S. Xiao, Zhilong Peng, Hui Wu, Yin Yao, Shaohua Chen
The fretting contact behavior of nanomaterials is significantly influenced by surface effect. A model of fretting contact between a nano-sized rigid cylindrical indenter and an elastic half-plane is established based on Gurtin-Murdoch (G-M) surface elasticity theory, with which the surface effects on the stress and displacement distributions and the size of stick region in the contact zone are studied. It is found that the surface effect induces an additional traction besides the external force applied by punch, which leads to smoother stress and displacement distributions. The normal surface-induced traction related to the residual surface stress is opposite to the externally applied compression, which results in a material stiffening in the contact zone so that the contact radius, normal displacement and normal stress decrease compared with classical predictions. The tangential surface-induced traction is opposite to the externally applied frictional stress, leading to reductions of the shear stress and tangential displacement in the contact zone. Furthermore, the surface effect leads to three possible states in the contact zone, including complete slip, partial slip and complete stick, instead of the solely partial slip state in classical fretting contact models. Among them, the complete stick is more beneficial for inhibiting the wear of contact devices, which can be realized by reducing the indenter size. The present research does not only help ones to better understand the physical mechanism in nano-scale fretting contact problems, but should also guide the anti-wear design in nano-electro-mechanical (NEMs) systems.
{"title":"Surface effect in nano-scale fretting contact problems","authors":"S. Xiao, Zhilong Peng, Hui Wu, Yin Yao, Shaohua Chen","doi":"10.1115/1.4062885","DOIUrl":"https://doi.org/10.1115/1.4062885","url":null,"abstract":"\u0000 The fretting contact behavior of nanomaterials is significantly influenced by surface effect. A model of fretting contact between a nano-sized rigid cylindrical indenter and an elastic half-plane is established based on Gurtin-Murdoch (G-M) surface elasticity theory, with which the surface effects on the stress and displacement distributions and the size of stick region in the contact zone are studied. It is found that the surface effect induces an additional traction besides the external force applied by punch, which leads to smoother stress and displacement distributions. The normal surface-induced traction related to the residual surface stress is opposite to the externally applied compression, which results in a material stiffening in the contact zone so that the contact radius, normal displacement and normal stress decrease compared with classical predictions. The tangential surface-induced traction is opposite to the externally applied frictional stress, leading to reductions of the shear stress and tangential displacement in the contact zone. Furthermore, the surface effect leads to three possible states in the contact zone, including complete slip, partial slip and complete stick, instead of the solely partial slip state in classical fretting contact models. Among them, the complete stick is more beneficial for inhibiting the wear of contact devices, which can be realized by reducing the indenter size. The present research does not only help ones to better understand the physical mechanism in nano-scale fretting contact problems, but should also guide the anti-wear design in nano-electro-mechanical (NEMs) systems.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44749444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Topologically Interlocked Structures (TIS) are structural assemblies that achieve stability and carrying capacity through the geometric arrangement of interlocking blocks, relying solely on contact and friction forces for load transfer. Unlike beam-like TIS, whose deflection never exceeds the height of the blocks, the deflection of slab-like TIS often does. Yet, the upper limit of deflection of slab-like TIS, a key parameter defining their loading energy capacity, remains unexplored. Here, we establish a theoretical upper bound for the deflection capacity of slab-like TIS and outline a systematic design strategy to approach this upper bound. This strategy is based on engineering the contact interfaces such that the non-central blocks are more engaged in the structural response, leading to a more global and holistic deformation mode with higher deflections. We demonstrate the application of this strategy in a numerical case study on a typical slab-like TIS and show that it leads to a 350% increase in deflection, yielding a value closer to the upper bound than previously reported in the literature. We find that the resulting deflection mode engages all the blocks equally, avoids localized sliding modes, and resembles that of monolithic equivalents. Lastly, we show that the strategy not only maximizes TIS' deflection capacity but also its loading energy capacity.
