subject:(Snap through)

University of Waterloo

1. Alneamy, Ayman. Electrostatic Micro-Tweezers.

Degree: 2020, University of Waterloo

► This dissertation presents a novel electrostatic micro-tweezers designed to manipulate particles with diameters in the range of 5-14 μm. The tweezers consist of two grip-arms… (more)

▼ This dissertation presents a novel electrostatic micro-tweezers designed to manipulate particles with diameters in the range of 5-14 μm. The tweezers consist of two grip-arms mounted to an electrostatically actuated initially curved micro-beam. The tweezers offer further control, via electrostatic actuation, to increase the pressure on larger objects and to grasp smaller objects. It can be operated in two modes. The first is a traditional quasi-static mode where DC voltage commands the tweezers along a trajectory to approach, hold and release micro-objects. It exploits nonlinear phenomena in electrostatic curved beams, namely snap-through, snap-back and static pull-in and the bifurcations underlying them. The second mode uses a harmonic voltage signal to release, probe and/or interact with the objects held by the tweezers in order to perform function such as cells lysis and characterization. It exploits additional electrostatic MEMS phenomena including dynamic pull-in as well as the orbits and attractors realized under harmonic excitation. Euler-Bernoulli beam theory is utilized to derive the tweezers governing equation of motion taking into account the arm rotary inertia, the electrostatic fringing field and the nonlinear squeeze-film damping. A reduced-order model (ROM) is developed utilizing two, three and five straight beam mode shapes in a Galerkin expansion. The adequacy of the ROM in representing the tweezers response was investigated by comparing its static and modal response to that of a 2D finite element model (FEM). Simulation results show small differences between the ROM and the FEM static models in the vicinity of snap-through and negligible differences elsewhere. The results also show the ability of the tweezers to manipulate micro-particles and to smoothly compress and hold objects over a voltage range extending from the snap-back voltage (89.01 V) to the pull-in voltage (136.44 V). Characterization of the curved micro-beam show the feasibility of using it as a platform for the tweezers. Evidence of the static snap-through, primary resonance and the superharmonic resonances of orders two and three are observed. The results also show the co-existence of three stable orbits around one stable equilibrium under excitation waveforms with a voltage less than the snap-back voltage. Three branches of orbits are identified as a one branch of small orbits within a narrow potential well and two branches of medium-sized and large orbits within a wider potential well. The transition between those branches results in a characteristic of double-peak frequency-response curve. We also report evidence of a bubble structure along the medium sized branch consisting of a cascade of period-doubling bifurcations and a cascade of reverse period-doubling bifurcations. Experimental evidence of a chaotic attractor developing within this structure is reported. Odd-periodic windows also appear within the attractor including period-three (P-3), period- five (P-5) and period-six (P-6) windows. The chaotic…

Subjects/Keywords: MEMS; Electrostatic; Arch beam; Snap-through; Micro-Tweezers; Rotary inertia

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APA (6^th Edition):

Alneamy, A. (2020). Electrostatic Micro-Tweezers. (Thesis). University of Waterloo. Retrieved from http://hdl.handle.net/10012/16017

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Alneamy, Ayman. “Electrostatic Micro-Tweezers.” 2020. Thesis, University of Waterloo. Accessed March 08, 2021. http://hdl.handle.net/10012/16017.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Alneamy, Ayman. “Electrostatic Micro-Tweezers.” 2020. Web. 08 Mar 2021.

Vancouver:

Alneamy A. Electrostatic Micro-Tweezers. [Internet] [Thesis]. University of Waterloo; 2020. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10012/16017.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Alneamy A. Electrostatic Micro-Tweezers. [Thesis]. University of Waterloo; 2020. Available from: http://hdl.handle.net/10012/16017

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Rice University

2. Chandra, Yenny. Transient behavior of curved structures.

Degree: PhD, Engineering, 2013, Rice University

URL: http://hdl.handle.net/1911/77346

► Slender curved structures can often be found as components of complex structures in civil, mechanical, and aerospace systems. Under extreme loadings, the structure might undergo… (more)

▼ Slender curved structures can often be found as components of complex structures in civil, mechanical, and aerospace systems. Under extreme loadings, the structure might undergo snap-through buckling, i.e., the structure is forced to its inverted configuration, inducing fatigue. The focus of this research is the development of a reliable and accurate model for simulating the nonlinear response of shallow arches under transient loading and characterizing these responses to assess the structure's ability to survive if the structure undergoes instabilities. Since no analytical solutions for general systems with snap-through exist, numerical models are needed in order to predict the response of the structure. The finite element method provides the most generality and can be applied to systems with arbitrarily complex geometries. Unfortunately there are barriers to the numerical prediction. First, the structures exhibit a very complex dynamic response. Coexisting responses are identified under different initial conditions. Chaotic responses are also observed. A framework for analyzing the dynamic responses of slender curved structures is proposed by identifying the relevant features useful in characterizing the transient behavior of shallow arches. State of the art time integrators are often unable to retrieve long time records of the response after a physical instability event. The performance of several time-stepping schemes is analyzed by identifying the important features that affect the numerical accuracy and robustness. We also identify the region where the schemes are stable for such simulations. The interactions between the time-stepping schemes and the spatial discretizations are examined. This investigation results in recommendations for finite elements and time integrators that give the best performance. A new time integrator that is robust and accurate for long-term simulations is proposed. The established numerical framework is validated against experimental data. Fabrication imperfections in the experimental arch and prestressing due to the applied boundary conditions are accounted for. A methodology to determine the boundaries of the stability regions in the parameter space under consideration is proposed. Finally, the effect of initial temperature variation on the transient behavior of shallow arches is also studied. The changes in the snap-through boundaries as the temperature increases are examined. Advisors/Committee Members: Stanciulescu, Ilinca (advisor), Padgett, Jamie E. (committee member), Riviere, Beatrice M. (committee member), Dick, Andrew J. (committee member), Eason, Thomas (committee member).

Subjects/Keywords: Snap-through; Curved structures; Finite element; Time-stepping schemes; Stability boundaries

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APA (6^th Edition):

Chandra, Y. (2013). Transient behavior of curved structures. (Doctoral Dissertation). Rice University. Retrieved from http://hdl.handle.net/1911/77346

Chicago Manual of Style (16^th Edition):

Chandra, Yenny. “Transient behavior of curved structures.” 2013. Doctoral Dissertation, Rice University. Accessed March 08, 2021. http://hdl.handle.net/1911/77346.

MLA Handbook (7^th Edition):

Chandra, Yenny. “Transient behavior of curved structures.” 2013. Web. 08 Mar 2021.

Vancouver:

Chandra Y. Transient behavior of curved structures. [Internet] [Doctoral dissertation]. Rice University; 2013. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1911/77346.

Council of Science Editors:

Chandra Y. Transient behavior of curved structures. [Doctoral Dissertation]. Rice University; 2013. Available from: http://hdl.handle.net/1911/77346

Clemson University

3. Lele, Aditya Girish. An Investigative Study of the Snapthrough, Snapback and the Stiffness Properties of a Kirigami Unit Cell.

Degree: MS, Mechanical Engineering, 2018, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/2994

► Until recently, Carbon Fiber was considered to be a space-age material because of its applications. However, due to the advancements in the synthesis of these… (more)

▼ Until recently, Carbon Fiber was considered to be a space-age material because of its applications. However, due to the advancements in the synthesis of these materials and manufacturing carbon fiber on a large scale, it has now become possible to use carbon fiber in day-to-day applications. Components which were traditionally being made out of steel or aluminum are now being redesigned and made using carbon fiber composites. The Boeing 787 Dreamliner fuselage is an excellent example where carbon fiber has been used as the major component. This is due to the fact that carbon fiber components are much lighter and have a higher strength to weight ratio. Moreover, carbon fiber can be synthesized according to the requirements of the application for possessing any custom-tailored properties. In the 1980’s, an important phenomenon termed as Bistability in composites was observed in unsymmetric CFRP laminates.[1] Bistability in composites is the existence of two stable states in the same composite structure. It is possible to transition between these two stable states by a snap-through or a snap-back process. The composite samples experience a large deformation while snapping-through or snapping-back and thus, a bistable composite can find an application as a part of an Adaptive Structure. The phenomenon of Bistability is observed due to the unsymmetric stacking sequence of the laminates and the thermal stresses developed during the curing process of these composite laminates. While a lot of work has been done on Bistable composites, this research aims at combining the concept of Kirigami with Bistable Composite structures. According to this method, the Bistable laminates are fabricated in a Kirigami pattern. The concept of Kirigami is very similar to Origami. The only difference is that Kirigami allows cutting in addition to folding along the creases of a 2-dimensional pattern. This results in the creation of complex 3-dimensional structures. Thus, the Kirigami pattern is used to lay the individual laminae in such a way that individually bistable laminates are connected to each other with the help of a tab. In this research, the curing process and the snap-through and the snap-back processes of a Kirigami unit cell are simulated using ABAQUS™. Further, the same tests are recreated using a Universal Testing Machine setup for qualitative validation of the FEA model. A separate testing procedure has also been developed to investigate the strength and the snapping phenomenon due to the presence of the tab in the structure. This procedure is again used to validate the FEA results obtained from ABAQUS™. In doing so, this research aims to answer some of the questions concerned with the snapping behavior and stiffness of Kirigami composites. Advisors/Committee Members: Dr. Oliver J. Myers, Committee Chair, Dr. Suyi Li, Dr. Georges Fadel.

Subjects/Keywords: Bistable Fiber Composites; Kirigami; Multistability; Snap-Through behavior; Variable Stiffness

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APA (6^th Edition):

Lele, A. G. (2018). An Investigative Study of the Snapthrough, Snapback and the Stiffness Properties of a Kirigami Unit Cell. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2994

Chicago Manual of Style (16^th Edition):

Lele, Aditya Girish. “An Investigative Study of the Snapthrough, Snapback and the Stiffness Properties of a Kirigami Unit Cell.” 2018. Masters Thesis, Clemson University. Accessed March 08, 2021. https://tigerprints.clemson.edu/all_theses/2994.

MLA Handbook (7^th Edition):

Lele, Aditya Girish. “An Investigative Study of the Snapthrough, Snapback and the Stiffness Properties of a Kirigami Unit Cell.” 2018. Web. 08 Mar 2021.

