monitoring of Thermal Protection Systems
.” 2011. Doctoral Dissertation, University of Arizona. Accessed April 17, 2021.
http://hdl.handle.net/10150/203011.
MLA Handbook (7th Edition):
Kabiri Rahani, Ehsan. “Modeling of Ultrasonic and Terahertz Radiations in Defective Tiles for Condition Monitoring of Thermal Protection Systems
.” 2011. Web. 17 Apr 2021.
Vancouver:
Kabiri Rahani E. Modeling of Ultrasonic and Terahertz Radiations in Defective Tiles for Condition Monitoring of Thermal Protection Systems
. [Internet] [Doctoral dissertation]. University of Arizona; 2011. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10150/203011.
Council of Science Editors:
Kabiri Rahani E. Modeling of Ultrasonic and Terahertz Radiations in Defective Tiles for Condition Monitoring of Thermal Protection Systems
. [Doctoral Dissertation]. University of Arizona; 2011. Available from: http://hdl.handle.net/10150/203011
20.
Washington Luiz Rodrigues de Queiroz.
Projeto de um equipamento de fadiga para caracterizaÃÃo do dano em telhas de aÃo devido à aÃÃo do vento aplicando correlaÃÃo digital de imagens e modelagem computacional.
Degree: 2013, Universidade Federal do CearÃ; Programa de PÃs-GraduaÃÃo em Engenharia e CiÃncia de Materiais; UFC; BR
URL: http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11184
► As coberturas constituem um elemento essencial para a sobrevivÃncia humana. As transformaÃÃes mais portantes das cobertas relacionaram-se, por um lado, com a prÃ-fabricaÃÃo do material…
(more)
▼ As coberturas constituem um elemento essencial para a sobrevivÃncia humana. As transformaÃÃes mais portantes das cobertas relacionaram-se, por um lado, com a prÃ-fabricaÃÃo do material a ser utilizado, que veio permitir maiores garantias de Ãxito em qualquer aplicaÃÃo, e por outro lado, com o aparecimento de novos materiais na construÃÃo, como o vidro laminado, peÃas de madeira, os materiais plÃsticos e principalmente o alumÃnio e o aÃo. Neste contexto os telhados de metal sÃo bem avaliados por vÃrios motivos, sÃo resistentes, durÃveis, vencem grandes vÃos, resistem à corrosÃo e sÃo mais leves em relaÃÃo Ãs cerÃmicas, gerando economia nos custos da estrutura e facilidade no manuseio, transporte e montagem. A problemÃtica dos ventos de alta velocidade, como furacÃes e tempestades, muitas vezes causam danos graves Ãs telhas metÃlicas. Os danos causados pelo vento mostraram que a fadiga promove uma trinca no telhado em torno dos furos do prendedor
ocasionando um despendimento das telhas em sequÃncia. Nesse trabalho desenvolve-se uma mÃquina para estudos de simulaÃÃo de carregamento cÃclico em telhas metÃlicas simulando a forÃa do vento. Utilizando a tÃcnica da CorrelaÃÃo Digital de Imagem (CDI) desenvolveu-se uma metodologia que auxiliou em termos quantitativos e qualitativos a avaliaÃÃo da integridade da telha.
Shelter is an essential element for human survival. The most important changes in shelter have been in regard, on the one hand, of pre-fabrication of the material to be used, which better guarantees success at any application, and, on the other hand, of the rise of new building materials, such as laminated glass, wooden parts, plastic materials, and mainly aluminum and steel. In this context, metal roofs are praised for several reasons. They are sturdy and durable, span across wide areas, stand corrosion, and are lighter compared to ceramic tiles, which leads to savings in structure costs and ease of handling,
transport, and assembly. The issue of high- speed winds, such as hurricanes and storms, often causes great damage to metal tiling. Wind damages show that the low-cycle wear fissures the roofing around the fastening holes, causing the tiles to become loose. This research developed a machine to study the simulation of cyclic loads in metal tiles by simulating wind force. By using the Digital Image Correlation (DIC) technique, a methodology was developed that will aid in assessing tile integrity both quantitatively and qualitatively.
Advisors/Committee Members: Ãnio Pontes de Deus, Ricardo EmÃlio Ferreira Quevedo Nogueira, Igor Frota de Vasconcelos, Rodrigo Nogueira de Codes, Cassius OlÃvio Figueiredo Terra Ruchert.
Subjects/Keywords: Damage mechanics, fracture mechanics, Digital Image Correlation.; ENGENHARIA DE MATERIAIS E METALURGICA
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APA (6th Edition):
Queiroz, W. L. R. d. (2013). Projeto de um equipamento de fadiga para caracterizaÃÃo do dano em telhas de aÃo devido à aÃÃo do vento aplicando correlaÃÃo digital de imagens e modelagem computacional. (Doctoral Dissertation). Universidade Federal do CearÃ; Programa de PÃs-GraduaÃÃo em Engenharia e CiÃncia de Materiais; UFC; BR. Retrieved from http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11184
Chicago Manual of Style (16th Edition):
Queiroz, Washington Luiz Rodrigues de. “Projeto de um equipamento de fadiga para caracterizaÃÃo do dano em telhas de aÃo devido à aÃÃo do vento aplicando correlaÃÃo digital de imagens e modelagem computacional.” 2013. Doctoral Dissertation, Universidade Federal do CearÃ; Programa de PÃs-GraduaÃÃo em Engenharia e CiÃncia de Materiais; UFC; BR. Accessed April 17, 2021.
http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11184.
