In this work, a numerical analysis of shaped charge impact process is conducted to investigate the jet formation process and its penetration performance on metal targets. Numerical results are compared with experimental data from published literature for liners made up of copper and iron. Conical and bowl-shaped liner geometries are simulated with various configurations to observe their effects on projectile shape and penetration capability using the finite element (FE) method. The exact shape of the explosively formed projectile at the onset of impact is modeled as a rigid 3D body to simulate the penetration process. #45 and Armox 500T steels are used as the target materials, and the material behavior and failure mechanisms are modeled using the Johnson-Cook (JC) plasticity and damage models. In addition to the FE method, smoothed particle hydrodynamics (SPH) is utilized as well to evaluate its capacity in predicting the failure behavior of the metal targets. It is concluded that the FE method outperforms the SPH method at predicting failure modes while SPH can still be used to predict residual velocity and hole diameters. Armox 500T demonstrates a higher impact resistance compared to #45 steel. Liner geometry is found to significantly affect penetration performance. Sharper and thinner projectiles formed from liners with small cone angles are shown to be highly efficient in penetrating through armor steel targets.
{"title":"A numerical study on the ballistic performance of projectiles formed by shaped charge","authors":"Yagmur Gocmen, Can Erdogan, T. Yalçinkaya","doi":"10.1115/1.4063002","DOIUrl":"https://doi.org/10.1115/1.4063002","url":null,"abstract":"\u0000 In this work, a numerical analysis of shaped charge impact process is conducted to investigate the jet formation process and its penetration performance on metal targets. Numerical results are compared with experimental data from published literature for liners made up of copper and iron. Conical and bowl-shaped liner geometries are simulated with various configurations to observe their effects on projectile shape and penetration capability using the finite element (FE) method. The exact shape of the explosively formed projectile at the onset of impact is modeled as a rigid 3D body to simulate the penetration process. #45 and Armox 500T steels are used as the target materials, and the material behavior and failure mechanisms are modeled using the Johnson-Cook (JC) plasticity and damage models. In addition to the FE method, smoothed particle hydrodynamics (SPH) is utilized as well to evaluate its capacity in predicting the failure behavior of the metal targets. It is concluded that the FE method outperforms the SPH method at predicting failure modes while SPH can still be used to predict residual velocity and hole diameters. Armox 500T demonstrates a higher impact resistance compared to #45 steel. Liner geometry is found to significantly affect penetration performance. Sharper and thinner projectiles formed from liners with small cone angles are shown to be highly efficient in penetrating through armor steel targets.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49393700","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}
Janel Chua, M. Karimi, Peter F. Kozlowski, M. Massoudi, S. Narasimhachary, K. Kadau, G. Gazonas, K. Dayal
We briefly compare the structure of two popular models to model poro- and chemo- mechanics wherein a fluid phase is transported within a solid phase. The multiplicative deformation decomposition has been used to model permanent inelastic shape change in plasticity and thermal expansion. However, the energetic decomposition provides a more transparent structure and advantages, such as to couple to phase-field fracture, for problems of poro- and chemo- mechanics.
{"title":"Deformation Decomposition versus Energy Decomposition for Chemo- and Poro- Mechanics","authors":"Janel Chua, M. Karimi, Peter F. Kozlowski, M. Massoudi, S. Narasimhachary, K. Kadau, G. Gazonas, K. Dayal","doi":"10.1115/1.4062967","DOIUrl":"https://doi.org/10.1115/1.4062967","url":null,"abstract":"\u0000 We briefly compare the structure of two popular models to model poro- and chemo- mechanics wherein a fluid phase is transported within a solid phase. The multiplicative deformation decomposition has been used to model permanent inelastic shape change in plasticity and thermal expansion. However, the energetic decomposition provides a more transparent structure and advantages, such as to couple to phase-field fracture, for problems of poro- and chemo- mechanics.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43537606","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 investigates the effects of large deflections on the energy release rate and mode partitioning of face/core debonds for the Single Cantilever Beam Sandwich Composite testing configuration, which is loaded with an applied shear force and/or a bending moment. Studies in this topic have been done by employing geometrically linear theories (either Euler-Bernoulli or Timoshenko beam theory). This assumes that the deflection at the tip of the loaded debonded part is small, which is not always the case. To address this effect, we employ the elastica theory, which is a nonlinear theory, for the debonded part. An elastic foundation analysis and the linear Euler Bernoulli theory is employed for the “joined” section where a series of springs exists between the face and the substrate (core and bottom face). A closed form expression for the energy release rate is derived by use of the J-integral. Another closed form expression for the energy release rate is derived from the energy released by a differential spring as the debond propagates. Furthermore, a mode partitioning angle is defined based on the displacement field solution. Results for a range of core materials are in very good agreement with the corresponding ones from a finite element analysis. The results show that large deflection effects reduce the energy release rate but do not have a noteworthy effect on the mode partitioning. A small deflection assumption can significantly overestimate the energy release rate for relatively large applied loads and/or relatively long debonds.
