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【新文速递】2024年9月27日固体力学SCI期刊最新文章

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今日更新:Journal of the Mechanics and Physics of Solids 2 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 1 篇

Journal of the Mechanics and Physics of Solids

Creasing instability of polydomain nematic elastomers in compression

Alireza Ahmadi, Neda Maghsoodi

doi:10.1016/j.jmps.2024.105870

压缩条件下多畴向列弹性体的增皱不稳定性

Polydomain liquid crystalline (nematic) elastomers exhibit unique mechanical properties such as soft elasticity, where the material largely deforms at nearly constant stress, due to microstructural evolution. In this paper, we numerically study the implication of such remarkable soft behavior on the surface instability of a half-space polydomain nematic elastomer, which is uniformly compressed parallel to the interface under a plane-strain condition. We compare the creasing instability of nematic elastomers with that of neo-Hookean elastomers by presenting bifurcation diagrams, stress and strain development in the elastomers, energy relaxation, and surface morphology at the creased state. Our results reveal that soft elasticity stabilizes nematic elastomers in plane-strain compression. Remarkably, the critical strain and stress at which the crease nucleates depend nonlinearly on the degree of anisotropy in nematic elastomers. Moreover, we find that the morphology of the creased surface in nematic elastomers exhibits the universal cusp shape previously observed in neo-Hookean elastomers.

多畴液晶(向列)弹性体表现出独特的机械性能,如软弹性,由于微观结构的演变,材料在几乎恒定的应力下很大程度上变形。本文用数值方法研究了在平面应变条件下平行于界面均匀压缩的半空间多域向列弹性体的这种显著的软行为对其表面不稳定性的影响。我们比较了向列弹性体与新胡克弹性体的折痕不稳定性,给出了弹性体的分岔图、应力和应变的发展、能量松弛和折痕状态下的表面形貌。我们的研究结果表明,软弹性在平面应变压缩中稳定了向列弹性体。值得注意的是,折痕成核的临界应变和应力与向列弹性体的各向异性程度呈非线性关系。此外,我们发现向列弹性体的折痕表面形态表现出先前在新胡克弹性体中观察到的通用尖头形状。


Analysis of shear localization in viscoplastic solids with pressure-sensitive structural transformations

J.D. Clayton

doi:10.1016/j.jmps.2024.105880

具有压敏结构转变的粘塑性固体剪切局部化分析

Localization, in the form of adiabatic shear, is analyzed in viscoplastic solids that may undergo structural transformation driven by pressure, shear stress, temperature, and magnetic field. As pertinent to polycrystalline metals, transformations may include solid–solid phase transitions, twinning, and dynamic recrystallization. A finite-strain constitutive framework for isotropic metals is used to solve a boundary value problem involving simple shearing with superposed hydrostatic pressure and constant external magnetic field. Three-dimensional theory is reduced to a formulation simple enough to facilitate analysis without advanced numerical methods, yet sophisticated enough to maintain the salient physics. Ranges of constitutive parameters (e.g., strain hardening, strain-rate sensitivity, thermal softening, and strain-driven structure transformation limits influenced by pressure and magnetic field) are obtained for which localization to infinite shear strain is possible. Motivated by experimental and theoretical studies suggesting a non-negligible role of shear on phase transformations in iron (Fe), the model is used to understand influences of pressure and phase transitions on applied strains for which localization should occur in pure Fe and a high-strength steel. Results show, among other trends for the two materials, that shear localization in conjunction with phase transformation is promoted when the transformed phase is softer than the parent phase. Localization that would occur in the isolated parent phase can be mitigated if strain hardening or thermal softening tendencies of the transformed phase are sufficiently increased or reduced, respectively.

在压力、剪切应力、温度和磁场驱动下可能发生结构转变的粘塑性固体中,以绝热剪切形式进行局部化分析。与多晶金属相关,转变可以包括固-固相变、孪生和动态再结晶。采用各向同性金属的有限应变本构框架,求解了具有叠加静水压力和恒外磁场的简单剪切边值问题。三维理论被简化为一个足够简单的公式,可以在没有先进的数值方法的情况下进行分析,但又足够复杂,可以保持显著的物理特性。得到了本构参数的范围(如应变硬化、应变率敏感性、热软化和受压力和磁场影响的应变驱动的结构转变极限),从而可以局部化到无限剪切应变。由于实验和理论研究表明剪切对铁(Fe)相变的作用不可忽视,该模型用于理解压力和相变对施加应变的影响,这些应变应在纯铁和高强度钢中局部化。结果表明,在两种材料的其他趋势中,当相变相比母相更软时,促进了剪切局部化与相变的结合。如果转变相的应变硬化或热软化倾向分别得到充分的增加或减少,则可以减轻孤立母相中可能发生的局部化。