Vancouver:

Lele AG. An Investigative Study of the Snapthrough, Snapback and the Stiffness Properties of a Kirigami Unit Cell. [Internet] [Masters thesis]. Clemson University; 2018. [cited 2021 Mar 08]. Available from: https://tigerprints.clemson.edu/all_theses/2994.

Council of Science Editors:

Lele AG. An Investigative Study of the Snapthrough, Snapback and the Stiffness Properties of a Kirigami Unit Cell. [Masters Thesis]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_theses/2994

Clemson University

4. Montalbano, Andrew S. Behavior and Energy Loss Optimization of an Elastic Material Metastructure.

Degree: MS, Mechanical Engineering, 2019, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/3132

► Advances in additive manufacturing expand the possibilities of what can be designed and produced. One such example is producing structures that possess designed properties.… (more)

Subjects/Keywords: Bistability; Energy Loss; Metamaterial; Metastructure; Optimization; Snap-through

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APA (6^th Edition):

Montalbano, A. S. (2019). Behavior and Energy Loss Optimization of an Elastic Material Metastructure. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/3132

Chicago Manual of Style (16^th Edition):

Montalbano, Andrew S. “Behavior and Energy Loss Optimization of an Elastic Material Metastructure.” 2019. Masters Thesis, Clemson University. Accessed March 08, 2021. https://tigerprints.clemson.edu/all_theses/3132.

MLA Handbook (7^th Edition):

Montalbano, Andrew S. “Behavior and Energy Loss Optimization of an Elastic Material Metastructure.” 2019. Web. 08 Mar 2021.

Vancouver:

Montalbano AS. Behavior and Energy Loss Optimization of an Elastic Material Metastructure. [Internet] [Masters thesis]. Clemson University; 2019. [cited 2021 Mar 08]. Available from: https://tigerprints.clemson.edu/all_theses/3132.

Council of Science Editors:

Montalbano AS. Behavior and Energy Loss Optimization of an Elastic Material Metastructure. [Masters Thesis]. Clemson University; 2019. Available from: https://tigerprints.clemson.edu/all_theses/3132

Louisiana State University

5. Francis, Varsha. Development of process techniques for bistable microbeam fabrication.

Degree: MSEE, Electrical and Computer Engineering, 2005, Louisiana State University

URL: etd-08252005-130402 ; https://digitalcommons.lsu.edu/gradschool_theses/119

► A design which uses bistable beams to modulate light is suggested in this thesis and appropriate processing techniques are presented. A beam when placed under… (more)

Subjects/Keywords: euler; snap through; bistable

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APA (6^th Edition):

Francis, V. (2005). Development of process techniques for bistable microbeam fabrication. (Masters Thesis). Louisiana State University. Retrieved from etd-08252005-130402 ; https://digitalcommons.lsu.edu/gradschool_theses/119

Chicago Manual of Style (16^th Edition):

Francis, Varsha. “Development of process techniques for bistable microbeam fabrication.” 2005. Masters Thesis, Louisiana State University. Accessed March 08, 2021. etd-08252005-130402 ; https://digitalcommons.lsu.edu/gradschool_theses/119.

MLA Handbook (7^th Edition):

Francis, Varsha. “Development of process techniques for bistable microbeam fabrication.” 2005. Web. 08 Mar 2021.

Vancouver:

Francis V. Development of process techniques for bistable microbeam fabrication. [Internet] [Masters thesis]. Louisiana State University; 2005. [cited 2021 Mar 08]. Available from: etd-08252005-130402 ; https://digitalcommons.lsu.edu/gradschool_theses/119.

Council of Science Editors:

Francis V. Development of process techniques for bistable microbeam fabrication. [Masters Thesis]. Louisiana State University; 2005. Available from: etd-08252005-130402 ; https://digitalcommons.lsu.edu/gradschool_theses/119

Georgia Tech

6. Che, Kaikai. Nonlinear mechanics of multimaterial thermoviscoelastic architected materials with snap-through instabilities.

Degree: PhD, Mechanical Engineering, 2018, Georgia Tech

URL: http://hdl.handle.net/1853/62190

► Architected materials have unusual and interesting properties that are typically unachievable using conventional materials. Many researchers have previously focused on the design and analysis of… (more)

▼ Architected materials have unusual and interesting properties that are typically unachievable using conventional materials. Many researchers have previously focused on the design and analysis of architected materials with snap-through instabilities. This thesis aims to investigate the influence of geometric parameters, temperature and time on the snap-through buckling of one-dimensional (1D) thermoviscoelastic architected materials for applications as reconfigurable architected materials. Rigorous theoretical models of a unit cell with snap-through instabilities are first developed for both the cases of elastic and thermoviscoelastic constitutive models. These theoretical models are utilized to analyze the influence of geometric design, temperature and strain rate on the mechanics of the unit cell. With the understanding of the nonlinear mechanics of the unit cells, strategies (such as introducing small geometric variations in the unit cell design or varying the temperature) are proposed and implemented to tune the snapping sequences of architected materials made of unit cells with snap-through instabilities. With the help of the theoretical model, FEA simulations and experiments, temperature is utilized to tune the snapping sequence of these multimaterial architected materials after their fabrication. Furthermore, it is shown that a time-dependent snapping behavior can be observed in a viscoelastic architected material that has snap-through instabilities. The influence of geometric parameters and temperature on this time-dependent snapping is analyzed. The results provide fundamental understandings of interesting mechanical response that depends on time and temperature, which could help to design and develop reconfigurable and programmable architected materials with tunable properties. Advisors/Committee Members: Meaud, Julien (advisor), Qi, H. Jerry (committee member), Erturk, Alper (committee member), Ruzzene, Massimo (committee member), Rimoli, Julian Jose (committee member).

Subjects/Keywords: Nonlinear mechanics; Thermoviscoelastic; Architected materials; Snap-through instabilities; Time-dependent; Temperature-dependent

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Che, K. (2018). Nonlinear mechanics of multimaterial thermoviscoelastic architected materials with snap-through instabilities. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/62190

Chicago Manual of Style (16^th Edition):

Che, Kaikai. “Nonlinear mechanics of multimaterial thermoviscoelastic architected materials with snap-through instabilities.” 2018. Doctoral Dissertation, Georgia Tech. Accessed March 08, 2021. http://hdl.handle.net/1853/62190.

MLA Handbook (7^th Edition):

Che, Kaikai. “Nonlinear mechanics of multimaterial thermoviscoelastic architected materials with snap-through instabilities.” 2018. Web. 08 Mar 2021.

Vancouver:

Che K. Nonlinear mechanics of multimaterial thermoviscoelastic architected materials with snap-through instabilities. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1853/62190.

Council of Science Editors:

Che K. Nonlinear mechanics of multimaterial thermoviscoelastic architected materials with snap-through instabilities. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/62190

University of Washington

7. Wielgus, Kayla. Finite Element Analysis of Post-buckled Composite Structures.

Degree: 2020, University of Washington

URL: http://hdl.handle.net/1773/45908

► During high-speed flight, an aircraft may experience high stress gradients as a result of high-frequency aerodynamic interactions. Exterior composite panels on an aircraft are also… (more)

Subjects/Keywords: buckled; composite; finite element; snap-through; stress analysis; Civil engineering; Aerospace engineering; Civil engineering

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APA (6^th Edition):

Wielgus, K. (2020). Finite Element Analysis of Post-buckled Composite Structures. (Thesis). University of Washington. Retrieved from http://hdl.handle.net/1773/45908

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Wielgus, Kayla. “Finite Element Analysis of Post-buckled Composite Structures.” 2020. Thesis, University of Washington. Accessed March 08, 2021. http://hdl.handle.net/1773/45908.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Wielgus, Kayla. “Finite Element Analysis of Post-buckled Composite Structures.” 2020. Web. 08 Mar 2021.

Vancouver:

Wielgus K. Finite Element Analysis of Post-buckled Composite Structures. [Internet] [Thesis]. University of Washington; 2020. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1773/45908.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Wielgus K. Finite Element Analysis of Post-buckled Composite Structures. [Thesis]. University of Washington; 2020. Available from: http://hdl.handle.net/1773/45908

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Duke University

8. Wiebe, Richard. Nonlinear Dynamics of Discrete and Continuous Mechanical Systems with Snap-through Instabilities .

Degree: 2012, Duke University

URL: http://hdl.handle.net/10161/6176

► The primary focus of this dissertation is the characterization of snap-through buckling of discrete and continuous systems. Snap-through buckling occurs as the consequence of… (more)

▼ The primary focus of this dissertation is the characterization of snap-through buckling of discrete and continuous systems. Snap-through buckling occurs as the consequence of two factors, first the destabilization, or more often the disappearance of, an equilibrium position under the change of a system parameter, and second the existence of another stable equilibrium configuration at a remote location in state space. In this sense snap-through buckling is a global dynamic transition as the result of a local static instability. In order to better understand the static instabilities that lead to snap-through buckling, the behavior of mechanical systems in the vicinity of various local bifurcations is first investigated. Oscillators with saddle-node, pitchfork, and transcritical bifurcations are shown analytically to exhibit several interesting characteristics, particularly in relation to the system damping ratio. A simple mechanical oscillator with a transcritical bifurcation is used to experimentally verify the analytical results. The transcritical bifurcation was selected since it may be used to represent generic bifurcation behavior. It is shown that the damping ratio may be used to predict changes in stability with respect to changing system parameters. Another useful indicator of snap-through is the presence of chaos in the dynamic response of a system. Chaos is usually associated snap-through, as in many systems large amplitude responses are typically necessary to sufficiently engage the nonlinearities that induce chaos. Thus, a pragmatic approach for identifying chaos in experimental (and hence noisy) systems is also developed. The method is applied to multiple experimental systems showing good agreement with identification via Lyapunov exponents. Under dynamic loading, systems with the requisite condition for snap-through buckling, that is co-existing equilibria, typically exhibit either small amplitude response about a single equilibrium configuration, or large amplitude response that transits between the static equilibria. Dynamic snap-through is the name given to the large amplitude response, which, in the context of structural systems, is obviously undesirable. This phenomenon is investigated using experimental, numerical, and analytical means and the boundaries separating safe (non-snap-through) from unsafe (snap-through) dynamic response in forcing parameter space are obtained for both a discrete and a continuous arch. Arches present an ideal avenue for the investigation of snap-through as they typically have multiple, often tunable, stable and unstable equilibria. They also have many direct applications in both civil engineering, where arches are a canonical structural element, and mechanical engineering, where arches may be used to approximate the behavior of curved plates and panels such as those used on aircraft. Advisors/Committee Members: Virgin, Lawrence N (advisor).

