【新文速递】2024年6月3日固体力学SCI期刊最新文章

 

今日更新：Journal of the Mechanics and Physics of Solids 10 篇，Mechanics of Materials 2 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 9 篇

Journal of the Mechanics and Physics of Solids

The elastica with pre-stress due to natural curvature

Sophie Leanza, Ruike Renee Zhao, John W. Hutchinson

doi:10.1016/j.jmps.2024.105690

由于自然弯曲，具有预应力的弹性材料

The axial buckling behavior is determined for an elastic beam or rod which has a uniform curvature in its natural state, is straightened by pure bending, and clamped at its ends. Buckling can be either identical to the classical two-dimensional behavior determined by Euler, or it can be three-dimensional involving twist and deflection out of the plane of natural curvature depending on the bending and torsional stiffnesses and the natural curvature. While the classical two-dimensional buckling behavior of Euler's elastica is stable under applied load, the three-dimensional buckling behavior can be stable or unstable. Theoretical and experimental examples are presented illustrating the full range of possibilities.

确定弹性梁或杆的轴向屈曲行为，该梁或杆在其自然状态下具有均匀曲率，通过纯弯曲进行拉直，并在其末端进行夹紧。屈曲可以是由欧拉确定的经典二维行为，也可以是三维的，根据弯曲和扭转刚度以及自然曲率的不同，包括扭曲和偏离自然曲率平面。经典的欧拉弹性结构在载荷作用下的二维屈曲行为是稳定的，而三维屈曲行为可以是稳定的，也可以是不稳定的。给出了理论和实验实例，说明了各种可能性。

Static topological mechanics with local resonance

Aoxi Wang, Zhiqiang Meng, Chang Qing Chen

doi:10.1016/j.jmps.2024.105705

具有局部共振的静态拓扑力学

The locally resonant band gaps that lie in the vicinity of resonant frequency have been extensively employed in metamaterials for ultralow-frequency wave control, such as vibration isolation, negative refraction, superlensing, and cloaking. The combination of local resonance and band topology allows for the broadband tunable topological boundary modes, ranging from audible to ultrasonic frequencies. Recently, nontrivial topological boundary modes have been reported in static mechanical systems beyond frequency-based wave dynamics, in which the band gap is typically Bragg-like. In this paper, the concept of local resonance is extended from dynamic to static systems where the inertial effects are absent, and is leveraged to customize the topological modes. We impart a pseudo-mass to the static systems and retrieve the locally resonant band gap. The eigenvalues and associated bulk deformation fields of the topological mode can be tailored by shifting the pseudo-resonant frequency. Moreover, an effective non-reciprocity is achieved by passively breaking the lattice symmetry, and its cooperation with local resonances enables the static metamaterial to shield eccentric deformations and selectively filter boundary loads. All of these models are experimentally validated in an assembled truss-like lattice. This study is expected to provide a platform for exploring locally resonant topological phases without relying on wave motion.

谐振频率附近的局部谐振带隙已被广泛应用于超材料的低频波控制，如隔振、负折射、超透镜和隐形。局部共振和频带拓扑的结合允许宽带可调谐拓扑边界模式，范围从可听到超声波频率。最近，在基于频率的波动动力学之外的静态机械系统中已经报道了非平凡拓扑边界模式，其中带隙是典型的布拉格样。本文将局域共振的概念从动态系统扩展到不存在惯性效应的静态系统，并利用局域共振自定义拓扑模式。我们赋予静态系统一个伪质量，并获得局部共振带隙。通过改变赝共振频率，可以调整拓扑模式的特征值和相应的体变形场。此外，静态超材料通过被动破坏晶格对称性实现了有效的非互易性，并与局部共振相配合，使其能够屏蔽偏心变形并选择性地过滤边界载荷。所有这些模型都在一个组装的桁架状晶格中进行了实验验证。该研究有望为探索局部共振拓扑相位提供一个平台，而不依赖于波动。

Variational operator learning: A unified paradigm marrying training neural operators and solving partial differential equations

Tengfei Xu, Dachuan Liu, Peng Hao, Bo Wang

doi:10.1016/j.jmps.2024.105714

变分算子学习:结合训练神经算子和求解偏微分方程的统一范例

Neural operators as novel neural architectures for fast approximating solution operators of partial differential equations (PDEs), have shown considerable promise for future scientific computing. However, the mainstream of training neural operators is still data-driven, which needs an expensive ground-truth dataset from various sources (e.g., solving PDEs’ samples with the conventional solvers, real-world experiments) in addition to training stage costs. From a computational perspective, marrying operator learning and specific domain knowledge to solve PDEs is an essential step for data-efficient and low-carbon learning. We propose a novel data-efficient paradigm that provides a unified framework of training neural operators and solving PDEs with the domain knowledge related to the variational form, which we refer to as the variational operator learning (VOL). We develop Ritz and Galerkin approach respectively with finite element discretization for VOL to achieve matrix-free approximation of the energy functional of physical systems and calculation of residual tensors derived from associated linear systems with linear time complexity and O(1) space complexity. We then propose direct minimization and iterative update as two possible optimization strategies. Various types of experiments based on reasonable benchmarks about variable heat source, Darcy flow, and variable stiffness elasticity are conducted to demonstrate the effectiveness of VOL. With a label-free training set, VOL learns solution operators with its test errors decreasing in a power law with respect to the amount of unlabeled data. To the best of the authors’ knowledge, this is the first study that integrates the perspectives of the weak form and efficient iterative methods for solving sparse linear systems into the end-to-end operator learning task. Codes and Datasets are publicly available at https://doi.org/10.5281/zenodo.11097870.

神经算子作为用于快速逼近偏微分方程（PDEs）解算子的新型神经架构，在未来的科学计算中大有可为。然而，训练神经算子的主流仍是数据驱动，除了训练阶段的成本外，还需要从各种来源（如用传统求解器求解 PDEs 样本、真实世界实验）获得昂贵的基础真实数据集。从计算的角度来看，将算子学习与特定领域知识相结合来求解 PDE 是实现数据高效和低碳学习的必要步骤。我们提出了一种新颖的数据高效范式，它提供了一个统一的框架，既能训练神经算子，又能利用与变分形式相关的领域知识求解 PDE，我们称之为变分算子学习（VOL）。我们为 VOL 分别开发了有限元离散化的 Ritz 和 Galerkin 方法，以实现物理系统能量函数的无矩阵近似，并计算相关线性系统的残差张量，其时间复杂度为线性，空间复杂度为 O(1)。然后，我们提出了直接最小化和迭代更新两种可能的优化策略。为了证明 VOL 的有效性，我们基于可变热源、达西流和可变刚度弹性等合理基准进行了各种类型的实验。在无标签训练集的情况下，VOL 学习求解算子的测试误差与无标签数据量成幂律递减。据作者所知，这是第一项将解决稀疏线性系统的弱形式和高效迭代法的观点整合到端到端算子学习任务中的研究。代码和数据集可通过 https://doi.org/10.5281/zenodo.11097870 公开获取。

