【新文速递】2023年12月8日固体力学SCI期刊最新文章

今日更新：International Journal of Solids and Structures 3 篇，Journal of the Mechanics and Physics of Solids 1 篇，Mechanics of Materials 1 篇，International Journal of Plasticity 5 篇，Thin-Walled Structures 3 篇International Journal of Solids and StructuresFracture energy and cohesive law analysis of adhesives using a recently developed SCB joint: The influence of joint geometry and mode mixityA. Ajdani, A. Akhavan-Safar, S. Jalali, L.F.M. da Silva, M.R. Ayatollahidoi:10.1016/j.ijsolstr.2023.112581使用最近开发的 SCB 接头对粘合剂进行断裂能和内聚律分析：接头几何形状和混合模式的影响In a prior study, the current authors proposed the utilization of semi-circular bend (SCB) specimens for analyzing the fracture energy of adhesive materials. However, similar to standard fracture test specimens, the geometry and size of the joint can impact the measured fracture energy when using SCB samples. Therefore, the objective of this research is to investigate the influence of adhesive layer thickness, substrate thickness, and disk radius of SCB specimens on cohesive law parameters and fracture energy of the adhesive. The study examines the fracture energy under different loading conditions, including pure mode I, pure mode II, and two mixed-mode conditions. By employing an inverse data reduction method, the cohesive law parameters of the tested adhesive are determined for various joint geometries. The results demonstrate that the disk radius does not affect the cohesive law of the joint. Furthermore, it is observed that bondline thicknesses of 0.2 mm and 0.4 mm lead to similar cohesive laws, whereas an adhesive thickness of 1 mm results in lower initial stiffness but higher fracture energy and damage initiation traction. Moreover, the study reveals that an increase in substrate thickness reduces the final fracture separation, indicating a more brittle fracture behavior. This can be attributed to a smaller fracture process zone caused by the plane strain load distribution in the adhesive layer.在之前的一项研究中，作者提出利用半圆形弯曲（SCB）试样来分析粘合材料的断裂能。然而，与标准断裂测试试样类似，在使用 SCB 试样时，接头的几何形状和尺寸也会影响测得的断裂能。因此，本研究的目的是调查 SCB 试样的粘合剂层厚度、基材厚度和圆盘半径对粘合剂内聚规律参数和断裂能的影响。研究考察了不同加载条件下的断裂能，包括纯模式 I、纯模式 II 和两种混合模式条件。通过采用逆数据还原法，确定了不同连接几何形状下测试粘合剂的内聚律参数。结果表明，圆盘半径不会影响接头的内聚规律。此外，研究还发现，粘合线厚度为 0.2 毫米和 0.4 毫米时，内聚规律相似，而粘合剂厚度为 1 毫米时，初始刚度较低，但断裂能和损伤起始牵引力较高。此外，研究还发现，基材厚度增加会降低最终断裂分离度，表明断裂行为更脆。这可能是由于粘合剂层中的平面应变载荷分布导致断裂过程区域较小。New geometry-inspired numerical convex analysis method for yield functions under isotropic and anisotropic hardeningsYanshan Lou, Chong Zhang, Pengfei Wu, Jeong Whan Yoondoi:10.1016/j.ijsolstr.2023.112582 各向同性和各向异性淬火条件下屈服函数的新几何启发数值凸分析方法Convexity of a yield function must be guaranteed to ensure unique relationship between plastic strain increments and stress components. A geometry-inspired numerical convex analysis (GINCA) approach is developed to analyze the convexity of a yield function. The numerical approach is verified by the computation of convex domains for several typical yield functions of Drucker, Cazacu-Barlat2004, Hu2017, Cazacu2018 and a newly proposed function for differential-anisotropic hardening. The verified GINCA is applied to analyze the convexity of the Gao2011 yield function since it was not determined yet. The numerical approach is also used to determine the convex domain evolution with respect to plastic deformation in an