Pub Date : 2024-11-18DOI: 10.1016/j.jmps.2024.105967
Cheng Gong, Robert O. Ritchie, Xingyu Wei, Qingxu Liu, Jian Xiong
The layer-by-layer additive manufacturing approach results in the 3D printed composite lattice structure fails to exploit fiber reinforcement, thereby resulting in inferior mechanical qualities. To address this challenge, this study proposes a novel approach leveraging composite fused filament fabrication (FFF) printing to design modular assembled composite lattice structures. Initially, three high-performance lattice structures were transformed into discrete 2D components and assembled into 3D lattice structures. Subsequently, the mechanical properties of these structures were comprehensively assessed using theoretical, experimental, and finite element analysis methods. Finally, the comparison between the assembled structures and integrated printed lattice structures in terms of surface quality, mechanical properties, and manufacturability revealed significant advantages. The theoretical and finite element analyses accurately predicted the mechanical properties of the lattice structures. The lattice structures that were assembled in a modular way displayed an impressive 74% improvement in surface finish. Additionally, they showed peak strength increases of 140%, 27%, and 26%, respectively, for the mentioned types of topology. The energy absorption also increased significantly by 510.83%, 44.18%, and 30.24%. Furthermore, these assembled structures required less printing support materials, enhancing their manufacturability and cost-effectiveness. This new method of designing modular space structures goes beyond the limitations imposed by equipment by using high-performance topology. It allows for the construction of large-scale, lightweight space structures that offer excellent performance. This study explores innovative opportunities in the field of space manufacturing, offering potential implications for the development of lunar habitats, space telescopes, and space power stations.
{"title":"Mechanical properties of modular assembled composite lattice architecture","authors":"Cheng Gong, Robert O. Ritchie, Xingyu Wei, Qingxu Liu, Jian Xiong","doi":"10.1016/j.jmps.2024.105967","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105967","url":null,"abstract":"The layer-by-layer additive manufacturing approach results in the 3D printed composite lattice structure fails to exploit fiber reinforcement, thereby resulting in inferior mechanical qualities. To address this challenge, this study proposes a novel approach leveraging composite fused filament fabrication (FFF) printing to design modular assembled composite lattice structures. Initially, three high-performance lattice structures were transformed into discrete 2D components and assembled into 3D lattice structures. Subsequently, the mechanical properties of these structures were comprehensively assessed using theoretical, experimental, and finite element analysis methods. Finally, the comparison between the assembled structures and integrated printed lattice structures in terms of surface quality, mechanical properties, and manufacturability revealed significant advantages. The theoretical and finite element analyses accurately predicted the mechanical properties of the lattice structures. The lattice structures that were assembled in a modular way displayed an impressive 74% improvement in surface finish. Additionally, they showed peak strength increases of 140%, 27%, and 26%, respectively, for the mentioned types of topology. The energy absorption also increased significantly by 510.83%, 44.18%, and 30.24%. Furthermore, these assembled structures required less printing support materials, enhancing their manufacturability and cost-effectiveness. This new method of designing modular space structures goes beyond the limitations imposed by equipment by using high-performance topology. It allows for the construction of large-scale, lightweight space structures that offer excellent performance. This study explores innovative opportunities in the field of space manufacturing, offering potential implications for the development of lunar habitats, space telescopes, and space power stations.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"21 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1016/j.jmps.2024.105950
Lukas Riedel, Valentin Wössner, Dominic Kempf, Falko Ziebert, Peter Bastian, Ulrich S. Schwarz
The mechanics of animal cells is strongly determined by stress fibers, which are contractile filament bundles that form dynamically in response to extracellular cues. Stress fibers allow the cell to adapt its mechanics to environmental conditions and to protect it from structural damage. While the physical description of single stress fibers is well-developed, much less is known about their spatial distribution on the level of whole cells. Here, we combine a finite element method for one-dimensional fibers embedded in an elastic bulk medium with dynamical rules for stress fiber formation based on genetic algorithms. We postulate that their main goal is to achieve minimal mechanical stress in the bulk material with as few fibers as possible. The fiber positions and configurations resulting from this optimization task alone are in good agreement with those found in experiments where cells in 3D-scaffolds were mechanically strained at one attachment point. For optimized configurations, we find that stress fibers typically run through the cell in a diagonal fashion, similar to reinforcement strategies used for composite material.
