Extreme Mechanics Letters最新文献_第4页

Exploring conformational landscapes of two-dimensional macromolecules via well-tempered metadynamics 通过调质元动力学探索二维大分子的构象景观

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

Extreme Mechanics Letters

Pub Date : 2025-11-15 DOI: 10.1016/j.eml.2025.102421

Yanyan Zhao , Ke Zhou , Yan Chen , Yilun Liu

Exploring conformational landscape of two-dimensional (2D) macromolecules poses a profound challenge due to their intrinsically complex free energy surfaces. Conventional computational approaches based on equilibrium molecular dynamics (MD) suffer from limited ergodic exploration, failing to adequately explore energy landscapes and transition pathways between metastable conformations. In this study, we employ well-tempered Metadynamics simulations with carefully designed collective variables to comprehensively map conformational space of 2D macromolecules. Our systematic exploration reveals three distinct metastable states, i.e., flat, fold and scroll conformations. Through detailed free energy analysis, we elucidate the delicate interplay between bending rigidity and interlayer adhesion that govern free energy surfaces of these conformations. Furthermore, we propose a temperature-modulated strategy to regulate conformational transitions among the three states. By decomposing the total free energy into entropic and enthalpic contributions, we quantitatively characterize the temperature-dependent thermodynamic driving forces underlying conformational transformations. This research establishes a robust computational framework for quantifying free energy and entropy associated with metastable conformations in 2D macromolecule systems. Our findings advance fundamental understanding of conformational transitions, regulation processes, and self-assembly behaviors in 2D macromolecular systems.

由于二维（2D）大分子的自由能表面本质上是复杂的，因此探索其构象景观带来了深刻的挑战。基于平衡分子动力学（MD）的传统计算方法的遍历探索有限，无法充分探索亚稳构象之间的能量景观和转变途径。在这项研究中，我们采用了精心设计的集体变量的良好调质元动力学模拟来全面绘制二维大分子的构象空间。我们的系统探索揭示了三种不同的亚稳态，即平面、折叠和涡旋构象。通过详细的自由能分析，我们阐明了支配这些构象的自由能表面的弯曲刚度和层间附着力之间微妙的相互作用。此外，我们提出了一种温度调制策略来调节三种状态之间的构象转变。通过将总自由能分解为熵和焓贡献，我们定量地描述了构象转化背后的温度依赖的热力学驱动力。本研究建立了一个强大的计算框架，用于量化二维大分子体系中与亚稳构象相关的自由能和熵。我们的发现促进了对二维大分子系统的构象转变、调节过程和自组装行为的基本理解。

{"title":"Exploring conformational landscapes of two-dimensional macromolecules via well-tempered metadynamics","authors":"Yanyan Zhao , Ke Zhou , Yan Chen , Yilun Liu","doi":"10.1016/j.eml.2025.102421","DOIUrl":"10.1016/j.eml.2025.102421","url":null,"abstract":"<div><div>Exploring conformational landscape of two-dimensional (2D) macromolecules poses a profound challenge due to their intrinsically complex free energy surfaces. Conventional computational approaches based on equilibrium molecular dynamics (MD) suffer from limited ergodic exploration, failing to adequately explore energy landscapes and transition pathways between metastable conformations. In this study, we employ well-tempered Metadynamics simulations with carefully designed collective variables to comprehensively map conformational space of 2D macromolecules. Our systematic exploration reveals three distinct metastable states, i.e., flat, fold and scroll conformations. Through detailed free energy analysis, we elucidate the delicate interplay between bending rigidity and interlayer adhesion that govern free energy surfaces of these conformations. Furthermore, we propose a temperature-modulated strategy to regulate conformational transitions among the three states. By decomposing the total free energy into entropic and enthalpic contributions, we quantitatively characterize the temperature-dependent thermodynamic driving forces underlying conformational transformations. This research establishes a robust computational framework for quantifying free energy and entropy associated with metastable conformations in 2D macromolecule systems. Our findings advance fundamental understanding of conformational transitions, regulation processes, and self-assembly behaviors in 2D macromolecular systems.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102421"},"PeriodicalIF":4.5,"publicationDate":"2025-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145579622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Tensegrity metastructure with tunable stiffness, strength, and energy dissipation 具有可调刚度、强度和能量耗散的张拉整体元结构

