You searched for +publisher:"Texas A&M University" +contributor:("Palazzolo, Alan").
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Texas A&M University
1.
Nanami, Norimichi.
Vibration and Structural Response of Hybrid Wind Turbine Blades.
Degree: MS, Mechanical Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8735 
► Renewable energy is a serious alternative to deliver the energy needs of an increasing world population and improve economic activity. Wind energy provides better environmental…
(more)
▼ Renewable energy is a serious alternative to deliver the energy needs of an increasing world population and improve economic activity. Wind energy provides better environmental and economic benefits in comparison with the other renewable energy sources. Wind energy is capable of providing 72 TW (TW = 10
12 W) of electric power, which is approximately four and half times the world energy consumption of 15.8 TW as reported in 2006. Since power output extracted from wind turbines is proportional to the square of the blade length and the cube of the wind speed, wind turbine size has grown rapidly in the last two decades to match the increase in power output. As the blade length increases, so does its weight opening up design possibilities to introduce hybrid glass and carbon fiber composite materials as lightweight structural load bearing alternatives.
Herein, we investigate the feasibility of introducing modular composite tubulars as well as hybrid sandwich composite skins in the next generation blades. After selecting a target energy output, 8 MW with 80
m blade, airfoil geometry and the layup for the skin as well as internal reinforcements are proposed. They are incorporated into the computational blade via linear shell elements for the skin, and linear beam elements for the composite tubulars to assess the relationship between weight reduction and structural performance. Computational simulations are undertaken to understand the static and dynamic regimes; specifically, displacements, stresses, and vibration modes. The results showed that the composite layers did not exhibit any damage. However, in the balsa core of the sandwich skin, the von Mises stress exceeded its allowable at wind speeds ranging from 11.0
m/sec to 12.6
m/sec. In the blades with composite tubular reinforcement, two different types of damage are observed: a. Stress concentrations at the tubular-skin attachments, and b. Highest von Mises stress caused by the flapping bending moment. The vibration studies revealed a strong coupling mode, bending and twist, at the higher natural frequencies of the blade with tubular truss configuration. The weight saving measures in developing lighter blades in this study did not detract from the blades structural response for the selected load cases.
Advisors/Committee Members: Ochoa, Ozden (advisor), Palazzolo, Alan (committee member), Strganac, Thomas (committee member).
Subjects/Keywords: wind turbine blade; CF/GF hybrid composite materials; composite tubulars; computational simulation
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APA (6th Edition):
Nanami, N. (2011). Vibration and Structural Response of Hybrid Wind Turbine Blades. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8735
Chicago Manual of Style (16th Edition):
Nanami, Norimichi. “Vibration and Structural Response of Hybrid Wind Turbine Blades.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8735.
MLA Handbook (7th Edition):
Nanami, Norimichi. “Vibration and Structural Response of Hybrid Wind Turbine Blades.” 2011. Web. 08 Mar 2021.
Vancouver:
Nanami N. Vibration and Structural Response of Hybrid Wind Turbine Blades. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8735.
Council of Science Editors:
Nanami N. Vibration and Structural Response of Hybrid Wind Turbine Blades. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8735
Texas A&M University
2.
Elwell, Roston Clement.
Miniature Hourglass Shaped Actuator Geometry Study Using A Finite Element Simulation.
Degree: MS, Mechanical Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7711
► This project investigated a miniature, hourglass-shaped actuator (MHA) and how its geometry affects performance. A custom, self-contained, finite-element simulation code predicts how each MHA deforms…
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▼ This project investigated a miniature, hourglass-shaped actuator (MHA) and how its geometry affects performance. A custom, self-contained, finite-element simulation code predicts how each MHA deforms when pressurized internally.
This analysis describes the MHA geometry's effects on four characteristics: a) work density b) mechanical advantage, c) work advantage and d) percent elongation. The first three characteristics are compared to a traditional actuator operating at the same pressure and elongation.
A finite-element modeling code was tailored to study the MHA at 5 MPa internal pressure when 1) MHA height and side-wall thickness are constant and side-wall arc length varies; 2) MHA side-wall arc length and thickness are constant and the height varies; and 3) MHA side-wall thickness varies while height and side-wall arc length are fixed. Case 3 was studied using the MHA geometry with the highest work density found in either condition 1 or 2.
Peak mechanical advantage, 6.47, occurs in a constant height MHA-Case 1-when the side-wall arc length is shortest. Highest elongation, 8.67%, occurs in the Case 1 MHA with the longest side-wall arc length. Finally, under Case 3, work density reaches 0.434 MJ/m3 when the side-wall thickness is 1.9 mm.
The MHA has potential for active structures because its work density is high-higher than traditional actuators with the same elongation. Their small elongations limit their use; however, much work remains to determine how MHAs might be arranged in a useful array. Never the less, morphing airfoils and other active structures might benefit from embedded MHAs.
Advisors/Committee Members: Creasy, Terry (advisor), Palazzolo, Alan (committee member), Talreja, Ramesh (committee member).
Subjects/Keywords: Miniature Actuator; Morphing Structure; Machine Augmented Composite
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APA (6th Edition):
Elwell, R. C. (2011). Miniature Hourglass Shaped Actuator Geometry Study Using A Finite Element Simulation. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7711
Chicago Manual of Style (16th Edition):
Elwell, Roston Clement. “Miniature Hourglass Shaped Actuator Geometry Study Using A Finite Element Simulation.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7711.
MLA Handbook (7th Edition):
Elwell, Roston Clement. “Miniature Hourglass Shaped Actuator Geometry Study Using A Finite Element Simulation.” 2011. Web. 08 Mar 2021.
Vancouver:
Elwell RC. Miniature Hourglass Shaped Actuator Geometry Study Using A Finite Element Simulation. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7711.
Council of Science Editors:
Elwell RC. Miniature Hourglass Shaped Actuator Geometry Study Using A Finite Element Simulation. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7711
Texas A&M University
3.
Graves, John.
Small Satellite Applications of Commercial off the Shelf Radio Frequency Integrated Circuits.
Degree: MS, Aerospace Engineering, 2012, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10387
► Within the first decade of the 21st century, the aerospace community has seen many more opportunities to launch small spacecraft in the 10 to 100…
(more)
▼ Within the first decade of the 21st century, the aerospace community has seen many more opportunities to launch small spacecraft in the 10 to 100 kg mass class. Coupled with this has been consistent interest from the government in developing small-spacecraft platforms to expand civil and military mission possibilities. Small spacecraft have also given small organizations such as universities an increased access to space.
Because small satellites are limited in size, power, and mass, new and often nontraditional capabilities must be explored and developed to make them viable and attractive when compared with larger and more proven spacecraft. Moreover, small organizations that wish to contribute technically are often limited by the small size of their teams and available resources, and need creative solutions for meeting mission requirements.
A key need is in space-to-ground communications. Complex missions typically require large amounts of data transfer to the ground and in a timely fashion. Available options trade hardware cost, available ground stations or networks, available operating-frequency range, data-rate performance, and ease of use.
A system for small spacecraft will be presented based upon Radio Frequency Integrated Circuits (RFIC) that minimizes development effort and maximizes interface control to meet typical small-spacecraft communications requirements. RFICs are low-cost components that feature pre-built radio hardware on a chip that can be expanded easily by developers with little or no radio experience. These devices are widespread in domestic applications for short-range connectivity.
A preliminary design and prototype is presented that meets basic spaceflight requirements, offers data rates in the 55 to 85 kbps range, and has completed basic proof-of-concept testing. While there are higher-data-rate alternatives in existence, the solution presented here strikes a useful balance among data rate, parts cost, and ease of use for non experts, and gives the user operational control necessary to make air-to-ground communications time effective.
Advisors/Committee Members: Reed, Helen (advisor), Palazzolo, Alan (committee member), Goulart, Ana (committee member).
Subjects/Keywords: Small satellites; RFIC; downlink communications; spacecraft; university satellites
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APA (6th Edition):
Graves, J. (2012). Small Satellite Applications of Commercial off the Shelf Radio Frequency Integrated Circuits. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10387
Chicago Manual of Style (16th Edition):
Graves, John. “Small Satellite Applications of Commercial off the Shelf Radio Frequency Integrated Circuits.” 2012. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10387.
MLA Handbook (7th Edition):
Graves, John. “Small Satellite Applications of Commercial off the Shelf Radio Frequency Integrated Circuits.” 2012. Web. 08 Mar 2021.
Vancouver:
Graves J. Small Satellite Applications of Commercial off the Shelf Radio Frequency Integrated Circuits. [Internet] [Masters thesis]. Texas A&M University; 2012. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10387.
Council of Science Editors:
Graves J. Small Satellite Applications of Commercial off the Shelf Radio Frequency Integrated Circuits. [Masters Thesis]. Texas A&M University; 2012. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10387
Texas A&M University
4.
Shaw, John.
Predicting Pulsations and Surge in Mixed Reciprocating and Centrifugal Compressor Piping Systems.
Degree: MS, Mechanical Engineering, 2015, Texas A&M University
URL: http://hdl.handle.net/1969.1/156489
► The purpose of this work is to develop a method for modelling centrifugal compressor surge in the presence of pressure pulsations in gas transmission lines,…
(more)
▼ The purpose of this work is to develop a method for modelling centrifugal compressor surge in the presence of pressure pulsations in gas transmission lines, and examine the effects of pulsation amplitude and frequency on centrifugal compressor operating stability. Anecdotal field evidence suggests that it is possible for a centrifugal compressor to enter surge when pressure pulsations are present, even in the case where the centrifugal compressor would otherwise operate at a stable point. In such a situation it has been concluded that the instability results from the pulsations.
The method used for the model of the piping system is a finite element model of the pipe acoustics, with a reciprocating compressor model and a centrifugal compressor model as boundary conditions. The details of these models and the methods for coupling them are a large portion of this work. The combined centrifugal compressor and piping acoustic model are used in a variety of numerical experiments investigating the effect of pulsation amplitude and frequency on the operating point of the centrifugal compressor.
The results of the numerical experiments show that piping system acoustic properties have a strong effect on pulsation amplitude, and pulsations have a strong effect on compressor operating point. The pulsations cause an oscillation in operating point away from the compressor’s steady state operating point. The effect is stronger as pulsation amplitude increases and as pulsation frequency approaches the natural frequency of the piping system. If the pulsations are strong enough, they can force the centrifugal compressor operating point over the surge limit, and then back into the stable operating region before the compressor enters a surge cycle. Numerical experiments show that the pulsations must push the centrifugal compressor over the surge limit and remain there long enough, if a surge cycle is to develop. Therefore, it is concluded that pulsations can cause a centrifugal compressor to cross the surge limit, and that larger pulsations will indeed cause surge when the operating point is across the surge limit for long enough.
Advisors/Committee Members: Palazzolo, Alan (advisor), Strganac, Thomas (committee member), Rathinam, Sivakumar (committee member).
Subjects/Keywords: Compressor; Centrifugal Compressor; Surge; Piping Systems; Acoustics
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APA (6th Edition):
Shaw, J. (2015). Predicting Pulsations and Surge in Mixed Reciprocating and Centrifugal Compressor Piping Systems. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/156489
Chicago Manual of Style (16th Edition):
Shaw, John. “Predicting Pulsations and Surge in Mixed Reciprocating and Centrifugal Compressor Piping Systems.” 2015. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/156489.
MLA Handbook (7th Edition):
Shaw, John. “Predicting Pulsations and Surge in Mixed Reciprocating and Centrifugal Compressor Piping Systems.” 2015. Web. 08 Mar 2021.
Vancouver:
Shaw J. Predicting Pulsations and Surge in Mixed Reciprocating and Centrifugal Compressor Piping Systems. [Internet] [Masters thesis]. Texas A&M University; 2015. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/156489.
Council of Science Editors:
Shaw J. Predicting Pulsations and Surge in Mixed Reciprocating and Centrifugal Compressor Piping Systems. [Masters Thesis]. Texas A&M University; 2015. Available from: http://hdl.handle.net/1969.1/156489
Texas A&M University
5.