{"title":"The positioning of stress fibers in contractile cells minimizes internal mechanical stress","authors":"Lukas Riedel, Valentin Wössner, Dominic Kempf, Falko Ziebert, Peter Bastian, Ulrich S. Schwarz","doi":"10.1016/j.jmps.2024.105950","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105950","url":null,"abstract":"The mechanics of animal cells is strongly determined by stress fibers, which are contractile filament bundles that form dynamically in response to extracellular cues. Stress fibers allow the cell to adapt its mechanics to environmental conditions and to protect it from structural damage. While the physical description of single stress fibers is well-developed, much less is known about their spatial distribution on the level of whole cells. Here, we combine a finite element method for one-dimensional fibers embedded in an elastic bulk medium with dynamical rules for stress fiber formation based on genetic algorithms. We postulate that their main goal is to achieve minimal mechanical stress in the bulk material with as few fibers as possible. The fiber positions and configurations resulting from this optimization task alone are in good agreement with those found in experiments where cells in 3D-scaffolds were mechanically strained at one attachment point. For optimized configurations, we find that stress fibers typically run through the cell in a diagonal fashion, similar to reinforcement strategies used for composite material.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"3 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.jmps.2024.105953
Louen Pottier, Anders Thorin, Francisco Chinesta
Nonlinear mechanical systems can exhibit non-uniqueness of the displacement field in response to a force field, which is related to the non-convexity of strain energy. This work proposes a Neural Network-based surrogate model capable of capturing this phenomenon while introducing an energy in a latent space of small dimension, that preserves the topology of the strain energy; this feature is a novelty with respect to the state of the art. It is exemplified on two mechanical systems of simple geometry, but challenging strong nonlinearities. The proposed architecture offers an additional advantage over existing ones: it can be used to infer both displacements from forces, or forces from displacements, without being trained in both ways.
{"title":"Latent-Energy-Based NNs: An interpretable Neural Network architecture for model-order reduction of nonlinear statics in solid mechanics","authors":"Louen Pottier, Anders Thorin, Francisco Chinesta","doi":"10.1016/j.jmps.2024.105953","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105953","url":null,"abstract":"Nonlinear mechanical systems can exhibit non-uniqueness of the displacement field in response to a force field, which is related to the non-convexity of strain energy. This work proposes a Neural Network-based surrogate model capable of capturing this phenomenon while introducing an energy in a latent space of small dimension, that preserves the topology of the strain energy; this feature is a novelty with respect to the state of the art. It is exemplified on two mechanical systems of simple geometry, but challenging strong nonlinearities. The proposed architecture offers an additional advantage over existing ones: it can be used to infer both displacements from forces, or forces from displacements, without being trained in both ways.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"255 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.jmps.2024.105964
Rupesh K. Mahendran, Surya R. Kalidindi, Aaron P. Stebner
A rate-dependent crystal-plasticity (CP) framework that captures the coupled phase transformation - plastic deformation behavior of shape memory alloys (SMAs) is presented. Here, different from previous models, the flow rule for martensitic phase transformation incorporates the entire deformation gradient for transformation, including the rotation. Predictions of transformation strain and variant selection of Nickel-Titanium (NiTi) using this model are directly compared with previous formulations that did not include the rotation. The results show that the rotation is essential to accurately calculate the single crystal and polycrystal micromechanics of variant selection and transformation strains of SMAs. The constitutive law formulation also includes current formulations for both slip and deformation twinning plasticity mechanisms, and the differences in transformation mechanisms are further shown to impact plasticity calculations through transformation-plasticity interactions. In addition to the advancement of the constitutive law, a computationally efficient implicit time integration scheme is given for numerical implementation and demonstrated using a user material subroutine (UMAT) in the commercial finite element code ABAQUS Standard. The proposed framework and the associated numerical protocols achieve stable solutions using strain increments on the order of 0.05 mm/mm in simulating inelastic deformations and strain increments 0.01 mm/mm in the elastic-inelastic transitions. Furthermore, the use of an analytic Jacobian results in stable convergence in fewer than 10 global Newton iterations while calculating solutions for elastic-inelastic transitions, making the computational benefits evident.