The role of adhesion on soft lubrication: a new theory

Chung-Yuen Hui, Xuemei Xiao, Hao Dong, Anand Jagota

doi:10.1016/j.jmps.2024.105720

黏附在软润滑中的作用:一种新理论

Recent experiments reveal that adhesive interactions can play a key role in causing surface instability in soft lubrication. Instances of instability include fluid entrapment in isolated pockets upon a soft sphere's normal contact with a hard substrate and surface wrinkling of a soft substrate as a hard sphere slides across it. These phenomena underscore a substantial distinction between hard and soft lubrication. They are of paramount importance from a fundamental standpoint, providing an entirely new explanation for the transition mechanism from elasto-hydrodynamics to the mixed lubrication regimes. Here, we introduce a new theory to elucidate these observations. Our theory modifies the Reynolds elasto-hydrodynamics equation by incorporating adhesive interaction across the fluid layer, investigating the interplay between adhesion, fluid flow and elastic instability. Our analysis proposes the addition of a new dimensionless parameter in lubrication theory, that compares the stiffness of the adhesive interaction to that of the substrate. When this parameter exceeds unity, the soft solid surface exhibits instability to small perturbations in its shape. In mathematical terms, the Reynolds equation undergoes a transition from a nonlinear diffusion equation to a nonlinear wave equation at this critical point. Post-transition, the diffusivity of the nonlinear diffusion equation turns negative, rendering the problem ill-posed. We investigate the transition using the method of characteristics and present an exact analytic solution. This solution offers insights into the occurrence of a vanishing liquid film thickness at specific locations, resulting in dry contact—initiating transition to mixed lubrication.

最近的实验表明，在软润滑中，黏合剂的相互作用是导致表面不稳定的关键因素。不稳定性的例子包括:软球与硬基板正常接触时，流体在孤立的口袋中被困住;硬球滑过软基板时，软基板表面起皱。这些现象强调了硬润滑和软润滑之间的本质区别。从基础的角度来看，它们是至关重要的，为从弹性流体力学到混合润滑的过渡机制提供了一个全新的解释。在这里，我们引入一个新的理论来阐明这些观察。我们的理论修正了雷诺弹性流体动力学方程，将粘着相互作用纳入流体层，研究粘着、流体流动和弹性不稳定性之间的相互作用。我们的分析提出了在润滑理论中增加一个新的无量纲参数，用于比较粘接相互作用的刚度和基材的刚度。当该参数超过1时，软固体表面对其形状的微小扰动表现出不稳定性。在数学上，雷诺方程在这个临界点处经历了从非线性扩散方程到非线性波动方程的转变。跃迁后，非线性扩散方程的扩散系数变为负，使问题不适定。我们用特征方法研究了这种转变，并给出了精确解析解。该解决方案提供了在特定位置液膜厚度消失的情况，从而导致干接触开始向混合润滑过渡。

Crossed-state bowing and the strength of binary dislocation junctions

Isaac Duan, Ryan B. Sills

doi:10.1016/j.jmps.2024.105696

交叉态弯曲与二元位错结的强度

The strength of binary dislocation junctions in face-centered cubic metals is analyzed via a large set of discrete dislocation dynamics (DDD) simulations and an energy-based line tension model. The simulations reveal that, contrary to the prevailing wisdom, junctions often remain unbroken even after they have fully unzipped, a phenomenon which we call crossed-state bowing. After incorporating crossed-state bowing into the line tension model, we demonstrate that in some cases prior works severely underpredicted junction strength by neglecting crossed-state bowing. Using the line tension model we analyze the statistics of junction strength from a large population of junction geometries showing the influence of stress on the forest slip system and crossed-state bowing. Our results indicate that junction strengths under single-slip loading are not representative of multi-slip loading, and that crossed state bowing controls junction strength about half of the time. The MATLAB code for our line tension model is available as an open-source code.

通过大量离散位错动力学(DDD)模拟和基于能量的线张力模型，分析了面心立方金属中二元位错结的强度。模拟结果显示，与普遍的认知相反，即使在完全拉开拉链后，连接点通常也不会断裂，这种现象我们称之为交叉状态弯曲。在将交叉状态弯曲纳入线张力模型后，我们证明在某些情况下，先前的工作由于忽略交叉状态弯曲而严重低估了连接强度。利用线张力模型，我们分析了大量结点几何形状的结点强度统计，显示了应力对森林滑移系统和交叉状态弯曲的影响。结果表明，单滑移载荷作用下的连接强度不能代表多滑移载荷作用下的连接强度，交叉状态弯曲约占连接强度的一半。我们的线张力模型的MATLAB代码是可用的开源代码。

On Inherent Hyperelastic Crease

Siyuan Song, Mrityunjay Kothari, Kyung-Suk Kim

doi:10.1016/j.jmps.2024.105716

固有超弹性折痕

We present analyses of the inherent hyperelastic crease that entails an unstable degenerative singular perturbation field over a uniformly compressed hyperelastic half-space. The analyses reveal asymptotic far-field characteristics of the singular field that bring out admissible incremental elastic deformation mechanisms of the inherent creasing instability typically observed at a compressive strain of ∼0.354 in neo-Hookean solids. The admissible singular perturbation field has an asymptotic leading-order incremental-stress singularity decaying 1/r2 as the distance from the crease tip r→∞. In general, asymptotic incremental-deformation fields of 1/r2 stress singularity can be introduced by surface flaws. We found that the singular field creates a far-field eigenmode of three energy-release angular sectors separated by two energy-elevating sectors of incremental deformation. The far-field eigenmode braces the near-tip energy-release field of the surface flaw against the transition to an unstable self-similar expansion field of creasing. Two asymptotic far-field parameters can characterize the braced-incremental-deformation (bid) and crease fields. One is the Burgers vector of a projected subsurface dislocation of the asymptotically singular far field. The other is a dimensionless shape factor representing the ratio of the subsurface depth of the dislocation to the Burgers vector. Our analyses show that the shape factor gauges the transition from the stable bid field to the unstable inherent crease field at the crease limit point as the compression increases. Two tangential-manifold conservation integrals are revealed to identify the two parameters. At the crease-limit point, matched asymptotes lead to the ratio between the two separate scaling parameters of the asymptotic solutions of the crease-tip folding field and the leading-order far field. To this end, we introduced a novel finite element method (FEM) for simulating the crease field nearly in a hyperelastic half-space with a finite-size simulation domain. Furthermore, we uncovered with the Gent model (1996) that strain-stiffening in hyperelasticity alters the dependence of the shape factor on the compressive strain, raising crease resistance. The new findings in hyperelastic crease mechanisms will help study ruga mechanics of self-organization and design soft-material structures and skin conditions for high crease resistance.