Abdelzaher, Omar Mohamed.
Downhole Wireline Mechatronics and Drillstring Vibration Dynamics.
Degree: MS, Mechanical Engineering, 2014, Texas A&M University
URL: http://hdl.handle.net/1969.1/157919
► The work is divided into two parts: The First part discusses and documents simulation investigations on the interactive effect of the different conveyance accessories tools…
(more)
▼ The work is divided into two parts: The First part discusses and documents simulation investigations on the interactive effect of the different conveyance accessories tools and their designs on the wireline cable tension force, and how it can influence the wireline cable performance especially in open hole logging operations with highly deviated and rugose zones. A computer simulation model was built to predict the cable tension force applied on conveyed wireline string so as to assess and analyze the effect of the different conveyance accessories, such as centralizers, bottom-nose tools, and wireline coating, on wireline penetration rates. A numerical computing approach was then utilized to represent and analyze the simulation studies output results in a friendly graphical form. Improving the wireline logging performance, especially in highly deviated rugose openhole wells, could increase the percentage of successful logging operations, reducing time, cost and improving data quality with the increased wellbore coverage. The second part discusses the possible violent drillstring vibrations encountered during drilling and its effect on the overall rate of penetration and sustainability. This entails a complete identification and modeling of the drillstring dynamics and the sources of vibrations excitation that include stick-slip, bit-bounce, and whirling with its two forward and backward types to better control its functional operation and improve its performance.
A Matlab numerical simulator model based on Finite-Element-Method of 3D- Timoshenko beam elements is developed for this purpose to predict and simulate the rotordynamic behavior of the bottom-hole-assembly (BHA) and the PDC-Drillbit cutting dynamics. The model also includes the coupling between the torsional and bending vibrations of drillstrings with the nonlinear effects of drillstring/wellbore friction contacts. The work extends previous models of drillstring vibrations in the literature to include the destructive drillstring vibration backward whirling type with Pure rolling behavior and answers some crucial questions: the operation conditions that possibly causes backward whirl vibrations, possible stabilizers’ configuration to reduce chance of backward whirl, best stabilizers locations in the BHA to minimize the sever vibration effects on the drillstring, and other arising questions.
Advisors/Committee Members: Palazzolo , Alan (advisor), Ahmed, Shehab (advisor), Kim, Won-jong (committee member).
Subjects/Keywords: Downhole; Wireline; Mechatronics; Drillstring; Vibration; Dynamics; simulation; centralizers; bottom-nose; logging; wellbore; drilling; penetration; stick-slip; bit-bounce; whirling; Matlab; Finite-Element-Method; Timoshenko; rotordynamic; bottom-hole-assembly; Drillbit; nonlinear; Pur-rolling; backward-whirl; stabilizers; BHA
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APA (6th Edition):
Abdelzaher, O. M. (2014). Downhole Wireline Mechatronics and Drillstring Vibration Dynamics. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/157919
Chicago Manual of Style (16th Edition):
Abdelzaher, Omar Mohamed. “Downhole Wireline Mechatronics and Drillstring Vibration Dynamics.” 2014. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/157919.
MLA Handbook (7th Edition):
Abdelzaher, Omar Mohamed. “Downhole Wireline Mechatronics and Drillstring Vibration Dynamics.” 2014. Web. 08 Mar 2021.
Vancouver:
Abdelzaher OM. Downhole Wireline Mechatronics and Drillstring Vibration Dynamics. [Internet] [Masters thesis]. Texas A&M University; 2014. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/157919.
Council of Science Editors:
Abdelzaher OM. Downhole Wireline Mechatronics and Drillstring Vibration Dynamics. [Masters Thesis]. Texas A&M University; 2014. Available from: http://hdl.handle.net/1969.1/157919
Texas A&M University
6.
Goncalves, Andressa Alves.
Use of an Experimental Test Rig to Study the Impact of Drilling Parameters and Side Loads in the Side Cutting Tendency of a PDC Bit in a Horizontal Set Up.
Degree: MS, Petroleum Engineering, 2016, Texas A&M University
URL: http://hdl.handle.net/1969.1/159066
► The demand for oil has increased considerably since its first discovery. Consequently, all of the reservoirs that were easy to access and/or explore have already…
(more)
▼ The demand for oil has increased considerably since its first discovery. Consequently, all of the reservoirs that were easy to access and/or explore have already been discovered. To overcome this challenge, the industry had to find a way to find new wells to explore, wells that were previously judged as non-economical, due to either their location or low porosity/permeability. For those reasons, the industry turned to directional wells, facilitated by the advances in technology. An important part of building a successful directional well is correctly predicting the well path. The objective of the present study is to analyze the influence of WOB, ROP, RPM and side load on the steerability of a PDC bit, bringing the work done by Ernst, Pastusek and Lutes (2007) to a horizontal set up and analyzing the response of MSE while sidecutting. Findings suggest how much of an influence the drilling parameters have on steering the bit, and the knowledge of how they affect the set up used during drilling can be a fundamental tool when creating a well path.
The tests were conducted on a horizontal test rig, built by the Mechanical Engineering Department at
Texas A&
M University, using 8 ksi average compressive strength samples. During the tests, modifications had to be made to the rig in order to accommodate the demands of a petroleum drilling operation. An innovative system was installed to measure shaft deflection through a HD Webcam, turning distance in the pixels from the images captured into real life distance. Through that system it was possible to back calculate the side load being applied to the system, controlling it in real time.
The results showed that two parameters were the most influential on the sidecutting angle of a PDC bit: side load and RPM. Side load was even more significant for lower values, where an increase is much more abrupt. ROP is also expected to have a smaller influence, and it was observed for the sample with the highest RPM. MSE showed an expected response, being opposite to the side load. The results observed were very similar to the ones found by Ernst, Pastusek and Lutes (2007), thus being possible to conclude that when drilling a vertical well, the bit will respond in a similar manner to the changes in drilling parameters as it would in a vertical well.
Advisors/Committee Members: Noynaert, Samuel (advisor), Schubert, Jerome (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: bit steerability; side load; horizontal well; horizontal drilling; PDC bit
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APA (6th Edition):
Goncalves, A. A. (2016). Use of an Experimental Test Rig to Study the Impact of Drilling Parameters and Side Loads in the Side Cutting Tendency of a PDC Bit in a Horizontal Set Up. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/159066
Chicago Manual of Style (16th Edition):
Goncalves, Andressa Alves. “Use of an Experimental Test Rig to Study the Impact of Drilling Parameters and Side Loads in the Side Cutting Tendency of a PDC Bit in a Horizontal Set Up.” 2016. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/159066.
MLA Handbook (7th Edition):
Goncalves, Andressa Alves. “Use of an Experimental Test Rig to Study the Impact of Drilling Parameters and Side Loads in the Side Cutting Tendency of a PDC Bit in a Horizontal Set Up.” 2016. Web. 08 Mar 2021.
Vancouver:
Goncalves AA. Use of an Experimental Test Rig to Study the Impact of Drilling Parameters and Side Loads in the Side Cutting Tendency of a PDC Bit in a Horizontal Set Up. [Internet] [Masters thesis]. Texas A&M University; 2016. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/159066.
Council of Science Editors:
Goncalves AA. Use of an Experimental Test Rig to Study the Impact of Drilling Parameters and Side Loads in the Side Cutting Tendency of a PDC Bit in a Horizontal Set Up. [Masters Thesis]. Texas A&M University; 2016. Available from: http://hdl.handle.net/1969.1/159066
Texas A&M University
7.
Smith, Sean Joseph.
Estimating Load Distributions for Retaining Structures Subjected to Railroad Live Loads.
Degree: MS, Civil Engineering, 2016, Texas A&M University
URL: http://hdl.handle.net/1969.1/187353
► Retaining structures in proximity to railroads experience a variety of lateral loading intensities depending on the live load surcharge. Current design guidelines recommend using the…
(more)
▼ Retaining structures in proximity to railroads experience a variety of lateral loading intensities depending on the live load surcharge. Current design guidelines recommend using the Boussinesq solution for computing lateral loads due to stress influence of the surcharge load. Although this method provides a conservative approach for design of retaining structures, it employs various assumptions that are no longer valid in the cases of non-uniform soil conditions and structures with flexible responses to loading. As a result, a model that captures a closer estimate of soil-structure interaction behavior is desired.
An analytical model derived from beam theory is presented in this thesis. This model implements the method of initial parameters to solve for a beam equation for a 3rd-order distributed load. A program was written in Python to solve for the coefficients in the beam equation using a least squares regression. The inputs for this program are strain measurements to be obtained from a test site, and the outputs are the regression coefficients and stresses associated with the input strains. The motivation behind this approach is to analyze future experimental data for a retaining wall constructed at a test site in proximity to a railroad. Analysis of sample strain values produced a regression curve that closely matched the expected distributions associated with strain values. It was also found that the order of the regression could be adjusted if needed to reduce error of the resulting curves. Ultimately, the model produced in this research can be used for estimating loads on a full-scale test wall.
Advisors/Committee Members: Fry, Gary (advisor), Aubeny, Charles (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: retaining wall; temporary shoring; load distribution; railroad; live load; earth pressure; method of initial parameters
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APA (6th Edition):
Smith, S. J. (2016). Estimating Load Distributions for Retaining Structures Subjected to Railroad Live Loads. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/187353
Chicago Manual of Style (16th Edition):
Smith, Sean Joseph. “Estimating Load Distributions for Retaining Structures Subjected to Railroad Live Loads.” 2016. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/187353.
MLA Handbook (7th Edition):
Smith, Sean Joseph. “Estimating Load Distributions for Retaining Structures Subjected to Railroad Live Loads.” 2016. Web. 08 Mar 2021.
Vancouver:
Smith SJ. Estimating Load Distributions for Retaining Structures Subjected to Railroad Live Loads. [Internet] [Masters thesis]. Texas A&M University; 2016. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/187353.
Council of Science Editors:
Smith SJ. Estimating Load Distributions for Retaining Structures Subjected to Railroad Live Loads. [Masters Thesis]. Texas A&M University; 2016. Available from: http://hdl.handle.net/1969.1/187353
Texas A&M University
8.
Hurley, Samuel J.
Development of a Longitudinal Rail Stress Measurement Device.
Degree: MS, Civil Engineering, 2014, Texas A&M University
URL: http://hdl.handle.net/1969.1/154019
► The continuous welded rails used in most of the United States lack expansion joints of any sort. This leads to a much smoother ride and…
(more)
▼ The continuous welded rails used in most of the United States lack expansion joints of any sort. This leads to a much smoother ride and a longer service life for rails and wheels, but also causes extreme temperatures to induce high stresses in these rails. In very warm conditions these stresses can incite sudden buckling of the rails, which is dangerous and difficult to predict. To alleviate these risks rail stresses need to be regularly monitored, but current practices are slow and labor intensive. This research develops a non-contact prototype apparatus designed to quickly measure longitudinal stress in rails. The measurement is performed by generating a Rayleigh wave along the surface of the web of the rail and analyzing the polarization of the Rayleigh wave some distance further down the rail.
An evaluation of this measurement technique is performed on rails of varying age and surface condition in a lab environment. A set of guidelines is then established to ensure the successful recreation of these results in a field environment. From these guidelines, a 3D model is developed to aid in the construction process. Finally, a prototype is manufactured based on this design.
Advisors/Committee Members: Hurlebaus, Stefan (advisor), Fry, Gary (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: rail stress; longitudinal rail stress; stress measurement; Rayleigh wave; Rayleigh wave polarization
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APA (6th Edition):
Hurley, S. J. (2014). Development of a Longitudinal Rail Stress Measurement Device. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/154019
Chicago Manual of Style (16th Edition):
Hurley, Samuel J. “Development of a Longitudinal Rail Stress Measurement Device.” 2014. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/154019.
MLA Handbook (7th Edition):
Hurley, Samuel J. “Development of a Longitudinal Rail Stress Measurement Device.” 2014. Web. 08 Mar 2021.
