Extreme Mechanics Letters最新文献

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Stabilizing the buckling instabilities of soft cylindrical shell grippers 软圆柱壳夹持器屈曲失稳的稳定研究

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2026-01-02 DOI: 10.1016/j.eml.2025.102437

Wenjie Li , Yu Herng Tan , Zhong Wang , Xuguang Dong , Huichan Zhao

Soft cylindrical shell grippers consist of a rigid outer shell and a soft inner layer that inflates inward under internal pressure. This inflatable ring actuator mechanism enables the gripper to conform to and stably grasp objects, offering unique advantages in handling irregular shapes and compliant materials, and making these grippers promising candidates for soft robotic manipulation. However, upon inflation, their soft inner walls often undergo a sequence of buckling instabilities—from wrinkling to creasing and more complex post-buckling behaviors. Due to the stochastic nature of these buckling instabilities, the resulting deformation patterns—such as the number, positions, and deflections of creases—vary unpredictably, leading to inconsistencies in gripper performance. This study investigates the factors governing the buckling instabilities of soft cylindrical shell grippers and proposes strategies for their stabilization. Through theoretical analysis and finite element (FE) simulations, we establish the relationship between geometric parameters and the predicted buckling instabilities. To control the instability morphology, we introduce evenly distributed geometric imperfections and implement a material training process to mitigate non-uniform deformation by leveraging the Mullins effect. We demonstrate that these combined strategies significantly improve grasping performance, including increased contact area, enhanced self-centering, and improved repeatability. Finally, we validate the gripper’s effectiveness in real-world scenarios through on-arm pick-and-place experiments. This work provides a framework for designing soft cylindrical shell grippers with greater reliability, while maintaining simplicity in fabrication.

软圆柱壳夹持器由坚硬的外壳和在内部压力下向内膨胀的软内层组成。这种充气环致动机构使夹持器符合并稳定地抓取物体，在处理不规则形状和柔性材料方面具有独特的优势，并使这些夹持器成为软机器人操作的有希望的候选者。然而，膨胀后，它们柔软的内壁往往经历一系列的屈曲不稳定——从起皱到折痕以及更复杂的后屈曲行为。由于这些屈曲不稳定性的随机性，所产生的变形模式（如折痕的数量、位置和挠度）不可预测地变化，导致夹持器性能不一致。本文研究了软壳夹持器屈曲失稳的影响因素，并提出了其稳定策略。通过理论分析和有限元模拟，建立了几何参数与预测屈曲失稳之间的关系。为了控制不稳定形态，我们引入均匀分布的几何缺陷，并实施材料训练过程，以利用穆林斯效应来减轻不均匀变形。我们证明了这些组合策略显着提高抓取性能，包括增加接触面积，增强自定心和提高可重复性。最后，我们通过手臂拾取和放置实验验证了抓手在现实场景中的有效性。这项工作为设计具有更高可靠性的软圆柱壳夹持器提供了框架，同时保持了制造的简单性。

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引用次数: 0

Front Cover CO1 封面CO1

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2026-01-01 DOI: 10.1016/S2352-4316(26)00001-5

引用次数: 0

Fatigue threshold of dual-crosslinking hydrogels 双交联水凝胶的疲劳阈值

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-12-30 DOI: 10.1016/j.eml.2025.102439

Yijian Zheng, Yang Gao, Tongqing Lu

The fatigue threshold of covalent hydrogels follows the Lake-Thomas model, equating to the energy needed to break covalent bonds between crosslinks at the crack tip. Dynamic bonds are widely introduced as secondary crosslinks to toughen hydrogels. Previous studies have reported that dynamic bonds contribute to the fatigue threshold in some tough hydrogels but not in others, making their contribution unclear. In this work, we prepare dual-crosslinking hydrogels (PAV-M²⁺) by introducing ligands along covalent polymer chains, enabling dynamic coordination with various M²⁺ ions to tune the relaxation time. In such hydrogels, we propose that covalent bonds contribute to the fatigue threshold via the Lake-Thomas model, while dynamic bonds contribute based on the competition between relaxation time and the crack-tip strain rate. When the strain rate greatly exceeds the inverse of the relaxation time, dynamic bonds cannot re-associate and contribute little to fatigue threshold. Conversely, when the strain rate is much lower than the inverse of relaxation time, they re-associate reversibly and enhance the threshold. The fatigue threshold of PAV-Ni hydrogels (relaxation time ∼ 300 ms) is 10.5 J/m² at a strain rate of 1 s⁻¹ (consistent with the Lake-Thomas prediction, 9.4 J/m²), and increases to 17.7 J/m² at 0.1 s⁻¹. The fatigue threshold of PAV-Zn hydrogels (relaxation time ∼ 0.3 ms) is 39.8 J/m² at 1 s⁻¹ and 41.4 J/m² at 0.1 s⁻¹, due to the recovery of dynamic bonds during loading cycles. Based on these results, we propose a modified Lake-Thomas model that incorporates the contribution of dynamic bonds to fatigue threshold, capturing the competition between relaxation time and strain rate.