我们对均匀压缩的超弹性半空间上的不稳定退化奇异扰动场引起的固有超弹性皱褶进行了分析。这些分析揭示了奇异场的渐近远场特性，从而引出了新胡肯固体在压缩应变为 ∼ 0.354 时通常观察到的固有折痕不稳定性的可容许增量弹性变形机制。可容许的奇异扰动场具有渐进的前导阶增量应力奇异性，随着与折痕尖端的距离 r→∞ 衰减 1/r2。一般来说，表面缺陷会引入 1/r2 应力奇点的渐近增量变形场。我们发现，奇异场会产生一个由三个能量释放角段和两个增量变形能量提升角段组成的远场特征模式。远场特征模式支撑着表面缺陷的近尖能量释放场，防止其过渡到不稳定的自相似膨胀皱褶场。有两个渐近远场参数可以表征支撑增量变形（bid）场和皱褶场。一个是渐近奇异远场的投影次表面位错的伯格斯向量。另一个是无量纲形状系数，代表差排的次表层深度与布尔格斯矢量之比。我们的分析表明，随着压缩量的增加，形状系数可测量在折痕极限点处从稳定的标距场向不稳定的固有折痕场的过渡。两个切向-褶皱守恒积分揭示了这两个参数。在折痕极限点，匹配的渐近线导致折痕尖端折叠场和前阶远场渐近解的两个独立缩放参数之间的比率。为此，我们引入了一种新颖的有限元方法（FEM），以有限大小的模拟域模拟超弹性半空间中的折痕场。此外，我们还利用 Gent 模型（1996 年）发现，超弹性中的应变刚性改变了形状因子对压缩应变的依赖关系，从而提高了折痕阻力。超弹性折痕机制的新发现将有助于研究自组织的地毯力学，并设计出具有高抗折痕性的软材料结构和皮肤条件。

Sharp-interface limits for brittle fracture via the inverse-deformation formulation

Timothy J. Healey, Roberto Paroni, Phoebus Rosakis

doi:10.1016/j.jmps.2024.105717

用反变形公式计算脆性断裂的锐界面极限

We derive sharp-interface models for one-dimensional brittle fracture via the inverse-deformation approach. Methods of  Γ-convergence are employed to obtain the singular limits of previously proposed models. The latter feature a local, non-convex stored energy of inverse strain, augmented by small interfacial energy, formulated in terms of the inverse-strain gradient. They predict spontaneous fracture with exact crack-opening discontinuities, without the use of damage (phase) fields or pre-existing cracks; crack faces are endowed with a thin layer of surface energy. The models obtained her ewith inherit the same properties, except that surface energy is now concentrated at the crack faces in the Γ-limit. Accordingly, we construct energy-minimizing configurations. For a composite bar with a breakable layer, our results predict a pattern of equally spaced cracks whose number is given as an increasing function of applied load.

我们通过反变形方法推导出一维脆性断裂的锐面模型。我们采用Γ收敛方法来获得之前提出的模型的奇异极限。后者的特点是反应变的局部非凸存储能，由小的界面能增强，以反应变梯度表示。它们预测了自发断裂，具有精确的开裂不连续性，不使用损伤（相）场或预先存在的裂缝；裂缝面具有薄层表面能。Ewith 所获得的模型继承了相同的特性，只是表面能现在集中在 Γ 极限的裂纹面上。因此，我们构建了能量最小的配置。对于带有可破损层的复合材料棒材，我们的结果预测出了一种等间距裂纹模式，其数量是外加载荷的递增函数。

Generalized continuum theory for nematic elastomers: Non-affine motion and characteristic behavior

Samuel C. Lamont, Franck J. Vernerey

doi:10.1016/j.jmps.2024.105718

向列弹性体的广义连续统理论:非仿射运动和特征行为

We develop a physically-motivated mechanical theory for predicting the behavior of nematic elastomers – a subset of liquid crystal elastomers (LCEs). We begin with a statistical description of network geometry that naturally incorporates independent descriptors for the mesogens, which create the nematic phase, and the polymer chains, which are assumed to not deform affinely with global deformations. From here, we develop thermodynamically consistent constitutive laws based on classical continuum mechanics principles and ultimately provide simple governing equations with transparent physical interpretation. We found that our framework converges identically to two previously developed mechanical theories, including the well-known neo-classical theory, when considering the extreme ends of our parametric space. We then explore the new predictive capabilities of our model inside these two extremes and illustrate its unique predictions at finite strains, which are distinct in form from other theories. We validate our model using published experimental data from four monodomain nematic liquid crystal elastomers.

我们开发了一种物理驱动的力学理论来预测向列弹性体的行为-液晶弹性体(LCEs)的一个子集。我们从网络几何的统计描述开始，该描述自然地包含了创建向列相的介元和聚合物链的独立描述符，假设它们不会随着全局变形而发生仿射变形。在此基础上，我们建立了基于经典连续介质力学原理的热力学一致的本构定律，并最终提供了具有透明物理解释的简单控制方程。我们发现，当考虑参数空间的极端端点时，我们的框架与两个先前发展的力学理论(包括著名的新古典理论)相同。然后，我们在这两个极端中探索我们的模型的新预测能力，并说明其在有限应变下的独特预测，这在形式上与其他理论不同。我们用四种单畴向列液晶弹性体发表的实验数据验证了我们的模型。

The chemo-mechanics of initiation of crack advance in Niobium Tungsten Oxide single crystals due to delithiation

Shrinidhi S. Pandurangi, Clare P. Grey, Vikram S. Deshpande, Norman A. Fleck

doi:10.1016/j.jmps.2024.105724

氧化铌钨单晶裂纹萌生的化学力学研究

Niobium tungsten oxide (NWO) micron-sized single crystals show promise as the active particles in the anodes of lithium ion batteries due to their fast charge/discharge and high storage capabilities. Within the “block” phases such as Nb16W5O55, Nb14W3O44 and the H-Nb2O5 polymorph, Li ion diffusion occurs in a unidirectional manner along a single axis of the crystal and lithiation results in significant length changes in this direction. A chemo-mechanics analysis is developed for delithiation of an NWO “block” phase single crystal that contains a pre-existing flaw in the form of a through-thickness edge crack. Galvanostatic delithiation occurs by the flux of Li ions through the free ends of the crystal and also through the faces of the crack, with concomitant shrinkage of the surface layer over a depth equal to that of the crack. The induced tensile stress in the surface layer can be of sufficient magnitude to advance the crack in the NWO crystal, consistent with recent experimental observations for Nb14W3O44. A 2D full-field finite element version of the chemo-mechanics model is used to explore the sensitivity of cracking to crack length, delithiation rate of the anode, diffusivity of Li ions within the NWO crystal and to the kinetics of Li ion transfer across its surface. Additionally, a simplified, lumped parameter model is developed by assuming that the Li ion occupancy is spatially uniform in a surface layer that extends to a depth of the pre-existing crack, and has a spatially uniform but different value in the underlying core of the particle. This simplified model can be expressed as a set of first order differential equations in time and gives the main features of delithiation and the associated transient stress state in the single crystal. Both the full model and the lumped parameter version predict that crack advance from a pre-existing defect is triggered by a high delithiation rate, consistent with the experimental literature.