Vancouver:
Hurley SJ. Development of a Longitudinal Rail Stress Measurement Device. [Internet] [Masters thesis]. Texas A&M University; 2014. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/154019.
Council of Science Editors:
Hurley SJ. Development of a Longitudinal Rail Stress Measurement Device. [Masters Thesis]. Texas A&M University; 2014. Available from: http://hdl.handle.net/1969.1/154019
Texas A&M University
9.
Martinez, Matthew Aaron.
Passively Actuated Vibration to Decrease Membrane Fouling Rate for Centrifugal Reverse Osmosis.
Degree: MS, Mechanical Engineering, 2018, Texas A&M University
URL: http://hdl.handle.net/1969.1/174056
► A novel method of shaking a CRO membrane was designed. This method, called the Plug and Pipe method, was simulated to determine how well it…
(more)
▼ A novel method of shaking a CRO membrane was designed. This method, called the Plug and
Pipe method, was simulated to determine how well it would work in a full CRO system. This
was done by a series of simulations. First, the geometry was meshed and a CFX simulation was
performed. This would be used to find the water velocity at discrete points along the radial direction
of the orifice. These discrete velocities were then put into a curve fitting program, MATLAB’s
cftool which provided a velocity distribution across the orifice. This velocity distribution was
then integrated and to find the flow requirements and water jet force, Fvjet. Fvjet was found to
depend in large part on the orifice size, while other variations, such as Pipe length and diameter,
had little to no effect. Fvjet varied from 27.13 N to 94.64 N, based on orifice size. This water jet
force was then included in a dynamic model, which was created to describe the nonlinear equation
of motion of the shaker. This dynamic model had two parts. The first was the script into which the
characteristics of the system were put, called osc
model, while the second was the function which
held the nonlinear forcing functions for the water jet and wall interactions. The simulated shaker
was designed based on a test size membrane of 28 kg. It was determined that the shaker would
be capable of providing the proper dynamic characteristics based on previous work, which were a
1mm amplitude of vibration at 20 Hz.
Another model was created to show the amount of mass that could be shaken by a full shaker
based on the orifice size and wall stiffness. The orifice diameter was varied from 0.16 in to 0.5 in,
while the wall stiffness varied from 10
5N=
m to 10
8N=
m. It was found that, as stiffness approached
10
8 N=
m, the amount of mass that could be shaken began to plateau, meaning that this was the
value at which the wall began to act rigidly for this system. The flow requirements were provided
for each orifice size as well, and it was determined that any orifice diameter above 0.25 in would
have excessive flow requirements and would limit a CRO rig’s ability to purify water.
An experimental rig was built based on the specifications set out in the simulations as well. A
high pressure gear pump was used to bring the water up to osmotic pressure, about 800 psi. This
high pressure water went into the shaker. It was intended that once the shaker showed vibration,
adjustments would be made to achieve the 1 mm and 20 Hz vibration set by previous work. Upon
final installation, however, there were misalignment problems between the shaft and the linear
bearings, which prevented the shaker from vibrating at all.
Advisors/Committee Members: Palazzolo, Alan (advisor), Keating, Peter (committee member), Pate, Michael (committee member).
Subjects/Keywords: Vibration; Passive; Design; Centrifugal; Reverse Osmosis
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APA (6th Edition):
Martinez, M. A. (2018). Passively Actuated Vibration to Decrease Membrane Fouling Rate for Centrifugal Reverse Osmosis. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/174056
Chicago Manual of Style (16th Edition):
Martinez, Matthew Aaron. “Passively Actuated Vibration to Decrease Membrane Fouling Rate for Centrifugal Reverse Osmosis.” 2018. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/174056.
MLA Handbook (7th Edition):
Martinez, Matthew Aaron. “Passively Actuated Vibration to Decrease Membrane Fouling Rate for Centrifugal Reverse Osmosis.” 2018. Web. 08 Mar 2021.
Vancouver:
Martinez MA. Passively Actuated Vibration to Decrease Membrane Fouling Rate for Centrifugal Reverse Osmosis. [Internet] [Masters thesis]. Texas A&M University; 2018. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/174056.
Council of Science Editors:
Martinez MA. Passively Actuated Vibration to Decrease Membrane Fouling Rate for Centrifugal Reverse Osmosis. [Masters Thesis]. Texas A&M University; 2018. Available from: http://hdl.handle.net/1969.1/174056
Texas A&M University
10.
Lyons, Kimberly.
Field Measurements for Estimating Impact Loads on Girder Supports for Ferry Ramps.
Degree: MS, Civil Engineering, 2015, Texas A&M University
URL: http://hdl.handle.net/1969.1/155100
► In Port Aransas, TX, movable bridges, ferry ramps, are used to dock ferry boats and load vehicles on and off of the boats to cross…
(more)
▼ In Port Aransas, TX, movable bridges, ferry ramps, are used to dock ferry boats and load vehicles on and off of the boats to cross the Corpus Christie, TX ship channel as part of State Highway 361. Fatigue cracks are present in several of the bearing assemblies that attach the ramps to the headwall at the ferry landing. The cracks were caused by axial forces in the main supporting beams of the ramps. Using strain gage instrumentation applied to the beams, estimates of the axial forces were obtained. A video camera was installed to allow the research team to distinguish between loading events caused by large or small ferry boats. The recorded data from the instrumentation was accessed remotely from
Texas A&
M University in College Station and analyzed using MatLAB, Mathematica, and Microsoft Excel. Load data was collected for several months. The information was used to develop recommendations for design loads to be used when the bearing assemblies are rebuilt. Results indicate that the exterior beams of the ramps experience the largest force values in compression caused by docking and thrusting of the ferry boats. The interior beams experience majority of the tension forces caused by vehicles crossing the ramps. To date, the largest force detected is 102.56 kips in compression.
Advisors/Committee Members: Fry, Gary (advisor), Keating, Peter (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: Impact Loads; Ferry Ramps
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APA (6th Edition):
Lyons, K. (2015). Field Measurements for Estimating Impact Loads on Girder Supports for Ferry Ramps. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/155100
Chicago Manual of Style (16th Edition):
Lyons, Kimberly. “Field Measurements for Estimating Impact Loads on Girder Supports for Ferry Ramps.” 2015. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/155100.
MLA Handbook (7th Edition):
Lyons, Kimberly. “Field Measurements for Estimating Impact Loads on Girder Supports for Ferry Ramps.” 2015. Web. 08 Mar 2021.
Vancouver:
Lyons K. Field Measurements for Estimating Impact Loads on Girder Supports for Ferry Ramps. [Internet] [Masters thesis]. Texas A&M University; 2015. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/155100.
Council of Science Editors:
Lyons K. Field Measurements for Estimating Impact Loads on Girder Supports for Ferry Ramps. [Masters Thesis]. Texas A&M University; 2015. Available from: http://hdl.handle.net/1969.1/155100
Texas A&M University
11.
Soape, Jack.
Investigating the Effects of Corrosion on the Fatigue Life of Welded Steel Attachments.
Degree: MS, Civil Engineering, 2012, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11179
► The railroad industry plays a pivotal role in commerce and greatly impacts America's economy. With this in mind, they cannot afford downtime or service interruptions…
(more)
▼ The railroad industry plays a pivotal role in commerce and greatly impacts America's economy. With this in mind, they cannot afford downtime or service interruptions due to bridge or member replacement. Corrosion of bridges causes millions of dollars each year for the railroad industry in terms of maintenance and inspection. Since a large number of these bridges are steel and their service life is typically governed by fatigue of welded details, it is important to determine the interactions of the corrosion and fatigue mechanisms. While there are differing opinions on the effects of corrosion on the fatigue life of welded steel attachments, the intent of this research is to experimentally investigate the relationship between fatigue and corrosion and determine whether this relationship is beneficial, neutral, or detrimental to the fatigue behavior of welded attachments.
In order to investigate the effects of corrosion on the fatigue life of welded steel attachments, a testing methodology simulating the conditions a bridge could be expected to experience during its service life is established, executed and the results evaluated. Thirty-two specimens were subjected to cycles of corrosion and interval fatigue loading at varying corrosion times and fatigue cycles. These corrosion-fatigue specimens were then compared to the five control (non-corroded) control specimens and three pre-corroded specimens.
The results show that the fatigue life of welded steel attachments is not decreased by the effects of corrosion until more than half of the cross section has been reduced. Specimens subjected to a 'pre-corrosion' period occurring in the absence of fatigue loading, then subjected to cyclic fatigue loading at a later time have drastically reduced fatigue lives.
Advisors/Committee Members: Keating, Peter (advisor), Fry, Gary (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: Corrosion; Fatigue
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APA (6th Edition):
Soape, J. (2012). Investigating the Effects of Corrosion on the Fatigue Life of Welded Steel Attachments. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11179
Chicago Manual of Style (16th Edition):
Soape, Jack. “Investigating the Effects of Corrosion on the Fatigue Life of Welded Steel Attachments.” 2012. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11179.
MLA Handbook (7th Edition):
Soape, Jack. “Investigating the Effects of Corrosion on the Fatigue Life of Welded Steel Attachments.” 2012. Web. 08 Mar 2021.
Vancouver:
Soape J. Investigating the Effects of Corrosion on the Fatigue Life of Welded Steel Attachments. [Internet] [Masters thesis]. Texas A&M University; 2012. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11179.
Council of Science Editors:
Soape J. Investigating the Effects of Corrosion on the Fatigue Life of Welded Steel Attachments. [Masters Thesis]. Texas A&M University; 2012. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11179
Texas A&M University
12.
Klooster, David.
Transient Lift-off Test Results for an Experimental Hybrid Bearing in Air.
Degree: MS, Mechanical Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7444
► A hybrid bearing designed for use in a next generation turbo-pump is evaluated for the performance of initial lift-off, referred to as start-transient. The radial…
(more)
▼ A hybrid bearing designed for use in a next generation turbo-pump is evaluated
for the performance of initial lift-off, referred to as start-transient. The radial test rig
features a high-speed spindle motor capable of 20,000 rpm that drives a 718 Inconel rotor
attached via a high-speed coupling. The drive end is supported by ceramic ball bearings,
while the hybrid bearing supports the opposite end. A magnetic bearing delivers the
applied loading along the mid-span of the rotor. Many parameters, including ramp rate
[rpm/s] (drive torque), supply pressure at 15,000 rpm, magnitude of the applied load, and
load orientation, are varied to simulate different start-transient scenarios. The data are
recorded in .dat files for future evaluation of transient predictions.
Analysis of the data includes an evaluation of hydrodynamic and hydrostatic liftoff,
an assessment of rub from passing through a lightly damped critical speed, and
observation of pneumatic hammer instability. Hydrodynamic lift-off occurs when the
hydrodynamic pressure, resulting from the relative motion of two surfaces, overcomes
the forces acting on the rotor; no indication of hydrodynamic lift-off is provided.
Hydrostatic lift-off results from the external supply pressure (which for this test rig is
speed dependent) overcoming the forces acting on the rotor as determined from rotor
centerline plots. With 0.263 bar applied unit load in the vertical direction, hydrostatic
lift-off occurs at 0 rpm and 2.08 bar supply pressure. With a much higher load of 1.53
bar, hydrostatic lift-off is at 12,337 rpm and 10.7 bar supply pressure.
The required supply pressure for hydrostatic lift-off is approximately a linear
function of the applied unit load. In a turbopump, hydrostatic lift-off depends on the
speed because the supply pressure is proportional to the speed squared. With the load in the horizontal direction, hydrostatic lift-off occurs at lower speeds and pressures. The
ramp rate did not affect the required supply pressure for hydrostatic lift-off. A lower
supply pressure at 15,000 rpm lowered the required supply pressure for hydrostatic liftoff
as well as the natural frequencies creating a rub. The hydrostatic lift-off speed should
be minimized to avoid damage to the rotor/bearing surfaces due to contact.
Advisors/Committee Members: Childs, Dara (advisor), Palazzolo, Alan (committee member), Beason, Lynn (committee member).