共价水凝胶的疲劳阈值遵循Lake-Thomas模型，等于断裂裂纹尖端交联共价键所需的能量。动态键作为二级交联被广泛引入以增强水凝胶。先前的研究已经报道了动态键对某些坚韧水凝胶的疲劳阈值有贡献，但对其他水凝胶没有贡献，这使得它们的贡献尚不清楚。在这项工作中，我们通过在共价聚合物链上引入配体来制备双交联水凝胶（PAV-M2+），使其能够与各种M2+离子动态配位来调节弛豫时间。在这种水凝胶中，我们提出共价键通过Lake-Thomas模型贡献疲劳阈值，而动态键基于松弛时间和裂纹尖端应变率之间的竞争贡献疲劳阈值。当应变速率大大超过松弛时间的倒数时，动态键不能重新结合，对疲劳阈值的贡献很小。相反，当应变速率远低于松弛时间的倒数时，它们会可逆地重新关联并提高阈值。当应变速率为1 s−1时，PAV-Ni水凝胶的疲劳阈值（松弛时间~ 300 ms）为10.5 J/m2（与Lake-Thomas预测一致，为9.4 J/m2），当应变速率为0.1 s−1时，疲劳阈值增加到17.7 J/m2。由于加载过程中动态键的恢复，PAV-Zn水凝胶的疲劳阈值（松弛时间~ 0.3 ms）在1 s−1时为39.8 J/m2，在0.1 s−1时为41.4 J/m2。基于这些结果，我们提出了一个改进的Lake-Thomas模型，该模型包含了动态键对疲劳阈值的贡献，捕捉了松弛时间和应变速率之间的竞争。

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引用次数: 0

Chebyshev physics-informed Kolmogorov-Arnold networks for diffusion-convection-reaction equation in soft material adhesion system 软材料黏附系统中扩散-对流-反应方程的Chebyshev物理Kolmogorov-Arnold网络

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-12-13 DOI: 10.1016/j.eml.2025.102436

Zheyu Dong , Jiabao Bai , Daochen Yin , Kunqing Yu , Siqi Yan , Zhi Sheng , Zheng Jia

Recent advances in soft material adhesion have attracted considerable interest due to their potential implications for various scientific disciplines. Solving the 1D Diffusion-Convection-Reaction Equation (DCR Equation) remains a critical challenge in adhesion systems of soft materials, often hindered by computational complexities. Specifically, solving the 1D DCR Equation is particularly challenging owing to its intrinsic complexity as a nonlinear dynamical system, which is governed by an equation combining temporal evolution with zeroth, first, and second-order spatial differential terms. While substantial progress has been made through both experimental and theoretical approaches, the application of neural network-based methods in this area remains relatively underdeveloped. In this study, we address this gap by introducing, for the first time, Chebyshev physics-informed Kolmogorov-Arnold networks (c-PIKANs) specifically for modeling 1D DCR Equation of soft-material adhesion, a framework that systematically optimizes architecture parameters (learning rate, polynomial order, layer size) to maximize predictive performance. The c-PIKAN architecture outperforms conventional multilayer perceptron (MLP)-based physics-informed neural networks (PINNs) in accuracy and efficiency while requiring a smaller network size. This work paves the way for future applications of Kolmogorov-Arnold Networks (KANs) in soft material mechanics and provides crucial guidance for the adjustment of network hyperparameters, potentially opening new avenues for innovation in the field.