铌钨氧化物(NWO)微米尺寸的单晶由于其快速充放电和高存储能力，在锂离子电池阳极中表现出良好的应用前景。在Nb16W5O55、Nb14W3O44和H-Nb2O5等“块状”相中，Li离子沿着晶体的单轴单向扩散，锂化导致沿该方向的长度发生显著变化。采用化学力学分析方法对NWO“块”相单晶的损耗进行了分析，该单晶含有一种通过厚度边缘裂纹形式存在的预先存在缺陷。电流衰减是由锂离子的通量通过晶体的自由端和裂纹的表面而发生的，伴随着表面层的收缩，其深度等于裂纹的深度。在Nb14W3O44中，表层的诱导拉伸应力足以推动NWO晶体的裂纹，这与最近的实验观察结果一致。利用化学力学模型的二维全场有限元模型，研究了裂纹对裂纹长度、阳极的衰减率、NWO晶体内锂离子的扩散率以及锂离子在其表面转移动力学的敏感性。此外，通过假设Li离子占用率在延伸到预先存在的裂纹深度的表面层中空间均匀，并且在颗粒的底层核心中具有空间均匀但不同的值，建立了一个简化的集总参数模型。该简化模型可表示为一阶时间微分方程，并给出了单晶中脆性及相关瞬态应力状态的主要特征。完整模型和集总参数模型都预测，高衰减率会触发预先存在缺陷的裂纹扩展，这与实验文献一致。

A multiscale dynamic model of cell–substrate interfaces

Huiyan Liang, Wei Fang, Xi-Qiao Feng

doi:10.1016/j.jmps.2024.105725

细胞-基质界面的多尺度动态模型

Cell–extracellular matrix (ECM) interactions play a pivotal role in many functions of cells, for example, sensing, signaling, migration, and gene expression. The spatial–temporal dynamic evolution of cell–substrate adhesions involves complicated mechano-bio-chemical coupling mechanisms of integrin, adaptor and signaling proteins, as well as the interplay between the cytoskeleton and ECM. In this paper, we establish a multiscale dynamic model of cell–substrate interfaces considering intermolecular force transmission pathways, i.e., intra- and extra-cellular bond dynamics, and mechanochemical coupling regulations. To illustrate its applications, this model is used to reproduce several adhesion-related experimental phenomena of cells, including substrate rigidity sensing, actin-assisted focal adhesion formation, and biphasic interface stress–actin speed relation. The results suggest that the cluster growth patterns are medicated by the intermolecular force transmission pathway and the actin flow speed, and that the integrin–ligand (IL) bond strengthening tends to inhibit the motion of clusters. We reveal that the monotonic-to-biphasic transition of force transmission and adhesion assembly is regulated by the bond rupture mechanosensitivity of integrin adhesion complexes (IACs). It is also demonstrated that this multiscale dynamic model can well describe the spatial–temporal evolutions of collective cell–substrate adhesions with the effects of actin flow and substrate deformation, and can also capture the morphological features of adhesion clusters and related interface force transmissions. This work provides a theoretical tool for studying mechano-biochemical mechanisms of cell–substrate interactions and for understanding various subcellular and cellular dynamic processes in, for example, tumors.

细胞-细胞外基质(ECM)相互作用在细胞的许多功能中起着关键作用，如传感、信号传导、迁移和基因表达。细胞-底物黏附的时空动态演化涉及整合素、接头蛋白和信号蛋白复杂的机械-生化耦合机制，以及细胞骨架与ECM之间的相互作用。在本文中，我们建立了考虑分子间力传递途径，即细胞内和细胞外键动力学以及机械化学耦合规律的细胞-基质界面多尺度动力学模型。为了说明其应用，我们使用该模型再现了几种与细胞黏附相关的实验现象，包括底物刚度感知、肌动蛋白辅助的焦点黏附形成以及双相界面应力-肌动蛋白速度关系。结果表明，簇的生长模式受分子间力传递途径和肌动蛋白流动速度的影响，整合素配体(IL)键的增强倾向于抑制簇的运动。我们揭示了力传递和粘附组装的单调到双相转变是由整合素粘附复合物(IACs)的键断裂力学敏感性调节的。研究还表明，该多尺度动力学模型可以很好地描述肌动蛋白流动和底物变形作用下细胞-底物集体黏附的时空演变，并能捕捉黏附团簇的形态特征和相关的界面力传递。这项工作为研究细胞-底物相互作用的机械生化机制以及理解肿瘤等各种亚细胞和细胞动力学过程提供了理论工具。

Mechanics of Materials

Surface effect on the partial-slip contact of a nano-sized flat indenter

Sha Xiao, Hui Wu, Zhilong Peng, Yin Yao, Shaohua Chen

doi:10.1016/j.mechmat.2024.105057

纳米平压头局部滑移接触的表面效应

The partial-slip contact at nano-scale is always influenced by a surface effect. A new model based on the Gurtin-Murdoch (G-M) surface elasticity theory is proposed in this paper to study the partial-slip contact behavior of a rigid flat nano-indenter on an elastic half-space. The surface effect in the partial-slip contact is characterized via a non-classical boundary condition involving a surface-induced normal traction related to the residual surface stress and a surface-induced tangential traction related to the surface elasticity, the influences of which on stress and displacement fields and the stick-slip state at the contact surface are investigated. It is found that, with the increase of residual surface stress, both the normal pressure and vertical and horizontal displacements in the contact zone decrease, the relative slip between indenter and substrate reduces and the stick region is enlarged. Such effects are basically attributed to the action of the surface-induced normal traction opposite to the externally applied compression. However, the increase of surface elastic constants is conductive to the relative slip and results in a shrinkage of the stick region, which is attributed to the action of the surface-induced tangential traction opposite to the frictional stress. An interesting phenomenon is further unveiled that, when the frictional coefficient increases, the dominant role in affecting the stick-slip state changes from the surface-induced tangential traction to the normal one, thus inspiring a feasible route to manipulate the surface effect by tuning the frictional coefficient of substrate. The present research enables one to better understand the partial-slip contact behavior of nano-indenters, which is of guiding value for anti-wear designs in nano-mechanical devices.

纳米尺度的部分滑移接触总是受到表面效应的影响。基于Gurtin-Murdoch (G-M)表面弹性理论，提出了一种研究刚性扁平纳米压头在弹性半空间上的局部滑移接触行为的新模型。通过与残余表面应力相关的表面诱导法向牵引和与表面弹性相关的表面诱导切向牵引的非经典边界条件来表征部分滑移接触中的表面效应，研究了它们对接触面应力场和位移场以及粘滑状态的影响。研究发现，随着残余表面应力的增大，接触区的法向压力和垂直、水平位移均减小，压头与基材之间的相对滑移减小，粘滞区域增大。这种效果基本上归因于表面诱导的正常牵引与外部施加的压缩相反的作用。然而，表面弹性常数的增加会导致相对滑移，并导致粘着区域的收缩，这是由于表面诱导的切向牵引与摩擦应力相反的作用。进一步揭示了一个有趣的现象，即当摩擦系数增加时，影响粘滑状态的主导作用由表面诱导的切向牵引转变为法向牵引，从而启发了通过调节衬底摩擦系数来操纵表面效应的可行途径。本研究使人们能够更好地理解纳米压头的部分滑移接触行为，对纳米机械器件的抗磨设计具有指导价值。

Effects of unit cell parameters on the thermal shock resistance of auxetic honeycomb sandwich structures: combining discrete and continuum model

P.Q. Li, K.F. Wang, B.L. Wang

doi:10.1016/j.mechmat.2024.105054

单元胞参数对消蚀蜂窝夹层结构抗热震性能的影响:结合离散与连续模型

This work reveals the influence of unit cell geometric parameters on the thermal fracture behavior and thermal shock resistance of honeycomb ceramics sandwich structures for the first time. The present study establishes a continuum model for the thermal fracture of sandwich structures, and a discrete numerical representation model for the equivalent fracture toughness of honeycombs, respectively. A novel evaluation approach for the thermal shock resistance of porous material structures has been provided by combining the two models. The effects of temperature dependence, face sheet thickness, honeycomb orientation and honeycomb geometrical parameters on thermal shock resistance are studied. Results indicate that changing the inclined angle of honeycomb can effectively increase the critical thermal shock temperature rise. Auxetic honeycomb sandwich structures with the inclined angle of -9° can reach the peak of the critical temperature rise. The results would contribute to the application of honeycomb sandwich structures in thermal protection systems.