MLA Handbook (7th Edition):
Queiroz, Washington Luiz Rodrigues de. “Projeto de um equipamento de fadiga para caracterizaÃÃo do dano em telhas de aÃo devido à aÃÃo do vento aplicando correlaÃÃo digital de imagens e modelagem computacional.” 2013. Web. 17 Apr 2021.
Vancouver:
Queiroz WLRd. Projeto de um equipamento de fadiga para caracterizaÃÃo do dano em telhas de aÃo devido à aÃÃo do vento aplicando correlaÃÃo digital de imagens e modelagem computacional. [Internet] [Doctoral dissertation]. Universidade Federal do CearÃ; Programa de PÃs-GraduaÃÃo em Engenharia e CiÃncia de Materiais; UFC; BR; 2013. [cited 2021 Apr 17].
Available from: http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11184.
Council of Science Editors:
Queiroz WLRd. Projeto de um equipamento de fadiga para caracterizaÃÃo do dano em telhas de aÃo devido à aÃÃo do vento aplicando correlaÃÃo digital de imagens e modelagem computacional. [Doctoral Dissertation]. Universidade Federal do CearÃ; Programa de PÃs-GraduaÃÃo em Engenharia e CiÃncia de Materiais; UFC; BR; 2013. Available from: http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11184
University of Utah
21.
Heller, Randal Evan.
Damage tolerance predictions for spar web cracking in a diminishing stress field.
Degree: MS, Mechanical Engineering, 2011, University of Utah
URL: http://content.lib.utah.edu/cdm/singleitem/collection/etd3/id/482/rec/602
► Current United States Air Force (USAF) Damage Tolerance Analysis (DTA) methodology yields short crack growth lives for webs in built-up beams as used in the…
(more)
▼ Current United States Air Force (USAF) Damage Tolerance Analysis (DTA) methodology yields short crack growth lives for webs in built-up beams as used in the construction of wing spars. This results in very short inspection intervals for these types of structures. Inspection data from fleet usage and fatigue tests do not support the analytically-based assertion that spar webs are as damage tolerant critical as typically predicted. Current analytical methods involve short edge distances predicting failure when the crack reaches the edge-of- part. In reality, there is remaining residual strength in the spar web. Current continuing damage methods allow for cracks that grow up into the part after the lower ligament fails. The assumption for this secondary cracking has been to use the same driving force as in the initial crack. However, the high driving force from bending found near the extreme fiber diminishes as the crack grows toward the neutral axis. This paper utilizes the test results from two specimens to help validate an analytical approach toward crack growth predictions in spar webs. The goal of this approach is to extend short inspection intervals currently required on some USAF aircraft. I would like to thank my wife, Mindy, for all of her encouragement and support during this long effort. Without you, I never would have started. Thanks to my children, Evan, Austin and Erin for your patience during the long hours away from home that this effort required. Thanks also to Dr. Paul Clark and Dr. Mark Thomsen of the United States Air Force. You rekindled my love of learning and convinced me that I had what it takes to tackle graduate work. A final thanks to Dr. David Hoeppner of the University of Utah Mechanical Engineering department. You have inspired me to pursue professional development and to strive to blend wisdom, skill, and ethics in all of my engineering endeavors.
Subjects/Keywords: Web cracking; Damage tolerance; Fatigue; Fracture mechanics; Airplanes – Maintenance and repair
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APA (6th Edition):
Heller, R. E. (2011). Damage tolerance predictions for spar web cracking in a diminishing stress field. (Masters Thesis). University of Utah. Retrieved from http://content.lib.utah.edu/cdm/singleitem/collection/etd3/id/482/rec/602
Chicago Manual of Style (16th Edition):
Heller, Randal Evan. “Damage tolerance predictions for spar web cracking in a diminishing stress field.” 2011. Masters Thesis, University of Utah. Accessed April 17, 2021.
http://content.lib.utah.edu/cdm/singleitem/collection/etd3/id/482/rec/602.
MLA Handbook (7th Edition):
Heller, Randal Evan. “Damage tolerance predictions for spar web cracking in a diminishing stress field.” 2011. Web. 17 Apr 2021.
Vancouver:
Heller RE. Damage tolerance predictions for spar web cracking in a diminishing stress field. [Internet] [Masters thesis]. University of Utah; 2011. [cited 2021 Apr 17].
Available from: http://content.lib.utah.edu/cdm/singleitem/collection/etd3/id/482/rec/602.
Council of Science Editors:
Heller RE. Damage tolerance predictions for spar web cracking in a diminishing stress field. [Masters Thesis]. University of Utah; 2011. Available from: http://content.lib.utah.edu/cdm/singleitem/collection/etd3/id/482/rec/602
Durban University of Technology
22.
Nhassengo, Sikhulile Khululeka.
Use of piezoelectric techniques monitoring continuum damage of structures.
Degree: 2011, Durban University of Technology
URL: http://hdl.handle.net/10321/699
► Submitted in partial fulfilment of the requirements for the Degree of Master of Technology: Mechanical Engineering, Durban University of Technology, 2011.
The objective of the…
(more)
▼ Submitted in partial fulfilment of the requirements for the Degree of Master of Technology: Mechanical Engineering, Durban University of Technology, 2011.
The objective of the present study was to investigate if piezoelectric techniques or sensors can be used in monitoring structural degradation. The study considers experimental results and analytical modelling of a ductile structure under tensile and cyclic loading. Throughout the project the emphasis was placed on the effectiveness of strain measuring sensors.
Conventional tensile testing was conducted using a Lloyds testing machine. The testing machine was calibrated to have a lateral movement of 2mm/min (tension force). Rectangular plates were pulled in tension until failure. From that experimental data was produced for a uni-axial loading system.