{"title":"The deflection limit of slab-like topologically interlocked structures","authors":"Silvan Ullmann, David S. Kammer, Shai Feldfogel","doi":"10.1115/1.4063345","DOIUrl":"https://doi.org/10.1115/1.4063345","url":null,"abstract":"\u0000 Topologically Interlocked Structures (TIS) are structural assemblies that achieve stability and carrying capacity through the geometric arrangement of interlocking blocks, relying solely on contact and friction forces for load transfer. Unlike beam-like TIS, whose deflection never exceeds the height of the blocks, the deflection of slab-like TIS often does. Yet, the upper limit of deflection of slab-like TIS, a key parameter defining their loading energy capacity, remains unexplored. Here, we establish a theoretical upper bound for the deflection capacity of slab-like TIS and outline a systematic design strategy to approach this upper bound. This strategy is based on engineering the contact interfaces such that the non-central blocks are more engaged in the structural response, leading to a more global and holistic deformation mode with higher deflections. We demonstrate the application of this strategy in a numerical case study on a typical slab-like TIS and show that it leads to a 350% increase in deflection, yielding a value closer to the upper bound than previously reported in the literature. We find that the resulting deflection mode engages all the blocks equally, avoids localized sliding modes, and resembles that of monolithic equivalents. Lastly, we show that the strategy not only maximizes TIS' deflection capacity but also its loading energy capacity.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42893317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper develops a general form of Gauss's Principle of Least Constraint, which deals with the manner in which Nature appears to orchestrate the motion of constrained mechanical systems. The theory of constrained motion has been at the heart of classical mechanics since the days of Lagrange, and it is used in various areas of science and engineering like analytical dynamics, quantum mechanics, statistical physics, and nonequilibrium thermodynamics. The new principle permits the constraints on any mechanical system to be inconsistent and shows that Nature handles these inconsistent constraints in the least squares sense. This broadening of Gauss's original principle leads to two forms of the General Gauss Principle obtained in this paper. They explain why the motion that Nature generates is robust with respect to inaccuracies with which constraints are often specified in modeling naturally occurring and engineered systems since their specification in dynamical systems are often only approximate, and many physical systems may not exactly satisfy them at every instant of time. An important byproduct of the new principle is a refinement of the notion of what constitutes a virtual displacement, a foundational concept in classical mechanics.
{"title":"The General Gauss Principle of Least Constraint","authors":"F. Udwadia","doi":"10.1115/1.4062887","DOIUrl":"https://doi.org/10.1115/1.4062887","url":null,"abstract":"\u0000 This paper develops a general form of Gauss's Principle of Least Constraint, which deals with the manner in which Nature appears to orchestrate the motion of constrained mechanical systems. The theory of constrained motion has been at the heart of classical mechanics since the days of Lagrange, and it is used in various areas of science and engineering like analytical dynamics, quantum mechanics, statistical physics, and nonequilibrium thermodynamics. The new principle permits the constraints on any mechanical system to be inconsistent and shows that Nature handles these inconsistent constraints in the least squares sense. This broadening of Gauss's original principle leads to two forms of the General Gauss Principle obtained in this paper. They explain why the motion that Nature generates is robust with respect to inaccuracies with which constraints are often specified in modeling naturally occurring and engineered systems since their specification in dynamical systems are often only approximate, and many physical systems may not exactly satisfy them at every instant of time. An important byproduct of the new principle is a refinement of the notion of what constitutes a virtual displacement, a foundational concept in classical mechanics.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45567267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A novel approach to enhance the shock vibration environment of multi-directions using a high-static-low-dynamic stiffness supported orthogonal six degree-of-freedoms (DOFs) nonlinear vibration isolation (OSNVI) system is presented in this paper. By combining spring positive stiffness and magnetic negative stiffness, the proposed system achieves high-static-low-dynamic stiffness. Under the multi-directions half-sine vibration, the dynamic equation of the OSNVI is obtained. Both dynamic and static analysis methods are utilized to explore the effect of various parameters on the shock isolation performance of the OSNVI from both the time and frequency domains. The results indicate that the proposed OSNVI can efficiently suppress multi-direction shocks at the cost of only one second. Although a nonlinear jump is usually not expected, the nonlinear jump of the OSNVI could improve the load capacity by increasing the spring stiffness without changing the shock isolation frequency band. Finally, a shock experiment is employed through a three-axis shaker platform to validate the shock isolation performance of the orthogonal six-DOFs nonlinear vibration isolator. The proposed OSNVI provides a promising approach to suppress the multi-directional shock vibrations.