Mechanics of Materials

A variational method for the simulation of hydrogen diffusion in metals

E.M. Andrés, I. Romero

doi:10.1016/j.mechmat.2024.105166

氢在金属中的扩散模拟的变分方法

We present a new method for the approximate solution of the strongly coupled, nonlinear stress-diffusion problem that appears when modeling hydrogen transport in metals. The most salient feature of the proposed approximation is that it is fully variational, meaning that all the discrete equations are obtained from the optimality conditions of an incremental potential, even for inelastic mechanical behavior. Like other variational methods, the proposed algorithm has remarkable properties, including the symmetry of the tangent operator, making its solution extremely efficient compared to other similar methods available in the literature.

本文提出了一种近似求解金属氢输运模型中出现的强耦合非线性应力扩散问题的新方法。所提出的近似的最显著特征是它是完全变分的,这意味着所有的离散方程都是从增量势的最优性条件中获得的,即使是非弹性力学行为也是如此。与其他变分方法一样,所提出的算法具有显著的性质,包括切线算子的对称性,使其求解与文献中其他类似方法相比非常有效。


Thin-Walled Structures

Experimental Investigation of Buckling and Post-Buckling Behaviour of Repaired Composite Laminates Under In-plane Shear Loading

M. Damghani, A. Bugaje, G.A. Atkinson, D. Cole

doi:10.1016/j.tws.2024.112489

面内剪切荷载作用下修复复合材料层合板屈曲及后屈曲行为试验研究

The performance of Ramped Scarf (RS) and Stepped Scarf (SS) repair schemes for highly loaded composite structures has been extensively studied under compressive, tensile, and flexural loadings. However, there is a lack of research on the buckling and post-buckling behaviour of RS and SS repairs under in-plane shear loading, which is critical for aerostructures. This paper addresses this gap by investigating the buckling and post-buckling performance of these repair schemes. Pristine (P) laminates, RS repairs with a scarf angle of 3°, and SS repairs with an overlap step length of 1/60 were manufactured and tested. The quality of the scarf repairs was inspected using artificial intelligence-based machine vision. Mechanical in-plane shear testing was conducted to evaluate the buckling and post-buckling behaviour of P, RS, and SS laminates. The experimental results indicate that RS repairs demonstrated an average of 35% higher maximum displacement and 12% higher failure load compared to pristine laminates. SS repairs showed 19% higher maximum displacement, and 5% higher failure load compared to pristine laminates. RS repairs excelled in all key mechanical performance indicators, including buckling load, Hooke's stiffness, maximum displacement, and failure load, compared to SS repairs. The failure modes of P, RS, and SS laminates were similar. However, RS repairs exhibited greater susceptibility to repair patch detachment compared to SS repairs.

在压缩、拉伸和弯曲载荷下,对高载荷复合材料结构的斜面丝巾(RS)和阶梯丝巾(SS)修复方案的性能进行了广泛的研究。然而,对于航空结构至关重要的面内剪切载荷作用下RS和SS修复的屈曲和后屈曲行为,目前还缺乏相关研究。本文通过研究这些修复方案的屈曲和后屈曲性能来解决这一差距。制造和测试了原始(P)层压板,围巾角为3°的RS修复,重叠步长为1/60的SS修复。使用基于人工智能的机器视觉检查围巾修复的质量。力学面内剪切试验进行了评估屈曲和后屈曲行为的P, RS和SS层合板。实验结果表明,与原始层压板相比,RS修复的最大位移平均高出35%,破坏载荷平均高出12%。与原始层压板相比,SS修复的最大位移增加了19%,破坏负荷增加了5%。与SS修复相比,RS修复在所有关键机械性能指标上都表现出色,包括屈曲载荷、胡克刚度、最大位移和失效载荷。P层板、RS层板和SS层板的破坏模式相似。然而,与SS修复相比,RS修复更容易出现修复补丁脱落。