Subjects/Keywords: Transient; Lift-off; Hybrid Bearing
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APA (6th Edition):
Klooster, D. (2011). Transient Lift-off Test Results for an Experimental Hybrid Bearing in Air. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7444
Chicago Manual of Style (16th Edition):
Klooster, David. “Transient Lift-off Test Results for an Experimental Hybrid Bearing in Air.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7444.
MLA Handbook (7th Edition):
Klooster, David. “Transient Lift-off Test Results for an Experimental Hybrid Bearing in Air.” 2011. Web. 08 Mar 2021.
Vancouver:
Klooster D. Transient Lift-off Test Results for an Experimental Hybrid Bearing in Air. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7444.
Council of Science Editors:
Klooster D. Transient Lift-off Test Results for an Experimental Hybrid Bearing in Air. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7444
Texas A&M University
13.
Zhang, Xiaohua.
Vibration Isolation of a Locomotive Mounted Energy Storage Flywheel.
Degree: MS, Mechanical Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7528
► Utilizing flywheels to store and reuse energy from regenerative braking on locomotives is a new technology being developed in the Vibration Control and Electromechanics Lab…
(more)
▼ Utilizing flywheels to store and reuse energy from regenerative braking on
locomotives is a new technology being developed in the Vibration Control and
Electromechanics Lab at
Texas A&
M. This thesis focuses on the motion analysis of a
locomotive mounted energy storage flywheel system for a variety of support motion
inputs. Two input cases, sinusoidal floor input and ramp input, are analyzed in different
sections. Simulation results and methods of ensuring the operating success of the
flywheel system are provided at the end of each section.
Section 1 introduces the problem and method being used to study the vibration
under different circumstances. Section 2 analyzes the response of the flywheel system to
sinusoidal floor input given by Ahmadian and Venezia 2000. Natural frequency and
transmissibility of the system are utilized to explain the simulation results carried out in
the frequency domain. It is found that the motion differences between flywheels(rotors)
and magnetic bearings(stators) are guaranteed to be small. Section 3 emulates the
locomotive traversing a bump with 1:150 slope. Simulation shows that catcher(backup)
bearings are needed to limit the vibration of rotors through a bump. It is also found that gyroscopic effect causes problems in vibration isolation. Section 4 explores de-levitation
method and installation of gimbals as possible remedies to this problem. Finally, a
summary of simulation results from different input cases is made.
Advisors/Committee Members: Palazzolo, Alan (advisor), Parlos, Alexander (committee member), Fry, Gary (committee member).
Subjects/Keywords: Vibration isolation; Locomotive; Energy storage flywheel
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Manager
APA (6th Edition):
Zhang, X. (2011). Vibration Isolation of a Locomotive Mounted Energy Storage Flywheel. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7528
Chicago Manual of Style (16th Edition):
Zhang, Xiaohua. “Vibration Isolation of a Locomotive Mounted Energy Storage Flywheel.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7528.
MLA Handbook (7th Edition):
Zhang, Xiaohua. “Vibration Isolation of a Locomotive Mounted Energy Storage Flywheel.” 2011. Web. 08 Mar 2021.
Vancouver:
Zhang X. Vibration Isolation of a Locomotive Mounted Energy Storage Flywheel. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7528.
Council of Science Editors:
Zhang X. Vibration Isolation of a Locomotive Mounted Energy Storage Flywheel. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2009-12-7528
Texas A&M University
14.
Martinez, Melissa Marisol.
Using Vehicle Dynamics Simulation and Metamodels to Evaluate Factors and Mechanisms Affecting Roll Angle: An Initial Assessment.
Degree: MS, Civil Engineering, 2018, Texas A&M University
URL: http://hdl.handle.net/1969.1/188887
► A rollover is defined as any vehicle rotation of 90 degrees or more about a longitudinal or lateral axis, according to NASS CDS. Rollover crashes…
(more)
▼ A rollover is defined as any vehicle rotation of 90 degrees or more about a longitudinal or
lateral axis, according to NASS CDS. Rollover crashes are still represented highly in terms of
frequency and fatalities when compared to other crash categories. Even though there are various
vehicular technical innovations that act as a preventative or protective improvement, rollover
crashes and subsequent loss of life and injuries are still prevalent in crash statistics. In 2015,
rollovers represented 33% of occupant fatalities. Existing research on rollover as it relates to
highway safety is often based on crash data analysis. Limited studies have investigated the
initiating mechanisms contributing to vehicular propensity to rollover. Hence, there is a gap in
knowledge to understand initiation factors that affect rollover events. Herein, vehicle dynamics
simulations will be utilized to examine several vehicle rollover crash scenarios.
A second aspect of this research is to develop a metamodel of vehicle roll angle as a function of
initiation/influencing factors. A total of 282 vehicle rollover scenarios were created and data
from the simulations was used to build metamodels. The vehicle rollover scenarios were split up
into 16 categories. The surface metamodel, accuracy model, and global sensitivities were
analyzed. These models show that for all the categories, speed had the greatest influence on the
vehicle’s propensity to roll over. Friction held a greater influence on the deviation from the
centerline of the right lane.
Advisors/Committee Members: Fry, Gary (advisor), Gharaibeh, Nasir (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: Vehicle dynamics simulations; metamodels; rollover
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APA (6th Edition):
Martinez, M. M. (2018). Using Vehicle Dynamics Simulation and Metamodels to Evaluate Factors and Mechanisms Affecting Roll Angle: An Initial Assessment. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/188887
Chicago Manual of Style (16th Edition):
Martinez, Melissa Marisol. “Using Vehicle Dynamics Simulation and Metamodels to Evaluate Factors and Mechanisms Affecting Roll Angle: An Initial Assessment.” 2018. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/188887.
MLA Handbook (7th Edition):
Martinez, Melissa Marisol. “Using Vehicle Dynamics Simulation and Metamodels to Evaluate Factors and Mechanisms Affecting Roll Angle: An Initial Assessment.” 2018. Web. 08 Mar 2021.
Vancouver:
Martinez MM. Using Vehicle Dynamics Simulation and Metamodels to Evaluate Factors and Mechanisms Affecting Roll Angle: An Initial Assessment. [Internet] [Masters thesis]. Texas A&M University; 2018. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/188887.
Council of Science Editors:
Martinez MM. Using Vehicle Dynamics Simulation and Metamodels to Evaluate Factors and Mechanisms Affecting Roll Angle: An Initial Assessment. [Masters Thesis]. Texas A&M University; 2018. Available from: http://hdl.handle.net/1969.1/188887
Texas A&M University
15.
Mishra, Sahil Rajesh.
Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.
Degree: MS, Mechanical Engineering, 2020, Texas A&M University
URL: http://hdl.handle.net/1969.1/192571
► Torsional vibrations in rotating machinery are crucial in determining the reliability of the machinery during operation. These vibrations can be induced by constant frequency and…
(more)
▼ Torsional vibrations in rotating machinery are crucial in determining the reliability of the machinery during operation. These vibrations can be induced by constant frequency and constant amplitude excitations in steady-state or by a motor drive in transient operation. In both the cases, it is essential to determine the torsional vibration response of the machinery and perform a fatigue life analysis of its components. Due to the complexity of rotating machinery, torsional vibration analysis is usually performed with the help of a numerical software. This thesis uses VFD Software, an in-house coupled electrical-mechanical system solver, to analyze torsional vibrations in steady-state and transient operation of Variable Frequency Drive (VFD) induction motor incorporated rotating machinery.
VFD Software uses complex variable approach to determine the torsional vibration response. Fatigue life is determined using the stress-based life approach with rainflow counting. The developed steady-state vibration response and life prediction code in VFD Software is benchmarked against XLRotor, a commercial rotordynamic analysis software, by comparing the results for natural frequencies, mode shapes, absolute and relative displacement, transmitted torque and shear stresses.
The electromagnetic torque provided by a VFD induction motor system has a rich harmonic spectrum due to pulse width modulation (PWM) switching of the current and voltage. These torque harmonics may cause resonant vibrations should the torque harmonic frequencies occur near the natural frequency of the system. VFD Software is used to simulate the motor-compressor train installed at Southwest Research Institute (SwRI) to experimentally verify their observation of severe
38 Hz resonant torsional vibrations in the open-loop Volts-hertz (V/Hz) operation of the VFD. The open-loop V/Hz simulation of the SwRI system show that the torsional vibrations can be reduced by increasing the coupling stiffness to more than two times their model value. Also, the SwRI simulations show a strong dependency of the amplitude and frequency of the electromagnetic torque harmonics with the damping and torsional natural frequency. Direct Torque Control (DTC) is implemented to reduce the torsional vibrations to further validate the SwRI experimental observation of reduction in torsional vibrations in closed-loop feedback control.
An in-house VFD test-rig is proposed for benchmarking the VFD Software’s coupled electrical-mechanical solver by experimentally measuring the amplitude and frequency of the dynamic torque and torsional vibrations in the system and correlating the results with the VFD Software’s predictions. A preliminary analysis is performed to ensure that the dynamic torque and torsional vibrations are within the operating range of the sensing apparatus.
Advisors/Committee Members: Palazzolo, Alan (advisor), Kim, Won-jong (advisor), Toliyat, Hamid (committee member).
Subjects/Keywords: Torsional Vibrations; VFD; Induction Motor; Electric Motors; V/Hz; V/f; Volts-Hertz; Open-loop Control; Closed-loop Control; Rotating Machinery; Compressors; Rotordynamics; Fatigue Life; Rainflow Counting; PWM
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APA ·
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CSE |
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APA (6th Edition):
Mishra, S. R. (2020). Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/192571
Chicago Manual of Style (16th Edition):
Mishra, Sahil Rajesh. “Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.” 2020. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/192571.
MLA Handbook (7th Edition):
Mishra, Sahil Rajesh. “Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.” 2020. Web. 08 Mar 2021.
Vancouver:
Mishra SR. Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. [Internet] [Masters thesis]. Texas A&M University; 2020. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/192571.
Council of Science Editors:
Mishra SR. Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. [Masters Thesis]. Texas A&M University; 2020. Available from: http://hdl.handle.net/1969.1/192571
Texas A&M University
16.
Mishra, Sahil Rajesh.
Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.
Degree: MS, Mechanical Engineering, 2020, Texas A&M University
URL: http://hdl.handle.net/1969.1/192573
► Torsional vibrations in rotating machinery are crucial in determining the reliability of the machinery during operation. These vibrations can be induced by constant frequency and…
(more)
▼ Torsional vibrations in rotating machinery are crucial in determining the reliability of the machinery during operation. These vibrations can be induced by constant frequency and constant amplitude excitations in steady-state or by a motor drive in transient operation. In both the cases, it is essential to determine the torsional vibration response of the machinery and perform a fatigue life analysis of its components. Due to the complexity of rotating machinery, torsional vibration analysis is usually performed with the help of a numerical software. This thesis uses VFD Software, an in-house coupled electrical-mechanical system solver, to analyze torsional vibrations in steady-state and transient operation of Variable Frequency Drive (VFD) induction motor incorporated rotating machinery.
VFD Software uses complex variable approach to determine the torsional vibration response. Fatigue life is determined using the stress-based life approach with rainflow counting. The developed steady-state vibration response and life prediction code in VFD Software is benchmarked against XLRotor, a commercial rotordynamic analysis software, by comparing the results for natural frequencies, mode shapes, absolute and relative displacement, transmitted torque and shear stresses.
The electromagnetic torque provided by a VFD induction motor system has a rich harmonic spectrum due to pulse width modulation (PWM) switching of the current and voltage. These torque harmonics may cause resonant vibrations should the torque harmonic frequencies occur near the natural frequency of the system. VFD Software is used to simulate the motor-compressor train installed at Southwest Research Institute (SwRI) to experimentally verify their observation of severe
38 Hz resonant torsional vibrations in the open-loop Volts-hertz (V/Hz) operation of the VFD. The open-loop V/Hz simulation of the SwRI system show that the torsional vibrations can be reduced by increasing the coupling stiffness to more than two times their model value. Also, the SwRI simulations show a strong dependency of the amplitude and frequency of the electromagnetic torque harmonics with the damping and torsional natural frequency. Direct Torque Control (DTC) is implemented to reduce the torsional vibrations to further validate the SwRI experimental observation of reduction in torsional vibrations in closed-loop feedback control.
