Possessing enhanced mechanical durability and multiple novel functions, hydrogel laminates have found wide application in diverse areas including stretchable and bio-integrated electronics, soft robotics, tissue engineering and biomedical devices. In the above scenarios, hydrogels are often required to sustain large deformation without mechanical failure over a long time. Compared to the fast movement in functions design, the failure mechanism of hydrogel laminates has been much less explored and researched, as well as laminates' fracture toughness – a key parameter characterizing their fracture behavior. To address this largely unexplored issue, this paper further studies the fracture toughness of hydrogel laminates both experimentally and theoretically. A kind of modified pure-shear test suitable for measuring the fracture toughness of hydrogel laminates is proposed, which is then applied to testing a PAAm-PAA laminate's toughness. Through theoretical analysis and numerical modeling, the experimentally observed enhancement in the fracture toughness of PAAm-PAA laminates is explained – the fracture toughness of the laminates covers the energy required for both the crack and concomitant interfacial delamination to propagate, and the theoretical predictions agree well with the experimental results. The results from this study provide quantitative guidance for understanding the fracture behavior of hydrogel laminates.
{"title":"Fracture toughness of hydrogel laminates: Experiments, theory and modeling","authors":"Yijie Cai, Zihang Shen, Zheng Jia","doi":"10.1115/1.4063144","DOIUrl":"https://doi.org/10.1115/1.4063144","url":null,"abstract":"Possessing enhanced mechanical durability and multiple novel functions, hydrogel laminates have found wide application in diverse areas including stretchable and bio-integrated electronics, soft robotics, tissue engineering and biomedical devices. In the above scenarios, hydrogels are often required to sustain large deformation without mechanical failure over a long time. Compared to the fast movement in functions design, the failure mechanism of hydrogel laminates has been much less explored and researched, as well as laminates' fracture toughness – a key parameter characterizing their fracture behavior. To address this largely unexplored issue, this paper further studies the fracture toughness of hydrogel laminates both experimentally and theoretically. A kind of modified pure-shear test suitable for measuring the fracture toughness of hydrogel laminates is proposed, which is then applied to testing a PAAm-PAA laminate's toughness. Through theoretical analysis and numerical modeling, the experimentally observed enhancement in the fracture toughness of PAAm-PAA laminates is explained – the fracture toughness of the laminates covers the energy required for both the crack and concomitant interfacial delamination to propagate, and the theoretical predictions agree well with the experimental results. The results from this study provide quantitative guidance for understanding the fracture behavior of hydrogel laminates.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42229786","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 presents a refined model for a mechanical diode based on a mass-spring system. The proposed model utilizes a bilinear spring to construct a frequency converter, which effectively disrupts the reciprocal transmission of acoustic waves. By employing a mass-spring-mass system as a filter, a nonlocal connection is introduced to establish a low-frequency band gap, thereby achieving a mechanical diode with a lower operating frequency. The feasibility of these low-frequency mechanical diodes is demonstrated through comprehensive numerical simulations and experimental analyses. In addition, we evaluated the effect of bilinear springs and nonlocal connection parameters on the diode performance.