来源:复合材料力学仿真Composites FEM
ACTMechanicalMAGNETDeform复合材料非线性通用航空UG理论材料试验人工智能机器视觉
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首次发布时间:2024-11-27
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【新文速递】2024年9月29日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 1 篇International Journal of Solids and StructuresDoes static friction information predict the onset of sliding for soft material?Huixin Wei, Zhiyong Wang, Xinhao Tu, Xuanshi Cheng, Linan Li, Shibin Wang, Chuanwei Lidoi:10.1016/j.ijsolstr.2024.113087静摩擦信息能否预测软质材料滑动的开始?Friction behavior between soft and hard materials has long been a question of great interest in the fields of artificial joints, human skin contact, robotic grippers, and others. In this study, we presented a combination of theoretical and experimental analyses to investigate the friction behavior of soft materials. Using some geometric and stick–slip features in the early stage of static friction, the friction property of the interface between a soft material and a hard material is determined. Moreover, the onset of slip, the threshold force at which a friction interface begins to slide, is also predicted by a theoretical model. The predictive ability of this model may provide insights for improving interaction property recognition, as well as for developing fine tactile feedback and dexterous operation of robotic grasping.软硬材料之间的摩擦行为长期以来一直是人工关节、人体皮肤接触、机器人抓手等领域非常感兴趣的问题。在这项研究中,我们提出了理论和实验相结合的分析来研究软材料的摩擦行为。利用静摩擦初期的一些几何特征和粘滑特征,确定了软、硬材料界面的摩擦性能。此外,滑移起始力,即摩擦界面开始滑动的阈值,也可以通过理论模型来预测。该模型的预测能力可为改进交互特性识别,以及开发精细触觉反馈和机器人抓取灵巧操作提供见解。Journal of the Mechanics and Physics of SolidsHyperelastic constitutive relations for porous materials with initial stressMengru Zhang, Weiting Chen, Xianfu Huang, Quanzi Yuan, Ya-Pu Zhaodoi:10.1016/j.jmps.2024.105886具有初始应力的多孔材料的超弹性本构关系Initial stress is widely observed in porous materials. However, its constitutive theory remains unknown due to the lack of a framework for modeling the interactions between initial stress and porosity. In this study, we construct the porous hyperelastic constitutive model with arbitrary initial stresses through the multiplicative decomposition approach. Based on the compression experiment of shale samples, the parameters in the constitutive equation are determined. Then, the explicit equations of in-plane elastic coefficients are proposed by linearizing the finite deformation formulation. The influences brought by the coexistence of initial stresses and porosity on these coefficients are revealed. Later, comparative analyses of the linearized equations between the present model, the initially-stressed models without pores, the Biot poroelasticity, and the porous hyperelastic model without initial stress are conducted to illustrate the performances of the two ingredients. As a specific example, we investigate the variation of pore sizes under external pressures and initial stresses since changes in pore sizes during deformation are crucial for understanding the accumulation and migration of shale oil and gas. The newly proposed model provides the first initially stressed porous hyperelasticity (ISPH), which is suitable for describing the finite deformation behavior of solid materials with large porosity and significant initial stress simultaneously.在多孔材料中广泛观察到初始应力。然而,由于缺乏一个框架来模拟初始应力和孔隙度之间的相互作用,其本构理论仍然未知。本文采用乘法分解方法,建立了具有任意初始应力的多孔超弹性本构模型。通过对页岩试样的压缩实验,确定了本构方程中的参数。然后,将有限变形公式线性化,建立了平面内弹性系数的显式方程。揭示了初始应力和孔隙度共存对这些系数的影响。然后,将该模型与无孔隙初始应力模型、Biot孔隙弹性模型和无初始应力的多孔超弹性模型的线性化方程进行对比分析,以说明两种成分的性能。作为一个具体的例子,我们研究了外部压力和初始应力下孔隙大小的变化,因为变形过程中孔隙大小的变化对于理解页岩油气的聚集和运移至关重要。该模型提供了第一初始应力多孔超弹性模型(ISPH),适用于描述大孔隙率和显著初始应力同时存在的固体材料的有限变形行为。