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

Extreme Mechanics Letters

Pub Date : 2025-11-13 DOI: 10.1016/j.eml.2025.102420

Filipe A. Santos

This paper introduces a tensegrity metastructure—a geometry-governed, structural-scale assembly—composed of three-dimensional Class-3 D-bar units. A proof-of-concept module was fabricated by fused-filament 3D printing with PETG struts and TPU ties and tested under cyclic axial loading. The metastructure exhibits a nonlinear force–displacement response with a two-stage mechanism: an initial softening regime governed by energy dissipation, followed by a sharp stiffening triggered by a locking transition as the struts align with the loading axis. Finite-element simulations, calibrated with manufacturer material data and validated against experiments, accurately reproduce this behavior.

A numerical parametric study demonstrates that the metastructure’s response can be tuned purely through geometry. Increasing the unit-cell orientation angle

β

leads to more than threefold gains in both stiffness and load capacity, and roughly a threefold increase in dissipated energy before locking. These results confirm the feasibility of geometry-based programmability, positioning tensegrity metastructures as lightweight, modular systems for adaptive mechanical performance in vibration mitigation, impact absorption, deployable architectures, and soft robotic mechanisms.

本文介绍了一种张拉整体元结构——由三维三维d -杆单元组成的几何控制的结构尺度组合。采用熔融长丝3D打印技术，采用PETG支柱和TPU纽带制作了一个概念验证模块，并在循环轴向载荷下进行了测试。元结构表现出非线性力-位移响应，具有两阶段机制：由能量耗散控制的初始软化状态，随后是由支撑与加载轴对齐时的锁定过渡触发的急剧硬化。使用制造商材料数据校准并通过实验验证的有限元模拟可以准确地再现这种行为。数值参数研究表明，元结构的响应可以完全通过几何来调整。增加单元格取向角β导致刚度和负载能力增加三倍以上，锁定前的耗散能量增加大约三倍。这些结果证实了基于几何的可编程性的可行性，将张拉整体元结构定位为轻量化、模块化系统，用于自适应机械性能的振动缓解、冲击吸收、可展开架构和软机器人机构。

{"title":"Tensegrity metastructure with tunable stiffness, strength, and energy dissipation","authors":"Filipe A. Santos","doi":"10.1016/j.eml.2025.102420","DOIUrl":"10.1016/j.eml.2025.102420","url":null,"abstract":"<div><div>This paper introduces a tensegrity metastructure—a geometry-governed, structural-scale assembly—composed of three-dimensional Class-3 D-bar units. A proof-of-concept module was fabricated by fused-filament 3D printing with PETG struts and TPU ties and tested under cyclic axial loading. The metastructure exhibits a nonlinear force–displacement response with a two-stage mechanism: an initial softening regime governed by energy dissipation, followed by a sharp stiffening triggered by a locking transition as the struts align with the loading axis. Finite-element simulations, calibrated with manufacturer material data and validated against experiments, accurately reproduce this behavior.</div><div>A numerical parametric study demonstrates that the metastructure’s response can be tuned purely through geometry. Increasing the unit-cell orientation angle <span><math><mi>β</mi></math></span> leads to more than threefold gains in both stiffness and load capacity, and roughly a threefold increase in dissipated energy before locking. These results confirm the feasibility of geometry-based programmability, positioning tensegrity metastructures as lightweight, modular systems for adaptive mechanical performance in vibration mitigation, impact absorption, deployable architectures, and soft robotic mechanisms.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102420"},"PeriodicalIF":4.5,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145529017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Rate-dependent molecular size effects govern the inverse thickness dependence of specific penetration energy in nanoscale thin films 速率依赖的分子尺寸效应决定了纳米薄膜中比穿透能的逆厚度依赖

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

Extreme Mechanics Letters

Pub Date : 2025-11-11 DOI: 10.1016/j.eml.2025.102419

Heather L. White , Wei Chen , Nicola M. Pugno , Sinan Keten

Laser-induced projectile impact tests (LIPIT) enable evaluation of thin film mechanical properties at strain rates on the order of 10

^{8}

s⁻¹. A popular metric for comparing material performance in LIPIT is the specific penetration energy (