Subjects/Keywords: Civil engineering; Mechanical engineering; Bifurcations; Buckling; Chaos; Nonlinear Dynamics; Snap-Through; Structural Dynamics

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APA (6^th Edition):

Wiebe, R. (2012). Nonlinear Dynamics of Discrete and Continuous Mechanical Systems with Snap-through Instabilities . (Thesis). Duke University. Retrieved from http://hdl.handle.net/10161/6176

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Wiebe, Richard. “Nonlinear Dynamics of Discrete and Continuous Mechanical Systems with Snap-through Instabilities .” 2012. Thesis, Duke University. Accessed March 08, 2021. http://hdl.handle.net/10161/6176.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Wiebe, Richard. “Nonlinear Dynamics of Discrete and Continuous Mechanical Systems with Snap-through Instabilities .” 2012. Web. 08 Mar 2021.

Vancouver:

Wiebe R. Nonlinear Dynamics of Discrete and Continuous Mechanical Systems with Snap-through Instabilities . [Internet] [Thesis]. Duke University; 2012. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10161/6176.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Wiebe R. Nonlinear Dynamics of Discrete and Continuous Mechanical Systems with Snap-through Instabilities . [Thesis]. Duke University; 2012. Available from: http://hdl.handle.net/10161/6176

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Washington

9. van Iderstein, Tyler. Stabilization of Unstable Equilibria in Bistable Structures.

Degree: 2018, University of Washington

URL: http://hdl.handle.net/1773/41756

► Snap-through buckling provides an intricate force-displacement relationship for study. With the possibility for multiple limit points and pitchfork bifurcations and large regions of instability, experimental… (more)

Subjects/Keywords: control system; experimental mechanics; nonlinear mechanics; snap through buckling; stability; Aerospace engineering; Civil engineering; Mechanical engineering; Civil engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

van Iderstein, T. (2018). Stabilization of Unstable Equilibria in Bistable Structures. (Thesis). University of Washington. Retrieved from http://hdl.handle.net/1773/41756

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

van Iderstein, Tyler. “Stabilization of Unstable Equilibria in Bistable Structures.” 2018. Thesis, University of Washington. Accessed March 08, 2021. http://hdl.handle.net/1773/41756.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

van Iderstein, Tyler. “Stabilization of Unstable Equilibria in Bistable Structures.” 2018. Web. 08 Mar 2021.

Vancouver:

van Iderstein T. Stabilization of Unstable Equilibria in Bistable Structures. [Internet] [Thesis]. University of Washington; 2018. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1773/41756.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

van Iderstein T. Stabilization of Unstable Equilibria in Bistable Structures. [Thesis]. University of Washington; 2018. Available from: http://hdl.handle.net/1773/41756

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

10. Hourlier-Fargette, Aurélie. Soft interfaces : from elastocapillary snap-through to droplet dynamics on elastomers : Dynamique de mouillage sur matière molle : du claquage élastocapillaire au dévalement de gouttes sur élastomères.

Degree: Docteur es, Mécanique, 2017, Université Pierre et Marie Curie – Paris VI

URL: http://www.theses.fr/2017PA066089

►

Dans cette thèse à l’interface entre élasticité et capillarité, nous présentons tout d’abord une instabilité élastique, le claquage, revisitée dans un contexte élastocapillaire. En déposant… (more)

▼

Dans cette thèse à l’interface entre élasticité et capillarité, nous présentons tout d’abord une instabilité élastique, le claquage, revisitée dans un contexte élastocapillaire. En déposant une goutte d’eau sous une lamelle flambée en position basse, nous parvenons à déclencher une instabilité de claquage à contresens de la gravité. Cette démonstration de la prédominance des effets capillaires à petite échelle s’accompagne d’une étude des positions d’équilibre et de la stabilité de systèmes goutte-lamelle. Nous démontrons l’influence importante de la taille et de la position de la goutte le long de la lamelle, puis étendons notre étude au cas de bulles ou de gouttes condensées à partir de vapeur d’eau. Enfin, nous nous intéressons à l’aspect dynamique de l’instabilité, qui est dictée principalement par l’élasticité, y compris dans le cas élastocapillaire.Nous mettons ensuite en évidence un phénomène surprenant : la dynamique de descente d’une goutte d’eau sur un élastomère silicone présente deux régimes successifs, caractérisés par deux vitesses différentes. Nous montrons que les chaînes libres non réticulées présentes dans l’élastomère sont à l’origine de cette dynamique inattendue. La goutte est progressivement recouverte par des chaînes de silicone, et sa vitesse change brutalement lorsqu’une concentration surfacique critique est atteinte, ce qui se traduit par une transition brutale de tension de surface. Nous nous intéressons aux vitesses de gouttes dans les deux régimes ainsi qu’aux échelles de temps mises en jeu lors de l’extraction de chaînes non réticulées, et montrons que l’extraction de ces chaînes se produit au niveau de la ligne triple.

This thesis focuses on interactions between liquids and elastic solids. We first revisit the snap-through instability from an elastocapillary point of view, showing that capillary forces are able to counterbalance gravity by inducing snap-through with a droplet deposited below a downward buckled elastic strip clamped at both ends. Equilibrium, stability, and dynamics of drop-strip systems are investigated, demonstrating the influence of droplet size and droplet position along the buckled strip, and showing that capillarity is driving the system toward instability but elasticity is ruling the subsequent dynamics. Spin-off versions of the experiment are also designed, including a humidity-controlled mechanical switch and upscaled experiments using soap bubbles.We then focus on interactions between silicone elastomers and aqueous droplets to understand the mechanisms underlying an unexpected two-regime droplet dynamics observed on vertical silicone elastomer plates. After demonstrating that this two-regime dynamics is due to the presence of uncrosslinked oligomers in the elastomer, we show that the speed transition coincides with a surface tension transition. A quantitative study of the droplets speeds in the two regimes is performed, and the timescale needed for uncrosslinked oligomers to cover the water-air…

Advisors/Committee Members: Antkowiak, Arnaud (thesis director), Neukirch, Sébastien (thesis director).

Subjects/Keywords: Élastocapillarité; Instabilités élastiques; Gouttes; Élastomère silicone; Tension de surface; Interfaces; Elastocapillarity; Elastic instabilities; Buckling; Snap-through; Slender structures; Droplets; 531.38

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APA (6^th Edition):

Hourlier-Fargette, A. (2017). Soft interfaces : from elastocapillary snap-through to droplet dynamics on elastomers : Dynamique de mouillage sur matière molle : du claquage élastocapillaire au dévalement de gouttes sur élastomères. (Doctoral Dissertation). Université Pierre et Marie Curie – Paris VI. Retrieved from http://www.theses.fr/2017PA066089

Chicago Manual of Style (16^th Edition):

Hourlier-Fargette, Aurélie. “Soft interfaces : from elastocapillary snap-through to droplet dynamics on elastomers : Dynamique de mouillage sur matière molle : du claquage élastocapillaire au dévalement de gouttes sur élastomères.” 2017. Doctoral Dissertation, Université Pierre et Marie Curie – Paris VI. Accessed March 08, 2021. http://www.theses.fr/2017PA066089.

MLA Handbook (7^th Edition):

Hourlier-Fargette, Aurélie. “Soft interfaces : from elastocapillary snap-through to droplet dynamics on elastomers : Dynamique de mouillage sur matière molle : du claquage élastocapillaire au dévalement de gouttes sur élastomères.” 2017. Web. 08 Mar 2021.

Vancouver:

Hourlier-Fargette A. Soft interfaces : from elastocapillary snap-through to droplet dynamics on elastomers : Dynamique de mouillage sur matière molle : du claquage élastocapillaire au dévalement de gouttes sur élastomères. [Internet] [Doctoral dissertation]. Université Pierre et Marie Curie – Paris VI; 2017. [cited 2021 Mar 08]. Available from: http://www.theses.fr/2017PA066089.

Council of Science Editors:

Hourlier-Fargette A. Soft interfaces : from elastocapillary snap-through to droplet dynamics on elastomers : Dynamique de mouillage sur matière molle : du claquage élastocapillaire au dévalement de gouttes sur élastomères. [Doctoral Dissertation]. Université Pierre et Marie Curie – Paris VI; 2017. Available from: http://www.theses.fr/2017PA066089

University of Maryland

11. Zhang, Zhao. Morphologic Instability of Graphene and its Potential Applications.

Degree: Mechanical Engineering, 2011, University of Maryland

URL: http://hdl.handle.net/1903/12266

► Graphene is a monolayer of graphite. The surge of interest in graphene, as epitomized by the Nobel Prize in Physics in 2010, is largely attributed… (more)

▼ Graphene is a monolayer of graphite. The surge of interest in graphene, as epitomized by the Nobel Prize in Physics in 2010, is largely attributed to its exceptional properties. Ultra thin, mechanically tough, electrically conductive, and transparent graphene films promise to enable a wealth of possible applications ranging from thin-film solar cells, flexible displays, to biochemical sensing arrays. However, significant gaps remain to realize these potential applications, largely due to the difficulty of precisely controlling graphene properties. Graphene is intrinsically non-flat and tends to be randomly corrugated. The random graphene morphology can lead to unstable performance of graphene devices as the corrugating physics of graphene is closely tied to its electronic properties. Future success of graphene-based applications hinges upon precise control of the graphene morphology, a significant challenge largely unexplored so far. This dissertation aims to explore viable pathways to tailoring graphene morphology and leverage possible morphologic instability of graphene for novel nano-device applications. Inspired by recent experiments, we propose and benchmark a strategy to precisely control the graphene morphology via extrinsic regulation (e.g., substrate surface features, patterned nanowires and nanoparticles). A general energetic framework is delineated to quantitatively determine the extrinsically regulated graphene morphology through energy minimization. Such a framework is benchmarked by determining the graphene morphology regulated by various types and dimensions of nanoscale extrinsic scafffolds, including two dimensional herringbone and checkerboard corrugations on substrate surfaces and one dimensional substrate surface grooves and patterned nanowires. The results reveal a snap-through instability of the graphene morphology, that is, depending on interfacial bonding energy and substrate surface roughness, the graphene morphology exhibits a sharp transition between two distinct states: (1) closely conforming to the substrate surface and (2) remaining nearly flat on the substrate surface. This snap-through instability of graphene holds potential to enable graphene-based functional nano-devices (e.g., ultrasensitive nano-switches). Another type of morphologic instability of graphene is the spontaneous scrolling of graphene into a carbon nanoscroll (CNS). The spiral multilayer nanostructure of CNSs is topologically open and thus distinct from that of carbon nanotubes (CNTs). The unique topological structure of CNSs can enable an array of novel applications, e.g., hydrogen storage, water channels and ultrafast nano-oscillators. However, the realization of CNS-based applications is hindered by the lack of reliable approach to fabricating high quality CNSs. We propose a simple physical approach to fabricating CNSs via CNT-initiated scrolling of graphene on a substrate. The successful formation of a CNS depends on the CNT diameter, the carbon-carbon interaction strength and the graphene-substrate interaction… Advisors/Committee Members: Li, Teng (advisor).