Mechanics of MaterialsQuantification of elastic incompatibilities at triple junctions via physics-based surrogate modelsAaditya Rau, Christopher Schuh, Raúl Radovitzkydoi:10.1016/j.mechmat.2024.105163通过基于物理的替代模型量化三联点的弹性不相容Stresses resulting from elastic incompatibilities at grain boundaries have long been known to drive the premature failure and loss of desirable macroscopic properties in polycrystalline materials. In this work, we employ machine learning to create a surrogate model that furnishes a functional relationship between grain boundary configurational data and metrics of incompatibility. A planar triple junction geometry composed of cubic grains rotated about their [001] axis was adopted as the grain boundary model. High-fidelity finite element simulations of this triple junction under hydrostatic extension were used to generate a synthetic dataset for training the surrogate model. A set of J integrals computed around microcracks placed along the triple junction boundaries were used to quantify the elastic incompatibilities between the grains. Using the grain rotation angles and J integrals as the feature and label data respectively, a multi-layer perceptron network was trained using the synthetic data produced with the physics-based model. We demonstrate that the network trained using data from the physics-based model establishes an accurate functional dependence between the triple junction angles and the J integrals that enables direct and fast evaluation. We use the surrogate model to efficiently sweep the configuration space and create contour maps of the largest stress intensification at the triple junction as a function of the grain rotation angles. Furthermore, we show that the analytical properties of the surrogate model can be utilized to identify the most and least compatible triple junction configurations via optimization.长期以来晶界弹性不相容所产生的应力会导致多晶材料过早失效并丧失理想的宏观特性。在这项工作中,我们利用机器学习创建了一个替代模型,该模型提供了晶界构型数据与不相容性指标之间的函数关系。晶界模型采用了由围绕 [001] 轴旋转的立方晶粒组成的平面三结点几何体。在流体静力学延伸条件下,对该三交界处进行高保真有限元模拟,生成用于训练代用模型的合成数据集。沿三重交界处的微裂缝周围计算的一组 J 积分用于量化晶粒之间的弹性不相容性。将晶粒旋转角度和 J 积分分别作为特征数据和标签数据,使用基于物理模型生成的合成数据训练多层感知器网络。我们证明,使用基于物理模型的数据训练的网络在三重交界角和 J 积分之间建立了精确的函数关系,从而可以进行直接和快速的评估。我们利用代用模型有效地扫描了构型空间,并绘制出了三重交界处最大应力增强与晶粒旋转角函数关系的等高线图。此外,我们还展示了代用模型的分析特性可用于通过优化确定最兼容和最不兼容的三重连接配置。Thin-Walled StructuresMorphogenesis Analysis of Icosahedral and Prismatic Tensegrity ModulesXinran Wang, Zhihong Zhang, Hai Liu, Zhenhua Wang, Mingshan Zhangdoi:10.1016/j.tws.2024.112500二十面体和棱柱张拉整体模的形态发生分析Morphogenesis is a critical aspect of tensegrity system design. This paper explores icosahedral and prismatic tensegrity modules' pattern formation and foundational theories. First, a material consumption functional and self-strain energy functional is introduced from an engineering perspective, along with a variational principle involving independent dual-variable in the morphogenesis process of tensegrity structures. Next, a Symbol Parsing Method is proposed and successfully applied to the optimal morphology analysis of the icosahedral tensegrity module. Due to memory limitations in personal computers, the Singular Value Decomposition of the symbolic equilibrium matrix for the prismatic tensegrity module is constrained. As an alternative, a discrete numerical solution, the semi-symbolic parsing method, is obtained by directly utilizing a numerical equilibrium matrix. This method was recently employed to analyze and optimize a practical tensegrity footbridge designed by the authors. Lastly, the paper delves into the stability of self-equilibrium states in icosahedral and classical prismatic tensegrity modules by employing a second-order variational analysis of the self-strain energy functional. The findings presented are expected to contribute to future research on the morphogenesis of tensegrity structures.形态发生是张拉整体系统设计的一个重要方面。本文探讨了二十面体和棱柱张拉整体模的模式形成及其基础理论。首先,从工程角度介绍了材料消耗函数和自应变能函数,以及张拉整体结构形态形成过程中涉及独立双变量的变分原理。其次,提出了一种符号解析方法,并成功应用于二十面体张拉整体模块的最优形态分析。由于个人计算机的内存限制,柱形张拉整体模块的符号平衡矩阵的奇异值分解受到了限制。作为一种替代方法,直接利用数值平衡矩阵得到离散数值解,即半符号解析法。最近将该方法应用于作者设计的实际张拉整体人行桥的分析和优化。最后,通过对自应变能泛函的二阶变分分析,探讨了二十面体和经典棱柱张拉整体模的自平衡态的稳定性。所提出的研究结果有望对张拉整体结构形态发生的未来研究做出贡献。来源:复合材料力学仿真Composites FEM

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