{"title":"Shock Isolation of an Orthogonal Six DOFs Platform with High-Static-Low-Dynamic Stiffness","authors":"Rong-Biao Hao, Ze-Qi Lu, H. Ding, Liqun Chen","doi":"10.1115/1.4062886","DOIUrl":"https://doi.org/10.1115/1.4062886","url":null,"abstract":"\u0000 A novel approach to enhance the shock vibration environment of multi-directions using a high-static-low-dynamic stiffness supported orthogonal six degree-of-freedoms (DOFs) nonlinear vibration isolation (OSNVI) system is presented in this paper. By combining spring positive stiffness and magnetic negative stiffness, the proposed system achieves high-static-low-dynamic stiffness. Under the multi-directions half-sine vibration, the dynamic equation of the OSNVI is obtained. Both dynamic and static analysis methods are utilized to explore the effect of various parameters on the shock isolation performance of the OSNVI from both the time and frequency domains. The results indicate that the proposed OSNVI can efficiently suppress multi-direction shocks at the cost of only one second. Although a nonlinear jump is usually not expected, the nonlinear jump of the OSNVI could improve the load capacity by increasing the spring stiffness without changing the shock isolation frequency band. Finally, a shock experiment is employed through a three-axis shaker platform to validate the shock isolation performance of the orthogonal six-DOFs nonlinear vibration isolator. The proposed OSNVI provides a promising approach to suppress the multi-directional shock vibrations.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49533752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Foam sandwich tube is composed of two tubes and a lightweight foam core possessing various advantages, i.e. low density, excellent mitigation performance and energy absorption, etc. With the hope of enhancing the load bearing and energy absorption capacity of energy absorbers, a novel efficient energy absorber composing of axial necking-expansion deformation mode for sandwich circular tube with metal foam core (SCMF-Tube) by an inner-outer conical-cylindrical die is proposed. Considering deformation modes including necking, stretching, bending and strain hardening of metal tubes as well as densification of the metal foam core, we established an analytical model of necking-expansion deformation for the SCMF-Tube. Then, FE simulations are conducted. Analytical deformation modes, load-displacement curves and bending radii all agree well with the FE results. Effects of material property and geometry on the necking-expansion deformation of SCMF-Tubes are discussed in detail based on the validated analytical model. Adjusting parameters, such as the wall thickness ratio of the inner tube to the outer tube and the maximum diameter of the die can improve the load bearing and energy absorption capacity of the novel energy absorber. Finally, the specific energy absorption (SEA) of the SCMF-Tube under necking-expansion deformation is 68% higher than that of the circular metal tube under expansion deformation.
{"title":"A novel efficient energy absorber with necking-expansion of foam sandwich tubes","authors":"Haoyuan Guo, Jianxun Zhang","doi":"10.1115/1.4062843","DOIUrl":"https://doi.org/10.1115/1.4062843","url":null,"abstract":"\u0000 Foam sandwich tube is composed of two tubes and a lightweight foam core possessing various advantages, i.e. low density, excellent mitigation performance and energy absorption, etc. With the hope of enhancing the load bearing and energy absorption capacity of energy absorbers, a novel efficient energy absorber composing of axial necking-expansion deformation mode for sandwich circular tube with metal foam core (SCMF-Tube) by an inner-outer conical-cylindrical die is proposed. Considering deformation modes including necking, stretching, bending and strain hardening of metal tubes as well as densification of the metal foam core, we established an analytical model of necking-expansion deformation for the SCMF-Tube. Then, FE simulations are conducted. Analytical deformation modes, load-displacement curves and bending radii all agree well with the FE results. Effects of material property and geometry on the necking-expansion deformation of SCMF-Tubes are discussed in detail based on the validated analytical model. Adjusting parameters, such as the wall thickness ratio of the inner tube to the outer tube and the maximum diameter of the die can improve the load bearing and energy absorption capacity of the novel energy absorber. Finally, the specific energy absorption (SEA) of the SCMF-Tube under necking-expansion deformation is 68% higher than that of the circular metal tube under expansion deformation.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48543720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chetna Srivastava, V. M., P. Pitchai, P. Guruprasad, N. Petrinic, F. Scarpa, D. Harursampath, Sathiskumar Anusuya Ponnusami
In this work, the variational asymptotic method (VAM) based homogenization framework is used for the first time to determine the equivalent elastic stiffness tensor of auxetic materials. The proposed method allows the structural elements of the auxetic unit cell to naturally incorporate rotational degrees of freedom, without any ad-hoc assumptions. The overall macroscale homogenized response of the unit-cells is considered to be fully anisotropic; specific possible responses, representative of orthotropy or transverse isotropy naturally emerge from the VAM-based homogenization, due to the arrangements of the structural elements making up the unit-cell. For all the auxetic unit cell geometries considered in this study, the predictions obtained from the in-house python-based implementation of the VAM-based homogenization framework are validated using commercial finite element software (Abaqus) and open literature. The results demonstrate the versatility and the computational efficiency of the VAM-based homogenization framework to describe auxetic metamaterials.