E_{p}^{*}

) which is meant to represent the microprojectile’s energy loss normalized by the impacted film plug. However, recent LIPIT and LIPIT-like simulations have revealed in polymer-based films an inverse dependence of

E_{p}^{*}

on nanoscale film thickness, indicating the presence of dissipative mechanisms unique to this scale. Here we report this same inverse thickness dependence in multilayered graphene oxide (GO) thin films subjected to LIPIT-like molecular dynamics simulations. A previously proposed analytical model is adjusted to suit layered materials such as GO. The influence of this model’s parameters is probed with the aid of a Gaussian process metamodel, revealing that the aforementioned scaling is most dramatic when graphene oxide flakes are large and impact velocity is low. This work builds upon many theories pertaining to the mechanisms contributing to inverse dependence of

E_{p}^{*}

on film thickness and will inform subsequent work on molecular design of ballistic impact-resistant thin films.

激光诱导弹射冲击试验（LIPIT）能够在108 s−1量级的应变速率下评估薄膜的力学性能。在LIPIT中比较材料性能的一个常用度量是比穿透能（Ep *），它表示微弹的能量损失经冲击膜塞归一化。然而，最近的LIPIT和类LIPIT模拟已经揭示了聚合物基薄膜中Ep *与纳米级薄膜厚度的反比依赖性，表明存在这种尺度特有的耗散机制。在这里，我们在多层氧化石墨烯（GO）薄膜中进行了类似lipt的分子动力学模拟，报告了相同的逆厚度依赖性。先前提出的分析模型进行了调整，以适应层状材料，如氧化石墨烯。借助高斯过程元模型探讨了模型参数的影响，发现当氧化石墨烯薄片较大且冲击速度较低时，上述结垢现象最为明显。这项工作建立在许多理论的基础上，这些理论与Ep *对薄膜厚度的反向依赖机制有关，并将为后续抗弹道冲击薄膜的分子设计工作提供信息。

{"title":"Rate-dependent molecular size effects govern the inverse thickness dependence of specific penetration energy in nanoscale thin films","authors":"Heather L. White , Wei Chen , Nicola M. Pugno , Sinan Keten","doi":"10.1016/j.eml.2025.102419","DOIUrl":"10.1016/j.eml.2025.102419","url":null,"abstract":"<div><div>Laser-induced projectile impact tests (LIPIT) enable evaluation of thin film mechanical properties at strain rates on the order of 10<span><math><msup><mrow></mrow><mrow><mn>8</mn></mrow></msup></math></span> s<sup>−1</sup>. A popular metric for comparing material performance in LIPIT is the specific penetration energy (<span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>p</mi></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span>) which is meant to represent the microprojectile’s energy loss normalized by the impacted film plug. However, recent LIPIT and LIPIT-like simulations have revealed in polymer-based films an inverse dependence of <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>p</mi></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span> on nanoscale film thickness, indicating the presence of dissipative mechanisms unique to this scale. Here we report this same inverse thickness dependence in multilayered graphene oxide (GO) thin films subjected to LIPIT-like molecular dynamics simulations. A previously proposed analytical model is adjusted to suit layered materials such as GO. The influence of this model’s parameters is probed with the aid of a Gaussian process metamodel, revealing that the aforementioned scaling is most dramatic when graphene oxide flakes are large and impact velocity is low. This work builds upon many theories pertaining to the mechanisms contributing to inverse dependence of <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>p</mi></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span> on film thickness and will inform subsequent work on molecular design of ballistic impact-resistant thin films.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102419"},"PeriodicalIF":4.5,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145579621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Viscoelasticity and crack growth in tanglemers 缠结物的粘弹性和裂纹扩展

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

Extreme Mechanics Letters

Pub Date : 2025-11-11 DOI: 10.1016/j.eml.2025.102418

Yu Zhou , Xianyang Bao , Zhigang Suo

A tanglemer is a polymer network in which chains are long, and entanglements greatly outnumber crosslinks. In a tanglemer, each chain is divided by crosslinks into many strands, and each strand is divided by entanglements into many segments. In synthesizing tanglemers, the crosslink density is readily varied, but the entanglement density is set by the chemistry of the polymer. Here we investigate how crosslink density affects the mechanical behavior of tanglemers. We find that viscoelasticity is unaffected by crosslink density when tanglemers are subject to stretches small enough without breaking strands. We then study crack growth in tanglemers under a static load. A load exists, called the slow-crack threshold, below which the crack does not grow. The threshold is high in a tanglemer of low crosslink density. Fast crack growth, however, is insensitive to crosslink density. We discuss how molecular mechanisms affect mechanical behavior.