An in-house VFD test-rig is proposed for benchmarking the VFD Software’s coupled electrical-mechanical solver by experimentally measuring the amplitude and frequency of the dynamic torque and torsional vibrations in the system and correlating the results with the VFD Software’s predictions. A preliminary analysis is performed to ensure that the dynamic torque and torsional vibrations are within the operating range of the sensing apparatus.
Advisors/Committee Members: Palazzolo, Alan (advisor), Kim, Won-jong (advisor), Toliyat, Hamid (committee member).
Subjects/Keywords: Torsional Vibrations; VFD; Induction Motor; Electric Motors; V/Hz; V/f; Volts-Hertz; Open-loop Control; Closed-loop Control; Rotating Machinery; Compressors; Rotordynamics; Fatigue Life; Rainflow Counting; PWM
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Manager
APA (6th Edition):
Mishra, S. R. (2020). Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/192573
Chicago Manual of Style (16th Edition):
Mishra, Sahil Rajesh. “Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.” 2020. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/192573.
MLA Handbook (7th Edition):
Mishra, Sahil Rajesh. “Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.” 2020. Web. 08 Mar 2021.
Vancouver:
Mishra SR. Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. [Internet] [Masters thesis]. Texas A&M University; 2020. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/192573.
Council of Science Editors:
Mishra SR. Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. [Masters Thesis]. Texas A&M University; 2020. Available from: http://hdl.handle.net/1969.1/192573
Texas A&M University
17.
Mishra, Sahil Rajesh.
Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.
Degree: MS, Mechanical Engineering, 2020, Texas A&M University
URL: http://hdl.handle.net/1969.1/192572
► Torsional vibrations in rotating machinery are crucial in determining the reliability of the machinery during operation. These vibrations can be induced by constant frequency and…
(more)
▼ Torsional vibrations in rotating machinery are crucial in determining the reliability of the machinery during operation. These vibrations can be induced by constant frequency and constant amplitude excitations in steady-state or by a motor drive in transient operation. In both the cases, it is essential to determine the torsional vibration response of the machinery and perform a fatigue life analysis of its components. Due to the complexity of rotating machinery, torsional vibration analysis is usually performed with the help of a numerical software. This thesis uses VFD Software, an in-house coupled electrical-mechanical system solver, to analyze torsional vibrations in steady-state and transient operation of Variable Frequency Drive (VFD) induction motor incorporated rotating machinery.
VFD Software uses complex variable approach to determine the torsional vibration response. Fatigue life is determined using the stress-based life approach with rainflow counting. The developed steady-state vibration response and life prediction code in VFD Software is benchmarked against XLRotor, a commercial rotordynamic analysis software, by comparing the results for natural frequencies, mode shapes, absolute and relative displacement, transmitted torque and shear stresses.
The electromagnetic torque provided by a VFD induction motor system has a rich harmonic spectrum due to pulse width modulation (PWM) switching of the current and voltage. These torque harmonics may cause resonant vibrations should the torque harmonic frequencies occur near the natural frequency of the system. VFD Software is used to simulate the motor-compressor train installed at Southwest Research Institute (SwRI) to experimentally verify their observation of severe
38 Hz resonant torsional vibrations in the open-loop Volts-hertz (V/Hz) operation of the VFD. The open-loop V/Hz simulation of the SwRI system show that the torsional vibrations can be reduced by increasing the coupling stiffness to more than two times their model value. Also, the SwRI simulations show a strong dependency of the amplitude and frequency of the electromagnetic torque harmonics with the damping and torsional natural frequency. Direct Torque Control (DTC) is implemented to reduce the torsional vibrations to further validate the SwRI experimental observation of reduction in torsional vibrations in closed-loop feedback control.
An in-house VFD test-rig is proposed for benchmarking the VFD Software’s coupled electrical-mechanical solver by experimentally measuring the amplitude and frequency of the dynamic torque and torsional vibrations in the system and correlating the results with the VFD Software’s predictions. A preliminary analysis is performed to ensure that the dynamic torque and torsional vibrations are within the operating range of the sensing apparatus.
Advisors/Committee Members: Palazzolo, Alan (advisor), Kim, Won-jong (advisor), Toliyat, Hamid (committee member).
Subjects/Keywords: Torsional Vibrations; VFD; Induction Motor; Electric Motors; V/Hz; V/f; Volts-Hertz; Open-loop Control; Closed-loop Control; Rotating Machinery; Compressors; Rotordynamics; Fatigue Life; Rainflow Counting; PWM
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APA (6th Edition):
Mishra, S. R. (2020). Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/192572
Chicago Manual of Style (16th Edition):
Mishra, Sahil Rajesh. “Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.” 2020. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/192572.
MLA Handbook (7th Edition):
Mishra, Sahil Rajesh. “Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery.” 2020. Web. 08 Mar 2021.
Vancouver:
Mishra SR. Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. [Internet] [Masters thesis]. Texas A&M University; 2020. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/192572.
Council of Science Editors:
Mishra SR. Torsional Vibrations in Variable Frequency Drive Induction Motor Driven Machinery. [Masters Thesis]. Texas A&M University; 2020. Available from: http://hdl.handle.net/1969.1/192572
Texas A&M University
18.
Jeung, Sung Hwa.
Performance of an Open Ends Squeeze Film Damper Operating with Large Amplitude Orbital Motions: Experimental Analysis and Assessment of the Accuracy of the Linearized Force Coefficients Model.
Degree: MS, Mechanical Engineering, 2013, Texas A&M University
URL: http://hdl.handle.net/1969.1/151648
► Squeeze Film Dampers (SFDs) aid to suppress rotor vibrations and enhance the stability of high-speed rotor-bearing systems. A SFD is a simple oil lubricated film…
(more)
▼ Squeeze Film Dampers (SFDs) aid to suppress rotor vibrations and enhance the stability of high-speed rotor-bearing systems. A SFD is a simple oil lubricated film between a stationary housing and a precessing (whirling) journal. Aircraft engines use SFDs as the only means to provide damping to otherwise rigid ball bearing supports. This thesis presents experimental results for the dynamic forced performance of a test open ends SFD operating with large amplitude whirl motions, centered and off centered within the bearing clearance. The test rig comprises of an elastically supported bearing with a damper section having two parallel film lands separated by a feed groove. A film land is 25.4 mm long, with diameter 127 mm and nominal radial clearance c=0.251 mm. Two orthogonally placed shakers apply dynamic loads on the bearing to induce circular orbit motions at prescribed whirl frequencies. A static loader, 45˚ away from each shaker, pulls the bearing to a static eccentric position.
Circular orbit tests were performed (10 – 100 Hz frequency range) for eight increasing orbit amplitudes (r=0.08c to ~0.71c) and under four static eccentricities (es=0.0c to ~0.76c). An identification method estimates the test damper force coefficients from transfer functions in the frequency domain. The analysis shows that the SFD damping force coefficients increase with the static eccentricity (es) increase. On the other hand, the damper inertia coefficients decrease as the orbit amplitude (r) becomes large and also increase modestly with the static eccentricity (es). Predictions from a physical model show good agreement with the test dynamic force coefficients.
The accuracy of the linearized SFD force coefficients (K, C,
M)SFD is evaluated from comparing the differences in mechanical work performed by actual and linear SFD reaction forces. The difference in mechanical work (Ediff) increases with increasing static eccentricity (es) and orbit amplitude (r). However, for most test conditions (r/c≤0.4,es/c≤0.25), Ediff is less than ~5%, thus showing the linearized SFD force coefficients represent well the forced response of the actual test SFD system.
The test and predicted force coefficients as well as the analysis of the pressure fields contribute to a better understanding of the kinetics of SFDs operating with moderate tolarge amplitude size whirl motions, centered and off-centered.
Advisors/Committee Members: San Andrés, Luis (advisor), Palazzolo, Alan (committee member), Hurlebaus, Stefan (committee member).
Subjects/Keywords: Squeeze Film Damper; Rotordynamics; Aircraft engine
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APA (6th Edition):
Jeung, S. H. (2013). Performance of an Open Ends Squeeze Film Damper Operating with Large Amplitude Orbital Motions: Experimental Analysis and Assessment of the Accuracy of the Linearized Force Coefficients Model. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/151648
Chicago Manual of Style (16th Edition):
Jeung, Sung Hwa. “Performance of an Open Ends Squeeze Film Damper Operating with Large Amplitude Orbital Motions: Experimental Analysis and Assessment of the Accuracy of the Linearized Force Coefficients Model.” 2013. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/151648.
MLA Handbook (7th Edition):
Jeung, Sung Hwa. “Performance of an Open Ends Squeeze Film Damper Operating with Large Amplitude Orbital Motions: Experimental Analysis and Assessment of the Accuracy of the Linearized Force Coefficients Model.” 2013. Web. 08 Mar 2021.
Vancouver:
Jeung SH. Performance of an Open Ends Squeeze Film Damper Operating with Large Amplitude Orbital Motions: Experimental Analysis and Assessment of the Accuracy of the Linearized Force Coefficients Model. [Internet] [Masters thesis]. Texas A&M University; 2013. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/151648.
Council of Science Editors:
Jeung SH. Performance of an Open Ends Squeeze Film Damper Operating with Large Amplitude Orbital Motions: Experimental Analysis and Assessment of the Accuracy of the Linearized Force Coefficients Model. [Masters Thesis]. Texas A&M University; 2013. Available from: http://hdl.handle.net/1969.1/151648
Texas A&M University
19.
Zhang, Xiaohua.
Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development.
Degree: PhD, Mechanical Engineering, 2014, Texas A&M University
URL: http://hdl.handle.net/1969.1/174186
► Following U.S. Army’s single fuel initiative, Wankel rotary engines used in U.S. Army’s shadow unmanned aerial vehicles (UAVs) need to be retrofitted from running on…
(more)
▼ Following U.S. Army’s single fuel initiative, Wankel rotary engines used in U.S. Army’s shadow unmanned aerial vehicles (UAVs) need to be retrofitted from running on aviation gasoline (AVGAS) to JP-8. The feasibility of retrofitting the engine with a flash vapor direct fuel injector was investigated. A commercial off-the-shelf direct fuel injector was used in the study. A photo detector measurement tool was developed to measure high frequency (>100 Hz) injection event. A coupled electrical-electomagnetics-fluid-mechanical system was simulated to understand the pintle dynamics during an injection event. Optimal injector power drive was revealed to be a multi-stage current profile. A flash heater was designed and tested to be capable of heating up JP-8 from room temperature to its vaporization temperature (>310F) under one tenth of a second at the required flow rate. An ignition test rig was built to compare ignition behavior between AVGAS and heated JP-8. Test result showed that the 550F pre-heated JP-8 had equal or superior ignition pressure rise / ignition delay time than AVGAS.
Advisors/Committee Members: Palazzolo, Alan (advisor), Kim, Won-jong (committee member), Petersen, Eric (committee member), Toliyat, Hamid (committee member).
Subjects/Keywords: fuel injector; flash heating; JP-8; Wankel rotary engine; multi-physics modeling; spray measurement; ignition test
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APA (6th Edition):
Zhang, X. (2014). Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/174186
Chicago Manual of Style (16th Edition):
Zhang, Xiaohua. “Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development.” 2014. Doctoral Dissertation, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/174186.
MLA Handbook (7th Edition):
Zhang, Xiaohua. “Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development.” 2014. Web. 08 Mar 2021.
Vancouver:
Zhang X. Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development. [Internet] [Doctoral dissertation]. Texas A&M University; 2014. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/174186.
Council of Science Editors:
Zhang X. Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development. [Doctoral Dissertation]. Texas A&M University; 2014. Available from: http://hdl.handle.net/1969.1/174186
Texas A&M University
20.