本文首次揭示了蜂窝陶瓷夹层结构的几何参数对其热断裂行为和抗热震性能的影响。本文分别建立了夹层结构热断裂的连续介质模型和蜂窝等效断裂韧性的离散数值表示模型。将这两种模型结合起来，为多孔材料结构的抗热震性评估提供了一种新的方法。研究了温度依赖性、面板厚度、蜂窝取向和蜂窝几何参数对蜂窝抗热震性能的影响。结果表明，改变蜂窝的倾斜角度可以有效地提高临界热冲击温升。倾斜角为-9°的辅助蜂窝夹层结构可达到临界温升峰值。研究结果将有助于蜂窝夹层结构在热防护系统中的应用。

International Journal of Plasticity

Optimization of tensile properties and anisotropy in a cryogenically treated laser additively manufactured high entropy alloy

Yuan Tian, Yunzhuo Lu, R. Lakshmi Narayan

doi:10.1016/j.ijplas.2024.104015

低温处理激光增材制造高熵合金拉伸性能和各向异性的优化

Repetitive deep cryogenic soaking treatment (DCT) of laser metal deposition (LMD) processed CrMnFeCoNi high entropy alloy (HEA) significantly enhances its strength without compromising ductility. This is attributed to the compressive stress induced nanotwin formation, which in turn facilitates twin induced plasticity. In this work, a parametric study on the effect of the residual stress profile and the DCT cycles on the tensile properties of the HEA, along the build and scan directions is conducted. Towards this end, builds fabricated with 5 different laser powers, 1100, 1400, 1700, 2000 and 2300 W, are examined and the ones with highest and lowest residual stress gradient are considered for further DCT treatments. Results indicate that the build fabricated with 1400 W laser power, which has the highest gradient in initial residual stresses, exhibits a greater enhancement in dislocation and twin density with increasing number of DCT treatments. Compared to its as-built statethe peak yield and tensile strength of the HEA (along the scanning direction) increases to 592 ± 13 and 778 ± 15 MPa, without significant decrease in its ductility after 12 DCT cycles. However, the enhancement in the dislocation, twin density and therefore, the strength, is minimal after it is treated to 15 DCT cycles. Anisotropy in both strength and ductility, which is of the order of 20-25%, is also observed in the DCT treated builds along the build and scan directions. These observations were rationalized on the basis of dislocation and twin evolution and distribution during DCT and deformation of the build when deformed in different directions. Implications of these results in the context of employing DCT for strengthening LMD fabricated HEA components are discussed.

激光金属沉积(LMD)加工的CrMnFeCoNi高熵合金(HEA)的重复深冷浸泡处理(DCT)在不影响延展性的情况下显著提高了其强度。这归因于压缩应力诱导的纳米孪晶形成，这反过来又促进了孪晶诱导的塑性。在这项工作中，对沿构建和扫描方向的残余应力分布和DCT循环对HEA拉伸性能的影响进行了参数化研究。为此，用5种不同的激光功率(1100,1400,1700,2000和2300w)制造的构件进行了测试，并考虑了残余应力梯度最高和最低的构件进行进一步的DCT处理。结果表明，当激光功率为1400 W时，初始残余应力梯度最大，随着DCT处理次数的增加，位错和孪晶密度的增强幅度更大。经过12次DCT循环后，HEA的峰值屈服和抗拉强度(沿扫描方向)分别增加到592±13和778±15 MPa，而其延性没有明显下降。然而，在处理到15 DCT循环后，位错、孪晶密度和强度的增强是最小的。沿构建和扫描方向，在DCT处理的构建中也观察到强度和延性的各向异性，其数量级为20-25%。这些观察结果是基于位错和孪晶在DCT过程中的演化和分布以及在不同方向变形时构建的变形进行合理化的。讨论了这些结果在采用DCT加强LMD制造的HEA组件的背景下的含义。

Thin-Walled Structures

Rapid Analysis Method for Process Parameter Determination of Transient Thermal Tensioning during Welding Buckling Distortion Mitigation

Bin Yi, Ling Fu, Dingqi Xue, Yanbin Liu, Weicheng Lei, Jiangchao Wang

doi:10.1016/j.tws.2024.112053

焊接失稳变形瞬态热拉伸工艺参数确定的快速分析方法

The effect of transient thermal tensioning (TTT) on mitigating buckling distortion is significantly influenced by the process parameters. TTT and conventional welding (CW) experiments were both performed on butt welded joints using induction heating as an additional heat source. The thermal elastic plastic (TEP) FE simulation was then carried out with consideration of material nonlinearity and geometrical nonlinearity to investigate the temperature, buckling distortion fields of the butt welded joints. A good agreement between computational results and the measurement was represented, and the buckling distortion of the butt welded joints with TTT was much smaller than that with CW. Based on the validated FE simulation, the sensitivity of process parameters (amount, sizes, tensioning temperature Ttmax, locations of induction heating) for TTT was examined in detail. The results show that amount and sizes exerted an evident impact on buckling distortion mitigation, which were determined by equipment. Tensioning temperature Ttmax and the offset from weld centerline d1 are more important parameters on effectively mitigating welding buckling distortion of thin plate structures than the offset from welding arc d2. Through optimizing Ttmax and d1, buckling distortion of examined butt welded joint can be reduced by more than 80%. Moreover, a method for determining the process parameters of TTT towards engineering applications was proposed. Firstly, the amount and sizes of additional heat sources are maximized per the available equipment. Secondly, Ttmax is recommended as yield temperature to implement TTT and d1 is optimized through an experiment or TEP FE simulation. Eventually, the offset from welding arc d2 is further optimized when the manufacturing precisions are not reached.

瞬态热拉伸(TTT)对减轻屈曲变形的效果受工艺参数的显著影响。采用感应加热作为附加热源对对接焊接接头进行TTT和常规焊接(CW)试验。在考虑材料非线性和几何非线性的情况下，对对接焊接接头的温度场、屈曲变形场进行热弹塑性(TEP)有限元模拟。计算结果与实测结果吻合较好，TTT对焊接头的屈曲变形比CW对焊接头的屈曲变形小得多。在验证的有限元仿真基础上，详细考察了工艺参数(量、尺寸、张紧温度Ttmax、感应加热位置)对TTT的敏感性。研究结果表明，材料的数量和尺寸对降低屈曲变形有明显的影响，这是由设备决定的。与焊接电弧偏移量d2相比，拉伸温度Ttmax和焊缝中心线偏移量d1是有效减轻薄板结构焊接屈曲变形的更重要参数。通过优化Ttmax和d1，可使被测对接焊接接头屈曲变形减小80%以上。提出了一种面向工程应用的TTT工艺参数确定方法。首先，根据可用设备最大化额外热源的数量和尺寸。其次，建议采用Ttmax作为实现TTT的屈服温度，并通过实验或TEP FE模拟对d1进行优化。最后，在未达到制造精度的情况下，进一步优化焊接电弧d2的偏移量。