缠结物是一种聚合物网络，其中的链很长，缠结远远超过交联。在缠结器中，每条链通过交联被分成许多股，每条股又通过缠结被分成许多片段。在合成缠结剂时，交联密度是容易变化的，但缠结密度是由聚合物的化学性质决定的。在这里，我们研究了交联密度如何影响缠结物的力学行为。我们发现，当缠结剂受到足够小的拉伸而不断裂链时，粘弹性不受交联密度影响。然后研究了静载荷作用下缠结材料的裂纹扩展。存在一个荷载，称为慢裂阈值，低于此荷载，裂纹不会扩展。在交联密度低的缠结物中，阈值较高。然而，快速裂纹扩展对交联密度不敏感。我们讨论分子机制如何影响力学行为。

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 : 2025-11-01 DOI: 10.1016/S2352-4316(25)00127-0

引用次数: 0

When and where do large cracks grow? Griffith energy competition constrained by material strength 大裂缝何时何地出现？格里菲斯能源竞争受材料强度制约

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

Extreme Mechanics Letters

Pub Date : 2025-11-01 DOI: 10.1016/j.eml.2025.102417

Oscar Lopez-Pamies, Farhad Kamarei

An abundance of comparisons with experimental evidence has long settled that the Griffith energy competition along a known crack path — commonly expressed as a criticality condition on the energy release rate — describes when a large crack grows in a nominally elastic brittle material that is subjected to quasi-static loading. However, the answer to the question of where — that is, in which direction — a large crack grows remains unresolved. A slew of criteria have been proposed over the decades, but comparisons with experiments have indicated that none of such criteria apply in general.

Directly guided by the mathematical structure of the regularized phase-field theory of fracture initiated by Kumar, Francfort, and Lopez-Pamies (J. Mech. Phys. Solids 112 (2018), 523–551), and motivated by the wide range of experiments that this theory has been validated against, this Letter introduces a new criterion to describe when and where large cracks grow in elastic brittle materials under quasi-static loading conditions. In a nutshell: the growth of a large crack takes place within and only within regions where the strength surface of the material has been exceeded, this in a manner such that the sum of the potential (that is, the elastic energy minus the work of the external loads) and surface energies are minimized. Importantly, this strength-constrained Griffith-energy-competition criterion is general in the sense that it applies to materials with any elasticity (linear or nonlinear) and any material symmetry (isotropic or anisotropic). In this Letter, for simplicity of presentation, attention is restricted to the most basic of settings, that of isotropic linear elastic brittle materials. Following its raison d’etre by means of a simple example and then general introduction, the proposed criterion is confronted with a set of classical experiments on glass.

大量与实验证据的比较早已确定了沿已知裂纹路径的格里菲斯能量竞争-通常表示为能量释放率的临界条件-描述了当名义上的弹性脆性材料受到准静态载荷时出现大裂纹时的情况。然而，一个大裂缝在哪里——也就是说，在哪个方向——生长的问题的答案仍然没有得到解决。几十年来，人们提出了一系列的标准，但与实验的比较表明，这些标准都不适用。在Kumar， Francfort, and Lopez-Pamies （J. Mech.）提出的裂缝正则相场理论的数学结构的直接指导下。理论物理。固体112(2018),523-551)，并受到该理论已被验证的广泛实验的启发，这封信引入了一个新的标准来描述在准静态加载条件下弹性脆性材料中的大裂纹何时何地产生。简而言之：大裂纹的增长发生在且仅发生在材料强度表面已被超过的区域内，这种方式使得势能（即弹性能减去外部负载的功）和表面能的总和最小。重要的是，这种强度约束的格里菲斯-能量竞争准则在某种意义上是通用的，它适用于具有任何弹性（线性或非线性）和任何材料对称性（各向同性或各向异性）的材料。在这封信中，为了表述简单，注意力被限制在最基本的设置，即各向同性线弹性脆性材料。通过一个简单的例子和一般的介绍，给出了该准则的存在理由，并与一系列经典的玻璃实验进行了对比。