Cyclic testing was carried out using an in-house designed and manufactured fatigue machine. It produced a reciprocating load (force) of 25rad/s on a rectangular plate. Two different sensor measuring instruments (strain gauge and piezoelectric) were used. The strain gauge sensor was attached to a specimen and connected to a Wheatstone bridge. The piezoelectric sensor was attached to the specimen and then linked directly to the capturing system. From these two sensors experimental results were obtained and compared.
The mathematical relationships for the rectangular plates were formulated using effective stress-strain behaviour based on the elastic and plastic behaviour of the plates. The analytical and experimental results were compared. Results from this investigation show that piezoelectric sensors can be useful for measuring fatigue failure on a ductile material.
Advisors/Committee Members: Tabakov, Pavel Y..
Subjects/Keywords: Piezoelectric materials; Continuum damage mechanics; Materials – Fatigue; Metals – Fatigue
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APA (6th Edition):
Nhassengo, S. K. (2011). Use of piezoelectric techniques monitoring continuum damage of structures. (Thesis). Durban University of Technology. Retrieved from http://hdl.handle.net/10321/699
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):
Nhassengo, Sikhulile Khululeka. “Use of piezoelectric techniques monitoring continuum damage of structures.” 2011. Thesis, Durban University of Technology. Accessed April 17, 2021.
http://hdl.handle.net/10321/699.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Nhassengo, Sikhulile Khululeka. “Use of piezoelectric techniques monitoring continuum damage of structures.” 2011. Web. 17 Apr 2021.
Vancouver:
Nhassengo SK. Use of piezoelectric techniques monitoring continuum damage of structures. [Internet] [Thesis]. Durban University of Technology; 2011. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/10321/699.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Nhassengo SK. Use of piezoelectric techniques monitoring continuum damage of structures. [Thesis]. Durban University of Technology; 2011. Available from: http://hdl.handle.net/10321/699
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Vanderbilt University
23.
Crouch, Robert Doyle.
Multiscale Modeling of Brittle Composites Using Reduced Order Computational Homogenization.
Degree: PhD, Civil Engineering, 2012, Vanderbilt University
URL: http://hdl.handle.net/1803/13883
► This dissertation presents a novel multiscale computational framework for simulating failure and damage accumulation in brittle composites. A reduced-order multiple spatial scale methodology is developed…
(more)
▼ This dissertation presents a novel multiscale computational framework for simulating failure and
damage accumulation in brittle composites. A reduced-order multiple spatial scale methodology is developed to efficiently model failure under monotonic loading conditions. This methodology is based on the computational homogenization approach. The proposed reduced order approach is computationally efficient when compared to standard computational homogenization. Modeling of individual failure modes, such as matrix cracking, matrix/fiber debonding, delamination, and fiber fracture are incorporated into this methodology. A multiple spatio-temporal scale technique is proposed for simulating failure in composites subjected to cyclic loading conditions. This technique is based on the generalization of the homogenization approach to temporal scales. An adaptive macrochronological time stepping algorithm is devised to predict
damage accumulation by resolving a small subset of cycles throughout the life of the composite. The proposed multiscale framework was verified by numerical simulation and was validated using experimental testing. Experimental validation involved a series of monotonic and fatigue experiments conducted on the carbon fiber reinforced polymer composite, IM7/977-3. Non-destructive inspection techniques including acoustic emission, X-ray radiography, and X-ray computed tomography were utilized to characterize progressive
damage accumulation in the composite material. The multiple spatio-temporal model was calibrated and employed to predict the failure response of IM7/977-3 specimens. The proposed model was demonstrated to accurately and efficiently predict strength, ductility, and
damage growth characteristics under both monotonic and cyclic loadings. The combined computational and experimental investigation provided a thorough picture of the failure processes of this material.
Advisors/Committee Members: Haoxiang Luo (committee member), Sankaran Mahadevan (committee member), Prodyot Basu (committee member), Stephen Clay (committee member), Caglar Oskay (Committee Chair).
Subjects/Keywords: life prediction; fatigue; damage mechanics; composite materials; multiscale modeling
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APA (6th Edition):
Crouch, R. D. (2012). Multiscale Modeling of Brittle Composites Using Reduced Order Computational Homogenization. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/13883
Chicago Manual of Style (16th Edition):
Crouch, Robert Doyle. “Multiscale Modeling of Brittle Composites Using Reduced Order Computational Homogenization.” 2012. Doctoral Dissertation, Vanderbilt University. Accessed April 17, 2021.
http://hdl.handle.net/1803/13883.
MLA Handbook (7th Edition):
Crouch, Robert Doyle. “Multiscale Modeling of Brittle Composites Using Reduced Order Computational Homogenization.” 2012. Web. 17 Apr 2021.
Vancouver:
Crouch RD. Multiscale Modeling of Brittle Composites Using Reduced Order Computational Homogenization. [Internet] [Doctoral dissertation]. Vanderbilt University; 2012. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1803/13883.
Council of Science Editors:
Crouch RD. Multiscale Modeling of Brittle Composites Using Reduced Order Computational Homogenization. [Doctoral Dissertation]. Vanderbilt University; 2012. Available from: http://hdl.handle.net/1803/13883
Vanderbilt University
24.
Bogdanor, Michael James.
Failure Prediction of Fiber Reinforced Composites Using
Reduced Order Multiscale Models.
