You searched for +publisher:"Virginia Tech" +contributor:("Inman, Daniel J.").
Showing records 1 – 30 of
201 total matches.
◁ [1] [2] [3] [4] [5] [6] [7] ▶
Virginia Tech
1.
Liam, Christopher Charles.
Testing and Modeling of Shock Mitigating Seats for High Speed Craft.
Degree: MS, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/32874 
► This study conducted a series of tests on a shock mitigating seat designed for high speed craft using various input excitations to better understand the…
(more)
▼ This study conducted a series of tests on a shock mitigating seat designed for high speed craft using various input excitations to better understand the relationship between various seat and operational conditions, and the response of the seat. A seat model of the test seat is used for a parametric study of various spring, damping and operational configurations.
A seat shake rig is implemented to simulate motions of multiple high-speed craft as well as various defined inputs. At each test input the occupant weight and suspension preload is varied and the response is analyzed to find changes in acceleration, which is representative of the changes in force and displacement. By representing the seat as a based-excitation two-degree-of-freedom system, we develop the equations of motion and model them in Simulink to analyze the effects of various spring rates and damping coefficients.
Based on the results it is found that an increase in occupant mass results in a decrease in observed acceleration. Increasing suspension preload is found to be detrimental to the mitigating abilities of the seat, changing the dynamics to those similar of a rigid-mounted seat. An analysis of the defined inputs resulted in confirming various seat characteristics. The analysis of the Simulink model revealed that increasing the spring rate results in an increase in acceleration. An increase in damping coefficient resulted in an increase in acceleration and ride harshness.
Advisors/Committee Members: Ahmadian, Mehdi (committeechair), Inman, Daniel J. (committee member), Taheri, Saied (committee member).
Subjects/Keywords: high speed craft; shock mitigating seats
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Liam, C. C. (2011). Testing and Modeling of Shock Mitigating Seats for High Speed Craft. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32874
Chicago Manual of Style (16th Edition):
Liam, Christopher Charles. “Testing and Modeling of Shock Mitigating Seats for High Speed Craft.” 2011. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/32874.
MLA Handbook (7th Edition):
Liam, Christopher Charles. “Testing and Modeling of Shock Mitigating Seats for High Speed Craft.” 2011. Web. 22 Feb 2020.
Vancouver:
Liam CC. Testing and Modeling of Shock Mitigating Seats for High Speed Craft. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/32874.
Council of Science Editors:
Liam CC. Testing and Modeling of Shock Mitigating Seats for High Speed Craft. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/32874
Virginia Tech
2.
Burke, William Churchill Taliaferro.
Large Force Range Mechanically Adjustable Dampers for Heavy Vehicle Applications.
Degree: MS, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/33386
► Semi-active dampers utilizing various working principles have been developed for a variety of vehicles. These semi-active dampers have been designed to resolve the ride and…
(more)
▼ Semi-active dampers utilizing various working principles have been developed for a variety of vehicles. These semi-active dampers have been designed to resolve the ride and handling compromise associated with conventional passive dampers, and increase vehicle stability. This thesis briefly reviews existing semi-active damper designs, including but not limited to MR dampers, before presenting two new prototype semi-active hydraulic dampers. Both prototype dampers are designed to provide a large force range while maintaining easily controllable valve characteristics.
The first of these dampers served primarily as a proof of concept and a means of understanding the dynamics of a disc valve housed inside the main piston. The valve design is presented, along with other information concerning the fabrication of the Initial Prototype damper. Test results are presented and analyzed, and a second iteration of the valve is designed. The Final Prototype damper is a scaled up version of the initial design, with refinements made in piston geometry, internal disc profile, and dynamic seals. This large force range damper is tested and results are compared with existing MR dampers. The Final Prototype damper provides a significantly larger force range when compared with typical MR dampers. Finally, to conclude this research, the vehicle dynamics implications of the Final Prototype damper are discussed and recommendations for further study are made.
Advisors/Committee Members: Ahmadian, Mehdi (committeechair), Taheri, Saied (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: electro-hydraulic damper; mechanically adjustable damper; magnetorheological damper; heavy truck
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Burke, W. C. T. (2010). Large Force Range Mechanically Adjustable Dampers for Heavy Vehicle Applications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33386
Chicago Manual of Style (16th Edition):
Burke, William Churchill Taliaferro. “Large Force Range Mechanically Adjustable Dampers for Heavy Vehicle Applications.” 2010. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/33386.
MLA Handbook (7th Edition):
Burke, William Churchill Taliaferro. “Large Force Range Mechanically Adjustable Dampers for Heavy Vehicle Applications.” 2010. Web. 22 Feb 2020.
Vancouver:
Burke WCT. Large Force Range Mechanically Adjustable Dampers for Heavy Vehicle Applications. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/33386.
Council of Science Editors:
Burke WCT. Large Force Range Mechanically Adjustable Dampers for Heavy Vehicle Applications. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/33386
Virginia Tech
3.
Adjerid, Khaled.
A Study on the Dynamic Characterization of a Tunable Magneto-Rheological Fluid-Elastic Mount in Squeeze Mode Vibration.
Degree: MS, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/33628
► This research undertakes the task of static and dynamic characterization for a squeeze mode Magneto-Rheological (MR) Fluid-Elastic mount. MR fluidâ s variable viscosity rate is…
(more)
▼ This research undertakes the task of static and dynamic characterization for a squeeze mode Magneto-Rheological (MR) Fluid-Elastic mount. MR fluidâ s variable viscosity rate is advantageously used to develop a mount capable of mitigating input vibrations of varying magnitudes and frequencies depending on electromagnetic flux. Various mechanical components are synthesized into a dynamic testing rig in order to extract vibrational characteristics of the mount and to compare it with existing mount technologies.
This project focuses on a mount design that was proposed and improved upon by previous researchers at the Center for Vehicle Systems and Safety (CVeSS). Using a previously designed electromagnet and test rig, the MR mounts are characterized using a quasi-static test. From this test we extract the stiffness and damping characteristics of the MR mount. A set of upper and lower limit baseline mounts made with rubber and steel inserts are also tested simultaneously with the MR mount. Their isolation improvements are compared with conventional passive mounts.
After acquiring the stiffness and damping characteristics of the mount, a model is used to simulate a response to input vibrations in the frequency domain. A dynamic test is run on both the baseline testers as well as the MR mount. Having the frequency-magnitude response allows us to determine a usable resonance range and magnitude of vibration mitigation. The results of this study indicate that the mounts tested here are an effective means of suppressing start-up vibrations within mechanical systems and show promise for further development and application. Future studies of these systems can include tests of MR metal-elastic mount designs for durability as well as parametric studies based on MR fluid type and other factors.
Advisors/Committee Members: Ahmadian, Mehdi (committeechair), Southward, Steve C. (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: mount; isolator; elastomer; magneto-rheological fluid; tunable isolator
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Adjerid, K. (2011). A Study on the Dynamic Characterization of a Tunable Magneto-Rheological Fluid-Elastic Mount in Squeeze Mode Vibration. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33628
Chicago Manual of Style (16th Edition):
Adjerid, Khaled. “A Study on the Dynamic Characterization of a Tunable Magneto-Rheological Fluid-Elastic Mount in Squeeze Mode Vibration.” 2011. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/33628.
MLA Handbook (7th Edition):
Adjerid, Khaled. “A Study on the Dynamic Characterization of a Tunable Magneto-Rheological Fluid-Elastic Mount in Squeeze Mode Vibration.” 2011. Web. 22 Feb 2020.
Vancouver:
Adjerid K. A Study on the Dynamic Characterization of a Tunable Magneto-Rheological Fluid-Elastic Mount in Squeeze Mode Vibration. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/33628.
Council of Science Editors:
Adjerid K. A Study on the Dynamic Characterization of a Tunable Magneto-Rheological Fluid-Elastic Mount in Squeeze Mode Vibration. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/33628
Virginia Tech
4.
Gustafson, Eric Andrew.
Design, Simulation, and Wind Tunnel Verication of a Morphing Airfoil.
Degree: MS, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/33663
► The application of smart materials to control the flight dynamics of a Micro Air Vehicle (MAV) has numerous benefits over traditional servomechanisms. Under study is…
(more)
▼ The application of smart materials to control the flight dynamics of a Micro Air Vehicle
(MAV) has numerous benefits over traditional servomechanisms. Under study is wing morphing achieved through the use of piezoelectric Macro Fiber Composites (MFCs). These devices exhibit low power draw but excellent bandwidth characteristics. This thesis provides a background in the 2D analytical and computer modeling tools and methods needed to design and characterize an MFC-actuated airfoil.
A composite airfoil is designed with embedded MFCs in a bimorph configuration. The deflection capabilities under actuation are predicted with the commercial finite element package NX Nastran. Placement of the piezoelectric actuator is studied for optimal effectiveness. A thermal analogy is used to represent piezoelectric strain. Lift and drag coefficients in low Reynolds number flow are explored with XFOIL. Predictions are made on static aeroelastic effects. The thin, cambered Generic Micro Aerial Vehicle (GenMAV) airfoil is fabricated with a bimorph actuator. Experimental data are taken with and without aerodynamic loading to validate the computer model. This is accomplished with in-house 2D wind tunnel testing.
Advisors/Committee Members: Kochersberger, Kevin Bruce (committeechair), Canfield, Robert A. (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: Macro Fiber Composite; Morphing; Thin Cambered Airfoil; GenMAV
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Gustafson, E. A. (2011). Design, Simulation, and Wind Tunnel Verication of a Morphing Airfoil. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33663
Chicago Manual of Style (16th Edition):
Gustafson, Eric Andrew. “Design, Simulation, and Wind Tunnel Verication of a Morphing Airfoil.” 2011. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/33663.
MLA Handbook (7th Edition):
Gustafson, Eric Andrew. “Design, Simulation, and Wind Tunnel Verication of a Morphing Airfoil.” 2011. Web. 22 Feb 2020.
Vancouver:
Gustafson EA. Design, Simulation, and Wind Tunnel Verication of a Morphing Airfoil. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/33663.
Council of Science Editors:
Gustafson EA. Design, Simulation, and Wind Tunnel Verication of a Morphing Airfoil. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/33663
Virginia Tech
5.
Thayer, Nicholas D.
Towards a Human-like Robot for Medical Simulation.