{"title":"Effective mechanical properties of auxetic materials: Numerical predictions using variational asymptotic method based homogenization","authors":"Chetna Srivastava, V. M., P. Pitchai, P. Guruprasad, N. Petrinic, F. Scarpa, D. Harursampath, Sathiskumar Anusuya Ponnusami","doi":"10.1115/1.4062845","DOIUrl":"https://doi.org/10.1115/1.4062845","url":null,"abstract":"\u0000 In this work, the variational asymptotic method (VAM) based homogenization framework is used for the first time to determine the equivalent elastic stiffness tensor of auxetic materials. The proposed method allows the structural elements of the auxetic unit cell to naturally incorporate rotational degrees of freedom, without any ad-hoc assumptions. The overall macroscale homogenized response of the unit-cells is considered to be fully anisotropic; specific possible responses, representative of orthotropy or transverse isotropy naturally emerge from the VAM-based homogenization, due to the arrangements of the structural elements making up the unit-cell. For all the auxetic unit cell geometries considered in this study, the predictions obtained from the in-house python-based implementation of the VAM-based homogenization framework are validated using commercial finite element software (Abaqus) and open literature. The results demonstrate the versatility and the computational efficiency of the VAM-based homogenization framework to describe auxetic metamaterials.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47222664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study the mechanical behavior of a thin elastic film that is affixed to a rigid substrate and subjected to a transverse force using a shaft with a finite radius. This scenario, also referred to as axisymmetric peeling, is encountered frequently in conventional blister tests as well as in our daily lives when removing an adhesive film from a substrate. Our primary objective is to gain a quantitative understanding of how the shaft's radius influences the relationships between force and displacement, as well as between force and delamination areas. These relationships can serve as a dependable method to determine both the film's elastic modulus and the adhesion strength between the film and its substrate. In this work, we provide a simple perturbation solution to this geometrically nonlinear problem while avoiding any use of ad hoc assumptions that were previously required in the literature. As a result, our results are in excellent agreement with numerical simulations and offer improved accuracy compared to analytical solutions available in the literature.