{"title":"Roton-enabled mechanical diode at extremely low frequency","authors":"Tianzhi Yang, Zhonglei Duan, Xiangbo Meng, Shuanglong Liu, Li-Qun Chen","doi":"10.1115/1.4063143","DOIUrl":"https://doi.org/10.1115/1.4063143","url":null,"abstract":"\u0000 This paper presents a refined model for a mechanical diode based on a mass-spring system. The proposed model utilizes a bilinear spring to construct a frequency converter, which effectively disrupts the reciprocal transmission of acoustic waves. By employing a mass-spring-mass system as a filter, a nonlocal connection is introduced to establish a low-frequency band gap, thereby achieving a mechanical diode with a lower operating frequency. The feasibility of these low-frequency mechanical diodes is demonstrated through comprehensive numerical simulations and experimental analyses. In addition, we evaluated the effect of bilinear springs and nonlocal connection parameters on the diode performance.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43402853","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}
Flexoelectricity, a remarkable size-dependent effect, means that strain gradients can give rise to electric polarization. This effect is particularly pronounced near defects within flexoelectric solids, where large strain gradients exist. A thorough understanding of the internal defects of flexoelectric devices and their surrounding multiphysics fields is crucial to comprehend their damage and failure mechanisms. Motivated by this, strain gradient elasticity theory is utilized to investigate the mechanical and electrical behaviors of flexoelectric solids with cylindrical cavities under biaxial tension. Closed-form solutions are obtained under the assumptions of plane strain and electrically impermeable defects. In particular, this study extends the Kirsch problem of classical elasticity theory to the theoretical framework of higher-order electroelasticity for the first time. Our research reveals that different length scale parameters of the strain gradient and bidirectional loading ratios significantly affect the hoop stress field, radial electric polarization field, and electric potential field near the inner cylindrical cavity of the flexoelectric solid. Furthermore, we validate our analytical solution by numerical verification using mixed finite elements. The congruence between the two methods confirms our analytical solution's accuracy. The findings presented in this paper provide deeper insights into the internal defects of flexoelectric materials and can serve as a foundation for studying more complex defects in flexoelectric solids.
{"title":"Analysis of Flexoelectric Solids with a Cylindrical Cavity","authors":"Jinchen Xie, C. Linder","doi":"10.1115/1.4063145","DOIUrl":"https://doi.org/10.1115/1.4063145","url":null,"abstract":"\u0000 Flexoelectricity, a remarkable size-dependent effect, means that strain gradients can give rise to electric polarization. This effect is particularly pronounced near defects within flexoelectric solids, where large strain gradients exist. A thorough understanding of the internal defects of flexoelectric devices and their surrounding multiphysics fields is crucial to comprehend their damage and failure mechanisms. Motivated by this, strain gradient elasticity theory is utilized to investigate the mechanical and electrical behaviors of flexoelectric solids with cylindrical cavities under biaxial tension. Closed-form solutions are obtained under the assumptions of plane strain and electrically impermeable defects. In particular, this study extends the Kirsch problem of classical elasticity theory to the theoretical framework of higher-order electroelasticity for the first time. Our research reveals that different length scale parameters of the strain gradient and bidirectional loading ratios significantly affect the hoop stress field, radial electric polarization field, and electric potential field near the inner cylindrical cavity of the flexoelectric solid. Furthermore, we validate our analytical solution by numerical verification using mixed finite elements. The congruence between the two methods confirms our analytical solution's accuracy. The findings presented in this paper provide deeper insights into the internal defects of flexoelectric materials and can serve as a foundation for studying more complex defects in flexoelectric solids.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47110964","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}
Knowing the mechanical properties of cardiac myofibrils isolated from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) can provide valuable insight into the structure and function of the heart muscle. Previous studies focused mostly on studying myofibrillar stiffness using simplified elastic models. In this study, the mechanical properties of myofibrils isolated from hiPSC-CMs were measured using atomic force microscopy (AFM). The Quasi Linear Viscoelastic (QLV) model was used to interpret the elastic and viscous properties of myofibrils. Since there have been no previous studies on the viscoelastic properties of myofibrils extracted from hiPSC-CMs, myofibrils extracted from porcine left-ventricular (LV) tissue were used to compare and verify experimental processes and QLV model parameters. The elastic modulus of myofibrils extracted from porcine LV tissue was determined to be 8.82 ± 6.09 kPa consistent with previous studies which reported that porcine LV tissue is less stiff on average than mouse and rat cardiac myofibrils. The elastic modulus of myofibrils extracted from hiPSC-CMs was found to be 9.78 ± 5.80 kPa, which is consistent with the range of 5 kPa to 20 kPa reported for myofibrils extracted from adult human heart. We found that myofibrils isolated from hiPSC-CMs relax slower than myofibrils extracted from porcine LV tissue, particularly in the first 0.25 seconds after the peak stress in the stress relaxation test. These findings provide important insights into the mechanical behavior of hiPSC-CMs and have implications for the development of treatments for heart disease.