Degree: MS, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/35077
► Medical mannequins provide the first hands-on training for nurses and doctors and help eliminate human mistakes that would otherwise take place with a real person.…
(more)
▼ Medical mannequins provide the first hands-on training for nurses and doctors and help eliminate human mistakes that would otherwise take place with a real person. The closer the mannequin is to mimicking a human being, the more effective the training; thus, additional features such as movable limbs and eyes, vision processing and realistic social interaction will provide a more fulfilling learning experience. A humanoid robot with a 23 degree of freedom (DOF) hand was developed which is capable of performing complex dexterous tasks such as typing on a keyboard. A single DOF elbow and two DOF shoulder was designed and optimized to maintain human form while being able to dynamically lift common household items. A 6 DOF neck and 13 DOF face with a highly expressive silicone skin-motor arrangement has been developed. The face is capable of talking and making several expressions and is used to train the student to pick up on emotional cues such as eye contact and body language during the interview stage. A pair of 3 DOF legs and a torso were also developed which allows the humanoid to be in either the laying down or sitting up position. An algorithm was developed that only activates necessary areas of code in order to increase its cycle time which greatly increases the vision tracking capabilities of the eyes. The simulator was tested at Carilion Clinic in Roanoke VA with several of the medical staff and their feedback is provided in this document.
Advisors/Committee Members: Priya, Shashank (committeechair), Inman, Daniel J. (committee member), Hong, Dennis W. (committee member).
Subjects/Keywords: biomimietic; medical simulator; humanoid; mechatronic
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Thayer, N. D. (2011). Towards a Human-like Robot for Medical Simulation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35077
Chicago Manual of Style (16th Edition):
Thayer, Nicholas D. “Towards a Human-like Robot for Medical Simulation.” 2011. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/35077.
MLA Handbook (7th Edition):
Thayer, Nicholas D. “Towards a Human-like Robot for Medical Simulation.” 2011. Web. 22 Feb 2020.
Vancouver:
Thayer ND. Towards a Human-like Robot for Medical Simulation. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/35077.
Council of Science Editors:
Thayer ND. Towards a Human-like Robot for Medical Simulation. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/35077
Virginia Tech
6.
Pasareanu, Stephanie.
A numerical hybrid method for modeling outdoor sound propagation  in complex urban environments.
Degree: MS, Mechanical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/47601
► Prediction of the sound field in large urban environments has been limited thus far by the heavy computational requirements of conventional numerical methods such as…
(more)
▼ Prediction of the sound field in large urban environments has been limited thus far by the heavy computational requirements of conventional numerical methods such as boundary element (BE), finite-difference time-domain (FDTD), or ray-tracing methods. Recently, a considerable amount of work has been devoted to developing energy-based methods for this application, and results have shown the potential to compete with conventional methods. However, these developments have been limited to two-dimensional (2-D) studies (along street axes), and no real description of the phenomena at issue has been exposed (e.g., diffraction effects on the predictions).
The main objectives of the present work were (i) to evaluate the feasibility of an energy-based method, the diffusion model (DM), for sound-field predictions in large, 3-D complex urban environments, (ii) to propose a numerical hybrid method that could improve the accuracy and computational time of these predictions, and (iii) to verify the proposed hybrid method against conventional numerical methods.
The proposed numerical hybrid method consists of a full-wave model coupled with an energy-based model. The full-wave model is used for predicting sound propagation (i) near the source, where constructive and destructive interactions between waves are substantial, and (ii) outside the cluttered environment, where free-field-like conditions apply. The energy-based model is used in regions where diffusion conditions are met. The hybrid approach, as implemented in this work, is a combination of FDTD and DM models.
Results from this work show the role played by diffraction near buildings edges close to the source and near the exterior boundaries of the computational domain, and its impact on the predictions. A wrong modeling of the diffraction effects in the environment leads to significant under or overpredictions of the sound levels in some regions, as compared to conventional numerical methods (in these regions, some differences are as high as 10 dB). The implementation of the hybrid method, verified against a full FDTD model, shows a significant improvement of the predictions. The mean error thus obtained inside the cluttered region of the environment is 1.5 dB.
Advisors/Committee Members: Inman, Daniel J. (committeechair), Burdisso, Ricardo A. (committeechair), Roan, Michael J. (committee member).
Subjects/Keywords: outdoor sound propagation; FDTD; energy-based method; energy density; geometrical acoustics; numerical hybrid method
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Pasareanu, S. (2014). A numerical hybrid method for modeling outdoor sound propagation  in complex urban environments. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/47601
Chicago Manual of Style (16th Edition):
Pasareanu, Stephanie. “A numerical hybrid method for modeling outdoor sound propagation  in complex urban environments.” 2014. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/47601.
MLA Handbook (7th Edition):
Pasareanu, Stephanie. “A numerical hybrid method for modeling outdoor sound propagation  in complex urban environments.” 2014. Web. 22 Feb 2020.
Vancouver:
Pasareanu S. A numerical hybrid method for modeling outdoor sound propagation  in complex urban environments. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/47601.
Council of Science Editors:
Pasareanu S. A numerical hybrid method for modeling outdoor sound propagation  in complex urban environments. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/47601
Virginia Tech
7.
Zhou, Dao.
Ultra Low-Power Wireless Sensor Node for Structural Health Monitoring.
Degree: MS, Electrical and Computer Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/31103
► Structural Health Monitoring (SHM) is the technology of monitoring and assessing the condition of aerospace, civil, and mechanical infrastructures using a sensing system integrated into…
(more)
▼ Structural Health Monitoring (SHM) is the technology of monitoring and assessing the condition of aerospace, civil, and mechanical infrastructures using a sensing system integrated into the structure. Among variety of SHM approaches, impedance-based method is efficient for local damage detection. This thesis focuses on system level concerns for impedance-based SHM. Two essential requirements are reached in the thesis: reduction of power consumption of wireless SHM sensor, and compensation of temperature dependency on impedance. The proposed design minimizes power by employing on-board signal processing, and by eliminating power hungry components such as ADC and DAC. The prototype implemented with MSP430 micro controller is verified to be able to handle SHM operation and wireless communication with extremely low-power: 0.15 mW during the inactive mode and 18 mW during the active mode. Each SHM operation takes about 13 seconds to consume 236 mJ. When our ASN-2 operates once in every four hours, it can run for about 2.5 years with two AAA-size batteries. To compensate for temperature change, we proposed an algorithm to select a small subset of baseline profiles for some critical temperatures and to estimate the baseline profile for a given ambient temperature through interpolation. Experimental results show that our method reduces the number of baseline profiles to be stored by 45%, and estimates the baseline profile of a given temperature accurately.
Advisors/Committee Members: Ha, Dong Sam (committeechair), Schaumont, Patrick Robert (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: Structural Health Monitoring; wireless sensor; impedance-based mothed; low power; temperature compesation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zhou, D. (2010). Ultra Low-Power Wireless Sensor Node for Structural Health Monitoring. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31103
Chicago Manual of Style (16th Edition):
Zhou, Dao. “Ultra Low-Power Wireless Sensor Node for Structural Health Monitoring.” 2010. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/31103.
MLA Handbook (7th Edition):
Zhou, Dao. “Ultra Low-Power Wireless Sensor Node for Structural Health Monitoring.” 2010. Web. 22 Feb 2020.
Vancouver:
Zhou D. Ultra Low-Power Wireless Sensor Node for Structural Health Monitoring. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/31103.
Council of Science Editors:
Zhou D. Ultra Low-Power Wireless Sensor Node for Structural Health Monitoring. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/31103
Virginia Tech
8.
Detrich, Kahlil.
Electroding Methods for in situ Reverse Osmosis Sensors.
Degree: MS, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/31207
► The purpose of this work is to develop and evaluate electroding methods for a reverse osmosis (RO) membrane that results in an in situ sensor…
(more)
▼ The purpose of this work is to develop and evaluate electroding methods for a reverse osmosis (RO) membrane that results in an in situ sensor able to detect RO membrane protein fouling. Four electroding techniques were explored: i) gold exchange-reduction, ii) encapsulated carbon grease, iii) â direct assembly processâ (DAP), and iv) platinized polymer graft. The novel platinized polymer graft method involves chemically modifying the RO membrane surface to facilitate platinization based on the hypothesis that deposition of foulant on the platinized surface will affect platinum/foulant/solution interfacial regions, thus sensor impedance. Platinized polymer graft sensors were shown to be sensitive to protein fouling.
Electrodes were characterized by their electrical properties, SEM and XPS. Assembled sensors were evaluated for sensitivity to electrolyte concentration and protein fouling. Micrographs showed coating layers and pre-soak solution influence gold exchange-reduction electrode formation. High surface resistance makes gold exchange-reduction an unsuitable method. Concentration sensitivity experiments showed carbon grease and DAP electroding methods produce unusable sensors. Carbon grease sensors have time-dependent impedance response due to electrolyte diffusion within the micro-porous polysulfone support. DAP electroded sensors proved quite fragile upon hydration; their impedance response is transient and lacks predictable trends with changes in concentration. A parametric study of the platinized polymer graft method shows amount of grafted monomer correlates to grafting time, and deposited platinum is a function of exchange-reduction repetitions and amount of grafted monomer. Platinized polymer graft sensors were fouled in both dead-end and cross-flow RO systems, and their impedance trends, while varying between sensors, indicate protein-fouling sensitivity.
Advisors/Committee Members: Goulbourne, Nakhiah C. (committeechair), Inman, Daniel J. (committee member), Vlachos, Pavlos P. (committee member).
Subjects/Keywords: in situ sensing; reverse osmosis membrane; platinized polymer graft; fouling; electrical impedance spectroscopy
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Detrich, K. (2010). Electroding Methods for in situ Reverse Osmosis Sensors. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31207
Chicago Manual of Style (16th Edition):
Detrich, Kahlil. “Electroding Methods for in situ Reverse Osmosis Sensors.” 2010. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/31207.
MLA Handbook (7th Edition):
Detrich, Kahlil. “Electroding Methods for in situ Reverse Osmosis Sensors.” 2010. Web. 22 Feb 2020.
Vancouver:
Detrich K. Electroding Methods for in situ Reverse Osmosis Sensors. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/31207.
Council of Science Editors:
Detrich K. Electroding Methods for in situ Reverse Osmosis Sensors. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/31207
Virginia Tech
9.
Corcoran, Joseph Michael.
Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms.
Degree: MS, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/31329
► In this thesis, an output-only experimental modal testing and analysis technique known as the Natural Excitation Technique (NExT) is examined for use with large residential…
(more)
▼ In this thesis, an output-only experimental modal testing and analysis technique known as the Natural Excitation Technique (NExT) is examined for use with large residential structures and interior cavities. The technique which assumes a random, stationary input causing the response data is reviewed and extended for the first time to include the assumption of an impulse input. This technique is examined with respect to the experimental modal analysis of single and two room residential structures. Each structure is first tested using conventional modal testing methods. Then, NExT is applied using each structureâ s response to a simulated sonic boom, an impulsive input. The results of these analyses along with the results obtained from a finite element model are compared. Then, the interior cavities enclosed by the residential structures are examined using NExT. Therefore, this thesis also demonstrates the successful use of NExT on acoustic systems for the first time. Three configurations of the interconnected cavities enclosed by the two room structure are considered to study physical phenomena. Both interior pressure response to random, stationary inputs and the sonic boom response are used with NExT to determine modal properties. The results of these analyses are compared to a theoretical analysis. Advantages to using NExT with both the response to a random, stationary input and an impulsive input are demonstrated for structural and acoustic systems.
