Extreme Mechanics Letters最新文献

Origami electronic membranes as highly shape-morphable mechanical and environmental sensing systems 作为高度可变形机械和环境传感系统的折纸电子膜

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-11-14 DOI: 10.1016/j.eml.2024.102264

Yao Yao , Guanghui Li , Xin Ning

This work introduces a concept of highly shape-morphable macro-scale origami electronic membranes based on the design and fabrication of flexible electronics and engineering origami. The origami electronic membranes can change shapes, provide multi-modal mechanical and environmental sensing capabilities in room and harsh temperatures, and/or switch functions by mechanical shape reconfiguration. This paper presents the materials, design, and fabrication methods for realizing six origami electronic membranes capable of reconfiguring planar or three-dimensional shapes based on the modified flasher, Kresling, Miura-ori, circular, letter, and Tachi-Miura origami patterns. They can be folded into small, stowed geometries and controllably deployed into larger areas or volumes to cover expanded spaces for spatial sensing, enabling significant shape adaptability for flexible electronics beyond simple stretching or bending. The mechanical and environmental sensing modalities include measuring motions, mechanical strains, temperatures, UV light, and humidity. The results reported here may expand the use of flexible electronics to applications that especially require aggressive shape transitions between a small, folded geometry and a large surface or volume such as deployable sensing systems for space explorations and accessing and monitoring highly confined locations.

这项研究基于柔性电子器件和工程折纸的设计与制造，提出了一种高度可变形的宏观尺度折纸电子膜的概念。这些折纸电子膜可以改变形状，在室温和严寒条件下提供多模式机械和环境传感功能，以及/或通过机械形状重构实现功能切换。本文介绍了实现六种折纸电子膜的材料、设计和制作方法，这些电子膜能够根据改良的飞鸟、克雷斯林、三浦织、圆形、字母和立三村折纸图案重新配置平面或三维形状。它们可以折叠成较小的收纳几何形状，并可控地部署到较大的区域或体积，以覆盖空间传感的扩展空间，从而使柔性电子器件的形状适应性大大超出简单的拉伸或弯曲。机械和环境传感模式包括测量运动、机械应变、温度、紫外线和湿度。本文报告的结果可将柔性电子器件的应用扩展到特别需要在折叠的小几何体与大表面或大体积之间进行积极形状转换的应用领域，例如用于太空探索的可部署传感系统，以及进入和监测高度密闭地点的传感系统。

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引用次数: 0

A large atomic partition model for materials discovery 用于材料发现的大原子分区模型

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-11-08 DOI: 10.1016/j.eml.2024.102262

Lintao Miao , Xiaoang Yuan , Chun Tang , Changfeng Chen , Enlai Gao

Accurate and efficient prediction of benchmark properties is essential to the discovery of diverse functional materials, but searching vast element combinatorial and bonding configurational spaces presents formidable challenges to current computational techniques. Here, we devise a large atomic partition (LAP) model featuring a scheme to partition material properties into constituent atomic attributes, which are validated by a data-driven calibration procedure and assigned to elements across the periodic table, then utilized as raw ingredients to assemble and assess targeted properties of new materials. Distinct subtypes are designated for each element based on local atomic environments such as coordination number and valence state, and the parameter count of the LAP model can be tuned widely to tailor prediction accuracy and computational efficiency. As demonstrative case studies, we explore volumetric cohesive energy, bulk modulus, and shear modulus, and the results showcase superior accuracy, efficiency, universality, and interpretability of the LAP model compared to alternative approaches. Moreover, based on the predicted elastic moduli, we discover a series of rare and highly sought-after compounds exhibiting concurrent superior hardness and toughness, highlighting the promise of the LAP model in high-throughput screening for advanced materials with targeted outstanding functionalities.

准确有效地预测基准属性对发现各种功能材料至关重要，但搜索庞大的元素组合和成键构型空间对当前的计算技术提出了严峻的挑战。在此，我们设计了一个大原子分区（LAP）模型，其特点是将材料特性划分为组成原子属性的方案，这些属性通过数据驱动的校准程序进行验证，并分配给元素周期表中的所有元素，然后利用这些元素作为原材料来组装和评估新材料的目标特性。根据配位数和价态等局部原子环境，为每种元素指定了不同的子类型，LAP 模型的参数数可进行广泛调整，以定制预测精度和计算效率。作为示范案例研究，我们探讨了体积内聚能、体积模量和剪切模量，结果表明与其他方法相比，LAP 模型具有更高的准确性、效率、通用性和可解释性。此外，根据预测的弹性模量，我们还发现了一系列稀有且备受追捧的化合物，它们同时表现出卓越的硬度和韧性，这凸显了 LAP 模型在高通量筛选具有目标性卓越功能的先进材料方面的前景。