本文提出了一种与速率相关的晶体塑性（CP）框架，该框架可捕捉形状记忆合金（SMA）的相变-塑性变形耦合行为。与以前的模型不同，这里的马氏体相变流动规则包含了相变的整个变形梯度，包括旋转。使用该模型对镍钛合金（NiTi）的转变应变和变体选择进行的预测，与之前不包含旋转的公式进行了直接比较。结果表明，旋转对于准确计算 SMA 变体选择和转化应变的单晶和多晶微观力学至关重要。构成法公式还包括滑移和变形孪生塑性机制的当前公式，并进一步表明转化机制的差异会通过转化-塑性相互作用影响塑性计算。除了构造定律的进步之外，还给出了一种计算效率高的隐式时间积分方案，用于数值实施，并使用商业有限元代码 ABAQUS Standard 中的用户材料子程序 (UMAT) 进行了演示。在模拟非弹性变形时，所提出的框架和相关的数值协议可在应变增量为 0.05 mm/mm 和在弹性-非弹性转换时应变增量为 0.01 mm/mm 的情况下获得稳定的解决方案。此外，在计算弹性-非弹性转换的解时，使用解析雅各布因子可在不到 10 次全局牛顿迭代中实现稳定收敛，计算优势显而易见。
{"title":"Implicit implementation of a coupled transformation – plasticity crystal mechanics model for shape memory alloys that includes transformation rotations","authors":"Rupesh K. Mahendran, Surya R. Kalidindi, Aaron P. Stebner","doi":"10.1016/j.jmps.2024.105964","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105964","url":null,"abstract":"A rate-dependent crystal-plasticity (CP) framework that captures the coupled phase transformation - plastic deformation behavior of shape memory alloys (SMAs) is presented. Here, different from previous models, the flow rule for martensitic phase transformation incorporates the entire deformation gradient for transformation, including the rotation. Predictions of transformation strain and variant selection of Nickel-Titanium (NiTi) using this model are directly compared with previous formulations that did not include the rotation. The results show that the rotation is essential to accurately calculate the single crystal and polycrystal micromechanics of variant selection and transformation strains of SMAs. The constitutive law formulation also includes current formulations for both slip and deformation twinning plasticity mechanisms, and the differences in transformation mechanisms are further shown to impact plasticity calculations through transformation-plasticity interactions. In addition to the advancement of the constitutive law, a computationally efficient implicit time integration scheme is given for numerical implementation and demonstrated using a user material subroutine (UMAT) in the commercial finite element code ABAQUS Standard. The proposed framework and the associated numerical protocols achieve stable solutions using strain increments on the order of <mml:math altimg=\"si61.svg\"><mml:mrow><mml:mn>0.05</mml:mn></mml:mrow></mml:math> mm/mm in simulating inelastic deformations and strain increments <mml:math altimg=\"si62.svg\"><mml:mrow><mml:mn>0.01</mml:mn></mml:mrow></mml:math> mm/mm in the elastic-inelastic transitions. Furthermore, the use of an analytic Jacobian results in stable convergence in fewer than 10 global Newton iterations while calculating solutions for elastic-inelastic transitions, making the computational benefits evident.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"14 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.jmps.2024.105957
Alok Tripathy, Shyam M. Keralavarma
Ductile failure by the onset of strain localization in rate sensitive porous materials is investigated using a linear perturbation stability analysis. A micromechanics-based constitutive model accounting for inhomogeneous yielding at the micro-scale, due to plastic strain concentration in the inter-void ligaments, is used. Strain and strain rate hardening of the material is accounted for using a phenomenological viscoplastic extension of the model. Unlike in earlier studies employing a rate-dependent model, an analytical closed form expression for the critical value of the hardening modulus at the onset of localization is derived. The predicted shape of the failure locus under proportional loading is shown to be consistent with known results in the literature for the loading path dependence of ductile failure. The model predicted failure loci are validated by comparison with mesoscopic unit cell model simulations of void growth in a viscoplastic power law hardening material. It is shown that the failure strains predicted by the model as a function of the hardening parameters are in good agreement with the strains to the onset of elastic unloading in the cell model simulations, signifying the onset of void coalescence at the micro-scale.