Kim, Eunseok.
CFD Based Prediction of Rotordynamic Coefficients and Stability Analysis for Centrifugal Pump/Compressor.
Degree: PhD, Mechanical Engineering, 2016, Texas A&M University
URL: http://hdl.handle.net/1969.1/158951
► Fluid forces acting on the shrouded centrifugal pump/compressor impellers are evaluated using the computational fluid dynamics (CFD) approach. A face-seal impeller is selected to study…
(more)
▼ Fluid forces acting on the shrouded centrifugal pump/compressor impellers are evaluated using the computational fluid dynamics (CFD) approach. A face-seal impeller is selected to study for predicting the rotordynamic coefficients of the whirling impeller. The resultant impedances of the face-seal impeller can be modeled as a quadratic polynomial of whirling frequency to calculate the rotordynamic coefficients. However, the impedances of a conventional wear-ring seal impeller have some inflection points in the curves. Some possible sources that can affect the fluctuating impedance curves are investigated by varying design parameters such as shape of leakage path, inlet tangential velocity, flow rate of primary passage, and seal clearance. Effects of the peaks in the impedance curves of the wear-ring seal impeller are evaluated by performing stability analysis of a rotordynamic finite element (FE) model with the unconventional impedances. A linear curve-fit algorithm is developed to identify the complex shape of impedance curves of the wear-ring seal impeller. A Jeffcott rotor model with the impeller forces is modeled to apply and validate the developed curve-fit algorithm and the stability analysis has been performed. The analysis results indicate that the bump and dip in the impedance curves destabilize the Jeffcott rotor.
Precessing motion of the shrouded centrifugal impeller is also an important vibration source that can cause the rotordynamic instability problem. By considering the tilted impeller, the reaction force and moment coefficients of the face-seal impeller are predicted utilizing CFD technique, and a full set of the rotordynamic coefficient matrices (4x4) is calculated. In order to evaluate the coupled motion of whirling and precessing for the face-seal impeller, a 3D impeller model with the dynamic eccentricity and the tilting angle is generated and the corresponding rotordynamic coefficients are obtained. The calculated results indicate that the precessing motion increases the tendency towards destabilization of the rotor.
Lastly, influence of static eccentricity on the face-seal impeller is investigated. In actual operation of the rotor, misalignment may be destabilizing and cause serious vibration problems. A CFD modeling approach is developed to evaluate the forces for the statically eccentric face-seal impeller, and it has been found that the presence of static eccentricity on the face-seal impeller has an adverse effect on rotordynamic stability.
Advisors/Committee Members: Palazzolo, Alan (advisor), Childs, Dara (committee member), Handler, Robert (committee member), Chen, Hamn-Ching (committee member).
Subjects/Keywords: Rotordynamics; Vibration; CFD; FEA; Impeller; Seal
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APA (6th Edition):
Kim, E. (2016). CFD Based Prediction of Rotordynamic Coefficients and Stability Analysis for Centrifugal Pump/Compressor. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/158951
Chicago Manual of Style (16th Edition):
Kim, Eunseok. “CFD Based Prediction of Rotordynamic Coefficients and Stability Analysis for Centrifugal Pump/Compressor.” 2016. Doctoral Dissertation, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/158951.
MLA Handbook (7th Edition):
Kim, Eunseok. “CFD Based Prediction of Rotordynamic Coefficients and Stability Analysis for Centrifugal Pump/Compressor.” 2016. Web. 08 Mar 2021.
Vancouver:
Kim E. CFD Based Prediction of Rotordynamic Coefficients and Stability Analysis for Centrifugal Pump/Compressor. [Internet] [Doctoral dissertation]. Texas A&M University; 2016. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/158951.
Council of Science Editors:
Kim E. CFD Based Prediction of Rotordynamic Coefficients and Stability Analysis for Centrifugal Pump/Compressor. [Doctoral Dissertation]. Texas A&M University; 2016. Available from: http://hdl.handle.net/1969.1/158951
Texas A&M University
21.
Zhai, Tianbo.
Prediction of Coupling Guard Temperature and Gearbox Windage Power Loss.
Degree: MS, Mechanical Engineering, 2016, Texas A&M University
URL: http://hdl.handle.net/1969.1/158983
► Gear Windage Power Loss (WPL) is due to fluid drag experienced by a gear when it is rotating in air or an air-oil mist. Gear…
(more)
▼ Gear Windage Power Loss (WPL) is due to fluid drag experienced by a gear when it is rotating in air or an air-oil mist. Gear WPL becomes significant and shall not be neglected in high speed applications. The temperature on coupling guard needs to comply with industry standards and is influenced by windage affect. There is practical significance in predicting coupling guard temperature and gearbox WPL.
Simulation models were built and results were obtained from Computational Fluid Dynamics (CFD) solvers. The simulation results were validated by experimental data from the literature. A case study was also conducted to further validate the predictability of coupling guard temperature. Simulation experiments were designed and data generated to obtain Multivariable Regression Formulas (MRF) for gear WPL and guard temperature prediction.
A comparison between CFD prediction of gear WPL and experimental results showed a relative error less than 12%. In the case study, the percentage difference between predicted guard temperature and test data was within 5%. For the given ranges of input parameters, MRF gave a better prediction than the empirical formula used in industry.
The proposed MRF was accurate for coupling guards and gears that were not included in the CFD modeled systems, which were used to generate the data for obtaining the MRF. The prediction expressions also helped in the product design stage to mitigate gearbox WPL and coupling guard temperature.
Advisors/Committee Members: Palazzolo, Alan (advisor), Han, Je-Chin (committee member), Chen, Hamn-Ching (committee member).
Subjects/Keywords: windage power loss; coupling guard heating; regression formula
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APA (6th Edition):
Zhai, T. (2016). Prediction of Coupling Guard Temperature and Gearbox Windage Power Loss. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/158983
Chicago Manual of Style (16th Edition):
Zhai, Tianbo. “Prediction of Coupling Guard Temperature and Gearbox Windage Power Loss.” 2016. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/158983.
MLA Handbook (7th Edition):
Zhai, Tianbo. “Prediction of Coupling Guard Temperature and Gearbox Windage Power Loss.” 2016. Web. 08 Mar 2021.
Vancouver:
Zhai T. Prediction of Coupling Guard Temperature and Gearbox Windage Power Loss. [Internet] [Masters thesis]. Texas A&M University; 2016. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/158983.
Council of Science Editors:
Zhai T. Prediction of Coupling Guard Temperature and Gearbox Windage Power Loss. [Masters Thesis]. Texas A&M University; 2016. Available from: http://hdl.handle.net/1969.1/158983
Texas A&M University
22.
Narayanaswamy, Ashwanth.
Study of Catcher Bearings for High Temperature Magnetic Bearing Application.
Degree: MS, Mechanical Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9509
► The Electron Energy Corporation (EEC) along with National Aeronautics and Space Administration (NASA) in collaboration with Vibration Control and Electro mechanics Lab (VCEL), Texas A…
(more)
▼ The Electron Energy Corporation (EEC) along with National Aeronautics and Space Administration (NASA) in collaboration with Vibration Control and Electro mechanics Lab (VCEL),
Texas A &
M University, College Station, TX are researching on high temperature permanent magnet based magnetic bearings.
The magnetic bearings are made of high temperature resistant permanent magnets (up to 1000 degrees F). A test rig has been developed to test these magnetic bearings. The test rig mainly consists of two radial bearings, one axial thrust bearing and two catcher bearings. The test rig that the catcher bearing is inserted in is the first ultra-high temperature rig with permanent magnet biased magnetic bearings and motor. The magnetic bearings are permanent magnet based which is a novel concept. The Graphalloy bearings represent a new approach for ultra-high temperature backup bearing applications.
One of the main objectives of this research is to insure the mechanical and electrical integrity for all components of the test rig. Some assemblies and accessories required for the whole assembly need to be designed. The assembly methods need to be designed. The preliminary tests for coefficient of friction, Young's modulus and thermal expansion characteristics for catcher bearing material need to be done. A dynamic model needs to be designed for studying and simulating the rotor drop of the shaft onto the catcher bearing using a finite element approach in MATLAB.
The assembly of the test rig was completed successfully by developing assembly fixtures and assembly methods. The components of the test rig were tested before assembly. Other necessary systems like Sensor holder system, Graphalloy press fit system were designed, fabricated and tested. The catcher bearing material (Graphalloy) was tested for coefficient of friction and Young's modulus at room and high temperatures. The rotor drop was simulated by deriving a dynamic model, to study the effect of system parameters like clearance, coefficient of friction, negative stiffness, initial spin speed on system behavior.
Increasing the friction increases the backward whirl and decreases the rotor stoppage time. Increasing the clearance reduces the stoppage time and increases the peak bearing force. Increasing the initial spin speed increases the rotor stoppage time. The maximum stress encountered for as built conditions is more than allowable limits.
Advisors/Committee Members: Palazzolo, Alan B. (advisor), Gaukler, Gary M. (committee member), Lau, Sai C. (committee member).
Subjects/Keywords: magnetic bearings; catcher bearings; rotor drop; negative stiffness
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APA (6th Edition):
Narayanaswamy, A. (2011). Study of Catcher Bearings for High Temperature Magnetic Bearing Application. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9509
Chicago Manual of Style (16th Edition):
Narayanaswamy, Ashwanth. “Study of Catcher Bearings for High Temperature Magnetic Bearing Application.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9509.
MLA Handbook (7th Edition):
Narayanaswamy, Ashwanth. “Study of Catcher Bearings for High Temperature Magnetic Bearing Application.” 2011. Web. 08 Mar 2021.
Vancouver:
Narayanaswamy A. Study of Catcher Bearings for High Temperature Magnetic Bearing Application. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9509.
Council of Science Editors:
Narayanaswamy A. Study of Catcher Bearings for High Temperature Magnetic Bearing Application. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9509
Texas A&M University
23.
Wadhvani, Vishal Ashok.
Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing System.
Degree: MS, Mechanical Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9477
► Magnetic bearings are increasingly being used in a wide variety of applications in the industry such as compressors, turbines, motors, generators etc. Also, there are…
(more)
▼ Magnetic bearings are increasingly being used in a wide variety of applications in the industry such as compressors, turbines, motors, generators etc. Also, there are different types available depending upon their construction. The research presented here investigates a high temperature permanent magnet biased magnetic bearing system which is jointly being researched by National Aeronautics and Space Administration (NASA) and Electron Energy Corporation (EEC). The purpose of this research was to develop a permanent magnet biased magnetic bearing system using high temperature (HT) permanent magnets (PM) developed by EEC. This system was designed for high performance, high temperature (1000F) and high speed applications. The entire system consisted of two radial bearings, two catcher bearings, one axial thrust bearing and a motor. The central rotor shaft is powered by a high temperature permanent magnet motor to be able to run at the designed conditions of 20,000 rpm. This thesis documents the design of a feedback control law that stabilizes this HTPM biased AMB levitated system and summarizes efforts to build a test rig for the HT tests of the machine. A decentralized PD control law is used to achieve successful levitation. An existing PD analog controller with single input single output (SISO) control law for each axis (previously used for a flywheel test rig) is used as a feedback controller for this HTPM magnetic bearing system. Modeling and simulation of the resulting closed loop system is done in Matlab to test for stability and an iterative approach leads to optimum values of proportional and derivative gain pairs. The notch filter locations are also determined through this closed loop iterative simulation.
Advisors/Committee Members: Palazzolo, Alan B. (advisor), Rasmussen, Bryan P. (committee member), Abu Al-Rub, Rashid K. (committee member).
Subjects/Keywords: Permanent Magnet Biased; Fault Tolerant; Homopolar
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APA (6th Edition):
Wadhvani, V. A. (2011). Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing System. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9477
Chicago Manual of Style (16th Edition):
Wadhvani, Vishal Ashok. “Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing System.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9477.
MLA Handbook (7th Edition):
Wadhvani, Vishal Ashok. “Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing System.” 2011. Web. 08 Mar 2021.