Subjects/Keywords: Mechanical engineering; Mechanics; Materials Science; Carbon Nanoscroll; Morphology of Graphene; Nano-oscillator; Nanopatterns; Snap-through Instability; Substrate Regulation

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APA (6^th Edition):

Zhang, Z. (2011). Morphologic Instability of Graphene and its Potential Applications. (Thesis). University of Maryland. Retrieved from http://hdl.handle.net/1903/12266

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Zhang, Zhao. “Morphologic Instability of Graphene and its Potential Applications.” 2011. Thesis, University of Maryland. Accessed March 08, 2021. http://hdl.handle.net/1903/12266.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Zhang, Zhao. “Morphologic Instability of Graphene and its Potential Applications.” 2011. Web. 08 Mar 2021.

Vancouver:

Zhang Z. Morphologic Instability of Graphene and its Potential Applications. [Internet] [Thesis]. University of Maryland; 2011. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1903/12266.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Zhang Z. Morphologic Instability of Graphene and its Potential Applications. [Thesis]. University of Maryland; 2011. Available from: http://hdl.handle.net/1903/12266

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Virginia Tech

12. Tiwari, Nachiketa. Secondary Buckling of Laminated Composite Plates.

Degree: PhD, Engineering Mechanics, 1999, Virginia Tech

URL: http://hdl.handle.net/10919/37789

► The postbuckling load carrying capacity of composite plates offers immense potential to their applications for loads exceeding their primary buckling load. However, such an efficient… (more)

▼ The postbuckling load carrying capacity of composite plates offers immense potential to their applications for loads exceeding their primary buckling load. However, such an efficient and economical usage of these plates can be reliable only if the nonlinear postbuckling behavior of these plates, which includes a good understanding of secondary buckling, is understood thoroughly. The present investigation is an attempt to understand secondary buckling of almost square composite clamped-simply supported plates, both unstiffened as well as stiffened, in some detail. With the help of the finite element method, a large number of numerical studies have been conducted to understand the secondary buckling characteristics. The sensitivity of these characteristics to variations in boundary conditions, lamination sequence, imperfections, and stiffener geometry has been considered. It has been found that the occurrence of secondary buckling in clamped-simply supported plates under uniform end shortening critically depends on the intensity of restrictions imposed on the inplane normal displacements along the unloaded simply supported edges of the plate. These restrictions could be due to the actual boundary conditions at these edges, or due to the presence of stiffeners along these edges. It has also been found that the presence of imperfections significantly delays the event of secondary buckling. Finally, it has been found that changes in lamination sequence of the plate alter its secondary buckling characteristics in ways that are, in general, quantitative in nature. The numerical investigations were followed by a limited number of experiments involving the testing of unstiffened as well as stiffened composite plates with the intent of augmenting the confidence in the numerical predictions made. Three different lamination sequences were considered during the testing phase of this investigation. It was found that the agreement between experimental data and numerical predictions was quite good. The occurrence of secondary buckling followed the predictions closely. Advisors/Committee Members: Hyer, Michael W. (committeechair), Johnson, Eric R. (committee member), Librescu, Liviu (committee member), Ragab, Saad A. (committee member), Plaut, Raymond H. (committee member).

Subjects/Keywords: snap through; secondary buckling; composites; boundary conditions; imperfections

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APA (6^th Edition):

Tiwari, N. (1999). Secondary Buckling of Laminated Composite Plates. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/37789

Chicago Manual of Style (16^th Edition):

Tiwari, Nachiketa. “Secondary Buckling of Laminated Composite Plates.” 1999. Doctoral Dissertation, Virginia Tech. Accessed March 08, 2021. http://hdl.handle.net/10919/37789.

MLA Handbook (7^th Edition):

Tiwari, Nachiketa. “Secondary Buckling of Laminated Composite Plates.” 1999. Web. 08 Mar 2021.

Vancouver:

Tiwari N. Secondary Buckling of Laminated Composite Plates. [Internet] [Doctoral dissertation]. Virginia Tech; 1999. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10919/37789.

Council of Science Editors:

Tiwari N. Secondary Buckling of Laminated Composite Plates. [Doctoral Dissertation]. Virginia Tech; 1999. Available from: http://hdl.handle.net/10919/37789

13. Simsek, Mehmet R. A Hybrid Position Feedback Controller for Bistable Structures.

Degree: MS, Mechanical & Aerospace Engineering, 2016, Old Dominion University

URL: 9781339893877 ; https://digitalcommons.odu.edu/mae_etds/5

► Bistability is the property of structures showing the ability to attain two statically stable states. Due to dynamic and static advantages such as no… (more)

Subjects/Keywords: Bistable structure; Hybrid feedback control; Morphing wing; Piezoletric actuation; Smart systems; Snap-through; Aerospace Engineering; Mechanical Engineering

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APA (6^th Edition):

Simsek, M. R. (2016). A Hybrid Position Feedback Controller for Bistable Structures. (Thesis). Old Dominion University. Retrieved from 9781339893877 ; https://digitalcommons.odu.edu/mae_etds/5

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Simsek, Mehmet R. “A Hybrid Position Feedback Controller for Bistable Structures.” 2016. Thesis, Old Dominion University. Accessed March 08, 2021. 9781339893877 ; https://digitalcommons.odu.edu/mae_etds/5.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Simsek, Mehmet R. “A Hybrid Position Feedback Controller for Bistable Structures.” 2016. Web. 08 Mar 2021.

Vancouver:

Simsek MR. A Hybrid Position Feedback Controller for Bistable Structures. [Internet] [Thesis]. Old Dominion University; 2016. [cited 2021 Mar 08]. Available from: 9781339893877 ; https://digitalcommons.odu.edu/mae_etds/5.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Simsek MR. A Hybrid Position Feedback Controller for Bistable Structures. [Thesis]. Old Dominion University; 2016. Available from: 9781339893877 ; https://digitalcommons.odu.edu/mae_etds/5

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Virginia Tech

14. Dano, Marie-Laure. SMA-Induced Deformations In general Unsymmetric Laminates.

Degree: PhD, Engineering Science and Mechanics, 1997, Virginia Tech

URL: http://hdl.handle.net/10919/30390

► General unsymmetric laminates exhibit large natural curvatures at room temperature. Additionally, inherent to most unsymmetric laminates is the presence of two stable configurations. Multiple configurations… (more)

▼ General unsymmetric laminates exhibit large natural curvatures at room temperature. Additionally, inherent to most unsymmetric laminates is the presence of two stable configurations. Multiple configurations and stability issues arise because of the geometric nonlinearities associated with the large curvatures. The laminate can be changed from one stable configuration to the other by a simple snap-through action. This situation offers the opportunity to use shape memory alloys (SMA) attached to the laminate to generate the snap-through forces and change the shape of the laminate on command. Presented is a model which can predict SMA-induced deformations in general unsymmetric laminates and, particularly, the occurrence of the snap through. First, a methodology is developed to predict the deformations of flat general unsymmetric epoxy-matrix composite laminates as they are cooled from their elevated cure temperature. Approximations to the strain fields are used in the expression for the total potential energy, and the Rayleigh-Ritz approach is used to study equilibrium. To further study the laminate deformations, finite-element analyses are performed. Experimental results are presented which confirm the predictions of the developed theory and the finite-element analyses regarding the existence of multiple solutions and the magnitude of the deformations. Results are compared with those of several other investigators. Next, the deformation behavior of general unsymmetric laminates subjected to applied forces is studied. The principle of virtual work is used to derive the equilibrium equations relating the laminate deformations to the applied forces. By solving the equilibrium equations as a function of the force level, relations between the laminate deformations and the applied force are derived, and the force level at which the laminate changes shape is determined. Finally, an existing SMA constitutive model is implemented into the developed theory to predict the deformations of simple structures to SMA-induced forces. Experiments on a narrow aluminium plate with an externally attached SMA actuator are conducted. The experimental results show good agreement with the predictions from the developed theory. Next, the deformation behavior of general unsymmetric laminates subjected to SMA actuators is predicted using the developed theory. Experiments using SMA actuators to generate the snap through of nsymmetric laminates are conducted. Good correlation with the developed theory is obtained. Advisors/Committee Members: Hyer, Michael W. (committeechair), Griffin, Odis Hayden Jr. (committee member), Johnson, Eric R. (committee member), Lalande, Frederic (committee member), Morris, Don H. (committee member).

Subjects/Keywords: snap through; instability; modeling of smart structures; shape control

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Dano, M. (1997). SMA-Induced Deformations In general Unsymmetric Laminates. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30390

Chicago Manual of Style (16^th Edition):

Dano, Marie-Laure. “SMA-Induced Deformations In general Unsymmetric Laminates.” 1997. Doctoral Dissertation, Virginia Tech. Accessed March 08, 2021. http://hdl.handle.net/10919/30390.