Degree: PhD, Civil Engineering, 2015, Vanderbilt University
URL: http://hdl.handle.net/1803/14575
► Fiber reinforced polymer (FRP) composites present a significant opportunity for increas- ing performance and energy efficiency in a number of technology sectors, most notably the…
(more)
▼ Fiber reinforced polymer (FRP) composites present a significant opportunity for increas-
ing performance and energy efficiency in a number of technology sectors, most notably the
automotive and aerospace industries. In order to reduce the development costs for FRP ma-
terials, accurate and efficient predictive methods are required which capture the evolution
of
damage at the heterogeneous microscale. The goal of this dissertation is to advance the
state of the art in the failure prediction of FRP composites through new multiscale methods
both for the mechanical response and propagation of uncertainty in the material. The contin-
ued development of the eigen-deformation based homogenization method with reduced order
models (EHM) is presented, including a new approach to address the tension-compression
stiffness anisotropy in the fiber direction and a novel parameter weighting method to capture
the disparate
damage evolution under uniaxial and shear loading. A blind prediction study
of laminated IM7/977-3 composites using the improved EHM approach is presented for three
composite layups ([0,45,90,-45]2S, [30,60,90,-60,-30]2S, and [60,0,-60]3S) under static tension
and compression and tension-tension fatigue with open hole and unnotched configurations.
Additionally, Bayesian parameter calibration is implemented within the EHM framework to
quantify uncertainty in the composite and is utilized to predict the probabilistic behavior of
laminated composite specimens
subject to strain rate-dependent effects.
Advisors/Committee Members: Douglas Adams (committee member), P.K. Basu (committee member), Stephen Clay (committee member), Haoxiang Luo (committee member), Sankaran Mahadevan (committee member), Caglar Oskay (Committee Chair).
Subjects/Keywords: multiscale mechanics; composites; uncertainty quantification; progressive damage; blind prediction
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Chicago ·
MLA ·
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APA (6th Edition):
Bogdanor, M. J. (2015). Failure Prediction of Fiber Reinforced Composites Using
Reduced Order Multiscale Models. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/14575
Chicago Manual of Style (16th Edition):
Bogdanor, Michael James. “Failure Prediction of Fiber Reinforced Composites Using
Reduced Order Multiscale Models.” 2015. Doctoral Dissertation, Vanderbilt University. Accessed April 17, 2021.
http://hdl.handle.net/1803/14575.
MLA Handbook (7th Edition):
Bogdanor, Michael James. “Failure Prediction of Fiber Reinforced Composites Using
Reduced Order Multiscale Models.” 2015. Web. 17 Apr 2021.
Vancouver:
Bogdanor MJ. Failure Prediction of Fiber Reinforced Composites Using
Reduced Order Multiscale Models. [Internet] [Doctoral dissertation]. Vanderbilt University; 2015. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1803/14575.
Council of Science Editors:
Bogdanor MJ. Failure Prediction of Fiber Reinforced Composites Using
Reduced Order Multiscale Models. [Doctoral Dissertation]. Vanderbilt University; 2015. Available from: http://hdl.handle.net/1803/14575
Texas A&M University
25.
You, Taesun.
Two- and Three-Dimensional Microstructural Modeling of Asphalt Particulate Composite Materials using a Unified Viscoelastic-Viscoplastic-Viscodamage Constitutive Model.
Degree: PhD, Civil Engineering, 2013, Texas A&M University
URL: http://hdl.handle.net/1969.1/151325
► The main objective of this study is to develop and validate a framework for microstructural modeling of asphalt composite materials using a coupled thermo-viscoelastic, thermo-viscoplastic,…
(more)
▼ The main objective of this study is to develop and validate a framework for microstructural modeling of asphalt composite materials using a coupled thermo-viscoelastic, thermo-viscoplastic, and thermo-viscodamage constitutive model. In addition, the dissertation presents methods that can be used to capture and represent the two-dimensional (2D) and three-dimensional (3D) microstructure of asphalt concrete.
The 2D representative volume elements (RVEs) of asphalt concrete were generated based on planar X-ray Computed Tomography (CT) images. The 2D RVE consists of three phases: aggregate, matrix, and interfacial transmission zone (ITZ). The 3D microstructures of stone matrix asphalt (SMA) and dense-graded asphalt (DGA) concrete were reconstructed from slices of 2D X-ray CT images; each image consists of the matrix and aggregate phases. The matrix and ITZ were considered thermo-viscoelastic, thermo-viscoplastic, and thermo-viscodamaged materials, while the aggregate is considered to be a linear, isotropic elastic material.
The 2D RVEs were used to study the effects of variation in aggregate shape, distribution, volume fraction, ITZ strength, strain rate, and temperature on the degradation and micro-
damage patterns in asphalt concrete. Moreover, the effects of loading rate, temperature, and loading type on the thermo-mechanical response of the 2D and 3D microstructures of asphalt concrete were investigated.
Finally, the model parameters for Fine Aggregate Mixture (FAM) and full asphalt mixture were determined based on the analysis of repeated creep recovery tests and constant strain rate tests. These material parameters in the model were used to simulate the response of FAM and full asphalt mixture, and the results were compared with the responses of the corresponding experimental tests.
The microstructural modeling presented in this dissertation provides the ability to link the microstructure properties with the macroscopic response. This modeling combines nonlinear constitutive model, finite element analysis, and the unique capabilities of X-ray CT in capturing the material microstructure. The modeling results can be used to provide guidelines for designing microstructures of asphalt concrete that can achieve the desired macroscopic behavior. Additionally, it can be helpful to perform 'virtual testing' of asphalt concrete, saving numerous resources used in conducting real experimental tests.
Advisors/Committee Members: Masad, Eyad (advisor), Little, Dallas (advisor), Hueste, Mary Beth (committee member), Reddy, J.N. (committee member).