{"title":"Investigating Viscoelastic Properties of Myofibrils Isolated from hiPSC-CMs Using Atomic Force Microscopy and Quasi-Linear Viscoelastic Model","authors":"Shayan Jannati, Y. Maaref, G. Tibbits, M. Chiao","doi":"10.1115/1.4063141","DOIUrl":"https://doi.org/10.1115/1.4063141","url":null,"abstract":"\u0000 Knowing the mechanical properties of cardiac myofibrils isolated from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) can provide valuable insight into the structure and function of the heart muscle. Previous studies focused mostly on studying myofibrillar stiffness using simplified elastic models. In this study, the mechanical properties of myofibrils isolated from hiPSC-CMs were measured using atomic force microscopy (AFM). The Quasi Linear Viscoelastic (QLV) model was used to interpret the elastic and viscous properties of myofibrils. Since there have been no previous studies on the viscoelastic properties of myofibrils extracted from hiPSC-CMs, myofibrils extracted from porcine left-ventricular (LV) tissue were used to compare and verify experimental processes and QLV model parameters. The elastic modulus of myofibrils extracted from porcine LV tissue was determined to be 8.82 ± 6.09 kPa consistent with previous studies which reported that porcine LV tissue is less stiff on average than mouse and rat cardiac myofibrils. The elastic modulus of myofibrils extracted from hiPSC-CMs was found to be 9.78 ± 5.80 kPa, which is consistent with the range of 5 kPa to 20 kPa reported for myofibrils extracted from adult human heart. We found that myofibrils isolated from hiPSC-CMs relax slower than myofibrils extracted from porcine LV tissue, particularly in the first 0.25 seconds after the peak stress in the stress relaxation test. These findings provide important insights into the mechanical behavior of hiPSC-CMs and have implications for the development of treatments for heart disease.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46699537","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}
Junyin Li, Zhanchao Huang, Yong Wang, Zhilong Huang, W. Zhu
Stochastic averaging, as an effective technique for dimension reduction, is of great significance in stochastic dynamics and control. However, its practical applications in industrial and engineering fields are severely hindered by its dependence on governing equations and the complexity of mathematical operations. Herein, a data-driven method, named data-driven stochastic averaging, is developed to automatically discover the low-dimensional stochastic differential equations using only the random state data captured from the original high-dimensional dynamical systems. This method includes two successive steps, i.e., extracting all slowly-varying processes hidden in fast-varying state data and identifying drift and diffusion coefficients by their mathematical definitions. It automates dimension reduction and is especially suitable for cases with unavailable governing equations and excitation data. Its application, efficacy and comparison with theory-based stochastic averaging are illustrated through several examples, numerical or experimental, with pure Gaussian white noise excitation or combined excitations.