MLA Handbook (7^th Edition):

Dano, Marie-Laure. “SMA-Induced Deformations In general Unsymmetric Laminates.” 1997. Web. 08 Mar 2021.

Vancouver:

Dano M. SMA-Induced Deformations In general Unsymmetric Laminates. [Internet] [Doctoral dissertation]. Virginia Tech; 1997. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10919/30390.

Council of Science Editors:

Dano M. SMA-Induced Deformations In general Unsymmetric Laminates. [Doctoral Dissertation]. Virginia Tech; 1997. Available from: http://hdl.handle.net/10919/30390

15. Al Hennawi, Qais M. Nonlinear Dynamics of Electrostatically Actuated MEMS Arches.

Degree: Physical Science and Engineering (PSE) Division, 2015, King Abdullah University of Science and Technology

URL: http://hdl.handle.net/10754/554394

► In this thesis, we present theoretical and experimental investigation into the nonlinear statics and dynamics of clamped-clamped in-plane MEMS arches when excited by an electrostatic… (more)

Subjects/Keywords: MEMS; Microarch; Snap-Through; Dynamics; Frequencies

…37 Figure 2.9: Snap-through motion of an arch… …75 Figure 4.9: (a) Arch prior to snap-through; (b) Arch after snap… …the snap-through phenomenon. Furthermore, the arch after the snap-though can withstand more… …rectangular pulse loads. Lock [8] studied the snap-through motion of a simply supported… …values. His results showed that there were two mechanisms that control the snap-through action…

11 more images…

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APA (6^th Edition):

Al Hennawi, Q. M. (2015). Nonlinear Dynamics of Electrostatically Actuated MEMS Arches. (Thesis). King Abdullah University of Science and Technology. Retrieved from http://hdl.handle.net/10754/554394

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Al Hennawi, Qais M. “Nonlinear Dynamics of Electrostatically Actuated MEMS Arches.” 2015. Thesis, King Abdullah University of Science and Technology. Accessed March 08, 2021. http://hdl.handle.net/10754/554394.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Al Hennawi, Qais M. “Nonlinear Dynamics of Electrostatically Actuated MEMS Arches.” 2015. Web. 08 Mar 2021.

Vancouver:

Al Hennawi QM. Nonlinear Dynamics of Electrostatically Actuated MEMS Arches. [Internet] [Thesis]. King Abdullah University of Science and Technology; 2015. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10754/554394.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Al Hennawi QM. Nonlinear Dynamics of Electrostatically Actuated MEMS Arches. [Thesis]. King Abdullah University of Science and Technology; 2015. Available from: http://hdl.handle.net/10754/554394

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Oxford

16. Gomez, Michael. Ghosts and bottlenecks in elastic snap-through.

Degree: PhD, 2018, University of Oxford

URL: http://ora.ox.ac.uk/objects/uuid:11ab7b19-ee4b-4cd6-ac9a-116363a4e4d7 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.757801

► Snap-through is a striking instability in which an elastic object rapidly jumps from one state to another. It is seen in the leaves of the… (more)

▼ Snap-through is a striking instability in which an elastic object rapidly jumps from one state to another. It is seen in the leaves of the Venus flytrap plant and umbrellas flipping on a windy day among many other examples. Similar structures that snap-through are used to generate fast motions in soft robotics, switches in micro-scale electronics and artificial heart valves. Despite the ubiquity of snap-through in nature and engineering, its dynamics is usually only understood qualitatively. In this thesis we develop analytical understanding of this dynamics, focussing on how the mathematical structure underlying the snap-through transition controls the timescale of instability. We begin by considering the dynamics of 'pull-in' instabilities in microelectromechanical systems (MEMS) - a type of snap-through caused by electrostatic forces in which the motions are dominated by fluid damping. Using a lumped-parameter model, we show that the observed time delay near the pull-in transition is a type of critical slowing down - a so-called 'bottleneck' due to the 'ghost' of a saddle-node bifurcation. We obtain a scaling law describing this slowing down, and, in the process, unify a large range of experiments and simulations that exhibit delay phenomena during pull-in. We also investigate the pull-in dynamics of MEMS microbeams, extending the lumped-parameter approach to incorporate the details of the beam geometry. This provides a model system in which to understand snap-through of a continuous elastic structure due to external loading. We develop a perturbation method that systematically exploits the proximity to pull-in to reduce the governing equations to a simpler evolution equation, with a structure that highlights the saddle-node bifurcation. This allows us to analyse the bottleneck dynamics in detail, which we compare with previous experimental and numerical data. The remainder of the thesis is concerned with the dynamics of snap-through in macroscopic systems. In particular, we explore the extent to which dissipation is required to explain anomalously slow snap-through. Considering an elastic arch as an archetype of a snapping system, we use the perturbation method developed earlier to show that two bottleneck regimes are possible, depending delicately on the relative importance of external damping. In particular, we show that critical slowing down occurs even in the absence of damping, leading to a new scaling law for the snap-through time that is confirmed by elastica simulations and experiments. In many real systems material viscoelasticity is present to some degree. Finally, we examine how this influences the snap-through dynamics of a simple truss-like structure. We present a regime diagram that characterises when the timescale of snap-through is controlled by viscous, elastic or viscoelastic effects.

Subjects/Keywords: 510; Applied Mathematics; MEMS; Elasticity; Viscoelasticity; Bistability; Snap-through; Microbeam; Creep; Saddle-node ghost; Dynamics; Instability; Buckling; Electrostatic pull-in; Critical slowing down; Elastic arch

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Gomez, M. (2018). Ghosts and bottlenecks in elastic snap-through. (Doctoral Dissertation). University of Oxford. Retrieved from http://ora.ox.ac.uk/objects/uuid:11ab7b19-ee4b-4cd6-ac9a-116363a4e4d7 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.757801

Chicago Manual of Style (16^th Edition):

Gomez, Michael. “Ghosts and bottlenecks in elastic snap-through.” 2018. Doctoral Dissertation, University of Oxford. Accessed March 08, 2021. http://ora.ox.ac.uk/objects/uuid:11ab7b19-ee4b-4cd6-ac9a-116363a4e4d7 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.757801.

MLA Handbook (7^th Edition):

Gomez, Michael. “Ghosts and bottlenecks in elastic snap-through.” 2018. Web. 08 Mar 2021.

Vancouver:

Gomez M. Ghosts and bottlenecks in elastic snap-through. [Internet] [Doctoral dissertation]. University of Oxford; 2018. [cited 2021 Mar 08]. Available from: http://ora.ox.ac.uk/objects/uuid:11ab7b19-ee4b-4cd6-ac9a-116363a4e4d7 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.757801.

Council of Science Editors:

Gomez M. Ghosts and bottlenecks in elastic snap-through. [Doctoral Dissertation]. University of Oxford; 2018. Available from: http://ora.ox.ac.uk/objects/uuid:11ab7b19-ee4b-4cd6-ac9a-116363a4e4d7 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.757801

University of Washington

17. Kim, Han-Gyu. Experimental Nonlinear Dynamics and Snap-Through of Post-Buckled Thin Laminated Composite Plates.

Degree: 2017, University of Washington

URL: http://hdl.handle.net/1773/39992

► Modern aerospace systems are increasingly being designed with composite panels and plates to achieve light weight and high specific strength and stiffness. For constrained panels,… (more)

Subjects/Keywords: Classical laminated plate theory (CLPT); Digital image correlation (DIC); Experimental nonlinear dynamics; Laminated composite plates; Post-buckled plates; Snap-through; Aerospace engineering; Civil engineering; Mechanical engineering; Civil engineering

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APA (6^th Edition):

Kim, H. (2017). Experimental Nonlinear Dynamics and Snap-Through of Post-Buckled Thin Laminated Composite Plates. (Thesis). University of Washington. Retrieved from http://hdl.handle.net/1773/39992

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Kim, Han-Gyu. “Experimental Nonlinear Dynamics and Snap-Through of Post-Buckled Thin Laminated Composite Plates.” 2017. Thesis, University of Washington. Accessed March 08, 2021. http://hdl.handle.net/1773/39992.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Kim, Han-Gyu. “Experimental Nonlinear Dynamics and Snap-Through of Post-Buckled Thin Laminated Composite Plates.” 2017. Web. 08 Mar 2021.

Vancouver:

Kim H. Experimental Nonlinear Dynamics and Snap-Through of Post-Buckled Thin Laminated Composite Plates. [Internet] [Thesis]. University of Washington; 2017. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1773/39992.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Kim H. Experimental Nonlinear Dynamics and Snap-Through of Post-Buckled Thin Laminated Composite Plates. [Thesis]. University of Washington; 2017. Available from: http://hdl.handle.net/1773/39992

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Virginia Tech

18. Schultz, Marc Robert. Use of Piezoelectric Actuators to Effect Snap-Through Behavior of Unsymmetric Composite Laminates.

Degree: PhD, Engineering Science and Mechanics, 2003, Virginia Tech

URL: http://hdl.handle.net/10919/27086

► As a new concept for morphing structures, the use of piezoelectric actuators to effect snap-through behavior of simple unsymmetric cross-ply composite laminates is examined. Many… (more)

Subjects/Keywords: morphing structures; MFC&174; actuator; unsymmetric laminates; composite materials; snap-through behavior

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APA (6^th Edition):

Schultz, M. R. (2003). Use of Piezoelectric Actuators to Effect Snap-Through Behavior of Unsymmetric Composite Laminates. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/27086

Chicago Manual of Style (16^th Edition):

Schultz, Marc Robert. “Use of Piezoelectric Actuators to Effect Snap-Through Behavior of Unsymmetric Composite Laminates.” 2003. Doctoral Dissertation, Virginia Tech. Accessed March 08, 2021. http://hdl.handle.net/10919/27086.

MLA Handbook (7^th Edition):

Schultz, Marc Robert. “Use of Piezoelectric Actuators to Effect Snap-Through Behavior of Unsymmetric Composite Laminates.” 2003. Web. 08 Mar 2021.

Vancouver:

Schultz MR. Use of Piezoelectric Actuators to Effect Snap-Through Behavior of Unsymmetric Composite Laminates. [Internet] [Doctoral dissertation]. Virginia Tech; 2003. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10919/27086.