{"title":"Axisymmetric peeling of thin elastic films: A perturbation solution","authors":"E. Chen, Zhaohe Dai","doi":"10.1115/1.4062831","DOIUrl":"https://doi.org/10.1115/1.4062831","url":null,"abstract":"\u0000 We study the mechanical behavior of a thin elastic film that is affixed to a rigid substrate and subjected to a transverse force using a shaft with a finite radius. This scenario, also referred to as axisymmetric peeling, is encountered frequently in conventional blister tests as well as in our daily lives when removing an adhesive film from a substrate. Our primary objective is to gain a quantitative understanding of how the shaft's radius influences the relationships between force and displacement, as well as between force and delamination areas. These relationships can serve as a dependable method to determine both the film's elastic modulus and the adhesion strength between the film and its substrate. In this work, we provide a simple perturbation solution to this geometrically nonlinear problem while avoiding any use of ad hoc assumptions that were previously required in the literature. As a result, our results are in excellent agreement with numerical simulations and offer improved accuracy compared to analytical solutions available in the literature.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41987793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Swapnil Patil, S. Khaderi, Ramji Manoharan, Vishwanath Chinthapenta
The problem of a completely debonded short fiber (rigid line inclusion/anticrack) embedded in a 2D isotropic elastic soft-matrix subjected to the remote loading condition is of fundamental interest. The current work investigates completely debonded anticrack embedded in a soft (isotropic) matrix using Kolosov Muskhelisvili's complex potential framework. Here two configurations are studied: debonded inclusion oriented (i) parallel and (ii) perpendicular to the loading direction. In particular, the potentials take the form of a non-homogeneous Riemann - Hilbert equation for the given problem. Upon solving analytical forms of potentials, the stress fields were obtained. The stress field for the fully debonded anticrack exhibited oscillatory singular behavior between r^(-3/4) and r^(-1/4) with the dependence on the oscillatory index e and material constants. The correctness of the analytical solution was validated using numerical simulation and experiments based on the digital photoelasticity technique. The analytical results were in good agreement with the experimental and numerically obtained stress fields confirming the accuracy of it. The magnitude of singularity is quantified by defining a complex stress intensity factor at the tip of the discontinuity and compared with the experimentally estimated value. So far in the literature, no full-field analytical solution exists for the completely debonded rigid inclusion embedded in an isotropic soft matrix. The solution obtained in the present work is of fundamental importance in developing the constitutive properties of short fiber reinforced thermoplastic (SFRT) composites.
{"title":"Full field solution for remotely loaded one side completely debonded short rigid line inclusion embedded in soft matrix: 2D Analytical and Experimental insights","authors":"Swapnil Patil, S. Khaderi, Ramji Manoharan, Vishwanath Chinthapenta","doi":"10.1115/1.4062771","DOIUrl":"https://doi.org/10.1115/1.4062771","url":null,"abstract":"\u0000 The problem of a completely debonded short fiber (rigid line inclusion/anticrack) embedded in a 2D isotropic elastic soft-matrix subjected to the remote loading condition is of fundamental interest. The current work investigates completely debonded anticrack embedded in a soft (isotropic) matrix using Kolosov Muskhelisvili's complex potential framework. Here two configurations are studied: debonded inclusion oriented (i) parallel and (ii) perpendicular to the loading direction. In particular, the potentials take the form of a non-homogeneous Riemann - Hilbert equation for the given problem. Upon solving analytical forms of potentials, the stress fields were obtained. The stress field for the fully debonded anticrack exhibited oscillatory singular behavior between r^(-3/4) and r^(-1/4) with the dependence on the oscillatory index e and material constants. The correctness of the analytical solution was validated using numerical simulation and experiments based on the digital photoelasticity technique. The analytical results were in good agreement with the experimental and numerically obtained stress fields confirming the accuracy of it. The magnitude of singularity is quantified by defining a complex stress intensity factor at the tip of the discontinuity and compared with the experimentally estimated value. So far in the literature, no full-field analytical solution exists for the completely debonded rigid inclusion embedded in an isotropic soft matrix. The solution obtained in the present work is of fundamental importance in developing the constitutive properties of short fiber reinforced thermoplastic (SFRT) composites.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42055986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lingling Chen, Xinyu Xing, Chuo Zhao, Shengyou Yang
Flexoelectricity exists in all inhomogeneously deformed dielectric materials and is greatly interesting in engineering science, especially in manufacturing microelectromechanical systems. However, the flexoelectricity is relatively small compared to the commonly known piezoelectricity. How to produce a considerably large flexoelectric effect and how to apply the effect to a large scale have concerned people for a long time. In this paper, we creatively enlarge the flexoelectric effect without decreasing the structure scale by harnessing the electromechanical instability—the snap-through instability—of a curved dielectric plate subjected to a concentrated load. We formulate the electrostatic energy of the system and obtain the governing equations by taking the first variation of the free energy. In the analysis, we find that the thickness of the plate and the initial configuration affect the onset of the snap-through. Beyond that, we notice that flexoelectricity can lower the critical load of the snap-through instability. Importantly, we find that a large flexoelectricity can be generated by harnessing the instability. For a dielectric plate with thickness 2 × 10−7 m, the effective electromechanical coefficient is equal to 35 pC/N in the beginning; however, by using the instability, the coefficient can be increased to as high as 740 pC/N, which is 21 times higher after the instability. In the end, we tune the electromechanical behaviors by designing the curved plate's thickness and configuration. This paper contributes to our understanding of the amplification of flexoelectric effects by harnessing snapping surfaces.