Advisors/Committee Members: Burdisso, Ricardo A. (committeechair), Reichard, Georg (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: acoustic cavity; residential structure; sonic boom; Natural Excitation Technique (NExT); Modal testing
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Corcoran, J. M. (2010). Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31329
Chicago Manual of Style (16th Edition):
Corcoran, Joseph Michael. “Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms.” 2010. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/31329.
MLA Handbook (7th Edition):
Corcoran, Joseph Michael. “Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms.” 2010. Web. 22 Feb 2020.
Vancouver:
Corcoran JM. Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/31329.
Council of Science Editors:
Corcoran JM. Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/31329
Virginia Tech
10.
Lanier, Prather Jonathan.
Stereovision Correction Using Modal Analysis.
Degree: MS, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/31662
► Presently, aerial photography remains a popular method for surveillance of landscapes, and its uses continually grow as it is used to monitor trends in areas…
(more)
▼ Presently, aerial photography remains a popular method for surveillance of landscapes, and its uses continually grow as it is used to monitor trends in areas such as plant distribution and urban construction. The use of computer vision, or more specifically stereo vision, is one common method of gathering this information. By mounting a stereo vision system on the wings of an unmanned aircraft it becomes very useful tool. This technique however, becomes less accurate as stereo vision baselines become longer, aircraft wing spans are increased, and aircraft wings become increasingly flexible. Typically, ideal stereo vision systems involve stationary cameras with parallel fields of view. For an operational aircraft with a stereo vision system installed, stationary cameras can not be expected because the aircraft will experience random atmospheric turbulence in the form of gusts that will excite the dominate frequencies of the aircraft.
A method of stereo image rectification has been developed for cases where cameras that will be allowed to deflect on the wings of an fixed wing aircraft that is subjected to random excitation. The process begins by developing a dynamic model the estimates the behavior of a flexible stereo vision system and corrects images collected at maximum deflection. Testing of this method was performed on a flexible stereo vision system subjected to resonance excitation where a reduction in stereo vision distance error is shown. Successful demonstration of this ability is then repeated on a flying wing aircraft by the using a modal survey to understand its behavior. Finally, the flying wing aircraft is subjected to random excitation and a least square fit of the random excitation signal is used to determine points of maximum deflection suitable for stereo image rectification. Using the same techniques for image rectification in resonance excitation, significant reductions in stereo distance errors are shown.
Advisors/Committee Members: Kochersberger, Kevin Bruce (committeechair), Inman, Daniel J. (committee member), Wicks, Alfred L. (committee member).
Subjects/Keywords: Stereo Vision; Modal Analysis; UAV; Photogrammetry; Gust Response
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lanier, P. J. (2010). Stereovision Correction Using Modal Analysis. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31662
Chicago Manual of Style (16th Edition):
Lanier, Prather Jonathan. “Stereovision Correction Using Modal Analysis.” 2010. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/31662.
MLA Handbook (7th Edition):
Lanier, Prather Jonathan. “Stereovision Correction Using Modal Analysis.” 2010. Web. 22 Feb 2020.
Vancouver:
Lanier PJ. Stereovision Correction Using Modal Analysis. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/31662.
Council of Science Editors:
Lanier PJ. Stereovision Correction Using Modal Analysis. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/31662
Virginia Tech
11.
Butrym, Brad A.
Crack Detection in Aluminum Structures.
Degree: MS, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/32276
► Structural health monitoring (SHM) is the process of using measurements of a structureâ s response to known excitations and trying to determine if damage has…
(more)
▼ Structural health monitoring (SHM) is the process of using measurements of a structureâ s response to known excitations and trying to determine if damage has occurred to the structure. This also fits the description of non-destructive evaluation (NDE). The main difference is that NDE takes place while the structure is out of service and SHM is intended to take place while the structure is in service. As such, SHM provides the opportunity to provide early warning against structural failure. This thesis intends to advance the state of the art in SHM by examining two approaches to SHM: vibration based and impedance based, and to associate these with the NDE method of stress intensity factors. By examining these methods the goal is to try and answer some of the important questions in SHM process. The first is to experimentally validate a crack model and to see how small of a crack can be detected by vibration methods. The second is to use the concept of stress intensity factor to perform an SHM type of measurement to determine the remaining life of a structure once the impedance method has determined that damage has occurred.
The measurement system considered consists of using several different piezoceramic materials as self-sensing actuators and sensors. The structures are a simple beam and a more complex lug element used in aircraft applications. The approach suggested here is to use the impedance and vibration methods to detect crack initiation and then to use the proposed stress intensity method to measure the stress intensity factor of the structure under consideration.
Advisors/Committee Members: Inman, Daniel J. (committeechair), Kasarda, Mary E. F. (committee member), Kim, Myung Hyun (committee member).
Subjects/Keywords: Structural Health Monitoring; Stress Intensity Factors; Macro Fiber Composite; Piezoelectric; NDE
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Butrym, B. A. (2010). Crack Detection in Aluminum Structures. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32276
Chicago Manual of Style (16th Edition):
Butrym, Brad A. “Crack Detection in Aluminum Structures.” 2010. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/32276.
MLA Handbook (7th Edition):
Butrym, Brad A. “Crack Detection in Aluminum Structures.” 2010. Web. 22 Feb 2020.
Vancouver:
Butrym BA. Crack Detection in Aluminum Structures. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/32276.
Council of Science Editors:
Butrym BA. Crack Detection in Aluminum Structures. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/32276
Virginia Tech
12.
Konchuba, Nicholas.
Temperature Compensation Improvements for Impedance Based Structural Health Monitoring.
Degree: MS, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/44455
► Structural Health Monitoring is a useful tool for reducing maintenance costs and improving the life and performance of engineering structures. Impedance-Based SHM utilizes the coupled…
(more)
▼ Structural Health Monitoring is a useful tool for reducing maintenance costs and improving the life and performance of engineering structures. Impedance-Based SHM utilizes the coupled electromechanical behavior of piezoelectric materials to detect adverse changes and material and mechanical failures of structures. Environmental variables such as temperature present a challenge to assessing the veracity of damage detected through statistical modeling of impedance signals. An effective frequency shift method was developed to compensate impedance measurements for changes resulting from environmental temperature fluctuations. This thesis investigates how the accuracy of this method can be improved and be applied to a 100oF range of temperatures. Building up the idea of eliminating temperature effects from impedance measurements, this thesis investigates the possibility of using statistical moments to create a temperature independent impedance baseline.
Advisors/Committee Members: Inman, Daniel J. (committeechair), Kurdila, Andrew J. (committee member), Seidel, Gary (committee member).
Subjects/Keywords: Structural Health Monitoring; Impedance-Based SHM; Piezoelectric Materials; Wavelets; Temperature Compensation; Effective Frequency Shift; Discrete Wavelet Transform
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Konchuba, N. (2011). Temperature Compensation Improvements for Impedance Based Structural Health Monitoring. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44455
Chicago Manual of Style (16th Edition):
Konchuba, Nicholas. “Temperature Compensation Improvements for Impedance Based Structural Health Monitoring.” 2011. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/44455.
MLA Handbook (7th Edition):
Konchuba, Nicholas. “Temperature Compensation Improvements for Impedance Based Structural Health Monitoring.” 2011. Web. 22 Feb 2020.
Vancouver:
Konchuba N. Temperature Compensation Improvements for Impedance Based Structural Health Monitoring. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/44455.
Council of Science Editors:
Konchuba N. Temperature Compensation Improvements for Impedance Based Structural Health Monitoring. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/44455
Virginia Tech
13.
Yun, Jinsik.
Development of Structural Health Monitoring Systems Incorporating Acoustic Emission Detection for Spacecraft and Wind Turbine Blades.
Degree: MS, Electrical and Computer Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/42507
► Structural Health Monitoring (SHM) is the science and technology of monitoring and can assess the condition of aerospace, civil, and mechanical infrastructures using a sensing…
(more)
▼ Structural Health Monitoring (SHM) is the science and technology of monitoring and can assess the condition of aerospace, civil, and mechanical infrastructures using a sensing system integrated into the structure. SHM is capable of detecting, locating, and quantifying various types of damage such as cracks, holes, corrosion, delamination, and loose joints, and can be applied to various kinds of infrastructures such as buildings, railroads, windmills, bridges, and aircraft.
A major technical challenge for existing SHM systems is high power consumption, which severely limits the range of its applications. In this thesis, we investigated adoption of acoustic emission detection to reduce power dissipation of SHM systems employing the impedance and the Lamb wave methods. An acoustic emission sensor of the proposed system continuously monitors acoustic events, while the SHM system is in sleep mode. The SHM system is evoked to perform the SHM operation only when there is an acoustic event detected by the acoustic emission sensor. The proposed system avoids unnecessary operation of SHM operations, which saves power, and the system is effective for certain applications such as spacecraft and wind turbine blades. We developed prototype systems using a Texas Instruments TMS320F2812 DSP evaluation board for the Lamb wave method and an MSP430 evaluation board for the impedance method.
Advisors/Committee Members: Ha, Dong Sam (committeechair), Schaumont, Patrick Robert (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: Wireless Sensor Network; Impedance-Based SHM; Acoustic Emission; Structural Health Monitoring
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yun, J. (2011). Development of Structural Health Monitoring Systems Incorporating Acoustic Emission Detection for Spacecraft and Wind Turbine Blades. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42507
Chicago Manual of Style (16th Edition):
Yun, Jinsik. “Development of Structural Health Monitoring Systems Incorporating Acoustic Emission Detection for Spacecraft and Wind Turbine Blades.” 2011. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/42507.
MLA Handbook (7th Edition):
Yun, Jinsik. “Development of Structural Health Monitoring Systems Incorporating Acoustic Emission Detection for Spacecraft and Wind Turbine Blades.” 2011. Web. 22 Feb 2020.
Vancouver:
Yun J. Development of Structural Health Monitoring Systems Incorporating Acoustic Emission Detection for Spacecraft and Wind Turbine Blades. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/42507.
Council of Science Editors:
Yun J. Development of Structural Health Monitoring Systems Incorporating Acoustic Emission Detection for Spacecraft and Wind Turbine Blades. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/42507
Virginia Tech
14.
Hills, Zachary Patrick.
Using Macro-Fiber Composite Actuators for Aquatic Locomotion.