{"title":"Strain localization in rate sensitive porous ductile materials","authors":"Alok Tripathy, Shyam M. Keralavarma","doi":"10.1016/j.jmps.2024.105957","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105957","url":null,"abstract":"Ductile failure by the onset of strain localization in rate sensitive porous materials is investigated using a linear perturbation stability analysis. A micromechanics-based constitutive model accounting for inhomogeneous yielding at the micro-scale, due to plastic strain concentration in the inter-void ligaments, is used. Strain and strain rate hardening of the material is accounted for using a phenomenological viscoplastic extension of the model. Unlike in earlier studies employing a rate-dependent model, an analytical closed form expression for the critical value of the hardening modulus at the onset of localization is derived. The predicted shape of the failure locus under proportional loading is shown to be consistent with known results in the literature for the loading path dependence of ductile failure. The model predicted failure loci are validated by comparison with mesoscopic unit cell model simulations of void growth in a viscoplastic power law hardening material. It is shown that the failure strains predicted by the model as a function of the hardening parameters are in good agreement with the strains to the onset of elastic unloading in the cell model simulations, signifying the onset of void coalescence at the micro-scale.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"49 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.jmps.2024.105966
I. Grega, I. Batatia, P.P. Indurkar, G. Csányi, S. Karlapati, V.S. Deshpande
Machine learning methods for strut-based architected solids are attractive for reducing computational costs in optimisation calculations. However, the space of all realizable strut-based periodic architected solids is vast: not only can the number of nodes, their positions and the radii of the struts be changed but the topological variables such as the connectivity of the nodes brings significant complexity. In this work, we first examine the structure-property relationships of a large dataset of strut-based architected solids (lattices). We enrich the dataset by perturbing nodal positions and observe four classes of mechanical behaviour. A graph neural network (GNN) method is then proposed that directly describes the topology of the strut-based architected solid as a graph. The differentiating feature of our work is that key physical principles are embedded into the GNN architecture. In particular, the GNN model predicts fourth-order tensor with the required major and minor symmetries. The predictions are equivariant to rigid body and self-similar transformations, invariant to the choice of unit cell and constrained to provide a positive semi-definite stiffness tensor. We further demonstrate that augmenting the training dataset with nodal perturbations enables the model to better generalize to unseen lattice topologies.
{"title":"Graph neural networks for strut-based architected solids","authors":"I. Grega, I. Batatia, P.P. Indurkar, G. Csányi, S. Karlapati, V.S. Deshpande","doi":"10.1016/j.jmps.2024.105966","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105966","url":null,"abstract":"Machine learning methods for strut-based architected solids are attractive for reducing computational costs in optimisation calculations. However, the space of all realizable strut-based periodic architected solids is vast: not only can the number of nodes, their positions and the radii of the struts be changed but the topological variables such as the connectivity of the nodes brings significant complexity. In this work, we first examine the structure-property relationships of a large dataset of strut-based architected solids (lattices). We enrich the dataset by perturbing nodal positions and observe four classes of mechanical behaviour. A graph neural network (GNN) method is then proposed that directly describes the topology of the strut-based architected solid as a graph. The differentiating feature of our work is that key physical principles are embedded into the GNN architecture. In particular, the GNN model predicts fourth-order tensor with the required major and minor symmetries. The predictions are equivariant to rigid body and self-similar transformations, invariant to the choice of unit cell and constrained to provide a positive semi-definite stiffness tensor. We further demonstrate that augmenting the training dataset with nodal perturbations enables the model to better generalize to unseen lattice topologies.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"43 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years, soft materials with reversible adhesion have come to the fore as a promising avenue of research. Compared to other reversible adhesion methods, electroadhesion enabled by the formation of ionic double layer (IDL) has been widely used due to its simplicity, low energy consumption, fast response, and reversibility. Despite the extensive experimental studies and qualitative mechanistic explanations, there remains a dearth of theoretical studies on this topic, particularly regarding the development of theoretical mechanics models. Our study aims to address this gap by establishing a mechanics model of IDL-enabled electroadhesion between soft materials. We specifically focus on modeling the low-voltage electroadhesion of heterojunctions between two polyelectrolyte hydrogels. The model decomposes the electroadhesion formation into two successive physical processes. First, under appropriate bias conditions, the applied voltage drives the mobile ions in each polyelectrolyte hydrogel to migrate toward the electrode, resulting in the formation of an IDL at the heterojunction interface and the generation of a potent built-in electric field inside the IDL. Second, driven by the strong built-in electric field of IDL, the dangling charged chains of the two polyelectrolyte hydrogels begin to cross the heterojunction interface and penetrate into the opposite hydrogel matrix to form ionic bonds with the oppositely-charged chains, resulting in a bridging network that sutures the interface. As a result, the electrostatic interactions inside the IDL as well as the bridging network across the interface leads to the electroadhesion of polyelectrolyte hydrogel heterojunctions. The modeling results show that the IDL thickness, the IDL electric field density, and the electroadhesion strength increase with the applied voltage. We also experimentally conduct the electroadhesion tests, and the measurements of electroadhesion strength quantitatively match the modeling results well. For the first time, we reveal the underlying mechanism of IDL-driven electroadhesion by establishing a theoretical mechanics model. We anticipate that our mechanics model can shed light on the design, optimization, and control of the electroadhesion of soft-material heterojunctions.