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引用次数: 0

Atomic insights into the ductile–brittle competition of cracks under dissolution 从原子角度洞察溶解条件下裂纹的韧性-脆性竞争

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-11-08 DOI: 10.1016/j.eml.2024.102256

Long Liu, Quanzi Yuan

Environmental effects can determine the ductile–brittle behavior of cracks at the atomic scale, but the underlying processes remain poorly understood and contentious. Here, we report the competition between ductile and brittle behaviors at crack tips induced by the prevalent environmental effect of dissolution. Our findings reveal that this competition is driven by two fundamental deformation mechanisms related to dissolution: crack blunting and defect accumulation. Through separate evaluations of dissolution-induced cleavage and dissolution-induced plasticity, we demonstrate that these deformation mechanisms not only dominate brittle fracture toughness but also lead to dislocation slip. We have developed a theoretical model to predict the ductile and brittle behavior of cracks under dissolution, and the theory aligns well with the simulation results and remains consistent with existing experimental trends. This work will broaden the microscopic understanding of ductile and brittle fracture of cracks in complex environments.

环境效应可在原子尺度上决定裂纹的韧性-脆性行为，但对其基本过程的了解仍然很少，也存在争议。在此，我们报告了在普遍的环境溶解效应诱导下，裂纹尖端的韧性和脆性行为之间的竞争。我们的研究结果表明，这种竞争是由与溶解相关的两种基本变形机制驱动的：裂纹钝化和缺陷累积。通过分别评估溶解诱导的劈裂和溶解诱导的塑性，我们证明这些变形机制不仅主导脆性断裂韧性，而且还导致位错滑移。我们建立了一个理论模型来预测溶解作用下裂纹的韧性和脆性行为，该理论与模拟结果非常吻合，并与现有的实验趋势保持一致。这项工作将拓宽人们对复杂环境下裂纹的韧性和脆性断裂的微观认识。

引用次数: 0

A model for micro-scale propulsion using flexible rotating flagella 利用柔性旋转鞭毛的微尺度推进模型

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-11-06 DOI: 10.1016/j.eml.2024.102251

Yifei Ren, P.K. Purohit

Micro-scale propulsion by rotating helical flagella is of interest for the study of bacteria and robotic micro-swimmers. The propulsive thrust and torque produced by the rotating flagella are usually estimated assuming that they are rigid. In this paper we assume the flagella to be deformable elastic rods and compute propulsive forces and torques by enforcing local equilibrium of the rod within the context of resistive force theory. The torque–speed characteristics of the flagellar motor driving the rotation are taken into account. We show that the problem can be cast as a system of algebraic equations if the flagella are assumed to be helical before and after deformation when no spontaneous curvature is included. If the assumption of helical shape is dropped then we show that the propulsion problem can be cast as a system of first order differential equations that can be solved numerically. Our results in both cases agree reasonably well with experimental observations of bacterial propulsion and deviate from the predictions of Purcell depending on the mechanical properties of the flagellum.

通过旋转螺旋鞭毛进行微尺度推进是细菌和微型游泳机器人研究的兴趣所在。旋转鞭毛产生的推进推力和扭矩通常是在假设鞭毛是刚性的情况下估算的。在本文中，我们假定鞭毛是可变形的弹性杆，并在阻力理论的背景下，通过强制杆的局部平衡来计算推进力和扭矩。同时还考虑了驱动旋转的鞭毛马达的扭矩-速度特性。我们的研究表明，如果假定鞭毛在变形前后均为螺旋形，且不包含自发曲率，则该问题可转化为一个代数方程系统。如果放弃螺旋形状的假设，我们将证明推进问题可以转化为一阶微分方程系统，并通过数值方法求解。我们在这两种情况下得出的结果都与细菌推进力的实验观察结果相当吻合，而与珀塞尔的预测结果之间的偏差则取决于鞭毛的机械特性。

引用次数: 0

Front cover CO1 封面 CO1

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-11-01 DOI: 10.1016/S2352-4316(24)00137-8

引用次数: 0

Harnessing centrifugal and Euler forces for tunable buckling of a rotating elastica 利用离心力和欧拉力实现旋转弹性体的可调屈曲

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-11-01 DOI: 10.1016/j.eml.2024.102246