{"title":"Large Deflection Effects on the Energy Release Rate and Mode Partitioning of the Single Cantilever Beam Sandwich Debond Configuration","authors":"Daniel Okegbu, G. Kardomateas","doi":"10.1115/1.4062936","DOIUrl":"https://doi.org/10.1115/1.4062936","url":null,"abstract":"\u0000 This paper investigates the effects of large deflections on the energy release rate and mode partitioning of face/core debonds for the Single Cantilever Beam Sandwich Composite testing configuration, which is loaded with an applied shear force and/or a bending moment. Studies in this topic have been done by employing geometrically linear theories (either Euler-Bernoulli or Timoshenko beam theory). This assumes that the deflection at the tip of the loaded debonded part is small, which is not always the case. To address this effect, we employ the elastica theory, which is a nonlinear theory, for the debonded part. An elastic foundation analysis and the linear Euler Bernoulli theory is employed for the “joined” section where a series of springs exists between the face and the substrate (core and bottom face). A closed form expression for the energy release rate is derived by use of the J-integral. Another closed form expression for the energy release rate is derived from the energy released by a differential spring as the debond propagates. Furthermore, a mode partitioning angle is defined based on the displacement field solution. Results for a range of core materials are in very good agreement with the corresponding ones from a finite element analysis. The results show that large deflection effects reduce the energy release rate but do not have a noteworthy effect on the mode partitioning. A small deflection assumption can significantly overestimate the energy release rate for relatively large applied loads and/or relatively long debonds.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45620729","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 behavior and evolution of stepped circular bi-laminates with edge damage under uniform thermal load are studied. The problem is treated as a moving intermediate boundaries problem in the calculus of variations. Varying boundaries are allowed for the evolving damage region from the smaller substructure's edge and the progressing/regressing sliding contact region adjacent to the intact composite structure. Transversality conditions define the locations of propagating boundaries for equilibrium configurations of the evolving composite structure, along with equilibrium equations and interior/exterior boundary conditions. The influence and progression of different contact configurations and detached segment behaviors on the overall composite structure evolution are evaluated. Closed-form analytical solutions for the geometrically non-linear problem yield expressions for the critical buckling load. The analytical solutions provide explicit forms of the total energy release rate along the delamination front and conditions for the propagation of the contact zone boundary. Numerical simulations unveil a rich evolution process, involving contact progression/recession, metamorphosis, buckling, and detachment progression during pre-buckling, sling-shot buckling, and post-buckling phases. These behaviors depend on material properties, sublaminates' geometry, initial damage size, and interfacial bond strength. The study explores the behavior of stepped circular bi-laminates with edge damage under thermal load, addressing their evolution, critical buckling loads, and characteristic damage propagation.
{"title":"ON THE INTERACTION OF DAMAGE EVOLUTION AND THERMAL BUCKLING IN STEPPED CIRCULAR BI-LAMINATES","authors":"Shuo Xu, W. Bottega","doi":"10.1115/1.4062935","DOIUrl":"https://doi.org/10.1115/1.4062935","url":null,"abstract":"\u0000 The behavior and evolution of stepped circular bi-laminates with edge damage under uniform thermal load are studied. The problem is treated as a moving intermediate boundaries problem in the calculus of variations. Varying boundaries are allowed for the evolving damage region from the smaller substructure's edge and the progressing/regressing sliding contact region adjacent to the intact composite structure. Transversality conditions define the locations of propagating boundaries for equilibrium configurations of the evolving composite structure, along with equilibrium equations and interior/exterior boundary conditions. The influence and progression of different contact configurations and detached segment behaviors on the overall composite structure evolution are evaluated. Closed-form analytical solutions for the geometrically non-linear problem yield expressions for the critical buckling load. The analytical solutions provide explicit forms of the total energy release rate along the delamination front and conditions for the propagation of the contact zone boundary. Numerical simulations unveil a rich evolution process, involving contact progression/recession, metamorphosis, buckling, and detachment progression during pre-buckling, sling-shot buckling, and post-buckling phases. These behaviors depend on material properties, sublaminates' geometry, initial damage size, and interfacial bond strength. The study explores the behavior of stepped circular bi-laminates with edge damage under thermal load, addressing their evolution, critical buckling loads, and characteristic damage propagation.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44057943","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 refined spherical cap model, combined with an elastic foundation model for the elastic substrate, is proposed to study static wetting of a liquid droplet on a soft elastic substrate. The strain energy of the substrate is evaluated by the JKR (Johnson-Kendall-Roberts) model, and the increase of the surface energy of the substrate outside the contact zone is calculated based on the elastic foundation model. The total potential energy of the droplet-substrate system is given in terms of four geometrical parameters: the contact radius, the contact angle of the droplet, the deflection angle inside the contact zone, and the maximum downward displacement of the substrate surface at the contact zone center. The equilibrium state is determined based on the stationary condition of total potential energy. The present model reduces to the Young's equation for a rigid substrate and to the Neumann's triangle for a liquid-like substrate. Three equations are given to determine the liquid droplet shape in terms of surface energies and substrate's elastic modulus. Reasonable agreement with existing experimental data and simulation results shows that the present model with derived formulas has the potential to catch the role of substrate's elastic deformation on static wetting and fill the gap between the Young's equation and the Neumann's triangle for a soft elastic substrate.