Degree: MS, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/42818
► The research presented herein aims to develop a bio-inspired swimming system for an autonomous underwater vehicle using Macro-Fiber Composite (MFC) actuators. The swimming system draws…
(more)
▼ The research presented herein aims to develop a bio-inspired swimming system for an autonomous underwater vehicle using Macro-Fiber Composite (MFC) actuators. The swimming system draws inspiration from the motion of carangiform fish, which limit their body motion while rapidly oscillating their caudal tail fin. The foundation for the bio-inspired swimming system is built upon a composite cantilever beam with MFC actuators in bimorph configuration. The MFC actuators excite the composite beam near its fundamental natural frequency to produce thrust as the vibration transfers momentum to the surrounding fluid. An analytical model that incorporates Euler-Bernoulli beam theory, linear piezoelectricity, and fluid mechanics is developed to predict the thrust generated by the beam vibration. Experimental testing is performed to verify aspects of, as well as recommend corrections to, the analytical model. A prototype carangiform swimmer is developed that employs a passive caudal tail fin to alter the vibratory motion of the system from a beam vibration mode to one more resembling carangiform swimming. This device is subjected to experimental testing to determine the swim speeds it is able to achieve. A maximum velocity of 90mm/s was observed when the system is excited at 900V. However, better performance may be achieved by increasing the excitation voltage.
Advisors/Committee Members: Inman, Daniel J. (committeechair), Priya, Shashank (committee member), Ross, Shane D. (committee member).
Subjects/Keywords: Locomotion; Carangiform; MFC; Piezoelectric
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hills, Z. P. (2010). Using Macro-Fiber Composite Actuators for Aquatic Locomotion. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42818
Chicago Manual of Style (16th Edition):
Hills, Zachary Patrick. “Using Macro-Fiber Composite Actuators for Aquatic Locomotion.” 2010. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/42818.
MLA Handbook (7th Edition):
Hills, Zachary Patrick. “Using Macro-Fiber Composite Actuators for Aquatic Locomotion.” 2010. Web. 22 Feb 2020.
Vancouver:
Hills ZP. Using Macro-Fiber Composite Actuators for Aquatic Locomotion. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/42818.
Council of Science Editors:
Hills ZP. Using Macro-Fiber Composite Actuators for Aquatic Locomotion. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/42818
Virginia Tech
15.
Siddens, Aaron Jeffrey.
A Predictive Methodology for Soft Impact Damage in Jet Engines Incorporating Hybrid Composite Structures.
Degree: MS, Mechanical Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/76957
► This work presents a detailed predictive modeling methodology for comprehensive crashworthiness analysis of advanced jet engine forward sections, containing hybrid and composite structures, when subjected…
(more)
▼ This work presents a detailed predictive modeling methodology for comprehensive crashworthiness analysis of advanced jet engine forward sections, containing hybrid and composite structures, when subjected to soft impact. Bird strike onto the fan assembly is chosen as the impact event to be studied. The aim is to develop a numerical methodology capable of accurately capturing the full range of multifaceted damage in hybrid and composite structures as they evolve throughout the forward section of a propulsion system.
Effective strategies are developed within an explicit finite element framework for modeling a bird, an engine forward section, intra-ply and inter-ply composite damage, and hybrid structural failure. The accuracy of each approach and their numerical modeling considerations are thoroughly investigated. These techniques are then combined to form the full crashworthiness methodology.
It is demonstrated that the complete methodology effectively captures progressive hybrid fan blade fracture, leading edge de-bonding, composite casing delamination, and other significant progressive damage effects caused by direct impact and subsequent engine component interactions. The full damage prognosis capabilities demonstrated by this approach encompass aspects which have remained mainly unaddressed in soft impact analysis. A methodology for assessing the complete extent of impact damage for advanced structural engine designs represents a breakthrough that can contribute greatly to the rapid development of these systems in the future.
Advisors/Committee Members: Bayandor, Javid (committeechair), Inman, Daniel J. (committee member), O'Brien, Walter F. Jr. (committee member).
Subjects/Keywords: Composite damage; Hybrid structures; Progressive failure; Jet engine forward section; Soft impact
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Siddens, A. J. (2012). A Predictive Methodology for Soft Impact Damage in Jet Engines Incorporating Hybrid Composite Structures. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76957
Chicago Manual of Style (16th Edition):
Siddens, Aaron Jeffrey. “A Predictive Methodology for Soft Impact Damage in Jet Engines Incorporating Hybrid Composite Structures.” 2012. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/76957.
MLA Handbook (7th Edition):
Siddens, Aaron Jeffrey. “A Predictive Methodology for Soft Impact Damage in Jet Engines Incorporating Hybrid Composite Structures.” 2012. Web. 22 Feb 2020.
Vancouver:
Siddens AJ. A Predictive Methodology for Soft Impact Damage in Jet Engines Incorporating Hybrid Composite Structures. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/76957.
Council of Science Editors:
Siddens AJ. A Predictive Methodology for Soft Impact Damage in Jet Engines Incorporating Hybrid Composite Structures. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/76957
Virginia Tech
16.
Malladi, Vijaya Venkata Narasimha Sriram.
Development and Design of Self-Sensing SMAs using Thermoelectric Effect.
Degree: MS, Mechanical Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/33407
► Active research of SMAs has shown that its Seebeck coefficient is sensitive to its martensitic phase transformation and has the potential to determine the SMAs…
(more)
▼ Active research of SMAs has shown that its Seebeck coefficient is sensitive to its martensitic phase transformation and has the potential to determine the SMAs state of transformation. The combination of Shape Memory Alloys, which have a positive Seebeck coefficient, and Constantan which has a negative Seebeck coefficient (-35 mV/K) results in a thermocouple capable of measuring temperature. The work presented in this thesis is based on the development and design of this sensor.
This sensor is used to study the hysteretic behaviour of SMAs. Although Shape Memory Alloys (SMAs) exhibit a myriad of nonlinearities, SMAs show two major types of nonlinear hysteresis. During cyclic loading of the SMAs, it is observed that one type of hysteretic behavior depends on the rate of heating the SMAs, whilst the variation of maximum temperature of an SMA in each cycle results in the other hysteretic behavior. This later hysteretic behavior gives rise to major and minor nonlinear loops of SMAs. The present work analyzes the nonlinearities of hysteretic envelopes which gives the different maximum temperatures reached for each hysteretic cycle with respect to stress and strain of the SMA. This work then models this behavior using Adaptive Neuro Fuzzy Inference System (ANFIS) and compares it to experimental results. The nonlinear learning and adaptation of ANFIS architecture makes it suitable to model the temperature path hysteresis of SMAs.
Advisors/Committee Members: Tarazaga, Pablo Alberto (committeechair), Kurdila, Andrew J. (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: ANN; Postion Control; ANFIS; Seebeck Coefficient; Thermoelectric Effects; Sensorless Control; Shape Memory Alloys
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Malladi, V. V. N. S. (2013). Development and Design of Self-Sensing SMAs using Thermoelectric Effect. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33407
Chicago Manual of Style (16th Edition):
Malladi, Vijaya Venkata Narasimha Sriram. “Development and Design of Self-Sensing SMAs using Thermoelectric Effect.” 2013. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/33407.
MLA Handbook (7th Edition):
Malladi, Vijaya Venkata Narasimha Sriram. “Development and Design of Self-Sensing SMAs using Thermoelectric Effect.” 2013. Web. 22 Feb 2020.
Vancouver:
Malladi VVNS. Development and Design of Self-Sensing SMAs using Thermoelectric Effect. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/33407.
Council of Science Editors:
Malladi VVNS. Development and Design of Self-Sensing SMAs using Thermoelectric Effect. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/33407
Virginia Tech
17.
Joyce, Bryan Steven.
Development of an Electromagnetic Energy Harvester for Monitoring Wind Turbine Blades.
Degree: MS, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/36354
► Wind turbine blades experience tremendous stresses while in operation. Failure of a blade can damage other components or other wind turbines. This research focuses on…
(more)
▼ Wind turbine blades experience tremendous stresses while in operation. Failure of a blade can damage other components or other wind turbines. This research focuses on developing an electromagnetic energy harvester for powering structural health monitoring (SHM) equipment inside a turbine blade. The harvester consists of a magnet inside a tube with coils outside the tube. The changing orientation of the blade causes the magnet to slide along the tube, inducing a voltage in the coils which in turn powers the SHM system. This thesis begins with a brief history of electromagnetic energy harvesting and energy harvesters in rotating environments. Next a model of the harvester is developed encompassing the motion of the magnet, the current in the electrical circuit, and the coupling between the mechanical and electrical domains. The nonlinear coupling factor is derived from Faradayâ s law of induction and from modeling the magnet as a magnetic dipole moment. Three experiments are performed to validate the model: a free fall test to verify the coupling factor expression, a rotating test to study the model with a load resistor circuit, and a capacitor charging test to examine the model with an energy storage circuit. The validated model is then examined under varying tube lengths and positions, varying coil sizes and positions, and variations in other parameters. Finally a sample harvester is presented that can power an SHM system inside a large scale wind turbine blade spinning up to 20 RPM and can produce up to 14.1 mW at 19 RPM.
Advisors/Committee Members: Inman, Daniel J. (committeechair), Kasarda, Mary E. F. (committee member), Tarazaga, Pablo Alberto (committee member).
Subjects/Keywords: energy harvesting; electromagnetic; wind turbine blades; structural health monitoring
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Joyce, B. S. (2011). Development of an Electromagnetic Energy Harvester for Monitoring Wind Turbine Blades. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36354
Chicago Manual of Style (16th Edition):
Joyce, Bryan Steven. “Development of an Electromagnetic Energy Harvester for Monitoring Wind Turbine Blades.” 2011. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/36354.
MLA Handbook (7th Edition):
Joyce, Bryan Steven. “Development of an Electromagnetic Energy Harvester for Monitoring Wind Turbine Blades.” 2011. Web. 22 Feb 2020.
Vancouver:
Joyce BS. Development of an Electromagnetic Energy Harvester for Monitoring Wind Turbine Blades. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/36354.
Council of Science Editors:
Joyce BS. Development of an Electromagnetic Energy Harvester for Monitoring Wind Turbine Blades. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/36354
Virginia Tech
18.
Pan, Jan Wei.
On-line Nonlinear Characterization of Anisotropic Materials.
Degree: PhD, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/30239
► This dissertation proposes a new framework to characterize the nonlinear behavior of anisotropic materials in an on-line manner. The proposed framework applies recursive estimation and…
(more)
▼ This dissertation proposes a new framework to characterize the nonlinear behavior of anisotropic materials in an on-line manner. The proposed framework applies recursive estimation and a multi-linear model to characterize the nonlinear behavior of anisotropic materials on-line using full-field strains, which are capable of capturing the multi-axial information of anisotropic materials.