anisotropic hardening function. It is also applied to investigate the convexity of polynomial yield functions for strong anisotropic metals. The result shows that the GINCA can effectively and correctly compute the convex domain for different yield functions. Besides, the numerical approach only needs to compute the effective stress from a yield function without any computation of the first- and second-order partial derivatives, compared to the complicated convex analysis by the Hessian matrix. Therefore, the proposed GINCA is user-friendly, effective and accurate to analyze the convexity of a yield function both for isotropic hardening and anisotropic/differential hardening. The Matlab codes are shared as electric attachments for scientists and engineers to check the convexity of a yield surface under biaxial loading, plane stress with shear stress and triaxial loading conditions.必须保证屈服函数的凸性，以确保塑性应变增量和应力分量之间的独特关系。本文开发了一种几何启发数值凸分析（GINCA）方法来分析屈服函数的凸性。通过计算 Drucker、Cazacu-Barlat2004、Hu2017、Cazacu2018 的几个典型屈服函数以及新提出的微分各向异性硬化函数的凸域，验证了该数值方法。由于 Gao2011 屈服函数的凸性尚未确定，因此应用经过验证的 GINCA 对其进行分析。数值方法还用于确定各向异性硬化函数中塑性变形的凸域演化。它还被用于研究强各向异性金属的多项式屈服函数的凸性。结果表明，GINCA 可以有效、正确地计算不同屈服函数的凸域。此外，与通过赫塞斯矩阵进行复杂的凸分析相比，该数值方法只需根据屈服函数计算有效应力，而无需计算一阶和二阶偏导数。因此，无论是各向同性硬化还是各向异性/差异硬化，所提出的 GINCA 在分析屈服函数的凸性方面都是友好、有效和准确的。现将 Matlab 代码作为电子附件提供给科学家和工程师，用于检查双轴加载、平面应力与剪应力以及三轴加载条件下屈服面的凸性。Minimal rebounding height on shell elucidated: Impact memory of bead on shellQing Peng, Xiaoming Liu, Yue-Guang Weidoi:10.1016/j.ijsolstr.2023.112594 阐明了贝壳上的最小反弹高度：珠子对贝壳的冲击记忆For the impact of a bead on a flat plate, the rebounding height decreases as the bead size increases. However, for the impact on a shell, a minimal rebounding height exists for a certain size of the bead. In this study, we revealed that the reason behind, which has never been comprehended, is the memory effect of impact of the bead on the shell. Separating the memory contribution analytically, we demonstrated that the memory effect will enhance the rebounding height as the bead size increases. In particular, we found that the single contact will split into two sub-contacts as the bead size increases; the memory of impact fundamentally changes the type of contacts. Moreover, the boundary of sub-contacts determines the condition for the minimal rebounding height.对于珠子对平板的冲击，反弹高度随着珠子尺寸的增大而减小。然而，当珠子撞击贝壳时，在珠子尺寸一定的情况下，反弹高度最小。在这项研究中，我们揭示了珠子撞击贝壳时的记忆效应，而这一原因从未被人理解。通过分析记忆效应的贡献，我们证明了记忆效应会随着珠子尺寸的增大而提高反弹高度。特别是，我们发现随着珠子尺寸的增大，单个接触将分裂成两个子接触；冲击记忆从根本上改变了接触的类型。此外，子接触的边界决定了最小反弹高度的条件。Journal of the Mechanics and Physics of SolidsA mechanically-derived contact model for adhesive elastic-perfectly plastic particles, Part II: Contact under high compaction—modeling a bulk elastic responseWilliam Zunker, Ken Kamrindoi:10.1016/j.jmps.2023.105493 粘合弹性-完全塑性颗粒的机械接触模型，第二部分：高压实度下的接触--体弹性响应建模In Part I of this two part series (Zunker and Kamrin, 2024), we presented a multi-neighbor dependent contact model for adhesive elastic–plastic particles built upon the method of dimensionality reduction that is valid for the elastic and fully-plastic contact regimes. In this Part II, we complete the contact model by proposing a treatment for the bulk elastic contact regime which is characterized by a rapid stiffening in the force–displacement curve as interstitial pore spaces vanish. A simple formulation is presented