{"title":"When and where do large cracks grow? Griffith energy competition constrained by material strength","authors":"Oscar Lopez-Pamies, Farhad Kamarei","doi":"10.1016/j.eml.2025.102417","DOIUrl":"10.1016/j.eml.2025.102417","url":null,"abstract":"<div><div>An abundance of comparisons with experimental evidence has long settled that the Griffith energy competition along a known crack path — commonly expressed as a criticality condition on the energy release rate — describes <em>when</em> a large crack grows in a nominally elastic brittle material that is subjected to quasi-static loading. However, the answer to the question of <em>where</em> — that is, in which direction — a large crack grows remains unresolved. A slew of criteria have been proposed over the decades, but comparisons with experiments have indicated that none of such criteria apply in general.</div><div>Directly guided by the mathematical structure of the regularized phase-field theory of fracture initiated by Kumar, Francfort, and Lopez-Pamies (<em>J. Mech. Phys. Solids</em> 112 (2018), 523–551), and motivated by the wide range of experiments that this theory has been validated against, this Letter introduces a new criterion to describe when and where large cracks grow in elastic brittle materials under quasi-static loading conditions. In a nutshell: <em>the growth of a large crack takes place within and only within regions where the strength surface of the material has been exceeded, this in a manner such that the sum of the potential (that is, the elastic energy minus the work of the external loads) and surface energies are minimized</em>. Importantly, this strength-constrained Griffith-energy-competition criterion is general in the sense that it applies to materials with any elasticity (linear or nonlinear) and any material symmetry (isotropic or anisotropic). In this Letter, for simplicity of presentation, attention is restricted to the most basic of settings, that of isotropic linear elastic brittle materials. Following its raison d’etre by means of a simple example and then general introduction, the proposed criterion is confronted with a set of classical experiments on glass.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102417"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145475483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Self-locking and stability of the bowline knot 自锁和稳定的蝴蝶结结

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

Extreme Mechanics Letters

Pub Date : 2025-10-27 DOI: 10.1016/j.eml.2025.102413

Bastien F.G. Aymon , Fani Derveni , Michael Gomez , Jérôme Crassous , Pedro M. Reis

We investigate the self-locking of the bowline knot through numerical simulations, experiments, and theoretical analysis. Specifically, we perform two complementary types of simulations using the 3D finite-element method (FEM) and a reduced-order model based on the discrete-element method (DEM). For the FEM simulations, we develop a novel mapping technique that automatically transforms the centerline of the rod into the required knot topology prior to loading. In parallel, we conduct experiments using a nearly inextensible elastic rod tied into a bowline around a rigid cylinder. One end of the rod is pulled to load the knot while the other is left free. The measured force–displacement response serves to validate both the FEM and DEM simulations. Leveraging these validated computational frameworks, we analyze the internal tension profile along the rod’s centerline, revealing that a sharp drop in tension concentrates around a strategic locking region, whose geometry resembles that observed in other knot types. By considering the coupling of tension, bending, and friction, we formulate a theoretical model inspired by the classic capstan problem to predict the stability conditions of the bowline, finding good agreement with our FEM and DEM simulations. Our methodology and findings offer new tools and insights for future studies on the performance and reliability of other complex knots.

本文通过数值模拟、实验和理论分析研究了弓形结的自锁特性。具体来说，我们使用三维有限元法（FEM）和基于离散元法（DEM）的降阶模型进行了两种互补类型的模拟。对于有限元模拟，我们开发了一种新的映射技术，可以在加载之前自动将杆的中心线转换为所需的结拓扑结构。与此同时，我们用一根几乎不可伸缩的弹性杆系在一个刚性圆柱体上的弓形线上进行实验。拉杆的一端用来装绳结，而另一端是空着的。测量的力-位移响应用于验证FEM和DEM模拟。利用这些经过验证的计算框架，我们分析了沿杆中心线的内部张力分布，发现张力急剧下降集中在一个战略锁定区域周围，其几何形状与其他类型的结相似。在考虑张力、弯曲和摩擦耦合的情况下，我们建立了一个受经典绞盘问题启发的理论模型来预测弓形索的稳定条件，结果与FEM和DEM模拟结果吻合较好。我们的方法和发现为未来研究其他复杂节的性能和可靠性提供了新的工具和见解。