A stochastic method is developed to characterize the linear behavior of anisotropic materials under the influence of full-field strain measurement noise. This method first derives stochastic equations based on the formulas of energy-based characterization that utilizes the principle of ener-gy conservation, and then recursively estimates elastic constants at every acquisition of measure-ment using a Kalman filter (KF). Since the measurement model is expressed nonlinearly, the KF utilizes a Kalman gain, which is newly derived in this dissertation through variance minimization, to achieve optimal characterization. The aforementioned method, namely stochastic linear characteri-zation in this dissertation, becomes a basis of the multi-linear characterization method. This method utilizes a multi-linear model, which is defined by partitions, to characterize the nonlinear constitu-tive relations. The multi-linear characterization scales up the number of estimates and identifies the coefficients of each linear partition using the previously derived KF. The recursive updates in measurements not only removes uncertainty through sensor measurements, but also enables the on-line capability of the nonlinear characterization of anisotropic materials.
A series of numerical and experimental studies were performed to demonstrate the performance of the proposed framework in characterizing the nonlinear behavior of anisotropic materials. The validity and applicability of the proposed framework were confirmed by the comparison with the known values of the characterized constitutive relations. It was found that the proposed framework identified elastic constants that were in good agreement with known values irrespective of the spec-imen geometry. The results of the multi-linear characterization method were well correlated with known nonlinear stress-strain relations and concluded that the proposed framework is capable of characterizing adequate nonlinear behavior on-line.
Advisors/Committee Members: Furukawa, Tomonari (committeechair), Batra, Romesh C. (committee member), Duke, John C. Jr. (committee member), Inman, Daniel J. (committee member), Pitchumani, Ranga (committee member).
Subjects/Keywords: anisotropic materials; on-line characterization; stochastic; nonlinear behavior; full-field measurements
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Pan, J. W. (2010). On-line Nonlinear Characterization of Anisotropic Materials. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30239
Chicago Manual of Style (16th Edition):
Pan, Jan Wei. “On-line Nonlinear Characterization of Anisotropic Materials.” 2010. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/30239.
MLA Handbook (7th Edition):
Pan, Jan Wei. “On-line Nonlinear Characterization of Anisotropic Materials.” 2010. Web. 22 Feb 2020.
Vancouver:
Pan JW. On-line Nonlinear Characterization of Anisotropic Materials. [Internet] [Doctoral dissertation]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/30239.
Council of Science Editors:
Pan JW. On-line Nonlinear Characterization of Anisotropic Materials. [Doctoral Dissertation]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/30239
Virginia Tech
19.
Karami, Mohammad Amin.
Micro-Scale and Nonlinear Vibrational Energy Harvesting.
Degree: PhD, Engineering Science and Mechanics, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/38612
► This work addresses issues in energy harvesting that have plagued the potential use of harvesting through the piezoelectric effect at the MEMS scale. Effective energy…
(more)
▼ This work addresses issues in energy harvesting that have plagued the potential use of harvesting through the piezoelectric effect at the MEMS scale. Effective energy harvesting devices typically consist of a cantilever beam substrate coated with a thin layer of piezoceramic material and fixed with a tip mass tuned to resonant at the dominant frequency of the ambient vibration. The fundamental natural frequency of a beam increases as its length decreases, so that at the MEMS scale the resonance condition occurs orders of magnitude higher than ambient vibration frequencies rendering the harvester ineffective. Here we study two new geometries for MEMS scale cantilever harvesters. The zigzag and spiral geometries have low fundamental frequencies which can be tuned to the ambient vibrations. The second issue in energy harvesting is the frequency sensitivity of the linear vibration harvesters. A nonlinear hybrid energy harvester is presented that has a wide frequency bandwidth and large power output. Finally, linear and nonlinear energy harvesting devices are designed for powering the cardiovascular pacemakers using the vibrations in the chest area induced by the heartbeats.
The mechanical and electromechanical vibrations of the zigzag structure are analytically modeled, verified with Rayleighâ s method, and validated with experiments. An analytical model of coupled bending torsional vibrations of spiral structure is presented. A novel approximation method is developed for analyzing the electromechanical vibrations of energy harvesting devices. The unified approximation method is effective for linear, nonlinear mono-stable, and nonlinear bi-stable energy harvesting. It can also be utilized for piezoelectric, electromagnetic or hybrid energy harvesters. The approximation method accurately approximates the effect of energy harvesting on vibrations of energy harvester with changes in damping ratio and excitation frequency. Experimental investigations are performed to verify the analytical model of the nonlinear hybrid energy harvester. A detailed experimental parametric study of the nonlinear hybrid design is also performed. Linear and nonlinear energy harvesting devices have been designed that can generate sufficient amounts of power from the heartbeat induced vibrations. The nonlinear devices are effective over a wide range of heart rate.
Advisors/Committee Members: Inman, Daniel J. (committeechair), Ross, Shane D. (committee member), Priya, Shashank (committee member), Hyer, Michael W. (committee member), Hajj, Muhammad R. (committee member).
Subjects/Keywords: Continuous Vibrations; Nonlinear Systems; Cardiac Pacemakers; MEMS; Energy Harvesting
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Karami, M. A. (2012). Micro-Scale and Nonlinear Vibrational Energy Harvesting. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/38612
Chicago Manual of Style (16th Edition):
Karami, Mohammad Amin. “Micro-Scale and Nonlinear Vibrational Energy Harvesting.” 2012. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/38612.
MLA Handbook (7th Edition):
Karami, Mohammad Amin. “Micro-Scale and Nonlinear Vibrational Energy Harvesting.” 2012. Web. 22 Feb 2020.
Vancouver:
Karami MA. Micro-Scale and Nonlinear Vibrational Energy Harvesting. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/38612.
Council of Science Editors:
Karami MA. Micro-Scale and Nonlinear Vibrational Energy Harvesting. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/38612
Virginia Tech
20.
Gheisarieha, Mohsen.
Topological chaos and chaotic mixing of viscous flows.
Degree: PhD, Engineering Science and Mechanics, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/27768
► Since it is difficult or impossible to generate turbulent flow in a highly viscous fluid or a microfluidic system, efficient mixing becomes a challenge. However,…
(more)
▼ Since it is difficult or impossible to generate turbulent flow in a highly viscous fluid or a microfluidic system, efficient mixing becomes a challenge. However, it is possible in a laminar flow to generate chaotic particle trajectories (well-known as chaotic advection), that can lead to effective mixing. This dissertation studies mixing in flows with the limiting case of zero Reynolds numbers that are called Stokes flows and illustrates the practical use of different theories, namely the topological chaos theory, the set-oriented analysis and lobe dynamics in the analysis, design and optimization of different laminar-flow mixing systems.
In a recent development, the topological chaos theory has been used to explain the chaos built in the flow only based on the topology of boundary motions. Without considering any details of the fluid dynamics, this novel method uses the Thurston-Nielsen (TN) classification theorem to predict and describe the stretching of material lines both qualitatively and quantitatively. The practical application of this theory toward design and optimization of a viscous-flow mixer and the important role of periodic orbits as "ghost rods" are studied.
The relationship between stretching of material lines (chaos) and the homogenization of a scalar (mixing) in chaotic Stokes flows is examined in this work. This study helps determining the extent to which the stretching can represent real mixing. Using a set-oriented approach to describe the stirring in the flow, invariance or leakiness of the Almost Invariant Sets (AIS) playing the role of ghost rods is found to be in a direct relationship with the rate of homogenization of a scalar. The mixing caused by these AIS and the variations of their structure are explained from the point of view of geometric mechanics using transport through lobes. These lobes are made of segments of invariant manifolds of the periodic points that are generators of the ghost rods.
A variety of the concentration-based measures, the important parameters of their calculation, and the implicit effect of diffusion are described. The studies, measures and methods of this dissertation help in the evaluation and understanding of chaotic mixing systems in nature and in industrial applications. They provide theoretical and numerical grounds for selection of the appropriate mixing protocol and design and optimization of mixing systems, examples of which can be seen throughout the dissertation.
Advisors/Committee Members: Stremler, Mark A. (committeechair), Ross, Shane D. (committee member), Paul, Mark R. (committee member), Inman, Daniel J. (committee member), Aref, Hassan (committee member).
Subjects/Keywords: Lobe Dynamics; Almost Invariant Sets; Topological Chaos; Chaotic Mixing; Stokes Flow
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Gheisarieha, M. (2011). Topological chaos and chaotic mixing of viscous flows. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/27768
Chicago Manual of Style (16th Edition):
Gheisarieha, Mohsen. “Topological chaos and chaotic mixing of viscous flows.” 2011. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/27768.
MLA Handbook (7th Edition):
Gheisarieha, Mohsen. “Topological chaos and chaotic mixing of viscous flows.” 2011. Web. 22 Feb 2020.
Vancouver:
Gheisarieha M. Topological chaos and chaotic mixing of viscous flows. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/27768.
Council of Science Editors:
Gheisarieha M. Topological chaos and chaotic mixing of viscous flows. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/27768
Virginia Tech
21.
Kim, Woon Kyung.
Design and Analysis of Switching Circuits for Energy Harvesting in Piezostrutures.
Degree: PhD, Mechanical Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/28646
► This study deals with a general method for the analysis of a semi-active control technique for a fast-shunt switching system. The benefit of the semi-active…
(more)
▼ This study deals with a general method for the analysis of a semi-active control technique for a fast-shunt switching system. The benefit of the semi-active system is the reduction in power consumption, which is a significant disadvantage of a fully active system compared with a passive system. A semi-active system under consideration is a semi-actively shunted piezoelectric system, which converts the strain energy into electrical energy through strong electromechanical coupling achieved though the piezoelectric phenomenon.
Our proposed semi-active approach combines a PZT-based energy harvesting with a fast switching system driven by a Pulse-Width Modulated (PWM) signal. The fast switching system enables continuous adaptation of vibration energy control/harvesting by varying the PWM duty cycle. This contrasts with a conventional capacitance switching system that can only change the capacitance at discrete values.
The analysis of the current piezoelectric system combined with a fast-switching system poses a considerable challenge as it contains both continuous and discrete characteristics.
The study proposes an enhanced averaging method for analyzing the piecewise linear system. The simulation of the averaged system is much faster than that of the time-varying system. Moreover, the analysis derives error bounds that characterize convergence in the time domain of the averaged system to the original system.
The dissertation begins with the derivation of the equations governing the physics of a piezostructure combined with an electrical switching shunt network. The results of the averaging analysis and numerical simulation are presented in order to provide a basis for estimating the structural responses that range between open- and short-circuit conditions which constitutes two limiting conditions. An experimental study demonstrates that the capacitive shunt bimorph piezostructure coupled with a single switch can be adjusted continuously by varying the PWM duty cycle. And the behavior of such hybrid system can be well predicted by the averaging analysis.