A COMPONENT METHOD APPROACH FOR SINGLE-SIDED BEAM-TO-COLUMN JOINTS WITH CHS COLUMN AND WELDED DOUBLE-TEE BEAM

Ali Ajwad, Sabatino Di Benedetto, Massimo Latour, Gianvittorio Rizzano

doi:10.1016/j.tws.2024.112055

采用构件法求解CHS柱与焊接双三通梁的单侧梁柱节点

This paper focuses on predicting the flexural stiffness and strength of beam-to-column joints with Circular-Hollow-Section (CHS) columns and externally welded double-tee beams using the Component Method approach. Currently, Eurocode 3 Part 1.8 lacks guidelines for assessing the stiffness of these joints, resulting in their practical modelling using extreme assumptions like pin or full restraint. Nevertheless, the literature demonstrates that these joints can exhibit semi-rigid behaviour due to the relatively high local deformability of the tube in the joint area. Another concern relates to the strength of these joints. In fact, recent studies have shown that Eurocode 3 Part 1.8 formula for predicting the yield resistance of these joints is over-conservative. Within this framework, the purpose of this study is to fill the current knowledge gaps (over-conservative strength prediction and lack of rules for determining the stiffness) by undertaking a thorough investigation involving numerical and analytical activities. Specifically, the research presents a component-based modelling approach for predicting stiffness and strength of CHS to double-tee beam connections. In this regard, the work presented in this paper has involved the selection of experimental tests from literature to validate a Finite Element (FE) model, specifically focusing on X- and T-joints and internal and external beam-to-column joints. The validated numerical models have been then employed to simulate the response under monotonic loading conditions of additional sets comprising forty T-joints and thirty external beam-to-column joints, respectively. The currently available formulations for predicting the resistance of T-joints were applied to the forty cases simulated, evaluating their accuracy. This allowed the individuation of the most accurate literature formula for the strength prediction of T-joints, showing that the recent proposal of Voth and Packer (2012) yields sufficiently accurate results. Instead, analytical formulations for predicting the stiffness of T-joints were properly derived in a closed-form solution and were validated against the results of the parametric study. Finally, drawing upon knowledge regarding the stiffness and strength of T-joints, the flexural response of external beam-to-columns connections was evaluated proposing a component model, whose accuracy was verified against the cases simulated in the parametric analysis.

本文主要研究了用构件法预测空心圆截面柱和外焊双三通梁的梁柱节点的抗弯刚度和强度。目前，欧洲规范3第1.8部分缺乏评估这些关节刚度的指导方针，导致其实际建模使用极端假设，如销钉或完全约束。然而，文献表明，这些关节可以表现出半刚性行为，由于相对较高的局部变形能力的管在关节区域。另一个问题与这些关节的强度有关。事实上，最近的研究表明，欧洲规范3第1.8部分用于预测这些节点的屈服阻力的公式过于保守。在此框架内，本研究的目的是通过开展涉及数值和分析活动的彻底调查来填补当前的知识空白(过度保守的强度预测和缺乏确定刚度的规则)。具体而言，研究提出了一种基于构件的模型方法来预测CHS与双三通梁连接的刚度和强度。在这方面，本文提出的工作涉及从文献中选择实验测试来验证有限元(FE)模型，特别关注X形和t形节点以及内部和外部梁柱节点。然后利用验证的数值模型分别模拟了包含40个t形节点和30个外部梁柱节点的附加组在单调荷载条件下的响应。将现有的t型接头阻力预测公式应用于40个模拟实例，对其精度进行了评价。这使得最准确的t型接头强度预测文献公式得以个性化，表明Voth和Packer(2012)最近提出的结果足够准确。相反，预测t型节点刚度的解析公式是在一个封闭的解中适当地推导出来的，并根据参数化研究的结果进行了验证。最后，利用关于t形节点刚度和强度的知识，对外部梁柱连接的弯曲响应进行了评估，提出了一个组件模型，其准确性通过参数分析中模拟的情况进行了验证。

Response of the orthogonal corrugated sandwich panel under low-velocity impact with different shaped impactors

Yunfei Deng, Haoyun Yu, Yinbo Zhang

doi:10.1016/j.tws.2024.112070

正交波纹夹芯板在不同形状冲击器低速冲击下的响应

This study aims at investigating the low-velocity impact resistance of the composite orthogonal corrugated sandwich panel through experimental and simulation methods, considering different shaped impactors. To that scope, the progressive damage model with the sandwich panel is developed and numerical investigations are carried out in ABAQUS / Explicit. The results show that as the impactor changes from flat to hemispherical and then to conical shape, the first peak load gradually decreases, and the maximum displacement of the impactor and total energy absorption gradually increase. The high impact energy makes the sandwich panel more compliant. Furthermore, the expansion area of fiber damage, matrix damage and delamination in the top face sheet, core and bottom face sheet depends on the impactor shape and impact energy. Under high impact energy, the damage under the conical impactor mainly expands along the thickness direction of the sandwich panel rather than in the in-plane direction, while the flat impactor causes large damage area in the in-plane direction as well.

在考虑不同形状冲击物的情况下，通过实验和仿真两种方法对正交波纹夹层板的低速抗冲击性能进行了研究。为此，建立了夹层板的渐进损伤模型，并在ABAQUS / Explicit中进行了数值研究。结果表明:随着冲击器由扁平形状变为半球形形状，再变为锥形形状，第一峰值载荷逐渐减小，冲击器最大位移和总能量吸收逐渐增大;高冲击能量使夹芯板更加柔顺。此外，纤维损伤、基体损伤和分层在顶板、芯板和底板上的扩展面积取决于冲击器的形状和冲击能量。在高冲击能下，锥形冲击器的损伤主要沿夹层板厚度方向扩展，而不是沿面内方向扩展，而扁平冲击器在面内方向上也造成较大的损伤面积。

Self-galloping of a liquid crystal elastomer catenary cable under a steady temperature field

Yong Yu, Lin Zhou, Changshen Du, Fayang Zhu, Yuntong Dai, Dali Ge, Kai Li

doi:10.1016/j.tws.2024.112071

稳态温度场下液晶弹性体悬链索的自驰性

Thermally-driven self-sustained motion allows for direct absorption of heat from a steady temperature field to maintain its own continuous motion, making it a valuable technology for thermal sensors, harvesters, and soft robotics. Exploring a straightforward and durable system that operates with self-sustained motion driven by heat is a formidable challenge. Based on a thin liquid crystal elastomer (LCE) fiber, we propose a thermally-driven self-galloping catenary cable system in this paper. Experiments show that the LCE catenary cable can engage in continuous periodic self-galloping in a steady temperature field with gradient. Combining the well-established dynamic LCE model and catenary theory, the governing equations of the self-galloping LCE catenary cable are established and its dynamics are theoretically investigated. The LCE catenary cable always develops into two motion modes, i.e., static and self-galloping modes, according to numerical calculations. The theoretical predictions are in general agreement with the experimental results. The LCE catenary cable maintains the self-galloping by absorbing thermal energy to offset the damping dissipation. The effects of system parameters on the amplitude, frequency and equilibrium position of the self-galloping are also obtained. This LCE catenary cable has advantages in terms of simple structure, customizable size, minimal requirement for movement space, and flexible adjustment, and it is anticipated to satisfy the demands of actual complex scenarios such as thermal sensors, energy harvesters, and autonomous robots.