Vancouver:
Wadhvani VA. Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing System. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9477.
Council of Science Editors:
Wadhvani VA. Feedback Control of a Permanent Magnet Biased, Homopolar Magnetic Bearing System. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9477
Texas A&M University
24.
Stancliffe, Devin Aldin.
Analysis and Design of a Test Apparatus for Resolving Near-Field Effects Associated With Using a Coarse Sun Sensor as Part of a 6-DOF Solution.
Degree: MS, Aerospace Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8440
► Though the Aerospace industry is moving towards small satellites and smaller sensor technologies, sensors used for close-proximity operations are generally cost (and often size and…
(more)
▼ Though the Aerospace industry is moving towards small satellites and smaller sensor technologies, sensors used for close-proximity operations are generally cost (and often size and power) prohibitive for
University-class satellites. Given the need for low-cost, low-mass solutions for close-proximity relative navigation sensors, this research analyzed the expected errors due to near-field effects using a coarse sun sensor as part of a 6-degree-of-freedom (6-dof) solution. To characterize these near-field effects, a test bed (Characterization Test Apparatus or CTA) was proposed, its design presented, and the design stage uncertainty analysis of the CTA performed. A candidate coarse sun sensor (NorthStarTM) was chosen for testing, and a mathematical model of the sensor’s functionality was derived. Using a Gaussian Least Squares Differential Correction (GLSDC) algorithm, the model parameters were estimated and a comparison between simulated NorthStarTM measurements and model estimates was performed. Results indicate the CTA is capable of resolving the near-field errors. Additionally, this research found no apparent show stoppers for using coarse sun sensors for 6-dof solutions.
Advisors/Committee Members: Reed, Helen L. (advisor), Hurtado, John E. (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: Coarse sun sensors; 6-dof; near-field effects; NorthStar; close-proximity; autonomous rendezvous and docking
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APA (6th Edition):
Stancliffe, D. A. (2011). Analysis and Design of a Test Apparatus for Resolving Near-Field Effects Associated With Using a Coarse Sun Sensor as Part of a 6-DOF Solution. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8440
Chicago Manual of Style (16th Edition):
Stancliffe, Devin Aldin. “Analysis and Design of a Test Apparatus for Resolving Near-Field Effects Associated With Using a Coarse Sun Sensor as Part of a 6-DOF Solution.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8440.
MLA Handbook (7th Edition):
Stancliffe, Devin Aldin. “Analysis and Design of a Test Apparatus for Resolving Near-Field Effects Associated With Using a Coarse Sun Sensor as Part of a 6-DOF Solution.” 2011. Web. 08 Mar 2021.
Vancouver:
Stancliffe DA. Analysis and Design of a Test Apparatus for Resolving Near-Field Effects Associated With Using a Coarse Sun Sensor as Part of a 6-DOF Solution. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8440.
Council of Science Editors:
Stancliffe DA. Analysis and Design of a Test Apparatus for Resolving Near-Field Effects Associated With Using a Coarse Sun Sensor as Part of a 6-DOF Solution. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8440
Texas A&M University
25.
Kumar, Dhruv Dileep.
Backward Precessional Whip and Whirl for a Two Point Rubbing Contact Model of a Rigid Rotor Supported by an Elastically Supported Rigid Stator.
Degree: MS, Mechanical Engineering, 2011, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8451
► The present work investigates the phenomena of whip and whirl for a rigid rotor contacting at two bearing locations. The idea originated from an anemometer…
(more)
▼ The present work investigates the phenomena of whip and whirl for a rigid rotor contacting at two bearing locations. The idea originated from an anemometer consisting of a rotor with an elastically supported stator undergoing the phenomena of dry friction whip and whirl at the two bushing contacts. To analyze the behavior, a mathematical model similar to the anemometer is developed and analyzed assuming two possible solutions, Mode1 (normal reaction forces in phase at two contacts) and Mode 2 (normal reaction forces out of phase at two contacts). Analytical solutions are only possible for the models with same RCl (Radius to Clearance ratio) at the two rub locations.
A simulation model is constructed using the
Texas A&
M University (TAMU) Turbomachinery Laboratory rotordynamics software suite XLTRC² comprised of Timoshenko beam finite elements to form multiple degrees of freedom rotor and stator models. The nonlinear connections at the rub surface are modeled using Hunt and Crossley‘s contact model with coulomb friction. Dry friction simulations are performed for three separate models depending on the rotor‘s mass disk location with respect to the contact locations. The three models used have (1) Disk at center location (2) Disk at 3/4 location (3) Disk at overhang location.
The adequacy of the analytical solution is investigated using the above simulations. Also, cases are explored where the general assumed solution would not solve the mathematical model, e.g. different RCl ratios at the two contacts. Simulations are performed for increasing as well as decreasing running speeds.
There is partial agreement between simulation predictions and the analytical solutions for the cases with the mass center at centered and at 3/4 location. First, whirl-to-whip transitions occur at near the combine rotor-stator bounce frequency for both disk at center and disk at 3/4 location. The case with overhang mass disk predicts the two contacts to whip and at different frequencies simultaneously. Neither of the analytical solutions predicts a case where precession occurs at two different frequencies at the two contact points. Predictions for models with different RCl on the Backward Precessional (BP) graph imitate whirling. The BP graph predicts increasing BP frequency with increasing rotor speeds which is a characteristic of whirling, whereas investigation of individual contact velocities suggest that they are slipping at all conditions, one of them slipping more than the other netting a whirling like motion. For the overhang model with different RCl, apart from whipping at different frequency the two contacts also whirl at different frequencies corresponding to the RCl at the respective contacts.
Simulations for decreasing rotor speed predict jump down from whirl- to-whip different BP frequency as compared to the jump up from whip-to-whirl for the speed up.
Advisors/Committee Members: Childs, Dara W. (advisor), Morgan, James (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: whirl; whip; backward precessional; vibration; two point contact
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APA (6th Edition):
Kumar, D. D. (2011). Backward Precessional Whip and Whirl for a Two Point Rubbing Contact Model of a Rigid Rotor Supported by an Elastically Supported Rigid Stator. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8451
Chicago Manual of Style (16th Edition):
Kumar, Dhruv Dileep. “Backward Precessional Whip and Whirl for a Two Point Rubbing Contact Model of a Rigid Rotor Supported by an Elastically Supported Rigid Stator.” 2011. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8451.
MLA Handbook (7th Edition):
Kumar, Dhruv Dileep. “Backward Precessional Whip and Whirl for a Two Point Rubbing Contact Model of a Rigid Rotor Supported by an Elastically Supported Rigid Stator.” 2011. Web. 08 Mar 2021.
Vancouver:
Kumar DD. Backward Precessional Whip and Whirl for a Two Point Rubbing Contact Model of a Rigid Rotor Supported by an Elastically Supported Rigid Stator. [Internet] [Masters thesis]. Texas A&M University; 2011. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8451.
Council of Science Editors:
Kumar DD. Backward Precessional Whip and Whirl for a Two Point Rubbing Contact Model of a Rigid Rotor Supported by an Elastically Supported Rigid Stator. [Masters Thesis]. Texas A&M University; 2011. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8451
Texas A&M University
26.
Han, Xu.
Analysis and Simulation of Mechanical Trains Driven by Variable Frequency Drive Systems.
Degree: MS, Mechanical Engineering, 2012, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8666
► Induction motors and Variable Frequency Drives (VFDs) are widely used in industry to drive machinery trains. However, some mechanical trains driven by VFD-motor systems have…
(more)
▼ Induction motors and Variable Frequency Drives (VFDs) are widely used in industry to drive machinery trains. However, some mechanical trains driven by VFD-motor systems have encountered torsional vibration problems. This vibration can induce large stresses on shafts and couplings, and reduce the lifetime of these mechanical parts. Long before the designed lifetime, the mechanical train may encounter failure. This thesis focuses on VFDs with voltage source rectifiers for squirrel-cage induction motors of open-loop Volts/Hertz and closed-loop Field Oriented Control (FOC). First, the torsional vibration problems induced by VFDs are introduced. Then, the mathematical model for a squirrel-cage induction motor is given. Two common control methods used in VFD are discussed - open-loop Volts/Hertz and closed-loop FOC. SimPowerSystems and SimMechanics are used as the modeling software for electrical systems and mechanical systems respectively. Based on the models and software, two interface methods are provided for modeling the coupled system. A simple system is tested to verify the interface methods. The study of open-loop Volts/Hertz control method is performed. The closed-form of electromagnetic torque sideband frequency due to Pulse Width Modulation is given. A torsional resonance case is illustrated. The effects of non-ideal power switches are studied, which shows little in uence on the system response but which uses little energy consumption. A study of a non-ideal DC bus indicates that a DC bus voltage ripple can also induce a big torsional vibration. Next, the study of the closed-loop FOC control method is presented. Simulation for a complete VFD machinery train is performed. With the recti er and DC bus dynamic braking, the system shows a better performance than the ideal-DC bus case. Lastly, a parametric study of the FOC controller is performed. The effects of primary parameters are discussed. The results indicate that some control parameters (i.e. speed ramps, proportional gain in speed PI controller) are also responsible for the mechanical torsional vibration.
Advisors/Committee Members: Palazzolo, Alan B. (advisor), Kim, Won-jong (committee member), Toliyat, Hamid A. (committee member).
Subjects/Keywords: Vibration; Variable Frequency Drive; VFD; Field Oriented Control; Mechanical System; Resonance; SimPowerSystems; SimMechanics
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APA (6th Edition):
Han, X. (2012). Analysis and Simulation of Mechanical Trains Driven by Variable Frequency Drive Systems. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8666
Chicago Manual of Style (16th Edition):
Han, Xu. “Analysis and Simulation of Mechanical Trains Driven by Variable Frequency Drive Systems.” 2012. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8666.
MLA Handbook (7th Edition):
Han, Xu. “Analysis and Simulation of Mechanical Trains Driven by Variable Frequency Drive Systems.” 2012. Web. 08 Mar 2021.
Vancouver:
Han X. Analysis and Simulation of Mechanical Trains Driven by Variable Frequency Drive Systems. [Internet] [Masters thesis]. Texas A&M University; 2012. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8666.
Council of Science Editors:
Han X. Analysis and Simulation of Mechanical Trains Driven by Variable Frequency Drive Systems. [Masters Thesis]. Texas A&M University; 2012. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8666
Texas A&M University
27.
Orsak, John.
A Theoretical Structural Impairment Detection System for Timber Railway Bridges.
Degree: MS, Civil Engineering, 2012, Texas A&M University
URL: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10919
► The objective of this research is to develop a theoretical Structural Impairment Detection System (SIDS) for timber railway bridges. Due to fatigue, the timber stringers…
(more)
▼ The objective of this research is to develop a theoretical Structural Impairment Detection System (SIDS) for timber railway bridges. Due to fatigue, the timber stringers in timber railway bridges develop shear cracks. These shear cracks lead to higher bridge deflections, higher stresses in the stringers and rail, and shorter fatigue life of the system. A SIDS is proposed which links wheel path accelerations obtained from traversing freight cars to the condition of the bridge.
In order to develop the SIDS, two models of timber railway bridges with various levels of structural impairment were developed. The first model was a quasi-static model developed from classical beam theory and implemented in MATLAB. The second model was a dynamic, finite element model created in LS-DYNA. Traversing axle loads were imposed on the models. The results obtained from the model were the wheel paths the axles take as they traverse the bridge. The paths were expressed as vertical displacements as a function of position on the bridge. Wheel path accelerations were obtained by numerically differentiating the vertical displacements.
The accelerations were then used to train neural networks to have an input of an acceleration vector and an output of a bridge condition vector. The neural networks were trained on results from both models under three train speeds: 40 mph, 30 mph, and 20 mph. The networks were able to determine the correct bridge condition 90% of the time when the train speed was 40 mph and 70% of the time when the train speed was 30 mph. The networks were not successful in determining bridge condition when the train speed was 20 mph.