{"title":"Static wetting of a liquid droplet on a soft elastic substrate","authors":"Jian Wu, C. Ru","doi":"10.1115/1.4062906","DOIUrl":"https://doi.org/10.1115/1.4062906","url":null,"abstract":"\u0000 A refined spherical cap model, combined with an elastic foundation model for the elastic substrate, is proposed to study static wetting of a liquid droplet on a soft elastic substrate. The strain energy of the substrate is evaluated by the JKR (Johnson-Kendall-Roberts) model, and the increase of the surface energy of the substrate outside the contact zone is calculated based on the elastic foundation model. The total potential energy of the droplet-substrate system is given in terms of four geometrical parameters: the contact radius, the contact angle of the droplet, the deflection angle inside the contact zone, and the maximum downward displacement of the substrate surface at the contact zone center. The equilibrium state is determined based on the stationary condition of total potential energy. The present model reduces to the Young's equation for a rigid substrate and to the Neumann's triangle for a liquid-like substrate. Three equations are given to determine the liquid droplet shape in terms of surface energies and substrate's elastic modulus. Reasonable agreement with existing experimental data and simulation results shows that the present model with derived formulas has the potential to catch the role of substrate's elastic deformation on static wetting and fill the gap between the Young's equation and the Neumann's triangle for a soft elastic substrate.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44820090","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}
Stretchable and flexible electronic sensors have been attracted due to their conformal integration onto complex curved surfaces for novel applications. Whereas, the mounting strains generated by the geometric mismatch of substrate surface and electronic sensors may cause non-conformal contact at the interface, thus would induce non-negligible effects on the performance of sensors. To figure out the influence rules of the shaped of electronic sensors and their geometric parameters on conformal contacts, this paper presents a novel conformal model to study the arbitrary shaped film as flexible sensors mounted onto general curved surface substrates. The principle of energy minimization and the method of integral summation play vital roles during the modeling, and three types of films with various shapes including rectangular, oval and hexagonal mounted onto bicurvature substrate are investigated. The influences of three dimensionless shape parameters of oval and hexagonal film/substrate contacts on dimensionless strain energy for conformal mounting are analyzed. The strain and critical dimensionless strain energy of three kinds of films/bicurvature substrate contacts are calculated and compared under the same conformal area. The results demonstrated that the contour shape of electronic sensor has a great effect on conformal mounting and strain. Thus, the developed conformal model would have great significance in guiding the design of flexible electronic devices and sensors when applied to general curved surface.