热驱动的自我持续运动允许从稳定的温度场直接吸收热量，以保持其自身的连续运动，使其成为热传感器，收割机和软机器人的宝贵技术。探索一种简单耐用的系统，它可以在热量驱动下自我维持运动，这是一项艰巨的挑战。本文提出了一种基于液晶弹性体(LCE)纤维的热驱动自驰悬链线电缆系统。实验表明，LCE悬链线在具有梯度的稳定温度场中可以进行连续的周期性自驰运动。结合已建立的LCE动力学模型和悬链线理论，建立了自驰LCE悬链线缆索的控制方程，并对其动力学进行了理论研究。数值计算表明，LCE悬链线的运动模式主要分为静态运动模式和自驰运动模式。理论预测与实验结果基本一致。LCE悬链线通过吸收热能抵消阻尼损耗来保持自驰。得到了系统参数对自驰幅值、频率和平衡位置的影响。该LCE悬链缆具有结构简单、尺寸可定制、对运动空间要求最小、调节灵活等优点，有望满足热传感器、能量采集器、自主机器人等实际复杂场景的需求。

Behavior of wire arc additively manufactured 316L austenitic stainless steel single shear bolted connections

Wenkang Zuo, Man-Tai Chen, Ou Zhao, Andi Su, Si-Wei Liu, Fangda Xu, Yuner Huang, Bin Cheng

doi:10.1016/j.tws.2024.112075

电弧增材制造316L奥氏体不锈钢单剪切螺栓连接的性能

This paper aims to investigate the behavior of single shear bolted connections made of wire arc additively manufactured 316L austenitic stainless steel. A set of 44 wire arc additive manufacturing (WAAM) 316L austenitic stainless steel single shear bolted connections were included with consideration of various bolt positions, surface conditions and loading orientations respective to the printing layer direction. The geometric dimensions of the WAAM austenitic stainless steel plates were measured with the assistance of non-contact 3D laser scanning prior to tensile testing. Monotonic tensile tests were carried out to investigate the load-deformation responses, failure patterns and resistances determined by both the deformation and strength criteria of the single shear bolted connections. The effects of geometric and printing parameters on the single shear bolted connections were analyzed. Due to the absence of codified design provisions for WAAM austenitic stainless steel bolted connections, the suitability of the existing design rules originally developed for traditionally manufactured carbon steel and stainless steel bolted connections was examined. Design resistances calculated by the Eurocode 3 (prEN 1993-1-8 and prEN 1993-1-4), the American Specification (ANSI/AISC 370-21) as well as the prevalent design recommendations proposed in existing literature were compared with the obtained experimental results. It is shown that the abovementioned design methods offer conservative predictions for the resistances of WAAM 316L austenitic stainless steel single shear bolted connections. Further study is needed to improve the accuracy of design resistance predictions.

研究了316L奥氏体不锈钢丝弧增材制造单剪切螺栓连接的性能。考虑到不同的螺栓位置、表面条件和加载方向对应于打印层方向，包括一组44丝电弧增材制造(WAAM) 316L奥氏体不锈钢单剪切螺栓连接。在拉伸试验之前，利用非接触式三维激光扫描测量了WAAM奥氏体不锈钢板的几何尺寸。进行了单调拉伸试验，研究了单剪切螺栓连接的变形和强度准则所确定的荷载-变形响应、破坏模式和阻力。分析了几何参数和印刷参数对单剪切螺栓连接的影响。由于WAAM奥氏体不锈钢螺栓连接缺乏规范的设计规定，因此对传统制造的碳钢和不锈钢螺栓连接设计规则的适用性进行了检验。根据欧洲规范3 (prEN 1993-1-8和prEN 1993-1-4)、美国规范(ANSI/AISC 370-21)以及现有文献中提出的流行设计建议计算的设计阻力与得到的实验结果进行了比较。结果表明，上述设计方法对WAAM 316L奥氏体不锈钢单剪切螺栓连接的抗力预测较为保守。需要进一步研究以提高设计阻力预测的准确性。

Damage effects of aluminum alloy honeycomb sandwich panel double-layer structure induced by reactive projectile hypervelocity impact

Siyuan Ren, Qiang Wu, Pingliang Zhang, Guangming Song, Zizheng Gong, Zhengyu Li, Jingtai Li, Chuan Chen

doi:10.1016/j.tws.2024.112076

反应弹丸超高速撞击对铝合金蜂窝夹层板双层结构的损伤效应

In this paper, the experiments of Al2024 and reactive projectiles with hypervelocity impact on aluminum alloy honeycomb sandwich panel double-layer structure respectively were carried out by using two-stage light-gas gun, and the impact processes were recorded through high speed camera. According to the analysis of the experimental results, the debris clouds motion process and the damage effects on double-layer structure were compared. The damage enhancement mechanism of reactive projectile was revealed through numerical simulation and theoretical methods. The impact-induced detonation reaction of the reactive projectile can significantly reduce the "channel effect" of the honeycomb sandwich panel by destroying the honeycomb core cell wall, increase the perforation on the back facesheet of the honeycomb sandwich panel, and generate the debris cloud with higher temperature and faster expansion velocity. The debris cloud induced by the reactive projectile has a larger load distribution area on the rear plate, avoiding the concentration of loads in the center of the rear plate, and cause large area impact and thermal combined damage effects on the rear plate and internal space of the double-layer structure, while ensuring that the target structure cannot be penetrated. The reactive projectile efficiently applies the kinetic energy and chemical energy released by the impact-induced reaction to the interior of the target structure, the waste of kinetic energy caused by whole structure penetration can be avoided, resulting in significantly higher damage effects than the inert Al2024 projectile.

本文采用两级光气 枪分别进行了Al2024和反应弹丸对铝合金蜂窝夹层板双层结构的超高速撞击实验，并通过高速摄像机记录了撞击过程。通过对实验结果的分析，比较了碎片云的运动过程和对双层结构的损伤效果。通过数值模拟和理论方法揭示了反应弹的增伤机理。反应弹的冲击起爆反应可通过破坏蜂窝芯细胞壁，显著降低蜂窝夹芯板的“通道效应”，增加蜂窝夹芯板背面的穿孔，产生温度更高、膨胀速度更快的碎片云。反应弹诱导的碎片云在后板上具有较大的载荷分布面积，避免了载荷集中在后板中心，对后板和双层结构内部空间产生大面积冲击和热复合损伤效应，同时保证了目标结构不能被击穿。反应弹丸有效地将冲击诱发反应释放的动能和化学能应用于目标结构内部，避免了整个结构侵彻所造成的动能浪费，损伤效果明显高于惰性Al2024弹丸。

Nonlinear vibrations and critical angular velocity information of the high-speed rotating eccentric disk made of Gori-metamaterials: Introducing data-driven solution for solving the nonlinear problems

Lei Chang, Kia Khademi, Mohamed Sharaf

doi:10.1016/j.tws.2024.112077

戈里超材料高速旋转偏心盘的非线性振动和临界角速度信息:介绍求解非线性问题的数据驱动方法

Eccentric discs in rotational motion are commonly utilized in various technical fields, including gas turbine engines, flywheels, gears, and brakes. So, improving its critical angular velocity and frequency characteristics is a challenging issue for engineers. So, in this work for the first time, nonlinear vibrations and buckling analysis of the high-speed rotating eccentric disks using mathematical simulation and data-driven solutions are presented. One of the suggestions for improving its mechanical properties is considering metamaterials in the construction of the eccentric disk. Metamaterial is a novel synthetic material that has distinctive physical and mechanical capabilities that are unattainable in natural materials due to its well-designed structure. The properties of the eccentric disks are controlled by the amount of graphene and the degree of folding of graphene origami (GOri) across the thickness of the eccentric disks. These properties, such as Poisson's ratio, vary depending on the position and can be estimated using micromechanical models assisted by genetic programming (GP). Using von-Karman nonlinearity, transformed differential quadrature method (TDQM), and Newton's method the nonlinear governing equations are obtained and solved, respectively. The results show that when the radius ratio of the rotating eccentric disk increases by 8%, the critical point is decreased from 420 HZ to 370 HZ, a reduction of around 12 %. Another suggestion for improving its mechanical properties is controlling the geometrics and physics of the presented structure according to the designer's purposes.