{"title":"Data-Driven Stochastic Averaging","authors":"Junyin Li, Zhanchao Huang, Yong Wang, Zhilong Huang, W. Zhu","doi":"10.1115/1.4063065","DOIUrl":"https://doi.org/10.1115/1.4063065","url":null,"abstract":"\u0000 Stochastic averaging, as an effective technique for dimension reduction, is of great significance in stochastic dynamics and control. However, its practical applications in industrial and engineering fields are severely hindered by its dependence on governing equations and the complexity of mathematical operations. Herein, a data-driven method, named data-driven stochastic averaging, is developed to automatically discover the low-dimensional stochastic differential equations using only the random state data captured from the original high-dimensional dynamical systems. This method includes two successive steps, i.e., extracting all slowly-varying processes hidden in fast-varying state data and identifying drift and diffusion coefficients by their mathematical definitions. It automates dimension reduction and is especially suitable for cases with unavailable governing equations and excitation data. Its application, efficacy and comparison with theory-based stochastic averaging are illustrated through several examples, numerical or experimental, with pure Gaussian white noise excitation or combined excitations.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43424268","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}
Xing Liu, Christos E. Athanasiou, C. López-Pernía, T. Zhu, N. Padture, B. Sheldon, Huajian Gao
Ceramic matrix composites (CMCs) reinforced by two-dimensional (2D) nanomaterials have shown extraordinary load-carrying capacities, even in the harsh environments required by emerging applications. Their exceptional mechanical performance, especially fracture toughness, primarily arises from their heterogeneous microstructures. The deliberate dispersion of 2D reinforcements enables toughening mechanisms that are extrinsic to the matrix and thus endows the composites with substantial resistance to catastrophic failure. However, the incomplete understanding of the fracture behavior of such nanocomposites, especially the complex energy dissipation process of the matrix/reinforcement interface, limits the development of stronger and tougher CMCs. To overcome these limitations, we investigate crack deflection and energy dissipation in nanocomposites using an extended cohesive shear-lag model. This new model accounts for interfacial debonding and friction, which critically control the toughening of nanocomposites. Our analysis provides mechanistic insights for optimizing the toughening effects of CMCs.
{"title":"Tailoring the toughening effects in two-dimensional nanomaterial-reinforced ceramic matrix composites","authors":"Xing Liu, Christos E. Athanasiou, C. López-Pernía, T. Zhu, N. Padture, B. Sheldon, Huajian Gao","doi":"10.1115/1.4063029","DOIUrl":"https://doi.org/10.1115/1.4063029","url":null,"abstract":"\u0000 Ceramic matrix composites (CMCs) reinforced by two-dimensional (2D) nanomaterials have shown extraordinary load-carrying capacities, even in the harsh environments required by emerging applications. Their exceptional mechanical performance, especially fracture toughness, primarily arises from their heterogeneous microstructures. The deliberate dispersion of 2D reinforcements enables toughening mechanisms that are extrinsic to the matrix and thus endows the composites with substantial resistance to catastrophic failure. However, the incomplete understanding of the fracture behavior of such nanocomposites, especially the complex energy dissipation process of the matrix/reinforcement interface, limits the development of stronger and tougher CMCs. To overcome these limitations, we investigate crack deflection and energy dissipation in nanocomposites using an extended cohesive shear-lag model. This new model accounts for interfacial debonding and friction, which critically control the toughening of nanocomposites. Our analysis provides mechanistic insights for optimizing the toughening effects of CMCs.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43193493","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}
Generation of a large network of hydraulic cracks is of key importance not only for the success of fracking of shale but also for the recent scheme of sequestration of CO2 in deep formations of basalt, peridotite and basalt with peridotite inclusions, which are mafic rocks that combine chemically with CO2. In numerical simulation of the development of fracture network, an important problem is the permeability of the porous rock. The objective of this paper is to calculate the effect of osmotic pressure gradients caused by gradients of concentration of the ions of Ca, Mg, Na, etc. on the effective permeability of rock. The basic differential equation are formulated and their explicit solution for appropriate initial and boundary conditions are obtained under certain plausible simplifications.