Advisors/Committee Members: Kurdila, Andrew J. (committeechair), Inman, Daniel J. (committee member), Priya, Shashank (committee member), Burns, John A. (committee member), Erturk, Alper (committee member).
Subjects/Keywords: PWM signal; averaging method; switching circuit systems; energy harvesting; piezoelectric material; hybrid continuous-discrete system
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kim, W. K. (2012). Design and Analysis of Switching Circuits for Energy Harvesting in Piezostrutures. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28646
Chicago Manual of Style (16th Edition):
Kim, Woon Kyung. “Design and Analysis of Switching Circuits for Energy Harvesting in Piezostrutures.” 2012. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/28646.
MLA Handbook (7th Edition):
Kim, Woon Kyung. “Design and Analysis of Switching Circuits for Energy Harvesting in Piezostrutures.” 2012. Web. 22 Feb 2020.
Vancouver:
Kim WK. Design and Analysis of Switching Circuits for Energy Harvesting in Piezostrutures. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/28646.
Council of Science Editors:
Kim WK. Design and Analysis of Switching Circuits for Energy Harvesting in Piezostrutures. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/28646
Virginia Tech
22.
Lloyd, John William.
Generalized Predictive Control Parameter Adaptation Using a Fuzzy Logic Approach.
Degree: PhD, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/29306
► A method to adapt the Generalized Predictive Control parameters to improve broadband disturbance rejection was developed and tested. The effect of the parameters on disturbance…
(more)
▼ A method to adapt the Generalized Predictive Control parameters to improve broadband disturbance rejection was developed and tested. The effect of the parameters on disturbance rejection has previously been poorly understood and a trial and error method was used to achieve adequate results. This dissertation provides insight on the effect of the parameters, as well as an adaptive tuning method to adjust them.
The study begins by showing the effect of the four GPC parameters, the control and prediction horizons, control weighting &lambda , and order, on the disturbance rejection and control effort of a vibrating plate. It is shown that the effect of increases in the control and prediction horizon becomes negligible after a certain point. This occurs at nearly the same point for a variety of &lambda 's and orders, and hence they can be eliminated from the tuning space.
The control effort and closed-loop disturbance rejection are shown to be highly dependant on &lambda and order, thereby becoming the parameters that need to be tuned. The behavior is categorized into various groups and further investigated. The pole and zero locations of the closed-loop system are examined to reveal how GPC gains control and how it can fail for non-minimum phase plants.
A set of fuzzy logic modules is developed to adapt &lambda with order fixed, and conversely to adapt order with &lambda fixed. The effectiveness of the method is demonstrated in both numerical simulations and laboratory experiments.
Advisors/Committee Members: Ahmadian, Mehdi (committeechair), Taheri, Saied (committee member), Southward, Steve C. (committee member), Sandu, Adrian (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: GPC; generalized predictive control; active control; adaptive control; fuzzy logic; fuzzy logic adaptation; vibration control; disturbance rejection
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lloyd, J. W. (2011). Generalized Predictive Control Parameter Adaptation Using a Fuzzy Logic Approach. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/29306
Chicago Manual of Style (16th Edition):
Lloyd, John William. “Generalized Predictive Control Parameter Adaptation Using a Fuzzy Logic Approach.” 2011. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/29306.
MLA Handbook (7th Edition):
Lloyd, John William. “Generalized Predictive Control Parameter Adaptation Using a Fuzzy Logic Approach.” 2011. Web. 22 Feb 2020.
Vancouver:
Lloyd JW. Generalized Predictive Control Parameter Adaptation Using a Fuzzy Logic Approach. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/29306.
Council of Science Editors:
Lloyd JW. Generalized Predictive Control Parameter Adaptation Using a Fuzzy Logic Approach. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/29306
Virginia Tech
23.
Kim, Daewon.
Phased Array Damage Detection and Damage Classification in Guided Wave Structural Health Monitoring.
Degree: PhD, Aerospace and Ocean Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/77073
► Although nondestructive evaluation techniques have been implemented in many industry fields and proved to be useful, they are generally expensive, time consuming, and the results…
(more)
▼ Although nondestructive evaluation techniques have been implemented in many industry fields and proved to be useful, they are generally expensive, time consuming, and the results may not always be reliable. To overcome these drawbacks, structural health monitoring (SHM) systems has received significant attention in the past two decades. As structural systems are becoming more complicated and new materials are being developed, new methodologies, theories, and approaches in SHM have been developed for damage detection, diagnosis, and prognosis.
Among the methods developed, the guided Lamb wave based SHM can be a promising technique for damage evaluation since it provides reliable damage information through signals propagating over large distance with little loss of amplitude. While this method is effective for damage assessment, the guided Lamb wave contains complicated mode characteristics, i.e. an infinite number of wave modes exist and these modes are generally dispersive. For this reason, a minimum number of wave modes and various signal processing algorithms are implemented to obtain better signal interpretations.
Phased array beamsteering is an effective means for damage detection in guided Lamb wave SHM systems. Using this method, the wave energy can be focused at localized directions or areas by controlled excitation time delay of each array element. In this research, two types of transducers are utilized as phased array elements to compare beamsteering characteristics. Monolithic piezoceramic (PZT) transducers are investigated for beamsteering by assuming omnidirectional point sources for each actuator. MacroFiber Composite (MFC) transducers with anisotropic actuation are also studied, considering the wave main lobe width, main lobe magnitude, and side lobe levels. Analysis results demonstrate that the MFC phased arrays perform better than the PZT phased arrays for a range of beamsteering angles and have reduced main lobe width and side lobe levels. Experiments using the PZT and MFC phased arrays on an aluminum plate are also performed and compared to the analysis results.
A time-frequency signal processing algorithm coupled with a machine learning method can form a robust damage diagnostic system. Four types of such algorithms, i.e. short time Fourier transform, Wigner-Ville distribution, wavelet transform, and matching pursuit, are investigated to select an appropriate algorithm for damage classification, and a spectrogram based on short time Fourier transform is adopted for its suitability. A machine learning algorithm called Adaboost is chosen due to its effectiveness and high accuracy performance. The classification is preformed using spectrograms and Adaboost for crack and corrosion damages. Artificial cracks and corrosions are created in Abaqus® to obtain the training samples consist of spectrograms. Several beam experiments in laboratory and additional simulations are also performed to get the testing samples for Adaboost. The analysis results show that not only correct damage classification is…
Advisors/Committee Members: Philen, Michael Keith (committeechair), Kapania, Rabesh K. (committee member), Inman, Daniel J. (committee member), Patil, Mayuresh J. (committee member).
Subjects/Keywords: Damage Classification; Signal Processing; Adaboost; Structural Health Monitoring; Phased Array Beamsteering; Damage Detection
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kim, D. (2011). Phased Array Damage Detection and Damage Classification in Guided Wave Structural Health Monitoring. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77073
Chicago Manual of Style (16th Edition):
Kim, Daewon. “Phased Array Damage Detection and Damage Classification in Guided Wave Structural Health Monitoring.” 2011. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/77073.
MLA Handbook (7th Edition):
Kim, Daewon. “Phased Array Damage Detection and Damage Classification in Guided Wave Structural Health Monitoring.” 2011. Web. 22 Feb 2020.
Vancouver:
Kim D. Phased Array Damage Detection and Damage Classification in Guided Wave Structural Health Monitoring. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/77073.
Council of Science Editors:
Kim D. Phased Array Damage Detection and Damage Classification in Guided Wave Structural Health Monitoring. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/77073
Virginia Tech
24.
Lee, Hyunwook.
A Polynomial Chaos Approach for Stochastic Modeling of Dynamic Wheel-Rail Friction.
Degree: PhD, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/77195
► Accurate estimation of the coefficient of friction (CoF) is essential to accurately modeling railroad dynamics, reducing maintenance costs, and increasing safety factors in rail operations.…
(more)
▼ Accurate estimation of the coefficient of friction (CoF) is essential to accurately modeling railroad dynamics, reducing maintenance costs, and increasing safety factors in rail operations. The assumption of a constant CoF is popularly used in simulation studies for ease of implementation, however many evidences demonstrated that CoF depends on various dynamic parameters and instantaneous conditions. In the real world, accurately estimating the CoF is difficult due to effects of various uncertain parameters, such as wheel and rail materials, rail roughness, contact patch, and so on. In this study, the newly developed 3-D nonlinear CoF model for the dry rail condition is introduced and the CoF variation is tested using this model with dynamic parameters estimated from the wheel-rail simulation model. In order to account for uncertain parameters, a stochastic analysis using the polynomial chaos (poly-chaos) theory is performed using the CoF and wheel-rail dynamics models.
The wheel-rail system at a right traction wheel is modeled as a mass-spring-damper system to simulate the basic wheel-rail dynamics and the CoF variation. The wheel-rail model accounts for wheel-rail contact, creepage effect, and creep force, among others. Simulations are performed at train speed of 20 m/s for 4 sec using rail roughness as a unique excitation source. The dynamic simulation has been performed for the deterministic model and for the stochastic model. The dynamics results of the deterministic model provide the starting point for the uncertainty analysis. Six uncertain parameters have been studied with an assumption of 50% uncertainty, intentionally imposed for testing extreme conditions. These parameters are: the maximum amplitude of rail roughness (MARR), the wheel lateral displacement, the track stiffness and damping coefficient, the sleeper distance, and semi-elliptical contact lengths. A symmetric beta distribution is assumed for these six uncertain parameters. The PDF of the CoF has been obtained for each uncertain parameter study, for combinations of two different uncertain parameters, and also for combinations of three different uncertain parameters.
The results from the deterministic model show acceptable vibration results for the body, the wheel, and the rail. The introduced CoF model demonstrates the nonlinear variation of the total CoF, the stick component, and the slip component. In addition, it captures the maximum CoF value (initial peak) successfully. The stochastic analysis results show that the total CoF PDF before 1 sec is dominantly affected by the stick phenomenon, while the slip dominantly influences the total CoF PDF after 1 sec. Although a symmetric distribution has been used for the uncertain parameters considered, the uncertainty in the response obtained displayed a skewed distribution for some of the situations investigated. The CoF PDFs obtained from simulations with combinations of two and three uncertain parameters have wider PDF ranges than those obtained for only one uncertain parameter.
FFT analysis using…
Advisors/Committee Members: Sandu, Corina (committeechair), Ahmadian, Medhi (committee member), Ross, Shane D. (committee member), Inman, Daniel J. (committee member), Sultan, Cornel (committee member).
Subjects/Keywords: Wheel-Rail Dynamics; Polynomial Chaos; Uncertain Parameters; Stochastic Analysis; Coefficient of Friction; Wheel-Rail Vibration; Contact Patch
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lee, H. (2010). A Polynomial Chaos Approach for Stochastic Modeling of Dynamic Wheel-Rail Friction. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77195
Chicago Manual of Style (16th Edition):
Lee, Hyunwook. “A Polynomial Chaos Approach for Stochastic Modeling of Dynamic Wheel-Rail Friction.” 2010. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/77195.