Subjects/Keywords: Microstructural modeling; Damage mechanics; Finite Element Analysis; Asphalt concrete
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APA ·
Chicago ·
MLA ·
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Export
to Zotero / EndNote / Reference
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APA (6th Edition):
You, T. (2013). Two- and Three-Dimensional Microstructural Modeling of Asphalt Particulate Composite Materials using a Unified Viscoelastic-Viscoplastic-Viscodamage Constitutive Model. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/151325
Chicago Manual of Style (16th Edition):
You, Taesun. “Two- and Three-Dimensional Microstructural Modeling of Asphalt Particulate Composite Materials using a Unified Viscoelastic-Viscoplastic-Viscodamage Constitutive Model.” 2013. Doctoral Dissertation, Texas A&M University. Accessed April 17, 2021.
http://hdl.handle.net/1969.1/151325.
MLA Handbook (7th Edition):
You, Taesun. “Two- and Three-Dimensional Microstructural Modeling of Asphalt Particulate Composite Materials using a Unified Viscoelastic-Viscoplastic-Viscodamage Constitutive Model.” 2013. Web. 17 Apr 2021.
Vancouver:
You T. Two- and Three-Dimensional Microstructural Modeling of Asphalt Particulate Composite Materials using a Unified Viscoelastic-Viscoplastic-Viscodamage Constitutive Model. [Internet] [Doctoral dissertation]. Texas A&M University; 2013. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1969.1/151325.
Council of Science Editors:
You T. Two- and Three-Dimensional Microstructural Modeling of Asphalt Particulate Composite Materials using a Unified Viscoelastic-Viscoplastic-Viscodamage Constitutive Model. [Doctoral Dissertation]. Texas A&M University; 2013. Available from: http://hdl.handle.net/1969.1/151325
Texas A&M University
26.
Kim, Sun-Myung.
Continuum-based Multiscale Computational Damage Modeling of Cementitous Composites.
Degree: PhD, Civil Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-8022
► Based on continuum damage mechanics (CDM), an isotropic and anisotropic damage model coupled with a novel plasticity model for plain concrete is proposed in this…
(more)
▼ Based on continuum
damage mechanics (CDM), an isotropic and anisotropic
damage
model coupled with a novel plasticity model for plain concrete is proposed in this
research. Two different
damage evolution laws for both tension and compression are
formulated for a more accurate prediction of the plain concrete behavior. In order to
derive the constitutive equations, the strain equivalence hypothesis is adopted. The
proposed constitutive model has been shown to satisfy the thermodynamics requirements,
and detailed numerical algorithms are developed for the Finite Element implementation
of the proposed model. Moreover, the numerical algorithm is coded using the user
subroutine UMAT and then implemented in the commercial finite element analysis
program Abaqus, and the overall performance of the proposed model is verified by
comparing the model predictions to various experimental data on macroscopic level.
Using the proposed coupled plasticity-
damage constitutive model, the effect of
the micromechanical properties of concrete, such as aggregate shape, distribution, and
volume fraction, the ITZ thickness, and the strength of the ITZ and mortar matrix on the tensile behavior of concrete is investigated on 2-D and 3-D meso-scale. As a result of
simulation, the tensile strength and thickness of the ITZ is the most important factor that
control the global strength and behavior of concrete, and the aggregate shape and
volume fraction has somewhat effect on the tensile behavior of concrete while the effect
of the aggregate distribution is negligible. Furthermore, using the proposed constitutive
model, the pull-out analysis of the single straight and curved CNT embedded in cement
matrix is carried out. In consequence of the analysis, the interfacial fracture energy is the
key parameter governing the CNT pull-out strength and ductility at bonding stage, and
the Young's modulus of the CNT has also great effect on the pull-out behavior of the
straight CNT. In case of the single curved CNT, while the ultimate pull-out force of the
curved CNT at sliding stage is governed by the initial sliding force when preexisting
normal force is relatively high, the ultimate pull-out force, when the preexisting normal
force is not significant, is increased linearly proportional to the curvature and the
Young's modulus of the CNT due to the additionally induced normal force by the
bending stiffness of the curved CNT.
Advisors/Committee Members: Abu Al-Rub, Rashid K. (advisor), Masad, Eyad (committee member), Grasley, Zachary (committee member), Muliana, Anastasia (committee member).
Subjects/Keywords: Damage Mechanics; Concrete Fracture; Meso-scale Analysis; Carbon Nanotube
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APA (6th Edition):
Kim, S. (2011). Continuum-based Multiscale Computational Damage Modeling of Cementitous Composites. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-8022
Chicago Manual of Style (16th Edition):
Kim, Sun-Myung. “Continuum-based Multiscale Computational Damage Modeling of Cementitous Composites.” 2011. Doctoral Dissertation, Texas A&M University. Accessed April 17, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-8022.
MLA Handbook (7th Edition):
Kim, Sun-Myung. “Continuum-based Multiscale Computational Damage Modeling of Cementitous Composites.” 2011. Web. 17 Apr 2021.
Vancouver:
Kim S. Continuum-based Multiscale Computational Damage Modeling of Cementitous Composites. [Internet] [Doctoral dissertation]. Texas A&M University; 2011. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-8022.
Council of Science Editors:
Kim S. Continuum-based Multiscale Computational Damage Modeling of Cementitous Composites. [Doctoral Dissertation]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-8022
University of Adelaide
27.
Fletcher, Lloyd.
Fatigue Fracture Interaction Mechanisms In Cortical Bone.