{"title":"Self-locking and stability of the bowline knot","authors":"Bastien F.G. Aymon , Fani Derveni , Michael Gomez , Jérôme Crassous , Pedro M. Reis","doi":"10.1016/j.eml.2025.102413","DOIUrl":"10.1016/j.eml.2025.102413","url":null,"abstract":"<div><div>We investigate the self-locking of the bowline knot through numerical simulations, experiments, and theoretical analysis. Specifically, we perform two complementary types of simulations using the 3D finite-element method (FEM) and a reduced-order model based on the discrete-element method (DEM). For the FEM simulations, we develop a novel mapping technique that automatically transforms the centerline of the rod into the required knot topology prior to loading. In parallel, we conduct experiments using a nearly inextensible elastic rod tied into a bowline around a rigid cylinder. One end of the rod is pulled to load the knot while the other is left free. The measured force–displacement response serves to validate both the FEM and DEM simulations. Leveraging these validated computational frameworks, we analyze the internal tension profile along the rod’s centerline, revealing that a sharp drop in tension concentrates around a strategic locking region, whose geometry resembles that observed in other knot types. By considering the coupling of tension, bending, and friction, we formulate a theoretical model inspired by the classic capstan problem to predict the stability conditions of the bowline, finding good agreement with our FEM and DEM simulations. Our methodology and findings offer new tools and insights for future studies on the performance and reliability of other complex knots.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102413"},"PeriodicalIF":4.5,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145475482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Peeling adhesion regime transition of elastic tapes 弹性胶带的剥离附着力转变

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

Extreme Mechanics Letters

Pub Date : 2025-10-25 DOI: 10.1016/j.eml.2025.102414

Jianyue Deng , Changhong Linghu 令狐昌鸿 , Shubo Zhang 张舒博 , Zhiyu Ng , Deon Low , Huajian Gao , K. Jimmy Hsia , Haibao Lu

Peeling phenomena are frequently observed in nature and in various applications, including wearables, heterogeneous integration, and 2D materials fabrication. Adhesion plays a critical role in the peeling process. The standard 90-degree peeling test is widely used to measure interfacial adhesion. However, a comprehensive mechanical understanding of the transition across different adhesion regimes—energy-controlled, intermediate, and strength-dominated—remains incomplete. Although many previous theoretical models have discussed these regimes individually, a unified solution with systematic experimental validation across the entire regime spectrum is yet to be obtained. Here we systematically investigate the 90-degree peeling of elastic tapes with varying bending stiffness from rigid substrates through a combination of theoretical analysis, experiments, and finite element analysis (FEA) simulations. A general and explicit expression for the peak peeling force is formulated, capturing the full spectrum of adhesion regimes and predicting the peak force as well as the transition points accurately. The theoretical results exhibit good agreement with experimental measurements and FEA simulations across all three regimes. This study provides a unified solution to the 90-degree peeling process and a practical guideline for the design and evaluation of 90-degree peeling adhesion behavior of elastic tapes.

在自然界和各种应用中经常观察到剥落现象，包括可穿戴设备，异质集成和二维材料制造。附着力在剥离过程中起着至关重要的作用。标准的90度剥离试验被广泛用于测量界面附着力。然而，对不同粘附状态（能量控制、中间和强度主导）之间的过渡的全面的机械理解仍然不完整。尽管许多先前的理论模型已经单独讨论了这些状态，但尚未获得一个统一的解决方案，并在整个状态谱中进行了系统的实验验证。本文通过理论分析、实验和有限元分析（FEA）模拟相结合的方法，系统地研究了具有不同弯曲刚度的弹性带从刚性基板上90度剥落的情况。对于峰值剥离力的一般和明确的表达式被制定，捕捉粘接力的全谱和预测峰值力以及准确的过渡点。理论结果与实验测量和有限元模拟结果吻合良好。本研究为90度剥离过程提供了统一的解决方案，并为弹性胶带90度剥离粘附性能的设计和评价提供了实用指南。