{"title":"Dramatic amplification of the flexoelectric effect in snapping surfaces","authors":"Lingling Chen, Xinyu Xing, Chuo Zhao, Shengyou Yang","doi":"10.1115/1.4062777","DOIUrl":"https://doi.org/10.1115/1.4062777","url":null,"abstract":"\u0000 Flexoelectricity exists in all inhomogeneously deformed dielectric materials and is greatly interesting in engineering science, especially in manufacturing microelectromechanical systems. However, the flexoelectricity is relatively small compared to the commonly known piezoelectricity. How to produce a considerably large flexoelectric effect and how to apply the effect to a large scale have concerned people for a long time. In this paper, we creatively enlarge the flexoelectric effect without decreasing the structure scale by harnessing the electromechanical instability—the snap-through instability—of a curved dielectric plate subjected to a concentrated load. We formulate the electrostatic energy of the system and obtain the governing equations by taking the first variation of the free energy. In the analysis, we find that the thickness of the plate and the initial configuration affect the onset of the snap-through. Beyond that, we notice that flexoelectricity can lower the critical load of the snap-through instability. Importantly, we find that a large flexoelectricity can be generated by harnessing the instability. For a dielectric plate with thickness 2 × 10−7 m, the effective electromechanical coefficient is equal to 35 pC/N in the beginning; however, by using the instability, the coefficient can be increased to as high as 740 pC/N, which is 21 times higher after the instability. In the end, we tune the electromechanical behaviors by designing the curved plate's thickness and configuration. This paper contributes to our understanding of the amplification of flexoelectric effects by harnessing snapping surfaces.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41628240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The foam sandwich tube contains inner and outer tubes and filling foam. The foam sandwich tube is widely used in engineering, due to the lightweight, high specific strength, energy absorption and other excellent characteristics. In this paper, the free inversion of the circular metal foam sandwich tube (CMFST) under axial loading is studied analytically and numerically. The plastic deformation occurs in the CMFST, and its main deformation modes include circumferential expansion, radial bending of the CMFST and compression of the metal sandwich foam. An analytical model for the free inversion of the CMFST under axial loading is established, considering metal tube expansion, the radial bending of metal circular tube wall, and metal foam compression. The commercial ABAQUS software is adopted to numerically study the free inversion behavior of the CMFST. The analytical predications agree well with the numerical ones. It is shown that the specific energy absorption (SEA) of the CMFST under free inversion is significantly better than the empty tube. When the non-dimensional foam strength is 0.05, the SEA of the CMFST under free inversion is 107.68% higher than the empty tube. Thus, the metal foam sandwich tube under free inversion is an excellent energy-absorbing device.
{"title":"Analytical and numerical investigations of circular metal foam sandwich tube under free inversion","authors":"Jinwen Bai, Jianxun Zhang","doi":"10.1115/1.4062772","DOIUrl":"https://doi.org/10.1115/1.4062772","url":null,"abstract":"\u0000 The foam sandwich tube contains inner and outer tubes and filling foam. The foam sandwich tube is widely used in engineering, due to the lightweight, high specific strength, energy absorption and other excellent characteristics. In this paper, the free inversion of the circular metal foam sandwich tube (CMFST) under axial loading is studied analytically and numerically. The plastic deformation occurs in the CMFST, and its main deformation modes include circumferential expansion, radial bending of the CMFST and compression of the metal sandwich foam. An analytical model for the free inversion of the CMFST under axial loading is established, considering metal tube expansion, the radial bending of metal circular tube wall, and metal foam compression. The commercial ABAQUS software is adopted to numerically study the free inversion behavior of the CMFST. The analytical predications agree well with the numerical ones. It is shown that the specific energy absorption (SEA) of the CMFST under free inversion is significantly better than the empty tube. When the non-dimensional foam strength is 0.05, the SEA of the CMFST under free inversion is 107.68% higher than the empty tube. Thus, the metal foam sandwich tube under free inversion is an excellent energy-absorbing device.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45969716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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