Eduardo Gutierrez-Prieto , Michael Gomez , Pedro M. Reis

We investigate the geometrically nonlinear deformation and buckling of a slender elastic beam subject to time-dependent ‘fictitious’ (non-inertial) forces arising from unsteady rotation. Using a rotary apparatus that accurately imposes an angular acceleration around a fixed axis, we demonstrate that dynamically coupled centrifugal and Euler forces can produce tunable structural deformations. Specifically, by systematically varying the acceleration ramp in a highly automated experimental setup, we show how the buckling onset of a cantilevered beam can be precisely tuned and its deformation direction selected. In a second configuration, we demonstrate that Euler forces can cause a pre-arched beam to snap-through, on demand, between its two stable states. We also formulate a theoretical model rooted in Euler’s elastica that rationalizes the problem and provides predictions in excellent quantitative agreement with the experimental data. Our findings demonstrate an innovative approach to the programmable actuation of slender rotating structures, where complex loading fields can be produced by controlling a single input parameter, the angular position of a rotating system. The ability to predict and control the buckling behaviors under such non-trivial loading conditions opens avenues for designing devices based on rotational fictitious forces.

我们研究了细长弹性梁在非稳定旋转产生的随时间变化的 "虚构"（非惯性）力作用下的几何非线性变形和屈曲。利用围绕固定轴精确施加角加速度的旋转装置，我们证明了动态耦合离心力和欧拉力可以产生可调的结构变形。具体来说，通过在高度自动化的实验装置中系统地改变加速度斜坡，我们展示了如何精确调整悬臂梁的屈曲起始点并选择其变形方向。在第二种配置中，我们证明了欧拉力可以使预弯曲梁按需在两种稳定状态之间快速穿越。我们还根据欧拉弹性原理建立了一个理论模型，使问题合理化，并提供了与实验数据非常一致的定量预测。我们的研究成果展示了一种创新的细长旋转结构可编程驱动方法，通过控制单一输入参数（旋转系统的角位置）就能产生复杂的加载场。能够预测和控制这种非微妙加载条件下的屈曲行为，为设计基于旋转虚力的装置开辟了道路。

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引用次数: 0

Wrinkling of compressible magnetic soft plates 可压缩磁性软板的皱褶

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-10-30 DOI: 10.1016/j.eml.2024.102255

Guozhan Xia

This paper establishes an analytical method for the wrinkling of compressible magnetic soft (MS) plates subject to an in-plane biaxial stretching and an out-of-plane magnetic induction field. The bifurcation analysis is performed with external Maxwell stress considered by combining the surface impedance matrix method and the Stroh formulation in terms of true magnetic field variables. We decouple the resulting bifurcation equations into antisymmetric and symmetric modes and provide the explicit expressions within a neo-Hookean ideal magnetoelastic model. Numerical examples show that the antisymmetric wrinkling usually occurs prior to the symmetric one, unless the permeability of the plates

μ

is much smaller than that of the surroundings

μ^{'}

, i.e., the normalized permeability

μ / μ^{'} \to 0

. This observation is consistent with the previous studies on incompressible case. However, for nearly incompressible plates with

μ / μ^{'} > 1

, the compressible constitutive relation may impose an additional deformation constraint that noticeably limits the occurrence and extent of wrinkling in the plates. One intriguing observation in particular is that the critical stretches for the thin-plate instability exhibit a nonmonotonic character as the compressibility of plate varies. Release of compressibility plays a positive role on stabilizing the MS plates when

0 < μ / μ^{'} < 1

, yet a negative role when

μ / μ^{'} > 1

. This phenomenon may be attributed to the coupling effect between the compressibility and the normalized permeability

μ / μ^{'}

, suggesting a potential way to regulate wrinkling behaviors of MS materials by tuning the surrounding permeability. The present work may serve as benchmark solutions for understanding structural failures in various related functional MS-based devices.

本文建立了可压缩磁性软板（MS）在平面内双轴拉伸和平面外磁感应场作用下起皱的分析方法。在考虑外部麦克斯韦应力的情况下，结合表面阻抗矩阵法和真实磁场变量的斯特罗公式进行了分叉分析。我们将分岔方程解耦为非对称和对称模式，并在新胡克理想磁弹性模型中提供了明确的表达式。数值示例表明，除非板的渗透率μ远小于周围环境的渗透率μ′，即归一化渗透率μ/μ′→0，否则反对称起皱通常发生在对称起皱之前。这一观察结果与之前对不可压缩情况的研究结果一致。然而，对于μ/μ′>1的近不可压缩板，可压缩构成关系可能会施加额外的变形约束，从而明显限制板材皱褶的发生和程度。一个特别有趣的观察结果是，随着板的可压缩性的变化，薄板不稳定性的临界拉伸表现出非单调性。这一现象可能归因于压缩性与归一化渗透率μ/μ′之间的耦合效应，表明通过调节周围渗透率可以调节 MS 材料的起皱行为。本研究可作为了解各种基于 MS 的相关功能器件结构故障的基准解决方案。