for an additional bulk elastic force. A novel criterion for triggering this force (i.e. detecting the bulk elastic regime) related to the remaining free surface area of the particle is also given. This bulk elastic force is then superimposed with the force response given in Part I to achieve a contact model capable of capturing a variety of complex loadings. In this way, the methodology for treating the bulk elastic regime presented here stands independent of Part I and could be appended to any contact model. Direct comparison is made to finite element simulations showcasing bulk elastic responses, revealing the accurate predictive capabilities of the contact model. Notably, the contact model is also demonstrated to detect and evolve contacts caused purely by outward displacement of the free surface with good precision. A numerical implementation suitable for the discrete element method is provided.在本系列文章两部分的第一部分（Zunker 和 Kamrin，2024 年）中，我们介绍了基于降维方法的粘性弹塑性粒子多邻域接触模型，该模型适用于弹性和全塑性接触状态。在这第二部分中，我们提出了对大块弹性接触机制的处理方法，从而完善了接触模型。大块弹性接触机制的特点是，随着间隙孔隙的消失，力-位移曲线迅速变硬。我们还提出了一个简单的附加体弹性力公式。此外，还给出了一个与粒子剩余自由表面积相关的触发该力（即检测体弹性机制）的新标准。然后，将这种体弹性力与第一部分中给出的力响应进行叠加，得到一个能够捕捉各种复杂载荷的接触模型。这样，本文介绍的处理体弹性机制的方法就独立于第一部分，可以附加到任何接触模型中。直接与有限元模拟进行比较，展示了体弹性响应，揭示了接触模型的精确预测能力。值得注意的是，该接触模型还能精确检测和演化纯粹由自由表面向外位移引起的接触。该模型提供了适合离散元方法的数值实现。Mechanics of MaterialsQuantification and comparison of the nonlinear mechanical properties of transcutaneous and human aortic valve leaflets: Experimental and numerical studiesAisa Rassoli, Nasser Fatouraee, Ze Zhang, Robert Guidoindoi:10.1016/j.mechmat.2023.104872量化和比较经皮主动脉瓣叶与人体主动脉瓣叶的非线性机械特性：实验和数值研究Background: Extracting the mechanical behaviors of tissue leaflets in prosthetic aortic valves is necessary for designing and manufacturing appropriate prostheses for percutaneous deployment. The goal of this study was to opt a proper tissue for bioprostheses.Methods: In this study, donkey and bovine pericardia and human aortic valve leaflets are compared mechanically. The uniaxial and biaxial tensile tests were performed on the tissue specimens. The measured uniaxial data were then fitted into Yeoh, and Mooney-Rivlin hyperelastic models, and the elastic modulus, failure strain, and ultimate tensile strength (UTS) for each sample were calculated. Furthermore, to determine the degree of anisotropy of the specimens, the biaxial hyperelastic properties of the samples were extracted using the Gasser-Ogden-Holzapfel (GOH) and Mooney-Rivlin models. In addition, the extracted anisotropic parameters were exerted to the finite element modeling of the bovine and donkey pericardia.Results: Donkey pericardium exhibited a low stiffer behavior, based on its lowest strain energy magnitude and the average slope of stress-stretch curves. This tissue was also high distensible than the bovine pericardium, due to its highest areal strain. Furthermore, the donkey finite element model induced low stress regions during the systole and diastole phases. On the other hand, decreased mechanical stress on the bioprosthetic leaflets may reduce tissue dehiscence and increase the long-term durability of the valve.Conclusion: The nonlinear behavior of the pericardial tissues can be well-characterized by the constitutive functions. The mechanical properties of the donkey pericardium are even closer to the native leaflets. The donkey pericardium might be a good candidate valve leaflet material for bioprostheses.