{"title":"Osmotic Pressure Gradient Effects on Water Diffusion in Porous Rock: Can They Pervert Permeability Tests?","authors":"Z. Bažant, A. Nguyen","doi":"10.1115/1.4063030","DOIUrl":"https://doi.org/10.1115/1.4063030","url":null,"abstract":"\u0000 Generation of a large network of hydraulic cracks is of key importance not only for the success of fracking of shale but also for the recent scheme of sequestration of CO2 in deep formations of basalt, peridotite and basalt with peridotite inclusions, which are mafic rocks that combine chemically with CO2. In numerical simulation of the development of fracture network, an important problem is the permeability of the porous rock. The objective of this paper is to calculate the effect of osmotic pressure gradients caused by gradients of concentration of the ions of Ca, Mg, Na, etc. on the effective permeability of rock. The basic differential equation are formulated and their explicit solution for appropriate initial and boundary conditions are obtained under certain plausible simplifications.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":"1 1","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"63503823","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}
Vatsa Gandhi, B. Lawlor, C. Kettenbeil, G. Ravichandran
Silica glasses, such as soda-lime glass (SLG), have found wide ranging applications in engineering due to their excellent optical properties, high strength, and relatively low cost. In such applications, SLG may be subjected to intense dynamic loading due to high/hyper-velocity impact and therefore necessitates understanding of the dynamic shear strength and kinetics for the development of constitutive models. However, while several investigations have generated Hugoniots for silicate glasses, none appear to have measured shearing resistance at pressures above ∼20 GPa. In this study, the role of pressure and strain rate on the shearing resistance of soda-lime glass is explored using sandwich configuration high pressure-pressure shear plate impact (HP-PSPI) experiments. These experiments are conducted at pressures ranging from 14 − 42 GPa and strain rates of 105 − 106 s−1, and analyzed using finite element simulations incorporating a modified Johnson-Holmquist (JH-2) material model. The yield strength of SLG is observed to decrease as a function of pressure, which is reminiscent of the evolution of shear strength in granular media at high pressures. This observation suggests a probable shear-induced damage progression from intact material to granular matter in SLG at high pressures.
{"title":"Role of shear on strength and damage evolution in soda-lime glass under high dynamic pressures","authors":"Vatsa Gandhi, B. Lawlor, C. Kettenbeil, G. Ravichandran","doi":"10.1115/1.4063031","DOIUrl":"https://doi.org/10.1115/1.4063031","url":null,"abstract":"\u0000 Silica glasses, such as soda-lime glass (SLG), have found wide ranging applications in engineering due to their excellent optical properties, high strength, and relatively low cost. In such applications, SLG may be subjected to intense dynamic loading due to high/hyper-velocity impact and therefore necessitates understanding of the dynamic shear strength and kinetics for the development of constitutive models. However, while several investigations have generated Hugoniots for silicate glasses, none appear to have measured shearing resistance at pressures above ∼20 GPa. In this study, the role of pressure and strain rate on the shearing resistance of soda-lime glass is explored using sandwich configuration high pressure-pressure shear plate impact (HP-PSPI) experiments. These experiments are conducted at pressures ranging from 14 − 42 GPa and strain rates of 105 − 106 s−1, and analyzed using finite element simulations incorporating a modified Johnson-Holmquist (JH-2) material model. The yield strength of SLG is observed to decrease as a function of pressure, which is reminiscent of the evolution of shear strength in granular media at high pressures. This observation suggests a probable shear-induced damage progression from intact material to granular matter in SLG at high pressures.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45951602","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 quest for safe lower bounds to the elastic buckling of axially loaded circular cylindrical shells has exercised researchers for the past 100 years. Recent work bringing together the capabilities of non-linear numerical simulation, interpreted within the context of extended linear classical theory, has come close to achieving this goal of defining safe lower bounds. This paper briefly summarises important predictions from previous work and presents new simulations confirming them. In particular, we show that for a specified maximum amplitude of the most sensitive, eigenmode-based geometric imperfections, normalised with respect to the shell thickness, lower bounds to the buckling loads remain constant beyond a well-defined value of the Batdorf parameter. Furthermore, we demonstrate how this convenient means of presenting the imperfection-sensitive buckling loads can be reinterpreted to develop practical design curves providing safe, but not overly conservative, design loads for monocoque cylinders with a given maximum permitted tolerance of geometric imperfection. Hence, once the allowable manufacturing tolerance is specified during design or is measured post-manufacturing, the greatest expected knockdown factor for a shell of any geometry is defined. With the recent research interest in localised imperfections, we also attempt to reconcile their relation to the more classical, periodic, and eigenmode-based imperfections. Overall, this paper provides analytical and computational arguments that motivate a shift in focus in defect-tolerant design of thin-walled cylinders, away from the knockdown experienced for a specific geometric imperfection, towards the worst possible knockdown expected for a specified manufacturing tolerance.