{"title":"Peeling adhesion regime transition of elastic tapes","authors":"Jianyue Deng , Changhong Linghu 令狐昌鸿 , Shubo Zhang 张舒博 , Zhiyu Ng , Deon Low , Huajian Gao , K. Jimmy Hsia , Haibao Lu","doi":"10.1016/j.eml.2025.102414","DOIUrl":"10.1016/j.eml.2025.102414","url":null,"abstract":"<div><div>Peeling phenomena are frequently observed in nature and in various applications, including wearables, heterogeneous integration, and 2D materials fabrication. Adhesion plays a critical role in the peeling process. The standard 90-degree peeling test is widely used to measure interfacial adhesion. However, a comprehensive mechanical understanding of the transition across different adhesion regimes—energy-controlled, intermediate, and strength-dominated—remains incomplete. Although many previous theoretical models have discussed these regimes individually, a unified solution with systematic experimental validation across the entire regime spectrum is yet to be obtained. Here we systematically investigate the 90-degree peeling of elastic tapes with varying bending stiffness from rigid substrates through a combination of theoretical analysis, experiments, and finite element analysis (FEA) simulations. A general and explicit expression for the peak peeling force is formulated, capturing the full spectrum of adhesion regimes and predicting the peak force as well as the transition points accurately. The theoretical results exhibit good agreement with experimental measurements and FEA simulations across all three regimes. This study provides a unified solution to the 90-degree peeling process and a practical guideline for the design and evaluation of 90-degree peeling adhesion behavior of elastic tapes.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102414"},"PeriodicalIF":4.5,"publicationDate":"2025-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145419845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The nonlinear elastic response of magnetorheological elastomers 磁流变弹性体的非线性弹性响应

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

Extreme Mechanics Letters

Pub Date : 2025-10-14 DOI: 10.1016/j.eml.2025.102412

Chao Wang , Yingqi Jia , Arvin Ardebili Sharma , Zhi Zhao , Xiaojia Shelly Zhang

Magnetorheological elastomers (MREs), consisting of a soft elastomeric matrix embedded with rigid (and typically magnetized) particles such as NdFeB, are increasingly used in mechanical and biomedical applications. Accurate modeling of their magneto-mechanical behavior requires first predicting their purely mechanical response. Traditionally, this mechanical prediction has relied on directly measuring the macroscopic response of MREs, either numerically or experimentally, for each particle fraction of interest, a procedure that is both time-consuming and labor-intensive. In this study, we replace that procedure with a simple computational framework that requires only a single measurement on the unfilled elastomer. The framework treats MREs as general incompressible filled elastomers and predicts their nonlinear elastic response by integrating several established modeling techniques. For any physically admissible particle volume fraction, it analytically predicts the macroscopic nonlinear response from the measured properties of the unfilled elastomer. We validate the framework experimentally across a wide range of cross-link densities in the elastomeric matrices, particle volume fractions (0%–28%), and specimen geometries, subjected to both uniform and highly localized large deformations (with local strains up to

\sim

600%). The experimental results show excellent agreement with the computational predictions, confirming the framework as a fast and reliable tool for predicting the nonlinear elastic response of MREs. Consequently, this study offers a practical tool for streamlining the modeling and design of MRE-based structures.

磁流变弹性体（MREs）由嵌入刚性（通常磁化）颗粒（如钕铁硼）的软弹性体基体组成，越来越多地用于机械和生物医学应用。要对其磁力学行为进行精确建模，首先需要预测其纯力学响应。传统上，这种力学预测依赖于直接测量MREs的宏观响应，无论是数值还是实验，对于每个感兴趣的粒子分数，这一过程既耗时又费力。在这项研究中，我们用一个简单的计算框架取代了这一过程，该框架只需要对未填充的弹性体进行一次测量。该框架将MREs视为一般的不可压缩填充弹性体，并通过集成几种已建立的建模技术来预测其非线性弹性响应。对于任何物理上允许的颗粒体积分数，它解析地预测了未填充弹性体的宏观非线性响应。我们在弹性体基质、颗粒体积分数（0%-28%）和试样几何形状的广泛交联密度范围内对框架进行了实验验证，这些结构受到均匀和高度局部化的大变形（局部应变高达~ 600%）的影响。实验结果与计算预测结果吻合良好，证实了该框架是一种快速、可靠的预测mre非线性弹性响应的工具。因此，本研究为简化基于mre的结构的建模和设计提供了实用的工具。