{"title":"Conformal Theoretical Modeling of Arbitrary Shape Flexible Electronic Sensors Mounted onto General Curved Surface Substrate","authors":"Shihang Wang, Jie Jin, Deqing Mei, Yan-cheng Wang","doi":"10.1115/1.4062905","DOIUrl":"https://doi.org/10.1115/1.4062905","url":null,"abstract":"\u0000 Stretchable and flexible electronic sensors have been attracted due to their conformal integration onto complex curved surfaces for novel applications. Whereas, the mounting strains generated by the geometric mismatch of substrate surface and electronic sensors may cause non-conformal contact at the interface, thus would induce non-negligible effects on the performance of sensors. To figure out the influence rules of the shaped of electronic sensors and their geometric parameters on conformal contacts, this paper presents a novel conformal model to study the arbitrary shaped film as flexible sensors mounted onto general curved surface substrates. The principle of energy minimization and the method of integral summation play vital roles during the modeling, and three types of films with various shapes including rectangular, oval and hexagonal mounted onto bicurvature substrate are investigated. The influences of three dimensionless shape parameters of oval and hexagonal film/substrate contacts on dimensionless strain energy for conformal mounting are analyzed. The strain and critical dimensionless strain energy of three kinds of films/bicurvature substrate contacts are calculated and compared under the same conformal area. The results demonstrated that the contour shape of electronic sensor has a great effect on conformal mounting and strain. Thus, the developed conformal model would have great significance in guiding the design of flexible electronic devices and sensors when applied to general curved surface.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45491963","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 ice buildup on airborne structures operating in cold weather conditions has detrimental impacts on both their safety and performance. Due to practical applications, there has been a significant interest in ice removal strategies. However, the current body of literature lacks comprehensive insights into the mechanistic aspects of the ice adhesion/breakage process, resulting in a wide range of reported adhesion strengths that differ by two orders of magnitude. To address this gap, we employed a fracture mechanics-based approach to investigate the fracture behavior of a typical ice/aluminum interface in terms of mode-I and II fractures. We examine a range of surface roughness values spanning 0.05-5 micrometers. An experimental framework employing a single cantilever beam and direct shear tests were developed. The near mode-I and II interfacial fracture toughness and strength values were extracted from the experimentally measured force and displacement by both analytical and numerical models employing cohesive surfaces. The combined experimental and numerical results show that ice adhesion is primarily driven by cohesive interfacial failure, which exhibits almost mode-independent fracture behavior. Mode-I fracture shows directional instability of crack propagation, which is attributed to thermally induced residual tensile stress within the ice layer. The fractographic inspection reveals similar ice-grain size over the examined range of substrate roughness values. For the examined range of surface roughness and temperature, which induces the Wenzel state with full surface wetting at the interface, ice adhesion is insensitive to the interfacial roughness and fracture modes.
{"title":"Ice Adhesion Characterization Using Mode-I and Mode-II Fracture Configurations","authors":"B. Dawood, Denizhan Yavas, A. Bastawros","doi":"10.1115/1.4062908","DOIUrl":"https://doi.org/10.1115/1.4062908","url":null,"abstract":"\u0000 The ice buildup on airborne structures operating in cold weather conditions has detrimental impacts on both their safety and performance. Due to practical applications, there has been a significant interest in ice removal strategies. However, the current body of literature lacks comprehensive insights into the mechanistic aspects of the ice adhesion/breakage process, resulting in a wide range of reported adhesion strengths that differ by two orders of magnitude. To address this gap, we employed a fracture mechanics-based approach to investigate the fracture behavior of a typical ice/aluminum interface in terms of mode-I and II fractures. We examine a range of surface roughness values spanning 0.05-5 micrometers. An experimental framework employing a single cantilever beam and direct shear tests were developed. The near mode-I and II interfacial fracture toughness and strength values were extracted from the experimentally measured force and displacement by both analytical and numerical models employing cohesive surfaces. The combined experimental and numerical results show that ice adhesion is primarily driven by cohesive interfacial failure, which exhibits almost mode-independent fracture behavior. Mode-I fracture shows directional instability of crack propagation, which is attributed to thermally induced residual tensile stress within the ice layer. The fractographic inspection reveals similar ice-grain size over the examined range of substrate roughness values. For the examined range of surface roughness and temperature, which induces the Wenzel state with full surface wetting at the interface, ice adhesion is insensitive to the interfacial roughness and fracture modes.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46819101","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}
Drishya Dahal, Juan-Sebastian Rincon-Tabares, D. Y. Risk-Mora, B. R. Rincon Troconis, David Restrepo