Degree: 2015, University of Adelaide
URL: http://hdl.handle.net/2440/119481
► The skeletal system accumulates microscale fatigue damage with everyday use. Bone has the ability to repair fatigue damage; however, the effectiveness of the repair mechanism…
(more)
▼ The skeletal system accumulates microscale fatigue
damage with everyday use. Bone has the ability to repair fatigue
damage; however, the effectiveness of the repair mechanism can deteriorate with age and disease leading to an accumulation of
damage. An increase in fatigue microdamage with age is thought to contribute to the occurrence of fragility fractures in the elderly. However, the mechanisms that are responsible for the interaction of fatigue
damage and the fracture resistance of bone are not well understood. Therefore this thesis aims to analyse the mechanisms of interaction between accumulated fatigue
damage and the fracture resistance of cortical bone (i.e. fatigue fracture interaction mechanisms). This aim is achieved by the application of engineering fracture
mechanics theory to investigate the effects of accumulated fatigue
damage on the fracture resistance of cortical bone. This thesis consists of two main components: 1) experimental studies and 2) numerical modelling. The experimental component is separated into three separate experiments, each designed to analyse the effects of fatigue
damage on the fracture resistance of cortical bone. The first experiment analysed the effects of tensile fatigue
damage on the longitudinal fracture resistance of cortical bone; the second experiment analysed the effects of tensile fatigue
damage on the longitudinal and transverse fracture resistance of cortical bone; and the third experiment analysed the effects of tensile and compressive fatigue
damage on the transverse fracture resistance of cortical bone. The general methodology used for these experiments included splitting specimens into control and damaged groups then ex-vivo fatigue loading the damaged group specimens. All specimens were then fracture resistance tested and the fracture behaviour of the control and damaged groups was compared. The results of these experiments were used to propose conceptual models of fatigue fracture interaction. In general the results showed that fatigue microdamage in the form of linear microcracks is detrimental to the fracture resistance of cortical bone. The second component of this thesis was the numerical modelling of the toughening mechanisms in cortical bone and their contribution to the overall fracture resistance behaviour. The specific mechanisms that were modelled include: uncracked ligament bridging, crack deflection and microcracking. The results from the numerical modelling were then combined with the experimental data to develop a model of toughening behaviour in bone. Overall, the results of this thesis show that fatigue microdamage is detrimental to the fracture resistance of cortical bone. In addition to this, microstructural changes with age or disease may exacerbate the detrimental effects of fatigue microdamage on the fracture resistance of cortical bone. Therefore the results of this thesis suggest that fatigue microdamage may be a contributing factor to clinical fractures.
Advisors/Committee Members: Codrington, John (advisor), School of Mechanical Engineering (school).
Subjects/Keywords: Cortical bone; Fatigue; Fatigue damage; Microdamage; Fracture mechanics; Fracture resistance
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APA (6th Edition):
Fletcher, L. (2015). Fatigue Fracture Interaction Mechanisms In Cortical Bone. (Thesis). University of Adelaide. Retrieved from http://hdl.handle.net/2440/119481
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):
Fletcher, Lloyd. “Fatigue Fracture Interaction Mechanisms In Cortical Bone.” 2015. Thesis, University of Adelaide. Accessed April 17, 2021.
http://hdl.handle.net/2440/119481.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Fletcher, Lloyd. “Fatigue Fracture Interaction Mechanisms In Cortical Bone.” 2015. Web. 17 Apr 2021.
Vancouver:
Fletcher L. Fatigue Fracture Interaction Mechanisms In Cortical Bone. [Internet] [Thesis]. University of Adelaide; 2015. [cited 2021 Apr 17].
Available from: http://hdl.handle.net/2440/119481.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Fletcher L. Fatigue Fracture Interaction Mechanisms In Cortical Bone. [Thesis]. University of Adelaide; 2015. Available from: http://hdl.handle.net/2440/119481
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Oxford
28.
Bianchi, Fabio.
Multi-scale effects of stretch on peripheral nerves.
Degree: PhD, 2018, University of Oxford
URL: http://ora.ox.ac.uk/objects/uuid:2c289bc8-c823-4d78-855c-3bceb5cebc4b
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.770758
► Peripheral nerve injury, leading to loss of motor and sensory function, is a burdensome consequence of trauma, surgery or chronic conditions. Mechanical forces play a…
(more)
▼ Peripheral nerve injury, leading to loss of motor and sensory function, is a burdensome consequence of trauma, surgery or chronic conditions. Mechanical forces play a substantial role in the onset of injury, and affect peripheral nerves at varying length scales, from tissues to individual cells. A multi-scale approach is therefore required to understand how supraphysiological levels of deformation at the nerve level can affect function at the single-cell level. The aim of this project was to investigate the multi-scale effects of stretch at the tissue and cell length scales, through the development of experimental in vitro models of peripheral nerve injury. At the macroscopic (tissue) level, the aim was to quantify the partitioning of strain between nerve and neurons, by measuring microscopic strains during in situ extension of peripheral nerves. At the microscopic level, the aim was to quantify the effects of cell strain and mechanical properties on the electrophysiolgical activity of neurons. At the whole tissue level, the transfer of tissue-scale strain to the micro-scale was investigated by X-ray diffraction and MPM imaging during tensile loading. Axially, the strain in peripheral nerves was shown to partly transfer to the axially aligned collagen fibres ensheathing the nerve core. The transfer of axial strain to axons was evaluated by using Nodes of Ranvier as markers for digital image correlation, providing a direct relationship between tissue and cell scale mechanics. Radially, a small fraction of the induced compression was transferred to the myelin sheath, suggesting a high stiffness and a potential protective role. Plastic damage in collagenous tissue was examined by evaluating changes in micro-scale mechanical properties, showing distinct behaviours at the collagen fibril and molecule levels. These results establish a mechanical link between nerve extension and microscopic deformations that affect individual cells within the tissue. In order to investigate the effect at the microscopic cell scale, novel \emph{in vitro} models were developed. A cell-stretching device was designed to apply uniaxial strain to cultured neurons, and simultaneously allow electrophysiological measurements. Human induced pluripotent cells were differentiated to functional motor neurons, and the effect of uniaxial strain was evaluated by measuring the alterations in network and single-cell electrophysiology. Calcium flux imaging showed an immediate decrease in spontaneous network activity with applied strain, and whole-cell patch clamping was used to show changes in ion channel dynamics. C-Laurdan imaging showed a linear fluidisation effect of stretch on the lipid packing of neural membranes, suggesting that the mechanical state of the membrane is changed during straining. Altering the cell membrane's mechanical properties by increasing cholesterol was shown to reduce membrane fluidisation and significantly mitigate the loss of spontaneous activity due to strain. The development of multi-scale mechanical models can help tissue…
Subjects/Keywords: Biomechanics; Nerve mechanics; Stem Cels; Tissue Engineering; Nerve damage
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MLA ·
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APA (6th Edition):
Bianchi, F. (2018). Multi-scale effects of stretch on peripheral nerves. (Doctoral Dissertation). University of Oxford. Retrieved from http://ora.ox.ac.uk/objects/uuid:2c289bc8-c823-4d78-855c-3bceb5cebc4b ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.770758
Chicago Manual of Style (16th Edition):
Bianchi, Fabio. “Multi-scale effects of stretch on peripheral nerves.” 2018. Doctoral Dissertation, University of Oxford. Accessed April 17, 2021.