Advisors/Committee Members: Fry, Gary T. (advisor), Palazzolo, Alan (committee member), Jones, Harry (committee member).
Subjects/Keywords: timber bridges; structural impairment detection; structural health monitoring; structural engineering
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APA (6th Edition):
Orsak, J. (2012). A Theoretical Structural Impairment Detection System for Timber Railway Bridges. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10919
Chicago Manual of Style (16th Edition):
Orsak, John. “A Theoretical Structural Impairment Detection System for Timber Railway Bridges.” 2012. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10919.
MLA Handbook (7th Edition):
Orsak, John. “A Theoretical Structural Impairment Detection System for Timber Railway Bridges.” 2012. Web. 08 Mar 2021.
Vancouver:
Orsak J. A Theoretical Structural Impairment Detection System for Timber Railway Bridges. [Internet] [Masters thesis]. Texas A&M University; 2012. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10919.
Council of Science Editors:
Orsak J. A Theoretical Structural Impairment Detection System for Timber Railway Bridges. [Masters Thesis]. Texas A&M University; 2012. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10919
Texas A&M University
28.
Nguyen, Vu Huy.
Universal Framework for Linear Motors and Multi-Axis Stages with Magnetic Levitation.
Degree: PhD, Mechanical Engineering, 2015, Texas A&M University
URL: http://hdl.handle.net/1969.1/156534
► This dissertation presents the electromagnetic design and experimental validation of a new framework for linear permanent-magnet (PM) machines with targeted applications in precision motion control.…
(more)
▼ This dissertation presents the electromagnetic design and experimental validation of a new framework for linear permanent-magnet (PM) machines with targeted applications in precision motion control. In this framework, a single forcer, which can generate two independent force components in two perpendicular directions, consists of a stationary Halbach magnet array and two Lorentz coils with a phase difference of 90° or 270°. Any number of coil pairs can be attached on the same moving frame to work with a common magnet array or matrix, forming a linear or planar PM motor. Key advantages of this framework are simple force calculation, a linear system model, and a reduced number of coils for force generation and allocation in multi-axis positioners. The proposed framework effectively allows for decoupled dynamics, simplifying the linear controller design and real-time implementation.
To experimentally verify the theoretical framework proposed herein, a high-precision 6-axis magnetically levitated (maglev) stage is designed, constructed, and controlled. The development of this 6-axis positioning system is an integrated work, including magnetic-force calculation and analysis, mechanical design, fabrication, assembly, system modeling, system identification, and control system design. The mechanical components of the system include a stationary superimposed Halbach magnet matrix, which was previously built, and a moving platen with a plastic frame, four sets of 2-phase coils, and two precision mirrors. For position measurements, there are three laser interferometers for in-plane position measurements, three laser displacement sensors for out-of-plane position sensing, and two 2-channel Hall-effect sensors for the position feedback to initialize the position and expand the travel ranges of the platen in the XY plane.
The positioning resolutions of 10 nm in the xy plane and in the vertical axis are demonstrated. In out-of-plane rotation about the two horizontal axes, experimental results show the unprecedented positioning resolution of 0.1 μrad. The maximum travel range in X and Y with nanoscale positioning resolution is 56 mm × 35 mm, limited by the lengths of the precision mirrors attached to the platen. With the trapezoidal-velocity input shaping, achieved performance specifications include the maximum acceleration and velocity of 0.6
m/s2 and 0.06
m/s, respectively, in translations in the horizontal plane. With the platen supported by the air bearings, the maximum acceleration and speed are 1.5
m/s2 and 0.15
m/s, respectively. A load test is performed with the platen carrying a load of 0.54 kg, which is 72% of its total mass, magnetically levitated in 6- axis closed-loop control. Experimental results show the reduced coupled dynamics between different axes in magnetic levitation. This framework of 2-phase Lorentz coils and linear Halbach arrays is highly applicable in precision-positioning linear motors and multi-axis stages, steppers, scanners, nano-scale manipulation and alignment systems, and vibration isolators.
Advisors/Committee Members: Kim, Won-jong (advisor), Langari, Reza (committee member), Palazzolo, Alan (committee member), Toliyat, Hamid (committee member).
Subjects/Keywords: Magnetic Levitation; Nanopositioning; Halbach Array; Positioning Stage; Mechatronics; Motion Control
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APA (6th Edition):
Nguyen, V. H. (2015). Universal Framework for Linear Motors and Multi-Axis Stages with Magnetic Levitation. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/156534
Chicago Manual of Style (16th Edition):
Nguyen, Vu Huy. “Universal Framework for Linear Motors and Multi-Axis Stages with Magnetic Levitation.” 2015. Doctoral Dissertation, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/156534.
MLA Handbook (7th Edition):
Nguyen, Vu Huy. “Universal Framework for Linear Motors and Multi-Axis Stages with Magnetic Levitation.” 2015. Web. 08 Mar 2021.
Vancouver:
Nguyen VH. Universal Framework for Linear Motors and Multi-Axis Stages with Magnetic Levitation. [Internet] [Doctoral dissertation]. Texas A&M University; 2015. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/156534.
Council of Science Editors:
Nguyen VH. Universal Framework for Linear Motors and Multi-Axis Stages with Magnetic Levitation. [Doctoral Dissertation]. Texas A&M University; 2015. Available from: http://hdl.handle.net/1969.1/156534
Texas A&M University
29.
Gu, Haoyuan.
Coupled Mooring Analysis of a CALM Buoy by a CFD Approach.
Degree: MS, Ocean Engineering, 2016, Texas A&M University
URL: http://hdl.handle.net/1969.1/159024
► The catenary anchor leg mooring (CALM) system is widely used as an efficient and economic single point mooring system in offshore engineering applications. CALM buoys…
(more)
▼ The catenary anchor leg mooring (CALM) system is widely used as an efficient and economic single point mooring system in offshore engineering applications. CALM buoys are often connected to FPSOs with large flowlines for offloading function. Compared to other floating structures like FPSOs or TLP, CALM buoy is more sensitive to the responses of mooring lines and oil offloading lines due to its special characteristics. These features for buoy can result in dangerous motions causing fatigue damage in mooring and flowlines systems. Therefore, it is essential to develop advanced numerical methods for accurate estimate of dynamic motion for CALM buoys.
In this research thesis, the Finite-Analytic Navier-Stokes (FANS) code is coupled with an in-house MOORING3D code for time-domain simulation of the hydrodynamic response of CALM buoy system. In the FANS code, the fluid domain is decomposed into multi-block overset grids. The Large Eddy Simulation (LES) turbulence model is used to provide accurate prediction of vortex-induced motion of the buoy. The mooring system is simulated with a nonlinear finite element module, MOORING3D. An interface module is established to facilitate interactive coupling between the buoy and mooring lines. The coupled FANS/MOORING3D code is calibrated first for free-decay case and compared with model test data. Then the coupled code is applied for the simulation of two degree-of-freedom vortex-induced motion of a CALM buoy in uniform currents to illustrate the capability of the present CFD approach for coupling mooring analysis of offshore structures.
With the study it can be verified that the coupled FANS/MOORING3D method is able to provide an accurate simulation of the hydrodynamic behavior of the CALM buoy system.
Advisors/Committee Members: Chen, Hamn-Ching (advisor), Mercier, Richard (committee member), Palazzolo, Alan (committee member).
Subjects/Keywords: CFD; CALM Buoy System; Hydrodynamics
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APA (6th Edition):
Gu, H. (2016). Coupled Mooring Analysis of a CALM Buoy by a CFD Approach. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/159024
Chicago Manual of Style (16th Edition):
Gu, Haoyuan. “Coupled Mooring Analysis of a CALM Buoy by a CFD Approach.” 2016. Masters Thesis, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/159024.
MLA Handbook (7th Edition):
Gu, Haoyuan. “Coupled Mooring Analysis of a CALM Buoy by a CFD Approach.” 2016. Web. 08 Mar 2021.
Vancouver:
Gu H. Coupled Mooring Analysis of a CALM Buoy by a CFD Approach. [Internet] [Masters thesis]. Texas A&M University; 2016. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/159024.
Council of Science Editors:
Gu H. Coupled Mooring Analysis of a CALM Buoy by a CFD Approach. [Masters Thesis]. Texas A&M University; 2016. Available from: http://hdl.handle.net/1969.1/159024
Texas A&M University
30.
Dai, Wei.
Tribological Characterization of Roles of Nanoparticles in Lubrication.
Degree: PhD, Mechanical Engineering, 2017, Texas A&M University
URL: http://hdl.handle.net/1969.1/187276
► This research investigates the tribological performance and rheological properties of nanoparticles as lubricant additives. Experimental approach combined with analysis were used to study the chemical…
(more)
▼ This research investigates the tribological performance and rheological properties of nanoparticles as lubricant additives. Experimental approach combined with analysis were used to study the chemical and physical interactions between nanoparticles and lubricating system. Three areas of investigation were carried out as summarized in the following.
Tribological performance and rheological properties of α-ZrP (Zr(HPO₄)₂•H₂O) and V₂O₅ nanoparticles were investigated as lubricant additives. α-ZrP showed 50% reduction in friction and 30% in wear compared to the conventional additives ZDDP. Spectroscopic characterization indicated that the tribofilm consists of iron oxide, zirconium oxide, and zirconium phosphates. Through Raman spectrum and EDS analysis, it was found that V₂O₅ involved tribochemical reaction during rubbing. Vanadium intermetallic alloy (V-Fe-Cr) was found to enhance the antiwear performance. This research revealed that nanoparticles could be effective additives to improve tribological performance.
Tribofilms play vital roles in protecting lubricated surfaces in mechanical systems in motion. Strategically-selected-illuminative nanoparticles of NaYF₄ were added to a base oil in order to enable their tracking. Electrical conductivity was monitored during sliding that was found to be linked to the state of the interface and the tribofilm. This work discovered three stages to form a tribofilm: running in, reactive, and growth. Interestingly, the formation of a tribofilm was more dominated by frictional force than applied load. This is significant because we can now use alternative strategies to generate quality tribofilms.
For the lubricating dynamics, the physical interaction between the nanoparticles and lubricating systems were investigated. Mechanisms of interfacial interaction between the shark skin and water have yet to be fully understood. In the present research, diamond particles worked as tracking particles in fluid. The shark-skinned surface with 90 degree orientation scale showed a more uniform distribution of diamond particles, which indicated to a lower gradient of velocity. Less momentum transfer between adjacent layers of fluid leads to a lower drag. Eventually, a viscosity map of shark-skinned surface with different scale orientation was created. It will facilitate the design of shark-skinned surface with better performance. The understanding generated in this study could be used as guideline for future study in surface design and texturing.
Advisors/Committee Members: Liang, Hong (advisor), Palazzolo, Alan (committee member), Jacobs, Timothy (committee member), Hemmer, Philip (committee member).
Subjects/Keywords: nanoparticles; tribofilm; textured surface
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APA (6th Edition):
Dai, W. (2017). Tribological Characterization of Roles of Nanoparticles in Lubrication. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/187276
Chicago Manual of Style (16th Edition):
Dai, Wei. “Tribological Characterization of Roles of Nanoparticles in Lubrication.” 2017. Doctoral Dissertation, Texas A&M University. Accessed March 08, 2021.
http://hdl.handle.net/1969.1/187276.
MLA Handbook (7th Edition):
Dai, Wei. “Tribological Characterization of Roles of Nanoparticles in Lubrication.” 2017. Web. 08 Mar 2021.
Vancouver:
Dai W. Tribological Characterization of Roles of Nanoparticles in Lubrication. [Internet] [Doctoral dissertation]. Texas A&M University; 2017. [cited 2021 Mar 08].
Available from: http://hdl.handle.net/1969.1/187276.
Council of Science Editors:
Dai W. Tribological Characterization of Roles of Nanoparticles in Lubrication. [Doctoral Dissertation]. Texas A&M University; 2017. Available from: http://hdl.handle.net/1969.1/187276
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Open Access Theses and Dissertations