研究背景：提取人工主动脉瓣中组织瓣叶的机械行为对于设计和制造经皮安装的合适人工瓣膜非常必要。本研究的目的是为生物假体选择合适的组织。研究方法：在本研究中，对驴和牛心包与人类主动脉瓣叶进行了机械比较。对组织样本进行了单轴和双轴拉伸试验。然后将测得的单轴数据拟合到 Yeoh 和 Mooney-Rivlin 超弹性模型中，并计算出每个样本的弹性模量、破坏应变和极限拉伸强度 (UTS)。此外，为了确定试样的各向异性程度，还使用 Gasser-Ogden-Holzapfel (GOH) 和 Mooney-Rivlin 模型提取了试样的双轴超弹性特性。此外，还将提取的各向异性参数用于牛和驴心包的有限元建模。研究结果：根据最低应变能大小和应力-拉伸曲线的平均斜率，驴心包表现出低刚度行为。与牛心包相比，驴心包的扩张性也较高，因为它的应变值最高。此外，驴的有限元模型在收缩期和舒张期诱导了低应力区域。另一方面，生物人工瓣叶受到的机械应力降低可减少组织开裂，提高瓣膜的长期耐用性。结论：心包组织的非线性行为可以用构成函数很好地描述。驴心包的机械特性甚至更接近于原生瓣叶。驴心包可能是生物瓣膜的理想候选瓣叶材料。International Journal of PlasticityA neural network-based material cell for elastoplasticity and its performance in FE analyses of boundary value problemsShaoheng Guan, Xue Zhang, Sascha Ranftl, Tongming Qudoi:10.1016/j.ijplas.2023.103811基于神经网络的弹塑性材料单元及其在边界值问题有限元分析中的表现This research focuses on evaluating the capacity and performance of a network-based material cell as a constitutive model for boundary-value problems. The proposed material cell aims to replicate constitutive relationships learned from datasets generated by random loading paths following a stochastic Gaussian process. The material cell demonstrates its effectiveness across three progressively complex constitutive models by incorporating physical extensions and symmetry constraint as prior knowledge. To address the challenge of magnitude gaps between strain increments in training sets and finite element simulations, an adaptive linear transformation is introduced to mitigate prediction errors. The material cell successfully replicates constitutive relationships in finite element simulations, and its performance is comprehensively evaluated by comparing two different material cells: the sequentially trained gated recurrent unit (GRU)-based material cell and the one-to-one trained deep network-based material cell. The GRU-based material cell can be trained without explicit calibration of the internal variables. This enables us to directly derive the constitutive model using stress–strain data without consideration of the physics of internal variables.这项研究的重点是评估基于网络的材料单元作为边界值问题构成模型的能力和性能。拟议的材料单元旨在复 制从随机加载路径生成的数据集中学习到的构成关系，这些数据集遵循随机高斯过程。通过将物理扩展和对称约束作为先验知识，材料单元在三个逐渐复杂的构成模型中展示了其有效性。为解决训练集和有限元模拟中应变增量之间的量级差距问题，引入了自适应线性变换，以减少预测误差。该材料单元成功复 制了有限元模拟中的构成关系，并通过比较两种不同的材料单元对其性能进行了全面评估：基于顺序训练的门控递归单元（GRU）材料单元和基于一对一训练的深度网络材料单元。基于 GRU 的材料单元无需对内部变量进行明确校准即可进行训练。这使我们能够利用应力-应变数据直接推导出构成模型，而无需考虑内部变量的物理特性。Interaction between basal edge/mixed dislocations and point defects in zirconiumRongxuan Xie, Chuanlong Xu, Xiaobao Tian, Qingyuan Wang, Wentao Jiang, Haidong Fandoi:10.1016/j.ijplas.2023.103815锆中基底边缘/混合位错与点缺陷之间的相互作用Zirconium alloys are widely used in nuclear reactors. Due to frequent displacement cascade events under irradiation, a large number of point defects are generated in zirconium alloys. In this work, the interactions between edge/mixed dislocations and point defects (vacancies and SIAs (self-interstitial atoms)) are studied by molecular dynamics (MD) simulations. The simulation results indicate that vacancies are not absorbed by edge dislocations but by mixed dislocations. Compared with their weak pinning effect on edge dislocation motion, vacancies have an intermediate pinning effect on the motion of mixed dislocation. In contrast, SIAs are all