旋转运动的偏心盘通常应用于各种技术领域，包括燃气涡轮发动机、飞轮、齿轮和制动器。因此，提高其临界角速度和频率特性是一个具有挑战性的问题。因此，本文首次采用数学模拟和数据驱动的方法对高速旋转偏心盘的非线性振动和屈曲进行了分析。改善其力学性能的建议之一是在偏心盘的构造中考虑使用超材料。超材料是一种新型的合成材料，由于其精心设计的结构，具有天然材料无法达到的独特的物理和机械性能。偏心盘的性能受石墨烯用量和石墨烯折纸(GOri)在偏心盘厚度上的折叠度的控制。这些特性，如泊松比，随位置的不同而变化，可以使用遗传规划(GP)辅助的微力学模型来估计。利用von-Karman非线性、变换微分正交法(TDQM)和牛顿法分别得到并求解了非线性控制方程。结果表明，当旋转偏心盘半径比增加8%时，临界点从420 HZ降低到370 HZ，降低约12%;改善其力学性能的另一个建议是根据设计者的目的控制所呈现结构的几何和物理特性。

A derivative-free phase-field theory for capturing local buckling induced damage in architected plates

Arjun Kaithavalappil, Saikat Sarkar

doi:10.1016/j.tws.2024.112068

结构板局部屈曲损伤的无导数相场理论

Architected plates are commonly used to enhance the load-bearing capacity and stability of structures such as ship hulls and aircraft components. Local buckling-induced damage in these plates are critical events that occur when the plate is subjected to external transverse loading. Performing the analysis to accurately capture this damage and estimation of local buckling load requires explicit 3D- modelling of the architected plate, which is computationally expensive. We address this issue by proposing a derivative-free phase-field theory to capture local buckling-induced damage in architected plates. Here the architected plate is modelled using the shear deformable plate theory and the internal web-core structure is preserved in terms of length scale parameters. The numerical value of the length scale parameter depends on the shape of the webcore structure so that any complicated shape of the webcore is handled based on this parameter. This approach makes the analysis simple to predict the damage behaviour with a lesser number of degrees of freedom. The extra energy required to attenuate the zero energy mode-induced oscillations in the solution is estimated from the in-plane buckling analysis of the architected plate. To showcase the efficiency, simulations are conducted based on the proposed approach with different loading cases. The local buckling load and the induced damage behaviour of the webcore are compared with the 3D-finite element solution obtained from ABAQUS. The comparison shows that the damage variable is an equivalent estimator of out-of-plane stretch of the webcore in predicting the buckling behaviour of the webcore with reduced computational cost and time.

建筑板材通常用于增强船体和飞机部件等结构的承载能力和稳定性。这些板材在承受外部横向荷载时，会发生局部屈曲引起的损坏，这是关键事件。要进行分析以准确捕捉这种损伤并估算局部屈曲载荷，需要对建筑板材进行明确的三维建模，而这种建模的计算成本很高。为了解决这个问题，我们提出了一种无导数相场理论来捕捉拱形板的局部屈曲诱导损伤。在这里，拱形板采用剪切变形板理论建模，并通过长度标度参数保留内部腹板-核心结构。长度标度参数的数值取决于腹杆结构的形状，因此腹杆的任何复杂形状都可以根据该参数进行处理。这种方法使分析变得简单，可以用较少的自由度来预测破坏行为。在解决方案中，衰减零能模式引起的振荡所需的额外能量是通过建筑板的面内屈曲分析估算出来的。为了展示这种方法的效率，我们根据所提出的方法对不同的加载情况进行了模拟。将腹板芯材的局部屈曲载荷和诱导损伤行为与 ABAQUS 获得的三维有限元解决方案进行了比较。比较结果表明，在预测腹杆屈曲行为时，损伤变量是腹杆平面外拉伸的等效估算值，同时还降低了计算成本和时间。

An optimization-assisted reduced order model for dynamics of plates using isogeometric analysis

Qui X. Lieu

doi:10.1016/j.tws.2024.112078

基于等几何分析的优化辅助板动力学降阶模型

This article first introduces a novel optimization-driven reduced order model (ROM) to the dynamics of plates utilizing isogeometric analysis (IGA). The proposed paradigm uses an iterated improved reduced system (IIRS) technique to condense the system’s dynamic properties. This model takes account of inertia items, the consistent mass matrix is therefore preserved. Moreover, master degrees of freedom (DOFs) defined at control points of the IGA in ROM are optimized via the derivative-free adaptive hybrid evolutionary firefly algorithm (AHEFA). Accordingly, the accuracy and the correlation of high-order shape modes can be improved. The Galerkin discretization is employed to establish the IGA-based ROM for the plate’s dynamic analysis with proportional damping. In which, its weak form relied upon a generalized shear deformation theory (GSDT) is derived from the Hamilton’s principle. Consequently, the reduced IGA can deal with both thick and thin plates without shear correction coefficients and the shear locking phenomenon. The Newmark-β method is then employed to achieve time–history responses of the reduced dynamic equation system. Several numerical examples are tested to illustrate the reliability and efficiency of the present methodology. Obtained outcomes have shown their useful and potential applications to the structural health monitoring (SHM) field, especially when the number of sensors is limited.

本文首先介绍了一种利用等距分析（IGA）对板块动力学进行优化的新型减阶模型（ROM）。所提出的范式使用迭代改进的简化系统（IIRS）技术来浓缩系统的动态特性。该模型考虑了惯性项，因此保留了一致的质量矩阵。此外，通过无导数自适应混合进化萤火虫算法（AHEFA）对 ROM 中 IGA 控制点上定义的主自由度（DOF）进行优化。因此，高阶形状模式的精度和相关性得以提高。采用 Galerkin 离散化方法建立了基于 IGA 的 ROM，用于带比例阻尼的板动态分析。其中，其弱形式依赖于从汉密尔顿原理推导出的广义剪切变形理论（GSDT）。因此，减弱的 IGA 可以同时处理厚板和薄板，而无需剪切修正系数和剪切锁定现象。然后采用 Newmark-β 方法实现简化动态方程系统的时态响应。为了说明本方法的可靠性和效率，对几个数值实例进行了测试。所获得的结果显示了其在结构健康监测（SHM）领域的有用性和潜在应用，尤其是在传感器数量有限的情况下。