{"title":"Mechanics of electroadhesion of polyelectrolyte hydrogel heterojunctions enabled by ionic double layers","authors":"Zheyu Dong, Zhi Sheng, Zihang Shen, Shaoxing Qu, Zheng Jia","doi":"10.1016/j.jmps.2024.105960","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105960","url":null,"abstract":"In recent years, soft materials with reversible adhesion have come to the fore as a promising avenue of research. Compared to other reversible adhesion methods, electroadhesion enabled by the formation of ionic double layer (IDL) has been widely used due to its simplicity, low energy consumption, fast response, and reversibility. Despite the extensive experimental studies and qualitative mechanistic explanations, there remains a dearth of theoretical studies on this topic, particularly regarding the development of theoretical mechanics models. Our study aims to address this gap by establishing a mechanics model of IDL-enabled electroadhesion between soft materials. We specifically focus on modeling the low-voltage electroadhesion of heterojunctions between two polyelectrolyte hydrogels. The model decomposes the electroadhesion formation into two successive physical processes. First, under appropriate bias conditions, the applied voltage drives the mobile ions in each polyelectrolyte hydrogel to migrate toward the electrode, resulting in the formation of an IDL at the heterojunction interface and the generation of a potent built-in electric field inside the IDL. Second, driven by the strong built-in electric field of IDL, the dangling charged chains of the two polyelectrolyte hydrogels begin to cross the heterojunction interface and penetrate into the opposite hydrogel matrix to form ionic bonds with the oppositely-charged chains, resulting in a bridging network that sutures the interface. As a result, the electrostatic interactions inside the IDL as well as the bridging network across the interface leads to the electroadhesion of polyelectrolyte hydrogel heterojunctions. The modeling results show that the IDL thickness, the IDL electric field density, and the electroadhesion strength increase with the applied voltage. We also experimentally conduct the electroadhesion tests, and the measurements of electroadhesion strength quantitatively match the modeling results well. For the first time, we reveal the underlying mechanism of IDL-driven electroadhesion by establishing a theoretical mechanics model. We anticipate that our mechanics model can shed light on the design, optimization, and control of the electroadhesion of soft-material heterojunctions.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"59 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-15DOI: 10.1016/j.jmps.2024.105958
Panpan Zhu, Ji Lin, Yimou Fu, Chun Shen, Haofei Zhou, Shaoxing Qu, Huajian Gao
Cell membrane rupture occurs universally and is long thought to be the terminal event of cell death; however, there is an inadequate understanding of the microscopic mechanisms of membrane rupture at the molecular level. In this study, we investigated the rupture mechanism of two model membranes, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and cholesterol bilayer membranes, under surface tension by all-atom molecular simulations and theoretical modeling. Under surface tension, the tail chains of POPC molecules become disordered, leading to ductile membrane deformation, while cholesterol membranes display limited deformation before rupture. We analyzed the orientation of tail chains and the internal stresses within the membranes, revealing that the mutual attraction among different tail chains and the resulting stress peak in the tail region of the membrane play substantial roles in the membrane rupture process. Based on these physical insights, we proposed a theoretical model that incorporates an internal variable of tail chain orientation to capture the variations in strain and orientation of different membrane components under varying surface tensions. The critical rupture threshold predicted by our theoretical model aligns well with the simulation results, demonstrating a brittle to ductile transition for membranes with different cholesterol contents. Our study unravels the impact of tail chain orientation and internal stress on membrane mechanics, which deepens the understanding of the microscale mechanisms underlying membrane rupture.