absorbed by edge and mixed dislocations and have a strong pinning effect. Then, force equilibrium is established on point defects to explain the absorption of point defects. The attractive force between dislocations and point defects is calculated from the binding energy, and friction force of point defects is calculated from the migration energy. We found that the friction force of vacancies on edge dislocations is larger than the attractive force, and thus the vacancies cannot be absorbed. For the other three cases, the attractive force is large enough to overcome the friction force, and the point defects are absorbed.锆合金广泛应用于核反应堆。由于辐照下频繁的位移级联事件，锆合金中产生了大量的点缺陷。在这项工作中，通过分子动力学（MD）模拟研究了边缘/混合位错与点缺陷（空位和 SIAs（自间隙原子））之间的相互作用。模拟结果表明，空位不是被边缘位错吸收，而是被混合位错吸收。与空位对边缘位错运动的微弱钉住效应相比，空位对混合位错运动具有中间钉住效应。相比之下，SIA 全部被边缘位错和混合位错吸收，具有很强的钉住效应。然后，在点缺陷上建立力平衡来解释点缺陷的吸收。位错与点缺陷之间的吸引力由结合能计算得出，点缺陷的摩擦力由迁移能计算得出。我们发现空位对边缘位错的摩擦力大于吸引力，因此空位不能被吸收。在其他三种情况下，吸引力足以克服摩擦力，点缺陷被吸收。Strength-ductility synergy of an additively manufactured metastable high-entropy alloy achieved by transformation-induced plasticity strengtheningChunmao Tian, Di Ouyang, Pengbo Wang, Lichao Zhang, Chao Cai, Kun Zhou, Yusheng Shidoi:10.1016/j.ijplas.2023.103823通过转化诱导塑性强化实现添加式制造的可转移高熵合金的强度-韧性协同效应This study investigated the microstructures and mechanical properties of a metastable high-entropy alloy (HEA) Fe34Co34Cr20Mn6Ni6 produced by laser powder bed fusion (LPBF) and compared them with those of an as-cast one. The LPBF-processed HEA exhibited a face-centered cubic (FCC) structure due to the high cooling rate of the laser-induced melt pools. In contrast, the as-cast HEA featured a mass of hexagonal close-packed (HCP) phase within the FCC matrix due to the elemental segregation resulting from low cooling rates. The LPBF-processed HEA exhibited superior strength-ductility synergy when compared to its as-cast counterpart. The yield strength, ultimate strength, and plasticity of the LPBF-processed HEA were 305 MPa, 808 MPa, and 18.9%, respectively, which were much higher than those of the as-cast HEA (171 MPa, 463 MPa, and 7.3%). This strength-ductility synergy was attributed to the in-situ formation of a fine HCP phase through the stress-induced phase transformation (TRIP) effect. The fine HCP phase provided abundant FCC/HCP interfaces, thus enhancing strong back stress hardening and facilitating the deformation uniformity. In contrast, the as-cast HEA displayed coarse and straight FCC/HCP interfaces that hindered back stress hardening. Moreover, the interaction between the pre-existing HCP phase and the stress-induced HCP phase in the as-cast HEA tended to cause stress concentration and subsequent crack initiation, leading to reduced ductility in the as-cast HEA. These findings are expected to provide valuable insights for a better understanding of additively manufactured TRIP-assisted HEAs.本研究研究了激光粉末床熔融（LPBF）法生产的可转移高熵合金（HEA）Fe34Co34Cr20Mn6Ni6的微观结构和力学性能，并将其与铸态合金进行了比较。由于激光诱导熔池的冷却速度较高，LPBF加工的HEA呈现出面心立方（FCC）结构。与此相反，由于低冷却速率导致的元素偏析，铸件HEA在FCC基体中形成了大量六方紧密堆积（HCP）相。LPBF 加工的 HEA 与铸造的 HEA 相比，表现出更高的强度-性能协同效应。经 LPBF 处理的 HEA 的屈服强度、极限强度和塑性分别为 305 兆帕、808 兆帕和 18.9%，远高于铸造 HEA 的屈服强度、极限强度和塑性（分别为 171 兆帕、463 兆帕和 7.3%）。这种强度-电导率协同作用归因于通过应力诱导相变（TRIP）效应在原位形成了细小的 HCP 相。细小的 HCP 相提供了丰富的 FCC/HCP 界面，从而增强了强背应力硬化并促进了变形均匀性。相比之下，铸造时的 HEA 显示出粗直的 FCC/HCP 界面，阻碍了背应力硬化。