http://ora.ox.ac.uk/objects/uuid:2c289bc8-c823-4d78-855c-3bceb5cebc4b ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.770758.
MLA Handbook (7th Edition):
Bianchi, Fabio. “Multi-scale effects of stretch on peripheral nerves.” 2018. Web. 17 Apr 2021.
Vancouver:
Bianchi F. Multi-scale effects of stretch on peripheral nerves. [Internet] [Doctoral dissertation]. University of Oxford; 2018. [cited 2021 Apr 17].
Available from: http://ora.ox.ac.uk/objects/uuid:2c289bc8-c823-4d78-855c-3bceb5cebc4b ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.770758.
Council of Science Editors:
Bianchi F. Multi-scale effects of stretch on peripheral nerves. [Doctoral Dissertation]. University of Oxford; 2018. Available from: http://ora.ox.ac.uk/objects/uuid:2c289bc8-c823-4d78-855c-3bceb5cebc4b ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.770758
29.
Geromel fischer, Arthur.
Variational approach to dynamic fracture and applications to the fragmentation of metals and ceramics : Approche variationnelle de la rupture dynamique et applications à la fragmentation des métaux et céramiques.
Degree: Docteur es, Mécanique des solides, 2018, Université Paris-Saclay (ComUE)
URL: http://www.theses.fr/2018SACLX096
► Le principal objectif de ce travail est l'étude de la fragmentation d'enveloppes métalliques. Cette thèse est divisée en quatre parties : la construction d'un modèle…
(more)
▼ Le principal objectif de ce travail est l'étude de la fragmentation d'enveloppes métalliques. Cette thèse est divisée en quatre parties : la construction d'un modèle d'endommagement, l'implémentation numérique, la calibration des paramètres du modèle en utilisant des données expérimentales, et des travaux analytiques.Tout d'abord, nous avons considéré des modèles qui couplent les modèles d'endommagement classiques avec la plasticité et la dynamique. En utilisant l'énergie et l'action du système, nous avons obtenu toutes les équations qui décrivent le modèle dynamique et ductile : l'équation de la dynamique, le critère de plasticité et le critère d'endommagement. Nous avons ensuite détaillé l'implémentation numérique de ces modèles.Des résultats qualitatifs ont ensuite pu être obtenus, comme le nombre et la direction des fissures, ainsi que la convergence vers le modèle quasi-statique.Afin de mieux comprendre l'influence de chaque paramètre du modèle, nous avons étudié analytiquement le problème. A partir de l'observation de l'amplitude des perturbations, nous avons pu décrire comment obtenir une approximation analytique du nombre de fissures dans le cas d'un anneau en expansion.Cependant, pour être capable de simuler des problèmes réalistes, il est nécessaire de calibrer les paramètres du modèle. Nous nous sommes intéressés plus particulièrement au cas des matériaux fragiles. Les données expérimentales ont été obtenues par une série d'expériences réalisée par le CEA.Afin d'empêcher la localisation de la déformation plastique dans des bandes d'épaisseur nulle, d'autres formes de régularisation ont été étudiées, comme par exemple, l'utilisation des propriétés dissipatives du champ de température.Enfin, nous avons conclu ce travail en proposant des modèles de plasticité où l'énergie dépend aussi du gradient de la déformation plastique (modèles de plasticité à gradient).
The main objective of this work was the study of the fragmentation of a metallic shell. This thesis is divided into four parts: construction of a damage model, numerical implementation, calibration of the model parameters using experimental data and analytical works.In this work, we considered a model that couples the standard gradient damage models with plasticity and dynamics. Using the energy and the action of the system, we could obtain all the equations necessary to describe the dynamic ductile model: the equations of dynamics, the plasticity criterion and the damage criterion. We then detail the numerical implementation of these models.Some qualitative behaviours are then obtained, such as the number and the direction of cracks, and the convergence to the quasi-static model.In order to better understand the influence of the parameters, we studied the problem analytically. By studying the amplitude of the perturbations, we describe how to obtain an analytic approximation for the number of cracks in a ring under expansion.In order to run realistic simulations, it is needed to calibrate the material parameters. We focus here on a simple case of…
Advisors/Committee Members: Marigo, Jean-Jacques (thesis director).