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引用次数: 0

Crack-growth inhibition by designing dendritic pattern for soft adhesives 通过为软质粘合剂设计树枝状图案抑制裂纹生长

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-10-28 DOI: 10.1016/j.eml.2024.102254

Yifan Zhang , Danming Zhong , Qiuxuan Wang , Ping Rao , Shaoxing Qu

Soft adhesive layers show promise in various engineering applications, including biomedicine, automotive, semiconductor, and aerospace industries. However, cavities trapped at the interface due to poor contact will significantly inhibit their adhesion capacity, leading to rapid crack-growth failure. Significant efforts in these applications within a confined contact area are focused on mitigating the effects and enhancing the debonding work of the interface without changing the materials, such as using bioinspired micropillars. However, soft adhesives with isolated contact elements face limitations due to manufacturing complexity and the collision of micropillars under large deformation. This study proposes a simple and effective method to reduce the hydrostatic pressure around the crack tips by designing a dendritic pattern within the confined area. This approach inhibited interface crack growth well and improved adhesive performance. As a result, the crack failure was delayed, with the stretch ratio enhanced by more than 36 %, while the debonding work increased by 85 % compared with the circular adhesive layer. This study demonstrates that adhesion capacity can be significantly improved while reducing material usage by designing dendritic patterns.

软粘合剂层在生物医学、汽车、半导体和航空航天等各种工程应用中大有可为。然而，由于接触不良而在界面处产生的空腔会极大地抑制其粘附能力，导致裂纹快速生长失效。在这些应用的有限接触区域内，人们主要致力于在不改变材料的情况下减轻影响和增强界面的脱粘功，例如使用生物启发微柱。然而，由于制造的复杂性和微柱在大变形下的碰撞，具有隔离接触元件的软粘合剂面临着种种限制。本研究提出了一种简单有效的方法，通过在限制区域内设计树枝状图案来降低裂纹尖端周围的静水压力。这种方法很好地抑制了界面裂纹的生长，并改善了粘合性能。因此，与圆形粘合层相比，裂纹失效延迟，拉伸比提高了 36% 以上，而脱粘功提高了 85%。这项研究表明，通过设计树枝状图案，可以显著提高粘附能力，同时减少材料用量。

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引用次数: 0

Broadband elastic energy harvesting based on achromatic meta-grating 基于消色差元光栅的宽带弹性能量采集技术

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-10-25 DOI: 10.1016/j.eml.2024.102253

Yizhou Shen , Yanlong Xu , Feng Liu , Fanglong Wang , Guan Wang , Zhichun Yang

Energy harvesting exploiting the inverse piezoelectric effect has been the subject of much attention and discussion in the field of elastic and structural dynamics. Recently, the ongoing development of elastic metamaterials and metasurfaces has opened up a new way to improve the quality of energy harvesting. Here, we proposed a new strategy for harvesting elastic energy in a plate, which is the use of the inverse piezoelectric effect to convert the elastic energy into electrical energy after the achromatic meta-grating has focused broadband flexural waves. A new theoretical method to design the achromatic meta-grating is proposed based on derived analytical expression of the phase shift of subunit. When a meta-grating, a thin plate and a piezoelectric patch are combined into an energy harvesting system, the elastic energy can be converted into electric energy by the system, and the output voltage can be amplified by twice that of the system without the meta-grating. A theoretical framework is built to analyze the performance of the energy harvesting system, and variational parametric analyses are carried out to obtain the optimal resistance, the optimal length, thickness and position of piezoelectric patch, which are

870 Ω

, 18 mm, 0.2 mm and 30 mm, respectively. For the optimized system, the power harvested rate of the system is close to 4 in the frequency band of 6–8 kHz. Finally, the design of the system based on the wave focusing principle is extended, and energy harvesters are designed for different frequency bands, which can all work under different excitation conditions (a local and a base excitations). Our work opens up a new route for elastic energy harvesting and may have broad application prospects in the development of self-powered sensors.