{"title":"Unraveling the molecular mechanisms of membrane rupture: Insights from all-atom simulations and theoretical modeling","authors":"Panpan Zhu, Ji Lin, Yimou Fu, Chun Shen, Haofei Zhou, Shaoxing Qu, Huajian Gao","doi":"10.1016/j.jmps.2024.105958","DOIUrl":"https://doi.org/10.1016/j.jmps.2024.105958","url":null,"abstract":"Cell membrane rupture occurs universally and is long thought to be the terminal event of cell death; however, there is an inadequate understanding of the microscopic mechanisms of membrane rupture at the molecular level. In this study, we investigated the rupture mechanism of two model membranes, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and cholesterol bilayer membranes, under surface tension by all-atom molecular simulations and theoretical modeling. Under surface tension, the tail chains of POPC molecules become disordered, leading to ductile membrane deformation, while cholesterol membranes display limited deformation before rupture. We analyzed the orientation of tail chains and the internal stresses within the membranes, revealing that the mutual attraction among different tail chains and the resulting stress peak in the tail region of the membrane play substantial roles in the membrane rupture process. Based on these physical insights, we proposed a theoretical model that incorporates an internal variable of tail chain orientation to capture the variations in strain and orientation of different membrane components under varying surface tensions. The critical rupture threshold predicted by our theoretical model aligns well with the simulation results, demonstrating a brittle to ductile transition for membranes with different cholesterol contents. Our study unravels the impact of tail chain orientation and internal stress on membrane mechanics, which deepens the understanding of the microscale mechanisms underlying membrane rupture.","PeriodicalId":17331,"journal":{"name":"Journal of The Mechanics and Physics of Solids","volume":"18 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1016/j.jmps.2024.105936
Martín I. Idiart
Explicit expressions for the free-energy and dissipation densities of viscoelastic composites at fixed temperature are proposed. The composites are comprised of an arbitrary number of distinct constituents exhibiting linear Maxwellian rheologies and distributed randomly at a length scale that is much smaller than that over which applied loads vary significantly. Central to their derivation is the recognition that any viscous deformation field can be additively decomposed into an irrotational field and a solenoidal field in such a way that variational approximations available for elastic potentials become applicative to viscoelastic potentials. The thermodynamic potentials conform to a generalized standard model with a finite number of effective internal variables with explicit physical meaning. Specific approximations of the Hashin–Shtrikman and the Self-Consistent types are worked out in detail. Under particular circumstances, these approximations may turn out exact. Macroscopic stress–strain relations and intraphase statistics of the stress field up to second order are also provided.
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Pub Date : 2024-11-14DOI: 10.1016/j.jmps.2024.105944
Geyong Cao, Xiaojun Wang
Continuum solid mechanics form the foundation of numerous theoretical studies and engineering applications. Distinguished from traditional mesh-based numerical solutions, the rapidly developing field of scientific machine learning, exemplified by methods such as physics-informed neural networks (PINNs), shows great promise for the study of forward and inverse problems in mechanics. However, accurately imposing boundary conditions (BCs) in the training and prediction of neural networks (NNs) has long been a significant challenge in the application and research of PINNs. This paper integrates the concept of isogeometric analysis (IGA) by parameterizing the physical model of the structure with spline basis functions to form analytical distance functions (DFs) for arbitrary structural boundaries. Meanwhile, by means of the energy approach to circumvent the solution of boundary stress components, the accurate imposition of both Dirichlet and Neumann BCs is ultimately achieved in PINNs. Additionally, to accommodate the complex mixed BCs often encountered in engineering applications, where Dirichlet and Neumann BCs simultaneously appear on adjacent irregular boundary segments, structural subdomain decomposition and multi-subdomain stitching strategies are introduced. The effectiveness and accuracy of the proposed method are verified through two numerical experiments with various cases.
连续固体力学是众多理论研究和工程应用的基础。有别于传统的基于网格的数值解法，以物理信息神经网络（PINNs）等方法为代表的科学机器学习领域发展迅速，为力学中正向和反向问题的研究带来了巨大前景。然而，在神经网络（NN）的训练和预测中准确施加边界条件（BC）一直是 PINNs 应用和研究中的重大挑战。本文整合了等几何分析（IGA）的概念，通过对结构物理模型进行参数化，用样条基函数形成任意结构边界的解析距离函数（DFs）。同时，通过能量方法规避边界应力分量的求解，最终在 PINNs 中实现了 Dirichlet 和 Neumann BC 的精确施加。此外，为了适应工程应用中经常遇到的复杂混合 BC，即 Dirichlet BC 和 Neumann BC 同时出现在相邻的不规则边界段上，引入了结构子域分解和多子域拼接策略。通过两种不同情况的数值实验，验证了所提方法的有效性和准确性。
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