Council of Science Editors:

Schultz MR. Use of Piezoelectric Actuators to Effect Snap-Through Behavior of Unsymmetric Composite Laminates. [Doctoral Dissertation]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/27086

Virginia Tech

19. Hause, Terry J. Thermomechanical Postbuckling of Geometrically Imperfect Anisotropic Flat and Doubly Curved Sandwich Panels.

Degree: PhD, Engineering Science and Mechanics, 1998, Virginia Tech

URL: http://hdl.handle.net/10919/30449

► Sandwich structures constitute basic components of advanced supersonic/hypersonic flight and launch vehicles. These advanced flight vehicles operate in hostile environments consisting of high temperature, moisture,… (more)

▼ Sandwich structures constitute basic components of advanced supersonic/hypersonic flight and launch vehicles. These advanced flight vehicles operate in hostile environments consisting of high temperature, moisture, and pressure fields. As a result, these structures are exposed to large lateral pressures, large compressive edge loads, and high temperature gradients which can create large stresses and strains within the structure and can produce the instability of the structure. This creates the need for a better understanding of the behavior of these structures under these complex loading conditions. Moreover, a better understanding of the load carrying capacity of sandwich structures constitutes an essential step towards a more rational design and exploitation of these constructions. In order to address these issues, a comprehensive geometrically non-linear theory of doubly curved sandwich structures constructed of anisotropic laminated face sheets with an orthotropic core under various loadings for simply supported edge conditions is developed. The effects of the radii of curvature, initial geometric imperfections, pressure, uniaxial compressive edge loads, biaxial edge loading consisting of compressive/tensile edge loads, and thermal loads will be analyzed. The effect of the structural tailoring of the facesheets upon the load carrying capacity of the structure under these various loading conditions are analyzed. In addition, the movability/immovability of the unloaded edges and the end-shortening are examined. To pursue this study, two different formulations of the theory are developed. One of these formulations is referred to as the mixed formulation, While the second formulation is referred to as the displacement formulation. Several results are presented encompassing buckling, postbuckling, and stress/strain analysis in conjunction with the application of the structural tailoring technique. The great effects of this technique are explored. Moreover, comparisons with the available theoretical and experimental results are presented and good agreements are reported. Advisors/Committee Members: Librescu, Liviu (committeechair), Thangjitham, Surot (committee member), Kapania, Rakesh K. (committee member), Henneke, Edmund G. II (committee member), Hajj, Muhammad R. (committee member), Librescu, Liviu (committee member).

Subjects/Keywords: Sandwich Structures; Buckling and Postbuckling; Geometrically Nonlinearities; Snap-Through; Geometric Imperfections

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APA (6^th Edition):

Hause, T. J. (1998). Thermomechanical Postbuckling of Geometrically Imperfect Anisotropic Flat and Doubly Curved Sandwich Panels. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30449

Chicago Manual of Style (16^th Edition):

Hause, Terry J. “Thermomechanical Postbuckling of Geometrically Imperfect Anisotropic Flat and Doubly Curved Sandwich Panels.” 1998. Doctoral Dissertation, Virginia Tech. Accessed March 08, 2021. http://hdl.handle.net/10919/30449.

MLA Handbook (7^th Edition):

Hause, Terry J. “Thermomechanical Postbuckling of Geometrically Imperfect Anisotropic Flat and Doubly Curved Sandwich Panels.” 1998. Web. 08 Mar 2021.

Vancouver:

Hause TJ. Thermomechanical Postbuckling of Geometrically Imperfect Anisotropic Flat and Doubly Curved Sandwich Panels. [Internet] [Doctoral dissertation]. Virginia Tech; 1998. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10919/30449.

Council of Science Editors:

Hause TJ. Thermomechanical Postbuckling of Geometrically Imperfect Anisotropic Flat and Doubly Curved Sandwich Panels. [Doctoral Dissertation]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/30449

Virginia Tech

20. Singh, Nitish. Equilibrium of a shallow arch subjected to PZT actuators and a deadweight load.

Degree: MS, Aerospace Engineering, 1996, Virginia Tech

URL: http://hdl.handle.net/10919/46296

► The geometrically nonlinear response of a shallow, circular, cylindrical panel under a midspan line load and induced strain actuation is presented. The panel is a… (more)

Subjects/Keywords: shallow; arch; panel; piezoelectric; snap-through; LD5655.V855 1996.S5464

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APA (6^th Edition):

Singh, N. (1996). Equilibrium of a shallow arch subjected to PZT actuators and a deadweight load. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/46296

Chicago Manual of Style (16^th Edition):

Singh, Nitish. “Equilibrium of a shallow arch subjected to PZT actuators and a deadweight load.” 1996. Masters Thesis, Virginia Tech. Accessed March 08, 2021. http://hdl.handle.net/10919/46296.

MLA Handbook (7^th Edition):

Singh, Nitish. “Equilibrium of a shallow arch subjected to PZT actuators and a deadweight load.” 1996. Web. 08 Mar 2021.

Vancouver:

Singh N. Equilibrium of a shallow arch subjected to PZT actuators and a deadweight load. [Internet] [Masters thesis]. Virginia Tech; 1996. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10919/46296.

Council of Science Editors:

Singh N. Equilibrium of a shallow arch subjected to PZT actuators and a deadweight load. [Masters Thesis]. Virginia Tech; 1996. Available from: http://hdl.handle.net/10919/46296

University of Washington

21. Kim, Han-Gyu. Experimental and Numerical Nonlinear Dynamics and Stress Field Analysis of Post-Buckled Composite Plates.

Degree: PhD, 2019, University of Washington

URL: http://hdl.handle.net/1773/44119

► Thermally-buckled composite panels in aircraft may experience dynamic snap-through due to aerodynamic loading, which can accelerate damage growth (or delamination) in these structures. Therefore, characterizing… (more)

▼ Thermally-buckled composite panels in aircraft may experience dynamic snap-through due to aerodynamic loading, which can accelerate damage growth (or delamination) in these structures. Therefore, characterizing post-buckled dynamic response and corresponding stress fields can be an important step to help assure the structural integrity of composite structures. To address this issue, this work experimentally and numerically investigates nonlinear dynamics and snap-through of post-buckled laminated composite plates under harmonic loading. In addition, stress fields induced by these phenomena are simulated to explore their potential impact on the fatigue failure of composite structures. The experimental investigation made in this work is intended to lead to a better fundamental understanding of the aforementioned phenomena and to provide benchmark data for robust model validation in the nonlinear regime. The dynamic response of a post-buckled composite specimen under various harmonic scenarios is captured using a full-field digital image correlation system. The spatio-temporal complexity and parameter sensitivity of the dynamic response are explored and the snap-through boundaries of the specimen are characterized. Several numerical models are built using in-house finite element codes written in MATLAB and are calibrated using the static full-field measurement of the buckled shape of the specimen. The primary objectives of the modeling done in this work are to develop reliable simulation tools for numerical analysis of nonlinear dynamics, and to investigate the impact of nonlinear dynamics and snap-through on stress fields. A model based on the classical laminated plate theory and nonconforming (semi-C1 continuity) cubic Hermite elements (free of shear locking) is shown to achieve excellent agreement with the experimental observations including the snap-through boundaries. As a ‘truth’ model in the thin plate limit, this model provides a new tool for developing benchmark data (displacement fields) for validation of computationally-demanding models which involve high computational costs or potential locking issues. For accurate and direct computation of stress fields, another model is generated based on the first-order shear deformation theory and bi-linear elements (C0 continuity). The shear and membrane locking issues of this model are exposed through linear and nonlinear analyses of its displacement and stress fields. To address these locking issues, two types of assumed strain methods are employed: the mixed interpolation of tensorial components (MITC4) and the enhanced assumed strain (EAS) method. The geometrically-nonlinear analysis presented herein shows that the EAS method effectively controls both shear and membrane locking, whereas the MITC4 method alleviates only shear locking with strong oscillations of membrane stresses which imply the occurrence of membrane locking. The simulation results obtained using the EAS model reveal that post-buckled response generates larger-amplitude stresses than the pre-buckled… Advisors/Committee Members: Wiebe, Richard (advisor).

Subjects/Keywords: Digital image correlation (DIC); Enhanced assumed strain (EAS); Mixed interpolation of tensorial components (MITC4); Nonlinear dynamics and snap-through boundaries; Shear and membrane locking; Stress and fatigue analysis of post-buckled composite plates; Aerospace engineering; Mechanical engineering; Civil engineering; Civil engineering

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APA (6^th Edition):

Kim, H. (2019). Experimental and Numerical Nonlinear Dynamics and Stress Field Analysis of Post-Buckled Composite Plates. (Doctoral Dissertation). University of Washington. Retrieved from http://hdl.handle.net/1773/44119

Chicago Manual of Style (16^th Edition):

Kim, Han-Gyu. “Experimental and Numerical Nonlinear Dynamics and Stress Field Analysis of Post-Buckled Composite Plates.” 2019. Doctoral Dissertation, University of Washington. Accessed March 08, 2021. http://hdl.handle.net/1773/44119.

MLA Handbook (7^th Edition):

Kim, Han-Gyu. “Experimental and Numerical Nonlinear Dynamics and Stress Field Analysis of Post-Buckled Composite Plates.” 2019. Web. 08 Mar 2021.

Vancouver:

Kim H. Experimental and Numerical Nonlinear Dynamics and Stress Field Analysis of Post-Buckled Composite Plates. [Internet] [Doctoral dissertation]. University of Washington; 2019. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1773/44119.