MLA Handbook (7th Edition):
Lee, Hyunwook. “A Polynomial Chaos Approach for Stochastic Modeling of Dynamic Wheel-Rail Friction.” 2010. Web. 22 Feb 2020.
Vancouver:
Lee H. A Polynomial Chaos Approach for Stochastic Modeling of Dynamic Wheel-Rail Friction. [Internet] [Doctoral dissertation]. Virginia Tech; 2010. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/77195.
Council of Science Editors:
Lee H. A Polynomial Chaos Approach for Stochastic Modeling of Dynamic Wheel-Rail Friction. [Doctoral Dissertation]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/77195
Virginia Tech
25.
Anton, Steven Robert.
Multifunctional Piezoelectric Energy Harvesting Concepts.
Degree: PhD, Mechanical Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/27388
► Energy harvesting technology has the ability to create autonomous, self-powered electronic systems that do not rely on battery power for their operation. The term energy…
(more)
▼ Energy harvesting technology has the ability to create autonomous, self-powered electronic systems that do not rely on battery power for their operation. The term energy harvesting describes the process of converting ambient energy surrounding a system into useful electrical energy through the use of a specific material or transducer. A widely studied form of energy harvesting involves the conversion of mechanical vibration energy into electrical energy using piezoelectric materials, which exhibit electromechanical coupling between the electrical and mechanical domains. Typical piezoelectric energy harvesting systems are designed as add-on systems to a host structure located in a vibration rich environment. The added mass and volume of conventional vibration energy harvesting designs can hinder to the operation of the host system. The work presented in this dissertation focuses on advancing piezoelectric energy harvesting concepts through the introduction of multifunctionality in order to alleviate some of the challenges associated with conventional piezoelectric harvesting designs.
The concept of multifunctional piezoelectric self-charging structures is explored throughout this work. The operational principle behind the concept is first described in which piezoelectric layers are directly bonded to thin-film battery layers resulting in a single device capable of simultaneously harvesting and storing electrical energy when excited mechanically. Additionally, it is proposed that self-charging structures be embedded into host structures such that they support structural load during operation. An electromechanical assumed modes model used to predict the coupled electrical and mechanical response of a cantilever self-charging structure subjected to harmonic base excitation is described. Experimental evaluation of a prototype self-charging structure is then performed in order to validate the electromechanical model and to confirm the ability of the device to operate in a self-charging manner. Detailed strength testing is also performed on the prototype device in order to assess its strength properties. Static three-point bend testing as well as dynamic harmonic base excitation testing is performed such that the static bending strength and dynamic strength under vibration excitation is assessed. Three-point bend testing is also performed on a variety of common piezoelectric materials and results of the testing provide a basis for the design of self-charging structures for various applications.
Multifunctional vibration energy harvesting in unmanned aerial vehicles (UAVs) is also investigated as a case study in this dissertation. A flight endurance model recently developed in the literature is applied to model the effects of adding piezoelectric energy harvesting to an electric UAV. A remote control foam glider aircraft is chosen as the test platform for this work and the formulation is used to predict the effects of integrating self-charging structures into the wing spar of the…
Advisors/Committee Members: Inman, Daniel J. (committeechair), Ha, Dong Sam (committee member), Leo, Donald J. (committee member), Priya, Shashank (committee member), Sodano, Henry A. (committee member).
Subjects/Keywords: piezoelectric; unmanned aerial vehicle; multifunctional; energy harvesting
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Anton, S. R. (2011). Multifunctional Piezoelectric Energy Harvesting Concepts. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/27388
Chicago Manual of Style (16th Edition):
Anton, Steven Robert. “Multifunctional Piezoelectric Energy Harvesting Concepts.” 2011. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/27388.
MLA Handbook (7th Edition):
Anton, Steven Robert. “Multifunctional Piezoelectric Energy Harvesting Concepts.” 2011. Web. 22 Feb 2020.
Vancouver:
Anton SR. Multifunctional Piezoelectric Energy Harvesting Concepts. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/27388.
Council of Science Editors:
Anton SR. Multifunctional Piezoelectric Energy Harvesting Concepts. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/27388
Virginia Tech
26.
Choi, Jiduck.
Investigation of the dynamic behavior of a cable-harnessed structure.
Degree: PhD, Mechanical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/49114
► To obtain predictive modeling of a spacecraft, the author investigates the effects of adding cables to a simple structure with the goal of developing an…
(more)
▼ To obtain predictive modeling of a spacecraft, the author investigates the effects of adding cables to a simple structure with the goal of developing an understanding of how cables interacting with a structure. In this research, the author presents predictive and accurate modeling of a cable-harnessed structure by means of the Spectral Element Method (SEM). A double beam model is used to emulate a cable-harnessed structure. SEM modeling can define the location and the number of connections between the two beams in a convenient fashion. The proposed modeling is applied and compared with the conventional FEM. The modeling approach was compared to and validated by measurement data. The validated modeling was implemented to investigate the effect of the number of connections, of the spring stiffness of interconnections, and of mass portion of an attached cable. Damping has an important role in structural design because it reduces the dynamic response, thereby avoiding excessive deflection or stress, fatigue loads, and settling times. Experimental results with some specimens indicate a clear change of damping on the main structure with the inclusion of cable dynamics. The author investigated the modification of the damping of the host structure induced by various attached cables. The identification of a damping matrix is performed using measured data. The effect of the flexibility of a cable harness on damping is observed through experiments with various types of cables. The effect of the number of connections on damping is also investigated by changing the number of connections. Moreover, to overcome the sensitivity to noise in measured data of damping matrix identification approach, various methods are compared with a simulated lumped model and real test results. An improved damping matrix identification approach is proposed and can generate the unique damping matrix over the full frequency range of interest.
Advisors/Committee Members: Inman, Daniel J. (committeechair), Kasarda, Mary E. (committee member), Ahmadian, Mehdi (committee member), Borggaard, Jeffrey T. (committee member), Tarazaga, Pablo Alberto (committee member).
Subjects/Keywords: Cable-Harnessed Structure; Spectral Element Method; Damping Matrix Identification; Finite Element Model Updating
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Choi, J. (2014). Investigation of the dynamic behavior of a cable-harnessed structure. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/49114
Chicago Manual of Style (16th Edition):
Choi, Jiduck. “Investigation of the dynamic behavior of a cable-harnessed structure.” 2014. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/49114.
MLA Handbook (7th Edition):
Choi, Jiduck. “Investigation of the dynamic behavior of a cable-harnessed structure.” 2014. Web. 22 Feb 2020.
Vancouver:
Choi J. Investigation of the dynamic behavior of a cable-harnessed structure. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/49114.
Council of Science Editors:
Choi J. Investigation of the dynamic behavior of a cable-harnessed structure. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/49114
Virginia Tech
27.
Nagode, Clement Michel Jean.
Electromechanical Suspension-based Energy Harvesting Systems for Railroad Applications.
Degree: PhD, Mechanical Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/50611
► Currently, in the railroad industry, the lack of electrical sources in freight cars is a problem that has yet to find practical solutions. Although the…
(more)
▼ Currently, in the railroad industry, the lack of electrical sources in freight cars is a problem that has yet to find practical solutions. Although the locomotive generates electricity to power the traction motors and all the equipment required to operate the train, the electrical power cannot, in a practical manner, be carried out along the length of the train, leaving freight cars unpowered. While this has not been a major issue in the past, there is a strong interest in equipping modern cars with a myriad of devices intended to improve safety, operational efficiency, or health monitoring, using devices such as GPS, active RFID tags, and accelerometers. The implementation of such devices, however, is hindered by the unavailability of electricity. Although ideas such as Timken\'s generator roller bearing or solar panels exist, the railroads have been slow in adopting them for different reasons, including cost, difficulty of implementation, or limited capabilities. The focus of this research is on the development of vibration-based electromechanical energy harvesting systems that would provide electrical power in a freight car. With size and shape similar to conventional shock absorbers, these devices are designed to be placed in parallel with the suspension elements, possibly inside the coil spring, thereby maximizing unutilized space. When the train is in motion, the suspension will accommodate the imperfections of the track, and its relative velocity is used as the input for the harvester, which converts the mechanical energy to useful electrical energy. Beyond developing energy harvesters for freight railcar primary suspensions, this study explores track wayside and miniature systems that can be deployed for applications other than railcars. The trackside systems can be used in places where electrical energy is not readily available, but where, however, there is a need for it. The miniature systems are useful for applications such as bicycle energy. Beyond the design and development of the harvesters, an extensive amount of laboratory testing was conducted to evaluate both the amount of electrical power that can be obtained and the reliability of the components when subjected to repeated vibration cycles. Laboratory tests, totaling more than two million cycles, proved that all the components of the harvester can satisfactorily survive the conditions to which they are subjected in the field. The test results also indicate that the harvesters are capable of generating up to 50 Watts at 22 Vrms, using a 10-Ohm resistor with sine wave inputs, and over 30 Watts at peak with replicated suspension displacements, making them suitable to directly power onboard instruments or to trickle charge a battery.
Advisors/Committee Members: Ahmadian, Mehdi (committeechair), Taheri, Saied (committee member), Burns, John A. (committee member), Inman, Daniel J. (committee member), Priya, Shashank (committee member).
Subjects/Keywords: Energy Harvesting; Railroad; Suspension; Electromagnetic; Truck; Energy Recovery
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Nagode, C. M. J. (2013). Electromechanical Suspension-based Energy Harvesting Systems for Railroad Applications. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50611
Chicago Manual of Style (16th Edition):
Nagode, Clement Michel Jean. “Electromechanical Suspension-based Energy Harvesting Systems for Railroad Applications.” 2013. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/50611.
MLA Handbook (7th Edition):
Nagode, Clement Michel Jean. “Electromechanical Suspension-based Energy Harvesting Systems for Railroad Applications.” 2013. Web. 22 Feb 2020.
Vancouver:
Nagode CMJ. Electromechanical Suspension-based Energy Harvesting Systems for Railroad Applications. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/50611.
Council of Science Editors:
Nagode CMJ. Electromechanical Suspension-based Energy Harvesting Systems for Railroad Applications. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/50611
Virginia Tech
28.
Harne, Ryan Lee.
The study and development of distributed devices for concurrent vibration attenuation and energy harvesting.