{"title":"Towards Tolerance Specifications for the Elastic Buckling Design of Axially Loaded Cylinders","authors":"R. Groh, J. Croll","doi":"10.1115/1.4063032","DOIUrl":"https://doi.org/10.1115/1.4063032","url":null,"abstract":"\u0000 The quest for safe lower bounds to the elastic buckling of axially loaded circular cylindrical shells has exercised researchers for the past 100 years. Recent work bringing together the capabilities of non-linear numerical simulation, interpreted within the context of extended linear classical theory, has come close to achieving this goal of defining safe lower bounds. This paper briefly summarises important predictions from previous work and presents new simulations confirming them. In particular, we show that for a specified maximum amplitude of the most sensitive, eigenmode-based geometric imperfections, normalised with respect to the shell thickness, lower bounds to the buckling loads remain constant beyond a well-defined value of the Batdorf parameter. Furthermore, we demonstrate how this convenient means of presenting the imperfection-sensitive buckling loads can be reinterpreted to develop practical design curves providing safe, but not overly conservative, design loads for monocoque cylinders with a given maximum permitted tolerance of geometric imperfection. Hence, once the allowable manufacturing tolerance is specified during design or is measured post-manufacturing, the greatest expected knockdown factor for a shell of any geometry is defined. With the recent research interest in localised imperfections, we also attempt to reconcile their relation to the more classical, periodic, and eigenmode-based imperfections. Overall, this paper provides analytical and computational arguments that motivate a shift in focus in defect-tolerant design of thin-walled cylinders, away from the knockdown experienced for a specific geometric imperfection, towards the worst possible knockdown expected for a specified manufacturing tolerance.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47057085","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}
Micro/nanoscale additive manufacturing provides a powerful tool for advanced materials and structures, which contains complex and precise features. For instance, the feature resolution of two-photon polymerization (2PP) can reach 200 nm. At this scale, many new material properties will occur, and the influence of the size effect cannot be ignored. Therefore, it is necessary to assess changes in the material mechanical properties considering size effects. In this work, several micrometric polymeric specimens were printed via 2PP and then their mechanical properties were assessed using compression tests. Detailed printing, testing procedures as well as the effects of parameter settings are provided. The experimental results show that the changes in the microstructures' size have a direct effect on Young's modulus. In particular, large surface-volume ratio results in a higher Young's modulus. That is, the smaller the structure size, the higher the stiffness. The reported findings play a significant role in the development of fabrication strategies of polymeric microstructures where high stiffness accuracy is fundamental.
{"title":"Size effect in the compression of 3D polymerized micro-structures","authors":"Jiayu Li, A. Accardo, Shutian Liu","doi":"10.1115/1.4063028","DOIUrl":"https://doi.org/10.1115/1.4063028","url":null,"abstract":"\u0000 Micro/nanoscale additive manufacturing provides a powerful tool for advanced materials and structures, which contains complex and precise features. For instance, the feature resolution of two-photon polymerization (2PP) can reach 200 nm. At this scale, many new material properties will occur, and the influence of the size effect cannot be ignored. Therefore, it is necessary to assess changes in the material mechanical properties considering size effects. In this work, several micrometric polymeric specimens were printed via 2PP and then their mechanical properties were assessed using compression tests. Detailed printing, testing procedures as well as the effects of parameter settings are provided. The experimental results show that the changes in the microstructures' size have a direct effect on Young's modulus. In particular, large surface-volume ratio results in a higher Young's modulus. That is, the smaller the structure size, the higher the stiffness. The reported findings play a significant role in the development of fabrication strategies of polymeric microstructures where high stiffness accuracy is fundamental.","PeriodicalId":54880,"journal":{"name":"Journal of Applied Mechanics-Transactions of the Asme","volume":" ","pages":""},"PeriodicalIF":2.6,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45822944","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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