软材料粘附的最新进展由于其对各种科学学科的潜在影响而引起了相当大的兴趣。一维扩散-对流-反应方程（DCR方程）的求解一直是软质材料黏附系统中的一个关键挑战，通常受到计算复杂性的阻碍。具体来说，由于其作为一个非线性动力系统的内在复杂性，求解一维DCR方程尤其具有挑战性，该系统由一个将时间演化与零阶、一阶和二阶空间微分项相结合的方程所控制。虽然通过实验和理论方法取得了实质性进展，但基于神经网络的方法在这一领域的应用仍然相对不发达。在本研究中，我们通过首次引入Chebyshev物理通知Kolmogorov-Arnold网络（c-PIKANs）来解决这一差距，该网络专门用于建模软材料粘附的1D DCR方程，该框架系统地优化了架构参数（学习率，多项式顺序，层大小）以最大化预测性能。c-PIKAN架构在精度和效率方面优于传统的基于多层感知器（MLP）的物理信息神经网络（pinn），同时需要更小的网络规模。这项工作为Kolmogorov-Arnold网络（KANs）在软材料力学中的未来应用铺平了道路，并为网络超参数的调整提供了重要指导，可能为该领域的创新开辟新的途径。

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引用次数: 0

Experimental characterization and modeling anisotropic mechanical responses of liquid crystal elastomers with exchangeable disulfide bonds 具有可交换二硫键的液晶弹性体各向异性力学响应的实验表征和建模

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-12-07 DOI: 10.1016/j.eml.2025.102435

Baihong Chen , Huxiao Yang , Rui Xiao

The exchangeable liquid crystal elastomers (LCEs) with dynamic disulfide bonds possess excellent processability, recyclability and room-temperature programmability, making them highly promising for applications in soft robotics and shape-morphing structures. In this work, we combine experimental and theoretical approaches to systematically investigate the effect of programming stretches on the anisotropic mechanical response of LCEs with exchangeable disulfide bonds. We first fabricated a series of monodomain LCEs by applying varying programming stretches using disulfide exchange reactions. The thermal actuation response of these specimens was then characterized. Uniaxial tensile tests were further conducted to elucidate the effects of the programming stretches on the anisotropic mechanical responses at different strain rates. A viscoelastic model is then applied to simulate the anisotropic and rate-dependent mechanical response of monodomain LCEs. The results reveal the existence of a saturation programming stretch. Below this threshold, increasing programming stretches extends the length of the stress plateau, while the plateau stress remains unchanged. Notably, the Young’s moduli along orthogonal directions are identical prior to director rotation, contrasting with conventional two-step polymerized monodomain LCEs. This suggests that the anisotropic modulus of conventional LCEs may originate from the prestretched network. The experimental results also reveal that hysteresis loops under uniaxial loading along the director are larger than those under perpendicular loading. This indicates that the viscosity associated with director rotation is significantly lower than that of network deformation. For the theoretical part, the viscoelastic model with multiple relaxation processes successfully captures the anisotropic and rate-dependent mechanical response of monodomain LCEs, while the model with a single relaxation process fails to predict the area of the hysteresis loop over a wide rate region.

具有动态二硫键的可交换液晶弹性体（LCEs）具有优异的可加工性、可回收性和室温可编程性，在软机器人和变形结构中具有很大的应用前景。在这项工作中，我们结合实验和理论方法系统地研究了规划拉伸对具有交换二硫键的lce各向异性力学响应的影响。我们首先通过使用二硫交换反应应用不同的编程拉伸来制备一系列单畴lce。然后对这些试样的热驱动响应进行了表征。进一步进行了单轴拉伸试验，阐明了不同应变速率下规划拉伸对各向异性力学响应的影响。然后应用粘弹性模型模拟了单畴LCEs的各向异性和速率相关的力学响应。结果表明饱和规划拉伸的存在。在此阈值以下，增加编程拉伸会延长应力平台的长度，而平台应力保持不变。值得注意的是，与传统的两步聚合单畴LCEs相比，在定向旋转之前，沿着正交方向的杨氏模量是相同的。这表明传统LCEs的各向异性模量可能来源于预拉伸网络。实验结果还表明，沿方向单轴加载时的滞回线比垂直加载时的滞回线要大。这表明与导向器旋转相关的粘度明显低于网络变形相关的粘度。在理论部分，具有多个弛豫过程的粘弹性模型成功地捕获了单域LCEs的各向异性和速率相关的力学响应，而具有单一弛豫过程的模型无法在宽速率区域内预测滞后环的面积。

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引用次数: 0

Control of dynamic frictional instability using mechanical metamaterials 利用机械超材料控制动态摩擦不稳定性

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-12-03 DOI: 10.1016/j.eml.2025.102428