Degree: PhD, Mechanical Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/26051
► This work focuses on the broadband attenuation of structural vibration and, in the process, employs a new perspective of vibrational energy harvesting devices. The first…
(more)
▼ This work focuses on the broadband attenuation of structural vibration and, in the process, employs a new perspective of vibrational energy harvesting devices. The first part of the research studies and develops a continuously distributed vibration control device which combines the benefits of point mass-spring-dampers at low frequencies as well as the resistive or dissipative influence of constraining treatments at high frequencies. This embodiment provides broadband passive vibration attenuation for a minimal cost in added mass, spanning the present divide between the ability to attenuate a single low frequency and the need to attenuate all frequencies. The second part adopts a vibration control perspective to energy harvesting analysis and considers the harvesting devices to be electromechanically stiffened and/or damped vibration absorbers. Rigorous analysis and experiments are carried out which show that vibration control and energy harvesting appear to be mutually beneficial given that maximum harvested energy from structural vibrations is achieved when the harvesters exert a finite dynamic influence on the host system. This suggests that vibration control concerns presently alleviated using tuned-mass-dampers are ideal energy harvesting applications.
A generalized analytical model is derived which is applicable to both portions of the work. Continuously distributed vibration control devices are studied in depth and a superposition method is presented which allows for convenient implementation of a realistic device design into the numerical model. Tests carried out with the distributed device validate the model as well as show the device's competitive benefits compared with traditional, and much heavier, vibration control treatments. The inclusion of electromechanical coupling effects into the modeling is straightforward and numerous analyses are carried out to observe how electromagnetic and piezoelectric energy harvesting devices affect the dynamics of the host vibrating structure while the harvesters themselves convert the 'absorbed' energy into electrical power. Altering the device created in the first portion of the research to use a piezoelectric material as the distributed spring yields one such embodiment capable of both surface vibration control and energy harvesting. Tests carried out with the device additionally serve as model validation but also indicate that, for a given harvester, the attenuation of and energy harvesting from structural vibrations are nearly simultaneously maximized as modeling predicted.
Advisors/Committee Members: Burdisso, Ricardo A. (committeechair), Inman, Daniel J. (committee member), Kapania, Rakesh K. (committee member), Leonessa, Alexander (committee member), Papenfuss, Cory M. (committee member).
Subjects/Keywords: vibration suppression; energy harvesting; structural dynamics; piezoelectricity; electromagnetism
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Harne, R. L. (2012). The study and development of distributed devices for concurrent vibration attenuation and energy harvesting. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26051
Chicago Manual of Style (16th Edition):
Harne, Ryan Lee. “The study and development of distributed devices for concurrent vibration attenuation and energy harvesting.” 2012. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/26051.
MLA Handbook (7th Edition):
Harne, Ryan Lee. “The study and development of distributed devices for concurrent vibration attenuation and energy harvesting.” 2012. Web. 22 Feb 2020.
Vancouver:
Harne RL. The study and development of distributed devices for concurrent vibration attenuation and energy harvesting. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/26051.
Council of Science Editors:
Harne RL. The study and development of distributed devices for concurrent vibration attenuation and energy harvesting. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/26051
Virginia Tech
29.
Wang, Ya.
Simultaneous Energy Harvesting and Vibration Control via Piezoelectric Materials.
Degree: PhD, Mechanical Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/26191
► This work examines a novel concept and design of simultaneous energy harvesting and vibration control on the same host structure. The motivating application is a…
(more)
▼ This work examines a novel concept and design of simultaneous energy harvesting and vibration control on the same host structure. The motivating application is a multifunctional composite sandwich wing spar for a small Unmanned Aerial Vehicle (UAV) with the goal of providing self-contained gust alleviation. The basic idea is that the wing itself is able to harvest energy from the ambient vibrations along with available sunlight during normal flight. If the wing experiences any strong wind gust, it will sense the increased vibration levels and provide vibration control to maintain its stability. This work holds promise for improving performance of small UAVs in wind gusts.
The proposed multifunctional wing spar integrates a flexible solar cell array, flexible piezoelectric wafers, a thin film battery and an electronic module into a composite sandwich structure. The basic design factors are discussed for a beam-like multifunctional wing spar with load-bearing energy harvesting, strain sensing and self-controlling functions. Three-point bending tests are performed on the composite sandwich structure for bending strength analysis and bending stiffness prediction under a given safety factor. Additional design factors such as the configuration, location and actuation type of each piezoelectric transducer are investigated for optimal power generation. The equivalent electromechanical representations of a multifunctional wing spar is derived theoretically, simulated numerically and validated experimentally.
Special attention is given to the development of a reduced energy control (REC) law, aiming to minimize the actuation energy and the dissipated heat. The REC law integrates a nonlinear switching algorithm with a positive strain feedback controller, and is represented by a positive feedback operation amplifier (op-amp) and a voltage buffer op-amp for each mode. Experimental results exhibit that the use of nonlinear REC law requires 67.3 % less power than a conventional nonlinear controller to have the same settling time under free vibrations.
Nonlinearity in the electromechanical coupling coefficient of the piezoelectric transducer is also observed, arising from the piezoelectric hysteresis in the constitutive equations coupling the strain field and the electric field. If a constant and voltage-independent electromechanical coupling coefficient is assumed, this nonlinearity results in considerable discrepancies between experimental measurements and simulation results. The voltage-dependent coupling coefficient function is identified experimentally, and a real time adaptive control algorithm is developed to account for the nonlinear coupling behavior, allowing for more accurate numerical simulations.
Experimental validations build upon recent advances in harvester, sensor and actuator technology that have resulted in thin, light-weight multilayered composite sandwich wing spars. These multifunctional wing spars are designed and validated to able to alleviate wind gust of small UAVs using the harvested energy.…
Advisors/Committee Members: Inman, Daniel J. (committeechair), Priya, Shashank (committee member), Leonessa, Alexander (committee member), Kasarda, Mary E. F. (committee member), Viehland, Dwight D. (committee member).
Subjects/Keywords: Energy Harvesting; Vibration Control; Multi-functionalities; Composite Structure; Piezoelectric Materials; Gust Alleviation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wang, Y. (2012). Simultaneous Energy Harvesting and Vibration Control via Piezoelectric Materials. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26191
Chicago Manual of Style (16th Edition):
Wang, Ya. “Simultaneous Energy Harvesting and Vibration Control via Piezoelectric Materials.” 2012. Doctoral Dissertation, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/26191.
MLA Handbook (7th Edition):
Wang, Ya. “Simultaneous Energy Harvesting and Vibration Control via Piezoelectric Materials.” 2012. Web. 22 Feb 2020.
Vancouver:
Wang Y. Simultaneous Energy Harvesting and Vibration Control via Piezoelectric Materials. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/26191.
Council of Science Editors:
Wang Y. Simultaneous Energy Harvesting and Vibration Control via Piezoelectric Materials. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/26191
Virginia Tech
30.
Najem, Joseph Samih.
Design and Development of a Bio-inspired Robotic Jellysh that Features Ionic Polymer Metal Composites Actuators.
Degree: MS, Mechanical Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/32197
► This thesis presents the design and development of a novel biomimetic jellyfish robot that features ionic polymer metal composite actuators. The shape and swimming style…
(more)
▼ This thesis presents the design and development of a novel biomimetic jellyfish robot that
features ionic polymer metal composite actuators. The shape and swimming style of this
underwater vehicle are based on oblate jellyfish species, which are known for their high
locomotive efficiency. Ionic polymer metal composites (IPMC) are used as actuators in
order to contract the bell and thus propel the jellyfish robot. This research focuses on
translating the evolutionary successes of the natural species into a jellyfish robot that mimics
the geometry, the swimming style, and the bell deformation cycle of the natural species. Key
advantages of using IPMC actuators over other forms of smart material include their ability
to exhibit high strain response due to a low voltage input and their ability to act as artificial
muscles in water environment. This research specifically seeks to implement IPMC actuators
in a biomimetic design and overcome two main limitations of these actuators: slow response
rate and the material low blocking force. The approach presented in this document is based
on a combination of two main methods, first by optimizing the performance of the IPMC
actuators and second by optimizing the design to fit the properties of the actuators by
studying various oblate species.
Ionic polymer metal composites consist of a semi-permeable membrane bounded by two
conductive, high surface area electrode. The IPMCs are manufactured is several variations
using the Direct Assembly Process (DAP), where the electrode architecture is controlled
to optimize the strain and stiffness of the actuators. The resulting optimized actuators
demonstrate peak to peak strains of 0.8 % in air and 0.7 % in water across a frequency range
of 0.1-1.0 Hz and voltage amplitude of 2 V.
A study of different oblate species is conducted in order to attain a model system that
best fits the properties of the IPMC actuators. The Aequorea victoria is chosen based on
its bell morphology and kinematic properties that match the mechanical properties of the
IPMC actuators. This medusa is characterized by it low swimming frequency, small bell
deformation during the contraction phase, and high Froude efficiency. The bell morphology
and kinematics of the Aequorea victoria are studied through the computation of the radius
of curvature and thus the strain energy stored in the during the contraction phase. The
results demonstrate that the Aequorea victoria stores lower strain energy compared to the
other candidate species during the contraction phase.
Three consecutive jellyfish robots have been built for this research project. The first generation
served as a proof of concept and swam vertically at a speed of 2.2 mm/s and consumed
3.2 W of power. The second generation mimicked the geometry and swimming style of the
Aurelia aurita. By tailoring the applied voltage waveform and the flexibility of the bell, the
robot swam at an average speed of 1.5 mm/s and consumed 3.5 W of power. The third
and final generation mimicked the morphology, swimming behavior, and…
Advisors/Committee Members: Leo, Donald J. (committeechair), Priya, Shashank (committee member), Sarles, Stephen A. (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: Jellyfish; actuators.; bell kinematics; biomimetic; IPMC; bio-inspired; AUV; UUV; Aequorea victoria; Aurelia aurita
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Najem, J. S. (2012). Design and Development of a Bio-inspired Robotic Jellysh that Features Ionic Polymer Metal Composites Actuators. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32197
Chicago Manual of Style (16th Edition):
Najem, Joseph Samih. “Design and Development of a Bio-inspired Robotic Jellysh that Features Ionic Polymer Metal Composites Actuators.” 2012. Masters Thesis, Virginia Tech. Accessed February 22, 2020.
http://hdl.handle.net/10919/32197.
MLA Handbook (7th Edition):
Najem, Joseph Samih. “Design and Development of a Bio-inspired Robotic Jellysh that Features Ionic Polymer Metal Composites Actuators.” 2012. Web. 22 Feb 2020.
Vancouver:
Najem JS. Design and Development of a Bio-inspired Robotic Jellysh that Features Ionic Polymer Metal Composites Actuators. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2020 Feb 22].
Available from: http://hdl.handle.net/10919/32197.
Council of Science Editors:
Najem JS. Design and Development of a Bio-inspired Robotic Jellysh that Features Ionic Polymer Metal Composites Actuators. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/32197
◁ [1] [2] [3] [4] [5] [6] [7] ▶
. 
Open Access Theses and Dissertations