此外，铸态 HEA 中预先存在的 HCP 相与应力诱发的 HCP 相之间的相互作用往往会导致应力集中和随后的裂纹萌生，从而降低铸态 HEA 的延展性。这些发现有望为更好地理解添加式制造的 TRIP 辅助 HEA 提供有价值的见解。Effect of Strain Gradient on Elastic and Plastic Size Dependency in Polycrystalline CopperJae-Hoon Choi, Hyemin Ryu, Kwang-Hyeok Lim, Ji-Young Kim, Hojang Kim, Gi-Dong Simdoi:10.1016/j.ijplas.2023.103824应变梯度对多晶铜弹性和塑性尺寸依赖性的影响This study unveils the presence of size effect not only in the plastic regime but also in the elastic regime under strain gradient. This discovery emerges from a comprehensive set of experiments encompassing micro-cantilever bending and micro-pillar compression tests. Subsequent finite element analysis serves to not only expose the limitation of classical continuum theory but also to effectively demonstrate the enhanced predictive capabilities of couple stress theory in both elastic and plastic size effects. To incorporate couple stress theory, a systematic and rigorous finite element analysis-based optimization was devised to determine length scale parameters, which are additional material properties in couple stress theory. The resulting length scale parameters for polycrystalline copper were found to be 0.536 and 0.669 μ m in the elastic and plastic regimes, respectively. The study also explores the physical interpretation of these length scale parameters in both regimes.这项研究揭示了尺寸效应不仅存在于塑性机制中，也存在于应变梯度下的弹性机制中。这一发现源于一系列全面的实验，包括微悬臂弯曲和微支柱压缩试验。随后的有限元分析不仅揭示了经典连续性理论的局限性，还有效地证明了耦合应力理论在弹性和塑性尺寸效应方面更强的预测能力。为了纳入耦合应力理论，我们设计了一种基于有限元分析的系统而严格的优化方法来确定长度标度参数，这些参数是耦合应力理论中的附加材料属性。结果发现，多晶铜在弹性和塑性状态下的长度尺度参数分别为 0.536 和 0.669 μ m。研究还探讨了这两种状态下这些长度尺度参数的物理解释。Enhancing strength and ductility of Al-matrix composite via a dual-heterostructure strategyJinfeng Nie, Yuyao Chen, Lei Song, Yong Fan, Yang Cao, Kewei Xie, Sida Liu, Xiangfa Liu, Yonghao Zhao, Yuntian Zhudoi:10.1016/j.ijplas.2023.103825通过双异构策略提高铝基质复合材料的强度和延展性Aluminum matrix composites (AMCs) often have low ductility, which has been a long-lasting issue in the last few decades. This problem arises largely from the non-deformability of reinforcement particles, which leads to premature failure of the matrix-particle interfaces. Here we propose a new microstructural design strategy for AMCs: distribute the reinforcement particles non-uniformly to form dual-heterostructured AMCs. The zones with high-density particles are recognized as the hard zones, which carry less plastic strain than the particle-free zones to prevent premature interfacial failure. A dual-heterostructured Al-matrix nanocomposite is fabricated, in which AlN nanoparticles are distributed in a dual-level hierarchy: first level heterogeneous nanoparticle distribution and second level heterogeneous zones with different grain sizes. The dual heterostructure produced a unique dual level hetero-deformation induced (HDI) strengthening and hardening to produce high strength and ductility. The dual level HDI strengthening effect has been revealed by the inflection points on the loading-unloading-reloading stress-strain curves. Furthermore, the evolution of local strain fields during the in-situ tensile deformation directly proved the occurrence of strain partitioning, in which the ductile particle free zones have carried a larger strain than the hard particle rich zones. Dispersive shear strain bands are observed for the first time in AMCs. These findings are expected to help design other metal matrix composites with superior mechanical properties.