Sourav Kumar Panja , Kunnath Ranjith

We investigate the control of frictional instabilities at bi-material interfaces using mechanical metamaterials with unconventional dynamic properties. Specifically, we examine two configurations: (i) an anti-plane shear problem involving a metaelastic layer with negative effective density and shear modulus slipping on a classical elastic half-space, and (ii) an in-plane problem where a metaelastic half-space exhibiting triple-negative properties (negative density, bulk modulus, and shear modulus) overlies a conventional elastic half-space. Guided by a linear stability analysis of quasi-static steady sliding, we carry out numerical simulations of spontaneous rupture propagation at the interface with a slip-weakening friction law. This work shows the possibility of rupture arrest or propagation control at bi-material interfaces by negative effective properties of mechanical metamaterial with implications for seismic fault engineering, tribology, and advanced material design.

我们使用具有非常规动态特性的机械超材料研究双材料界面摩擦不稳定性的控制。具体来说，我们研究了两种配置：(i)涉及具有负有效密度和剪切模量的元弹性层在经典弹性半空间上滑动的反平面剪切问题，以及（ii）平面内问题，其中具有三负性质的元弹性半空间（负密度，体模量和剪切模量）覆盖在传统弹性半空间上。在准静态稳态滑动线性稳定性分析的指导下，采用滑移弱化摩擦规律对界面处的自发破裂扩展进行了数值模拟。这项工作显示了通过机械超材料的负有效特性在双材料界面上阻止破裂或控制传播的可能性，这对地震断层工程、摩擦学和先进材料设计具有重要意义。

引用次数: 0

How does chain length affect fracture of a brittle polymer glass? 链长如何影响脆性聚合物玻璃的断裂？

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-12-02 DOI: 10.1016/j.eml.2025.102431

Christine Heera Ahn, Zheqi Chen, Xianyang Bao, Zhigang Suo

In a brittle polymer glass, a fracture property increases with the length of polymer chains and then plateaus. Here, we use poly(methyl methacrylate) to study such transitions in several fracture properties. We measure strength using samples without precut crack, and measure toughness and fatigue threshold using samples with precut crack. The three properties plateau at different chain lengths. These transitions arise from a change in fracture mechanism—from chain pullout to chain scission. The chain length for a fracture property to plateau is understood using a shear-lag model. The plateau length is set by the balance of the strengths of bonds of two types: the covalent bonds along the chains, which resists scission, and the noncovalent bonds between the chains, which resist pullout. For each of the three fracture properties, we discuss the chain length for the property to plateau, as well as the value of the plateau.

在脆性聚合物玻璃中，断裂性能随着聚合物链的长度而增加，然后趋于平稳。在这里，我们使用聚甲基丙烯酸甲酯来研究几种断裂性质中的这种转变。我们用无预切裂纹的试样测量强度，用有预切裂纹的试样测量韧性和疲劳阈值。这三种性质在不同链长处趋于平稳。这些转变是由断裂机制的变化引起的——从链拔出到链断裂。断裂特性达到平台的链长可以用剪切滞后模型来理解。平台长度是由两种化学键强度的平衡决定的：沿链的共价键抵抗断裂，链之间的非共价键抵抗拔出。对于这三种断裂性质，我们讨论了到达平台的链长度，以及平台的值。

引用次数: 0

Front cover CO1 前盖CO1

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-12-01 DOI: 10.1016/S2352-4316(25)00144-0

引用次数: 0

Discrete differential geometry for simulating nonlinear behaviors of flexible systems: A survey 模拟柔性系统非线性行为的离散微分几何：综述

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-12-01 DOI: 10.1016/j.eml.2025.102430

Dezhong Tong , Andrew Choi , Jiaqi Wang , Weicheng Huang , Zexiong Chen , Jiahao Li , Xiaonan Huang , Mingchao Liu , Huajian Gao , K. Jimmy Hsia