Council of Science Editors:

Kim H. Experimental and Numerical Nonlinear Dynamics and Stress Field Analysis of Post-Buckled Composite Plates. [Doctoral Dissertation]. University of Washington; 2019. Available from: http://hdl.handle.net/1773/44119

22. Zhou, Yang. Computational Analysis of Curved Structures Exhibiting Instabilities.

Degree: PhD, Engineering, 2017, Rice University

URL: http://hdl.handle.net/1911/95985

► The United States Air Force and the National Aeronautics and Space Administration have made great efforts and spent untold resources to develop reusable hypersonic vehicles… (more)

▼ The United States Air Force and the National Aeronautics and Space Administration have made great efforts and spent untold resources to develop reusable hypersonic vehicles since the early 1950s. In spite of great progress, many scientific and technical challenges still exist. This thesis focuses on developing a robust and efficient computational framework for analyzing snap-through, which is a particular concern for the commonly used slender curved structural components of reusable hypersonic vehicles since it can significantly exacerbate fatigue failure. Snap-through is a type of instability where a curved structure suddenly jumps to a remote configuration. This behavior is highly nonlinear involving sudden and large deformations. Snap-through is a dynamic instability triggered by the loss of stability of an equilibrium state. Examining equilibria and their stability is useful and necessary before costlier transient simulations of snap-through. Curved structures undergoing snap-through can have equilibrium states that cannot be captured by path following algorithms. Two types of ``hidden" equilibria are identified: secondary equilibrium branches bifurcated from the primary path and coexisting equilibria unconnected with the primary path. A numerical procedure that combines branch-switching and arclength methods is proposed to retrieve bifurcated secondary branches, and an analytical approach is introduced to obtain unconnected equilibria. With knowledge of the entire equilibrium manifold, transient simulations of snap-through are then investigated. Time integration of snap-through is very challenging because it is a highly nonlinear behavior involving sudden jumps. Even state-of-the-art schemes fail to provide accurate and efficient long-time predictions. This dissertation extends the preliminary work on an efficient composite scheme with significantly enhanced numerical accuracy and computational efficiency in simulating snap-through. In the design of slender curved components of reusable hypersonic vehicles, it is beneficial to efficiently identify the stability boundaries that separate non-snap from post-snap responses for different designs and loading conditions. Obtaining stability boundaries directly from parametric studies is computationally costly even with the most efficient algorithms. To alleviate the cost, an alternative approach to quickly approximate dynamic stability boundaries is proposed. This approach significantly decreases the number of transient simulations needed and therefore greatly accelerates the exploration of dynamic stability boundaries. Advisors/Committee Members: Stanciulescu, Ilinca (advisor).

Subjects/Keywords: Snap-through Buckling; Curved Structures; Time Integration; Static Stability; Dynamic Stability

…Efficient time integration for snap-through . . . . . . . . . . . 120 6.1.3 Fast approximations… …123 Bibliography 126 Illustrations 1.1 Snap-through buckling of a curved panel… …4 1.2 The equilibrium states of two types of snap-through buckling . . . . . 5 2.1… …90 5.1 A schematic diagram of the scaled snap-through boundary. . . . . . . 96 5.2 A… …coefficient. . . . . . . . . . . . . . 104 5.8 The scaled snap-through boundaries of half-sine and…

1 more image…

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APA (6^th Edition):

Zhou, Y. (2017). Computational Analysis of Curved Structures Exhibiting Instabilities. (Doctoral Dissertation). Rice University. Retrieved from http://hdl.handle.net/1911/95985

Chicago Manual of Style (16^th Edition):

Zhou, Yang. “Computational Analysis of Curved Structures Exhibiting Instabilities.” 2017. Doctoral Dissertation, Rice University. Accessed March 08, 2021. http://hdl.handle.net/1911/95985.

MLA Handbook (7^th Edition):

Zhou, Yang. “Computational Analysis of Curved Structures Exhibiting Instabilities.” 2017. Web. 08 Mar 2021.

Vancouver:

Zhou Y. Computational Analysis of Curved Structures Exhibiting Instabilities. [Internet] [Doctoral dissertation]. Rice University; 2017. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1911/95985.

Council of Science Editors:

Zhou Y. Computational Analysis of Curved Structures Exhibiting Instabilities. [Doctoral Dissertation]. Rice University; 2017. Available from: http://hdl.handle.net/1911/95985

Virginia Tech

23. Das, Kaushik. Analysis of Instabilities in Microelectromechanical Systems, and of Local Water Slamming.

Degree: PhD, Engineering Science and Mechanics, 2009, Virginia Tech

URL: http://hdl.handle.net/10919/29809

► Arch-shaped microelectromechanical systems (MEMS) have been used as mechanical memories, micro-sensors, micro-actuators, and micro-valves. A bi-stable structure, such as an arch, is characterized by a… (more)

▼ Arch-shaped microelectromechanical systems (MEMS) have been used as mechanical memories, micro-sensors, micro-actuators, and micro-valves. A bi-stable structure, such as an arch, is characterized by a multivalued load deflection curve. Here we study the symmetry breaking, the snap-through instability, and the pull-in instability of bi-stable arch shaped MEMS under steady and transient electric loads. We analyze transient finite electroelastodynamic deformations of perfect electrically conducting clamped-clamped beams and arches suspended over a flat rigid semi-infinite perfect conductor. The coupled nonlinear partial differential equations (PDEs) for mechanical deformations are solved numerically by the finite element method (FEM) and those for the electrical problem by the boundary element method. The coupled nonlinear PDE governing transient deformations of the arch based on the Euler-Bernoulli beam theory is solved numerically using the Galerkin method, mode shapes for a beam as basis functions, and integrated numerically with respect to time. For the static problem, the displacement control and the pseudo-arc length continuation (PALC) methods are used to obtain the bifurcation curve of archâ s deflection versus the electric potential. The displacement control method fails to compute archâ s asymmetric deformations that are found by the PALC method. For the dynamic problem, two distinct mechanisms of the snap-through instability are found. It is shown that critical loads and geometric parameters for instabilities of an arch with and without the consideration of mechanical inertia effects are quite different. A phase diagram between a critical load parameter and the arch height is constructed to delineate different regions of instabilities. The local water slamming refers to the impact of a part of a ship hull on stationary water for a short duration during which high local pressures occur. We simulate slamming impact of rigid and deformable hull bottom panels by using the coupled Lagrangian and Eulerian formulation in the commercial FE software LS-DYNA. The Lagrangian formulation is used to describe planestrain deformations of the wedge and the Eulerian description of motion for deformations of the water. A penalty contact algorithm couples the wedge with the water surface. Damage and delamination induced, respectively, in a fiber reinforced composite panel and a sandwich composite panel and due to hydroelastic pressure are studied. Advisors/Committee Members: Batra, Romesh C. (committeechair), Paul, Mark R. (committee member), Dowling, Norman E. (committee member), Hendricks, Scott L. (committee member), Cramer, Mark S. (committee member).

Subjects/Keywords: pull-in instability; symmetry breaking; fluid-structure interaction; local water slamming; snap-through instability

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Das, K. (2009). Analysis of Instabilities in Microelectromechanical Systems, and of Local Water Slamming. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/29809

Chicago Manual of Style (16^th Edition):

Das, Kaushik. “Analysis of Instabilities in Microelectromechanical Systems, and of Local Water Slamming.” 2009. Doctoral Dissertation, Virginia Tech. Accessed March 08, 2021. http://hdl.handle.net/10919/29809.

MLA Handbook (7^th Edition):

Das, Kaushik. “Analysis of Instabilities in Microelectromechanical Systems, and of Local Water Slamming.” 2009. Web. 08 Mar 2021.

Vancouver:

Das K. Analysis of Instabilities in Microelectromechanical Systems, and of Local Water Slamming. [Internet] [Doctoral dissertation]. Virginia Tech; 2009. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/10919/29809.

Council of Science Editors:

Das K. Analysis of Instabilities in Microelectromechanical Systems, and of Local Water Slamming. [Doctoral Dissertation]. Virginia Tech; 2009. Available from: http://hdl.handle.net/10919/29809

24. Ling, Yu. Nonlinear Response of a Skin Panel under Combined Thermal and Structural Loading.

Degree: MS, Computational Science and Engineering, 2012, Miami University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=miami1344731818

► Future hypersonic vehicle will operate in an extreme environment, which involves extreme aerodynamic heating, fluctuating pressure and acoustic loading. Hypersonic vehicle must be reusable,… (more)

Subjects/Keywords: Mechanical Engineering; hypersonic aircraft; skin panel; nonlinear response; thermal buckling; snap-through

…49 FIGURE 5. 19 ONSET OF SNAP-THROUGH BEHAVIOR… …63 FIGURE 6. 16 BOUNDARY OF SNAP-THROUGH UNDER DIFFERENT TEMPERATURE DISTRIBUTION… …68 FIGURE 7. 5 BOUNDARY OF SNAP-THROUGH USING DIFFERENT BOUNDARY CONDITION UNDER UNIFORM… …69 FIGURE 7. 6 BOUNDARY OF SNAP-THROUGH USING DIFFERENT BOUNDARY CONDITION UNDER… …Thermal buckling, snap-through, and snap-buckling behaviors have been investigated. Rigid and…

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APA (6^th Edition):

Ling, Y. (2012). Nonlinear Response of a Skin Panel under Combined Thermal and Structural Loading. (Masters Thesis). Miami University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=miami1344731818

Chicago Manual of Style (16^th Edition):

Ling, Yu. “Nonlinear Response of a Skin Panel under Combined Thermal and Structural Loading.” 2012. Masters Thesis, Miami University. Accessed March 08, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1344731818.

MLA Handbook (7^th Edition):

Ling, Yu. “Nonlinear Response of a Skin Panel under Combined Thermal and Structural Loading.” 2012. Web. 08 Mar 2021.

Vancouver:

Ling Y. Nonlinear Response of a Skin Panel under Combined Thermal and Structural Loading. [Internet] [Masters thesis]. Miami University; 2012. [cited 2021 Mar 08]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=miami1344731818.

Council of Science Editors:

Ling Y. Nonlinear Response of a Skin Panel under Combined Thermal and Structural Loading. [Masters Thesis]. Miami University; 2012. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=miami1344731818

University of Illinois – Urbana-Champaign

25. Dai, Xiangyu. Mechanical response of polyether polyurethane foams under multiaxial stress and the initial yielding of ultrathin films.