铝基复合材料（AMC）通常具有较低的延展性，这在过去几十年中一直是一个长期存在的问题。这一问题主要源于增强颗粒的不变形性，这导致了基体-颗粒界面的过早失效。在此，我们提出了一种新的 AMC 微结构设计策略：将增强粒子非均匀分布，形成双异构 AMC。高密度颗粒区被视为硬区，与无颗粒区相比，硬区承载的塑性应变较小，可防止界面过早失效。我们制备了一种双异质结构的铝基质纳米复合材料，其中 AlN 纳米颗粒以双层层次结构分布：第一层为异质纳米颗粒分布，第二层为具有不同晶粒尺寸的异质区。这种双层异质结构产生了独特的双层异质变形诱导（HDI）强化和硬化，从而产生了高强度和延展性。加载-卸载-再加载应力-应变曲线上的拐点揭示了双级 HDI 增强效应。此外，原位拉伸变形过程中局部应变场的演变直接证明了应变分区的发生，其中无韧性颗粒区比富含硬颗粒区承载了更大的应变。在 AMC 中首次观察到了分散剪切应变带。这些发现有望帮助设计出具有优异机械性能的其他金属基复合材料。Thin-Walled StructuresStiffness optimisation of sandwich structures with elastically isotropic lattice coreYifan Zhu, Efstratios Polyzos, Lincy Pyldoi:10.1016/j.tws.2023.111408带弹性各向同性晶格核心的夹层结构的刚度优化This study concerns homogenisation-based stiffness optimisation with elastically isotropic plate and truss-based lattice structures. Due to the lattices’ isotropy, an optimised design can be obtained without including each lattice's rotational degree of freedom (DOF) as a design variable. Stiffness optimisation was performed on sandwich structures with lattice cores. Two optimised sandwich structures were fabricated using material extrusion additive manufacturing, and their deformation behaviour was studied using digital image correlation (DIC). DIC results revealed that when using a truss-based lattice as the core, certain trusses were susceptible to local strain concentration. On the other hand, sandwich structures with a plate-based lattice as the core showed an evenly distributed strain field, indicating loads can be more efficiently carried. Optimisation results in a maximum increase of 14.0 % for bending stiffness and 24.2 % for energy absorption. This research stands out for its novel selection of lattices and in-depth analysis of the full-field strain distribution in optimised sandwich lattice structures during bending. Combining experimental and numerical methods, the study sheds light on the deformation mechanism of these additively manufactured lattices, offering additional insights.本研究涉及基于各向同性板和桁架网格结构的同质化刚度优化。由于晶格的各向同性，无需将每个晶格的旋转自由度（DOF）作为设计变量，即可获得优化设计。对带有晶格核心的夹层结构进行了刚度优化。使用材料挤压增材制造技术制造了两种优化的夹层结构，并使用数字图像相关技术（DIC）对其变形行为进行了研究。DIC 结果显示，当使用基于桁架的晶格作为核心时，某些桁架容易出现局部应变集中。另一方面，以板式晶格为核心的夹层结构则显示出均匀分布的应变场，这表明可以更有效地承载载荷。通过优化，弯曲刚度最大提高了 14.0%，能量吸收最大提高了 24.2%。这项研究的突出之处在于其对晶格的新颖选择，以及对优化夹层晶格结构在弯曲过程中的全场应变分布的深入分析。该研究结合实验和数值方法，揭示了这些叠加制造晶格的变形机制，为我们提供了更多启示。Spectral Geometry Solutions for Random Vibration of Functionally Graded Graphene Platelet Reinforced Conical ShellsZhengyang Gao, Xianjie Shi, Zhou Huang, Rui Zhong, Qingshan Wangdoi:10.1016/j.tws.2023.111410功能分级石墨烯小板增强锥壳随机振动的光谱几何解决方案This study delved into the random vibration characteristics of a conical shell constructed from a functionally graded graphene platelet-reinforced composite (FG-GPLRC) under the influence of basic acceleration excitation. The investigation employed a synthesis of two methodologies: the spectral geometry method (SGM) and the pseudo-excitation method (PEM). Commencing with the application of the Halpin-Tsai micromechanics approach and the law of mixtures, the effective material characteristics of the FG-GPLRC structure were determined. Subsequently, the displacement field vector for the conical shell structure was established using the SGM. By employing the framework of the first-order shear deformation theory (FSDT), the