Subjects/Keywords: Endommagement; Fragmentation dynamique; Plasticité; Damage mechanics; Dynamic fragmentation; Plasticity; 620.112 92
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APA ·
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MLA ·
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Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Geromel fischer, A. (2018). Variational approach to dynamic fracture and applications to the fragmentation of metals and ceramics : Approche variationnelle de la rupture dynamique et applications à la fragmentation des métaux et céramiques. (Doctoral Dissertation). Université Paris-Saclay (ComUE). Retrieved from http://www.theses.fr/2018SACLX096
Chicago Manual of Style (16th Edition):
Geromel fischer, Arthur. “Variational approach to dynamic fracture and applications to the fragmentation of metals and ceramics : Approche variationnelle de la rupture dynamique et applications à la fragmentation des métaux et céramiques.” 2018. Doctoral Dissertation, Université Paris-Saclay (ComUE). Accessed April 17, 2021.
http://www.theses.fr/2018SACLX096.
MLA Handbook (7th Edition):
Geromel fischer, Arthur. “Variational approach to dynamic fracture and applications to the fragmentation of metals and ceramics : Approche variationnelle de la rupture dynamique et applications à la fragmentation des métaux et céramiques.” 2018. Web. 17 Apr 2021.
Vancouver:
Geromel fischer A. Variational approach to dynamic fracture and applications to the fragmentation of metals and ceramics : Approche variationnelle de la rupture dynamique et applications à la fragmentation des métaux et céramiques. [Internet] [Doctoral dissertation]. Université Paris-Saclay (ComUE); 2018. [cited 2021 Apr 17].
Available from: http://www.theses.fr/2018SACLX096.
Council of Science Editors:
Geromel fischer A. Variational approach to dynamic fracture and applications to the fragmentation of metals and ceramics : Approche variationnelle de la rupture dynamique et applications à la fragmentation des métaux et céramiques. [Doctoral Dissertation]. Université Paris-Saclay (ComUE); 2018. Available from: http://www.theses.fr/2018SACLX096
Delft University of Technology
30.
Aukselis, A. (author).
Homogeneous Orthotropic Masonry Material Model: Research, development and implementation for explicit analysis.
Degree: 2017, Delft University of Technology
URL: http://resolver.tudelft.nl/uuid:b0ca8953-de6f-49b1-9692-3e7bb1b1f687
► The Groningen region, in the Netherlands, experiences earthquakes since 1986. These earthquakes are new to the region and the structures built there are not designed…
(more)
▼ The Groningen region, in the Netherlands, experiences earthquakes since 1986. These earthquakes are new to the region and the structures built there are not designed for it. Therefore, they pose a great risk for the historical structures and people living in the area. Most of the buildings there are built using masonry and to analyze such structures on how they will be affected by earthquakes using currently available tools and methods is rather complicated. In this report, the author investigates the use of available continuum damage mechanics models for the purpose of simulating orthotropic masonry behavior during an explicit integration analysis. The material behavior is described in Fortran programming language and is used as a custom user subroutine (VUMAT) in Simulia Abaqus finite element analysis software. The developed material model exhibits 3D elasticity and 2D plane plasticity. Furthermore, it is assumed that two general failure mechanisms are present. One associated with tensile and shear brittle fracture represented by Rankine type yield surface and other with distributed crushing of a material represented by Hill type yield surface. The model exhibits uncoupled damage evolution in the tension regime and coupled in compression. Additionally, the model supports tensile crack closure, while in compression it accumulates the plastic deformations and if an element is crushed it can be flagged for deletion from the mesh. The model is formulated in such a way that most of the properties in material directions are independent of one another. The developed model was tested by examining its behavior in analyses where numerical models were composed out of one or few elements. Additionally, for experimental comparison, four shear walls were modelled, three subjected to monotonic loading and one to cyclic. The analyses closely agree to experimental results even when using raw test data. The material model is stable due to the explicit approach and provides qualitative results as it is flexible enough to be used for various types of analyses, either static or cyclic.In the final part of the report, further developments are considered, including improvements to the code base, additional testing, and development of a custom element.
Civil Engineering and Geosciences
Structural Engineering
Advisors/Committee Members: Rots, J.G. (mentor), Hendriks, M.A.N. (mentor), Yang, Y. (mentor), Hoorn, H. (mentor), Koot, A. (mentor).
Subjects/Keywords: material model; Masonry; FEM; damage mechanics; earthquakes; Groningen; Fortran; Python
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APA (6th Edition):
Aukselis, A. (. (2017). Homogeneous Orthotropic Masonry Material Model: Research, development and implementation for explicit analysis. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:b0ca8953-de6f-49b1-9692-3e7bb1b1f687
Chicago Manual of Style (16th Edition):
Aukselis, A (author). “Homogeneous Orthotropic Masonry Material Model: Research, development and implementation for explicit analysis.” 2017. Masters Thesis, Delft University of Technology. Accessed April 17, 2021.
http://resolver.tudelft.nl/uuid:b0ca8953-de6f-49b1-9692-3e7bb1b1f687.
MLA Handbook (7th Edition):
Aukselis, A (author). “Homogeneous Orthotropic Masonry Material Model: Research, development and implementation for explicit analysis.” 2017. Web. 17 Apr 2021.
Vancouver:
Aukselis A(. Homogeneous Orthotropic Masonry Material Model: Research, development and implementation for explicit analysis. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2021 Apr 17].
Available from: http://resolver.tudelft.nl/uuid:b0ca8953-de6f-49b1-9692-3e7bb1b1f687.
Council of Science Editors:
Aukselis A(. Homogeneous Orthotropic Masonry Material Model: Research, development and implementation for explicit analysis. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:b0ca8953-de6f-49b1-9692-3e7bb1b1f687
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