Degree: PhD, 0242, 2010, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/16023

► In the first part of this thesis, we study the mechanical response of elastic polyether polyurethane (EPP) foams by means of experiments, theory, and modeling.… (more)

▼ In the first part of this thesis, we study the mechanical response of elastic polyether polyurethane (EPP) foams by means of experiments, theory, and modeling. The experiments include five loading cases: uniaxial compression along the rise direction; uniaxial compression along two mutually perpendicular transverse directions; uniaxial tension along the rise direction; shear combined with compression along the rise direction; and hydrostatic pressure combined with compression along the rise direction. We use a commercial series of five EPP foams of apparent densities (mass per unit volume of foam) 50.3, 63.0, 77.0, 162.9 and 220:5 kg/m3. We perform a test for each foam in the series and each loading case. In every test we measure the mechanical response in the form of a stress-strain curve or a force-displacement curve; in several tests we use a Digital Image Correlation (DIC) technique to compute the strain fields on the surface of the specimen. For some loading cases, including uniaxial compression along the rise direction, the mechanical response of the three foams of lower density exhibits a stress plateau. This stress plateau has been commonly interpreted as a manifestation of a bifurcation of equilibrium (Euler buckling of the microstruture of the foam), a global phenomenon that encompasses the entire microstructure of the foam at once. In this interpretation, the plateau stress (i.e., the value of stress on the stress plateau) is the eigenvalue associated with the bifurcation of equilibrium. Nevertheless, our experimental results indicate that a stress plateau is invariably accompanied by heterogeneous, two-phase strain fields, consistent with the occurrence of a configurational phase transition. Thus we argue that the plateau stress is the Maxwell stress associated with the attainment of a limit point (snap-through buckling of a cell of the foam), a local phenomenon which progressively sweeps through the microstructure of the foam. For other loading cases, including uniaxial compression along a transverse direction, the mechanical response does not exhibit a stress plateau, and the stress-strain curves harden monotonically regardless of the density of the foam. The strain fields remain homogeneous, even for the least dense foam. We use our experimental results to calibrate a mean-field model of EPP foams. In this model, a unit cell composed of several bars is cut off from an idealized, perfectly periodic foam microstrusture. The tips of the bars of the cell are subjected to a set of displacements affine with the applied mean deformation gradient, and left to rotate freely. The unit cell is characterized using a few physically meaningful material and geometric parameters whose values may be readily estimated for any given foam. We verify that under uniaxial loading the model predicts configurational phase transitions, stress plateaus, and two-phase fields for low-density foams; a critical point for foams of a critical density; and monotonically hardening stress-strain curves for… Advisors/Committee Members: Gioia, Gustavo (advisor), Gioia, Gustavo (Committee Chair), Sottos, Nancy R. (committee member), Phillips, James W. (committee member), Wagoner Johnson, Amy J. (committee member).

Subjects/Keywords: Polyther Polyurethane FOAMS; Multiaxial Stress; Initial yielding; Ultrathin Films; Phase Transition; Snap-through Buckling; Critical Exponents; Mean-field Model; Nonconvex Strain Energy Function; Digital Image Correlation; Punching; Self-similar; Surface Stress

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Dai, X. (2010). Mechanical response of polyether polyurethane foams under multiaxial stress and the initial yielding of ultrathin films. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/16023

Chicago Manual of Style (16^th Edition):

Dai, Xiangyu. “Mechanical response of polyether polyurethane foams under multiaxial stress and the initial yielding of ultrathin films.” 2010. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed March 08, 2021. http://hdl.handle.net/2142/16023.

MLA Handbook (7^th Edition):

Dai, Xiangyu. “Mechanical response of polyether polyurethane foams under multiaxial stress and the initial yielding of ultrathin films.” 2010. Web. 08 Mar 2021.

Vancouver:

Dai X. Mechanical response of polyether polyurethane foams under multiaxial stress and the initial yielding of ultrathin films. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2010. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/2142/16023.

Council of Science Editors:

Dai X. Mechanical response of polyether polyurethane foams under multiaxial stress and the initial yielding of ultrathin films. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2010. Available from: http://hdl.handle.net/2142/16023

26. Tawfik, Samer Anwar. Stability and morphing characteristics of bistable composite laminates.

Degree: PhD, Aerospace Engineering, 2008, Georgia Tech

URL: http://hdl.handle.net/1853/24702

► The focus of the current research is to investigate the potential of using bistable unsymmetric cross-ply laminated composites as a means for achieving structures with… (more)

Subjects/Keywords: Bistable behavior; Finite element analysis; Composite materials; Structural stability; Testing and experiments; Snap-through behavior; Morphing; Laminated materials; Composite materials; Structural stability; Morphology; Microstructure

…Predictions of snap-through and snap-back loads of [02/902]T square laminates 46 Table 3… …1: Geometry of square specimens 64 Table 3-2: Experimental snap-through and snap-back… …loads of square specimens 65 Table 3-3: FE snap-through and snap-back loads of square… …Table 3-5: Geometry of rectangular specimens 69 Table 3-6: Experimental snap-through and… …snap-back loads of rectangular specimens 70 Table 3-7: FE snap-through and snap-back loads of…

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APA (6^th Edition):

Tawfik, S. A. (2008). Stability and morphing characteristics of bistable composite laminates. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/24702

Chicago Manual of Style (16^th Edition):

Tawfik, Samer Anwar. “Stability and morphing characteristics of bistable composite laminates.” 2008. Doctoral Dissertation, Georgia Tech. Accessed March 08, 2021. http://hdl.handle.net/1853/24702.

MLA Handbook (7^th Edition):

Tawfik, Samer Anwar. “Stability and morphing characteristics of bistable composite laminates.” 2008. Web. 08 Mar 2021.

Vancouver:

Tawfik SA. Stability and morphing characteristics of bistable composite laminates. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Mar 08]. Available from: http://hdl.handle.net/1853/24702.

Council of Science Editors:

Tawfik SA. Stability and morphing characteristics of bistable composite laminates. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/24702

27. Goodpaster, Benjamin A. Analytical Modeling and Impedance Characterization of Nonlinear, Steady-State Structural Dynamics in Thermomechanical Loading Environments.

Degree: MS, Mechanical Engineering, 2018, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1524063139635613

► This research advances the state-of-the-art of analytical techniques to study the steady-state nonlinear dynamics of multi-degree-of-freedom, multistable structures subjected to harmonic excitations. A recently formulated… (more)

▼ This research advances the state-of-the-art of analytical techniques to study the steady-state nonlinear dynamics of multi-degree-of-freedom, multistable structures subjected to harmonic excitations. A recently formulated analytical methodology, validated by numerical and experimental evidence, has been shown to accurately predict the steady-state dynamics of a discrete, multistable structure. Yet, the analysis is limited to lumped-parameter systems and cannot account for multiphysics phenomena, such as thermomechanical effects. Additionally, the analysis is challenged by an inefficient solution procedure, since the completeness of the dynamic predictions is highly dependent upon the generation of initial conditions. This research develops an enhanced solution procedure and normalization scheme to rectify these limitations, providing a robust and efficient analytical tool in the process. The analytical formulation is then extended to encompass distributed-parameter structures that exhibit global nonlinear coupling among all degrees-of-freedom in a form typical of reduced order models. In the process, assumptions inherent to traditional analyses, such as considering only single-degree-of-freedom systems or systems exhibiting weak nonlinear response, are overcome. Comparisons between the analytical and computational results indicate that the generalized analysis accurately characterizes the nonlinear dynamics of such multistable structures at speeds over two orders of magnitude faster than numerical simulation. Furthermore, the analysis is extended to encompass two-way coupling between thermal and mechanical domains, overcoming limitations of previous thermomechanical analyses. The thermomechanical analysis is capable of predicting the pre- and post-buckled nonlinear dynamics of a distributed-parameter beam model, the efficacy of which is verified with experimental evidence.In the process of developing these advancements to the analytical formulation, the analysis is leveraged to deliver significant, new insight into various aspects of nonlinear structural dynamics. The normalized analytical procedure enables the application of standard modal analysis techniques to structures that exhibit nonlinear deformation. A built-up structure of linearly coupled Duffing oscillators is studied, through which it is revealed that the characteristic displacement response of a single bistable Duffing oscillator is preserved in the higher degree-of-freedom composition by way of the fundamental equivalent nonlinear mode. The thermomechanical analysis is utilized in order to newly characterize the impedance of a distributed parameter structure exhibiting nonlinear dynamics. Furthermore, a measure of thermomechanical impedance that relates the temperature gradient to the velocity response of a structure is proposed and characterized. Both mechanical and thermomechanical impedances are observed to exhibit distinguishing trends that may be utilized to forecast dynamic bifurcations that have various positive or negative ramifications based… Advisors/Committee Members: Harne, Ryan (Advisor).

Subjects/Keywords: Mechanical Engineering; Mechanics; analysis; nonlinear dynamics; thermomechanical coupling; multi-degree-of-freedom structure; impedance; mechanical impedance; thermomechanical impedance; dynamic bifurcation; snap-through; lumped-parameter; distributed-parameter; equivalent linearization

…Intrawell dynamic responses. (b) Snap-through dynamic responses… …nonlinear dynamics denoted by dark gray indicators. Progression of snap-through indicated by light… …of snap-through indicated by light gray arrows. (c-e) Frequency dependence of 1st… …2nd/3rd snap-through eigenvectors, respectively… …Snap-through dynamic responses. ............. 28 Figure 2.11. Analytical and numerical…

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APA (6^th Edition):

Goodpaster, B. A. (2018). Analytical Modeling and Impedance Characterization of Nonlinear, Steady-State Structural Dynamics in Thermomechanical Loading Environments. (Masters Thesis). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1524063139635613

Chicago Manual of Style (16^th Edition):

Goodpaster, Benjamin A. “Analytical Modeling and Impedance Characterization of Nonlinear, Steady-State Structural Dynamics in Thermomechanical Loading Environments.” 2018. Masters Thesis, The Ohio State University. Accessed March 08, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524063139635613.

MLA Handbook (7^th Edition):

Goodpaster, Benjamin A. “Analytical Modeling and Impedance Characterization of Nonlinear, Steady-State Structural Dynamics in Thermomechanical Loading Environments.” 2018. Web. 08 Mar 2021.

Vancouver:

Goodpaster BA. Analytical Modeling and Impedance Characterization of Nonlinear, Steady-State Structural Dynamics in Thermomechanical Loading Environments. [Internet] [Masters thesis]. The Ohio State University; 2018. [cited 2021 Mar 08]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1524063139635613.

Council of Science Editors:

Goodpaster BA. Analytical Modeling and Impedance Characterization of Nonlinear, Steady-State Structural Dynamics in Thermomechanical Loading Environments. [Masters Thesis]. The Ohio State University; 2018. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1524063139635613

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