Characterizing the adhesion between thin films and rigid substrates is crucial in engineering applications. Still, existing standard methods suffer from issues such as poor reproducibility, difficulties in quantifying adhesion parameters, or overestimation of adhesion strength and fracture energy. Recent studies have shown that the blister test (BT) is a superior method for characterizing adhesion, as it provides a quantifiable measurement of mix-mode fracture energy, and it is highly reproducible. In this paper, we present a novel method to characterize mechanical mix-mode adhesion between thin films and rigid substrates using the BT. Our method combines the full triaxial displacement field obtained through Digital Image Correlation with inverse Finite Element Method simulations using Cohesive Zone Elements. This approach eliminates the need for making any mechanistic or kinematic assumptions of the blister formation and allows the characterization of the full traction-separation law governing the adhesion between the film and the substrate. To demonstrate the efficacy of this methodology, we conducted a case study analyzing the adhesion mechanics of a polymeric pressure-sensitive adhesive on an aluminum substrate. Our results indicate that the proposed technique is a reliable and effective method for characterizing the mix-mode traction separation law governing the mechanical behavior of the adhesive interface and could have broad applications in the field of materials science and engineering. Also, by providing a comprehensive understanding of the adhesion mechanics between thin films and rigid substrates, our method can aid in the design and optimization of adhesively bonded structures
{"title":"Characterizing the adhesion between thin films and rigid substrates using DIC-informed inverse finite elements and the blister test","authors":"Drishya Dahal, Juan-Sebastian Rincon-Tabares, D. Y. Risk-Mora, B. R. Rincon Troconis, David Restrepo","doi":"10.1115/1.4062907","DOIUrl":"https://doi.org/10.1115/1.4062907","url":null,"abstract":"\u0000 Characterizing the adhesion between thin films and rigid substrates is crucial in engineering applications. Still, existing standard methods suffer from issues such as poor reproducibility, difficulties in quantifying adhesion parameters, or overestimation of adhesion strength and fracture energy. Recent studies have shown that the blister test (BT) is a superior method for characterizing adhesion, as it provides a quantifiable measurement of mix-mode fracture energy, and it is highly reproducible. In this paper, we present a novel method to characterize mechanical mix-mode adhesion between thin films and rigid substrates using the BT. Our method combines the full triaxial displacement field obtained through Digital Image Correlation with inverse Finite Element Method simulations using Cohesive Zone Elements. This approach eliminates the need for making any mechanistic or kinematic assumptions of the blister formation and allows the characterization of the full traction-separation law governing the adhesion between the film and the substrate. To demonstrate the efficacy of this methodology, we conducted a case study analyzing the adhesion mechanics of a polymeric pressure-sensitive adhesive on an aluminum substrate. Our results indicate that the proposed technique is a reliable and effective method for characterizing the mix-mode traction separation law governing the mechanical behavior of the adhesive interface and could have broad applications in the field of materials science and engineering. Also, by providing a comprehensive understanding of the adhesion mechanics between thin films and rigid substrates, our method can aid in the design and optimization of adhesively bonded structures","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48781600","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 mechanics of detachment (e.g., a cylindrical fibril separating from a dissimilar substrate) has been treated in the perspectives of contact mechanics and fracture mechanics theory along with numerical simulations, but systematic experimental studies on the adhesion of an individual microfibrils is still scarce. In this work, we conducted detailed experiment on the adhesion tests of individual cylindrical microfibrils within a large range of varying diameters from 4 to 400 mm made of three different polyurethanes with moduli among ~1-40 MPa. We confirmed the scaling effect of an individual microfibril, i.e. the adhesion sad of the individual fibril scales with fibrillar diameters D with an exponent of ~ -0.4 to -0.45. As the fibrillar diameter is reduced below 10 mm, the adhesion becomes unchanged and size-insensitive. This result is in good agreement with the theoretical predictions. Furthermore, the effects of the Young's modulus and retraction rates during the adhesion tests on the adhesion strength were also investigated. Our experimental work will provide a guide for optimal design of the micron-scale surfaces with improved adhesion.
{"title":"Scaling Effect of Dry Adhesion for Microfibrils and Transition Size to Flaw Insensitivity","authors":"Xuan Zhang, Xiaoyan Li","doi":"10.1115/1.4062884","DOIUrl":"https://doi.org/10.1115/1.4062884","url":null,"abstract":"\u0000 The mechanics of detachment (e.g., a cylindrical fibril separating from a dissimilar substrate) has been treated in the perspectives of contact mechanics and fracture mechanics theory along with numerical simulations, but systematic experimental studies on the adhesion of an individual microfibrils is still scarce. In this work, we conducted detailed experiment on the adhesion tests of individual cylindrical microfibrils within a large range of varying diameters from 4 to 400 mm made of three different polyurethanes with moduli among ~1-40 MPa. We confirmed the scaling effect of an individual microfibril, i.e. the adhesion sad of the individual fibril scales with fibrillar diameters D with an exponent of ~ -0.4 to -0.45. As the fibrillar diameter is reduced below 10 mm, the adhesion becomes unchanged and size-insensitive. This result is in good agreement with the theoretical predictions. Furthermore, the effects of the Young's modulus and retraction rates during the adhesion tests on the adhesion strength were also investigated. Our experimental work will provide a guide for optimal design of the micron-scale surfaces with improved adhesion.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46301472","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}
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":" ","pages":""},"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}
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