energy function of the FG-GPLRC conical shell was derived, with external random excitation energy being incorporated using the PEM. To construct a dynamic model for the conical shell structure, the Rayleigh-Ritz method was applied, subjecting the energy function to variational extremization. This approach yielded a comprehensive dynamic representation. The validity of the proposed model was substantiated through comparison with existing literature and finite element analysis. Ultimately, this study explored the influence of graphene material properties and geometric parameters of the conical shell on the random vibration characteristics of the FG-GPLRC conical shell.本研究探讨了由功能分级石墨烯血小板增强复合材料（FG-GPLRC）构建的锥形壳体在基本加速度激励影响下的随机振动特性。研究综合运用了两种方法：光谱几何法（SGM）和伪激励法（PEM）。首先应用 Halpin-Tsai 微机械方法和混合物定律，确定了 FG-GPLRC 结构的有效材料特性。随后，利用 SGM 建立了锥壳结构的位移场矢量。通过采用一阶剪切变形理论（FSDT）框架，得出了 FG-GPLRC 锥壳的能量函数，并利用 PEM 将外部随机激励能量纳入其中。为了构建锥形壳结构的动态模型，应用了雷利-里兹方法，对能量函数进行变分极化。这种方法产生了一个全面的动态表示。通过与现有文献和有限元分析的比较，证实了所提出模型的有效性。最终，本研究探讨了石墨烯材料特性和锥壳几何参数对 FG-GPLRC 锥壳随机振动特性的影响。Bending Behavior of Diamane and Twisted Bilayer Graphene: Insights from Four-point Bending DeformationShangchun Jiang, Liangfeng Sun, Haifei Zhan, Zhuoqun Zheng, Xijian Peng, Chaofeng Lüdoi:10.1016/j.tws.2023.111415 二烷和扭曲双层石墨烯的弯曲行为：四点弯曲变形的启示The intriguing physical properties of two-dimensional (2D) nanomaterials make them promising building blocks for flexible electronics. Using a four-point bending approach, this work establishes a comprehensive understanding of the bending behavior of diamane – a 2D diamoand nanostructure, from elastic deformation to structural failure through atomistic simulations. The four-point bending method accurately reproduces the pure bending of the sample, and the obtained force-displacement curve fit well with the classical Euler beam theory. Structural failure is observed from diamane under bending when its thickness or the number of layers increases. Atomic insights reveal that the crack initiates from the tension side of the sample, resulting in a tension-induced bending failure. Specifically, the bending limit is found to be slightly larger than the fracture strain under tensile deformation. Additionally, the bending behaviour of the diamane analogous – twisted bilayer graphene with interlayer-bonding (TBGIB), has been investigated. Different from diamane, TBGIB bends elastically at the initial stage and then experiences structural failures with increasing bending strain. Higher interlayer bonding density is observed to result in a higher bending stiffness. Meanwhile, significant interlayer shear strain is detected during bending, which leads to interlayer bond breakage, rippling, and buckling of the graphene layer. This work provides a full description of the pure bending behavior of diamane and its analogous structure, which could be beneficial for their applications in flexible electronics.二维（2D）纳米材料具有引人入胜的物理特性，是柔性电子器件的理想构件。本研究采用四点弯曲方法，通过原子模拟全面了解了二维二元纳米结构二元烷从弹性变形到结构破坏的弯曲行为。四点弯曲法精确再现了样品的纯弯曲，所获得的力-位移曲线与经典的欧拉梁理论非常吻合。当二元胺的厚度或层数增加时，在弯曲条件下会出现结构破坏。原子研究表明，裂纹从样品的拉伸侧开始，导致拉伸引起的弯曲失效。具体来说，弯曲极限略大于拉伸变形下的断裂应变。此外，我们还研究了二胺烷的类似物--具有层间结合的扭曲双层石墨烯（TBGIB）的弯曲行为。与二胺烷不同的是，TBGIB 在初始阶段会发生弹性弯曲，然后随着弯曲应力的增加而发生结构破坏。据观察，层间结合密度越高，弯曲刚度越大。同时，在弯曲过程中会检测到明显的层间剪切应变，从而导致层间结合断裂、波纹和石墨烯层屈曲。这项研究全面描述了二乙烷及其类似结构的纯弯曲行为，这将有助于它们在柔性电子产品中的应用。来源：复合材料力学仿真Composites FEM