Flexible slender structures such as rods, ribbons, plates, and shells exhibit extreme nonlinear responses – bending, twisting, buckling, wrinkling, and self-contact – that defy conventional simulation frameworks. Discrete Differential Geometry (DDG) has emerged as a geometry-first, structure-preserving paradigm for modeling such behaviors. Unlike finite element or mass–spring methods, DDG discretizes geometry rather than governing equations, allowing curvature, twist, and strain to be defined directly on meshes. This approach yields robust large-deformation dynamics, accurate handling of contact, and differentiability essential for inverse design and learning-based control. This review consolidates the rapidly expanding landscape of DDG models across 1D and 2D systems, including discrete elastic rods, ribbons, plates, and shells, as well as multiphysics extensions to contact, magnetic actuation, and fluid–structure interaction. We synthesize applications spanning mechanics of nonlinear instabilities, biological morphogenesis, functional structures and devices, and robotics from manipulation to soft machines. Compared with established approaches, DDG offers a unique balance of geometric fidelity, computational efficiency, and algorithmic differentiability, bridging continuum rigor with real-time, contact-rich performance. We conclude by outlining opportunities for multiphysics coupling, hybrid physics–data pipelines, and scalable GPU-accelerated solvers, and by emphasizing DDG’s role in enabling digital twins, sim-to-real transfer, and intelligent design of next-generation flexible systems.

灵活的细长结构，如棒、带、板和壳，表现出极端的非线性响应-弯曲、扭曲、屈曲、起皱和自接触-与传统的模拟框架相抵触。离散微分几何（DDG）作为一种以几何优先、结构保留的模式出现，用于对此类行为进行建模。与有限元或质量弹簧方法不同，DDG离散几何而不是控制方程，允许曲率，扭曲和应变直接在网格上定义。这种方法产生了鲁棒的大变形动力学，精确的接触处理，以及对逆设计和基于学习的控制至关重要的可微分性。这篇综述整合了快速扩展的一维和二维DDG模型，包括离散弹性棒、带状、板和壳，以及多物理场扩展到接触、磁致动和流固相互作用。我们综合了非线性不稳定性力学，生物形态发生，功能结构和设备，以及从操作到软机器的机器人技术的应用。与现有方法相比，DDG提供了几何保真度、计算效率和算法可微分性的独特平衡，将连续统一性与实时、接触丰富的性能相结合。最后，我们概述了多物理场耦合、混合物理场数据管道和可扩展gpu加速求解器的机会，并强调了DDG在实现数字孪生、模拟到真实传输和下一代灵活系统智能设计方面的作用。

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引用次数: 0

The role of dynamic covalent bonds on mechanical properties of rubber vitrimer with hybrid networks 动态共价键对杂化网络橡胶聚合物力学性能的影响

IF 4.5 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2025-11-29 DOI: 10.1016/j.eml.2025.102429

Dichao Ning, Zihan Zhang, Chenyu Jin, Qian Shi

Rubber is widely applied due to its high elasticity and durability, but traditional crosslinked networks are non-recyclable. The incorporation of dynamic covalent bonds endows vitrimers with recyclability and self-healing ability. However, the regulatory effect of curing kinetics and chemical ratio on dynamic covalent bonds has not been systematically studied, and such regulation is crucial for designing high-performance rubber vitrimers. In this work, rubber vitrimers with hybrid network were synthesized by using epoxy monomers and curing agent containing disulfide bonds. By varying the chemical ratio of soft segments (PEG) and hard segments (BPDG or DGEBA), and tuning curing time, we characterized their dynamic performance, tensile properties and fracture toughness. Furthermore, kinetic equation was incorporated into and used to extend the Lake–Thomas model, enabling quantitative description and prediction of fracture energy. The results demonstrate that increased curing degree and disulfide bond proportion enhance the fracture toughness and fracture strain of the rubber polymer, but slightly reduce its strength and modulus. Moreover, the introduction of dynamic covalent bonds favors both fracture toughness and dynamic performance. This work provides theoretical guidance and processing strategies for the design of high-performance rubbers.

橡胶因其高弹性和耐久性而得到广泛应用，但传统的交联网络是不可回收的。动态共价键的结合赋予了玻璃体可回收性和自愈能力。然而，硫化动力学和化学配比对动态共价键的调节作用尚未得到系统的研究，而这种调节作用对于设计高性能橡胶玻璃体至关重要。本文以环氧单体和含二硫键的固化剂为原料，合成了杂化网络橡胶玻璃体。通过改变软段（PEG）和硬段（BPDG或DGEBA）的化学配比，以及调整固化时间，对其动态性能、拉伸性能和断裂韧性进行了表征。此外，将动力学方程引入Lake-Thomas模型并加以扩展，实现了裂缝能的定量描述和预测。结果表明：增大硫化度和二硫键比例，可提高橡胶聚合物的断裂韧性和断裂应变，但强度和模量略有降低；此外，引入动态共价键有利于断裂韧性和动态性能。该工作为高性能橡胶的设计提供了理论指导和加工策略。

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