利用反压电效应进行能量收集一直是弹性和结构动力学领域备受关注和讨论的主题。最近，弹性超材料和超表面的不断发展为提高能量收集的质量开辟了一条新途径。在此，我们提出了一种在板中采集弹性能量的新策略，即利用反压电效应，在消色差元光栅聚焦宽带挠曲波后，将弹性能量转化为电能。根据子单元相移的推导分析表达式，提出了一种设计消色差元光栅的新理论方法。当元光栅、薄板和压电贴片组合成能量收集系统时，系统可将弹性能转化为电能，输出电压可放大为无元光栅系统的两倍。本文建立了一个理论框架来分析能量收集系统的性能，并通过变分参数分析得出了最佳电阻，压电贴片的最佳长度、厚度和位置，分别为 870Ω、18 mm、0.2 mm 和 30 mm。对于优化系统，在 6-8 kHz 频段内，系统的功率收获率接近 4。最后，我们扩展了基于波聚焦原理的系统设计，为不同频段设计了能量收集器，这些能量收集器都能在不同的激励条件（局部激励和基本激励）下工作。我们的工作为弹性能量收集开辟了一条新的途径，并可能在自供电传感器的开发中具有广阔的应用前景。

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引用次数: 0

Understanding the role of chain stiffness in the mechanical response of cross-linked polymer: Flexible vs. semi-flexible chains 了解链刚度在交联聚合物机械响应中的作用：柔性链与半柔性链

IF 4.3 3区工程技术 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Extreme Mechanics Letters

Pub Date : 2024-10-24 DOI: 10.1016/j.eml.2024.102252

Xiangrui Zheng , Wenjie Xia , Yao Zhang

Cross-linked polymers are widely used in structural, engineering, and biomedical applications due to their lightweight and superior properties. Although chain bending stiffness has been recognized to play an essential role in their thermodynamical and mechanical properties, how it influences these properties of cross-linked polymers with flexible or semi-flexible chains remains under debate. Here, we systematically explore its influences utilizing coarse-grained (CG) molecular dynamics (MD) simulations based on a bead-spring CG model. It is found that with chain bending stiffness increasing, both density and elastic moduli (i.e., shear modulus and tensile modulus) of cross-linked polymers first decrease slightly and then decrease significantly followed by a gradual increase, along with the polymer transition from a dense cross-linked thermoset to a highly porous fibrous network. The moduli of cross-linked polymers with flexible and semi-flexible chains exhibit distinct scaling laws with the density. For cross-linked polymers with flexible chains, their moduli increase significantly with increasing strain rate, which correlates to the change in potential energy of interchain interaction during deformation. However, the moduli display slight dependence on strain rate for porous cross-linked polymers with sufficiently stiff chains, where the intrachain interactions (i.e., bond stretching and angle bending energies) become dominant and independent of strain rate. Moreover, the elastic moduli exhibit scaling laws with Debye-Waller factor for both dense cross-linked thermosets with flexible chains and highly porous networks with stiff backbones. Our work facilitates a better understanding for mechanical properties and deformation mechanism of cross-linked polymers with variable chain bending stiffness at molecular level, shedding light on tailoring mechanical properties of cross-linked polymers via chain engineering.

交联聚合物由于重量轻、性能优越而被广泛应用于结构、工程和生物医学领域。虽然人们已经认识到链弯曲刚度在其热力学和机械性能中起着至关重要的作用，但它如何影响具有柔性或半柔性链的交联聚合物的这些性能仍存在争议。在此，我们利用基于珠链 CG 模型的粗粒度（CG）分子动力学（MD）模拟，系统地探讨了其影响因素。结果发现，随着链弯曲刚度的增加，交联聚合物的密度和弹性模量（即剪切模量和拉伸模量）先是略有下降，然后显著下降，接着逐渐增加，聚合物也从致密交联热固性过渡到高多孔性纤维网络。具有柔性链和半柔性链的交联聚合物的模量随密度的变化呈现出不同的缩放规律。对于具有柔性链的交联聚合物，其模量随着应变速率的增加而显著增加，这与变形过程中链间相互作用势能的变化有关。然而，对于具有足够刚性链的多孔交联聚合物，模量对应变速率的依赖性很小，链内相互作用（即键拉伸能和角弯曲能）成为主导，与应变速率无关。此外，对于具有柔性链的致密交联热固性塑料和具有刚性骨架的高孔隙网络，弹性模量都呈现出与 Debye-Waller 因子成比例的规律。我们的研究工作有助于更好地理解具有可变链弯曲刚度的交联聚合物在分子水平上的机械性能和变形机制，为通过链工程定制交联聚合物的机械性能提供了启示。

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引用次数: 0