{"title":"The nonlinear elastic response of magnetorheological elastomers","authors":"Chao Wang , Yingqi Jia , Arvin Ardebili Sharma , Zhi Zhao , Xiaojia Shelly Zhang","doi":"10.1016/j.eml.2025.102412","DOIUrl":"10.1016/j.eml.2025.102412","url":null,"abstract":"<div><div>Magnetorheological elastomers (MREs), consisting of a soft elastomeric matrix embedded with rigid (and typically magnetized) particles such as NdFeB, are increasingly used in mechanical and biomedical applications. Accurate modeling of their magneto-mechanical behavior requires first predicting their purely mechanical response. Traditionally, this mechanical prediction has relied on directly measuring the macroscopic response of MREs, either numerically or experimentally, for each particle fraction of interest, a procedure that is both time-consuming and labor-intensive. In this study, we replace that procedure with a simple computational framework that requires only a single measurement on the unfilled elastomer. The framework treats MREs as general incompressible filled elastomers and predicts their nonlinear elastic response by integrating several established modeling techniques. For any physically admissible particle volume fraction, it analytically predicts the macroscopic nonlinear response from the measured properties of the unfilled elastomer. We validate the framework experimentally across a wide range of cross-link densities in the elastomeric matrices, particle volume fractions (0%–28%), and specimen geometries, subjected to both uniform and highly localized large deformations (with local strains up to <span><math><mo>∼</mo></math></span>600%). The experimental results show excellent agreement with the computational predictions, confirming the framework as a fast and reliable tool for predicting the nonlinear elastic response of MREs. Consequently, this study offers a practical tool for streamlining the modeling and design of MRE-based structures.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"81 ","pages":"Article 102412"},"PeriodicalIF":4.5,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145365822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Cross-scale magnetic catheter-magnetic swarm strategy for precise thrombus clearance 跨尺度磁导管-磁群策略精确清除血栓

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

Extreme Mechanics Letters

Pub Date : 2025-10-11 DOI: 10.1016/j.eml.2025.102411

Yunqi Xu , Congcong Lou , Ken Cham-Fai Leung , Xinglong Gong , Shouhu Xuan

Thrombotic vascular occlusion presents a critical clinical emergency requiring rapid and precise intervention to restore blood flow and prevent tissue necrosis. Current therapies are constrained by poor accessibility to deeply seated thrombus and a lack of controlled navigation. Here, we propose a cross-scale thrombus removal strategy based on an integrated "magnetic catheter-magnetic swarm" system that couples a steerable magnetic catheter (macro-scale) with dynamically assembled Fe₃O₄@PDA swarm (micro-scale). Anisotropic Fe₃O₄@PDA nanoparticles were synthesized and magnetically actuated to form dynamic swarm under a rotating magnetic field. The swarm exhibited excellent maneuverability, deformation, and transport in complex and confined environments, while the magnetic catheter enabled precise macroscopic delivery. Driven by external magnetic fields, the swarm generated localized shear forces and hydrodynamic stresses to mechanically disrupt and loosen thrombus, promoting fragmentation and removal. The resulting debris, together with the swarm, was magnetically guided back to the catheter for retrieval, ensuring efficient clearance and minimizing embolism risk. This cross-scale system was validated in a cardiac vascular model, demonstrating safe, controllable, and minimally invasive thrombus removal in complex vascular structures. The proposed approach establishes a mechanics-driven platform for minimally invasive thrombus removal and offers a new paradigm for designing multifunctional micro/nanorobotic systems in biomedical applications.

血栓性血管闭塞是一个关键的临床紧急情况，需要快速和精确的干预，以恢复血液流动和防止组织坏死。目前的治疗方法受到深层血栓难以接近和缺乏控制导航的限制。在这里，我们提出了一种基于集成“磁管-磁群”系统的跨尺度血栓清除策略，该系统将可操纵的磁管（宏观尺度）与动态组装的Fe3O4@PDA群（微观尺度）耦合在一起。合成了各向异性Fe3O4@PDA纳米粒子，并在旋转磁场下磁驱动形成动态蜂群。在复杂和受限的环境中，蜂群表现出出色的机动性、变形性和运输能力，而磁导管则能够实现精确的宏观输送。在外部磁场的驱动下，蜂群产生局部剪切力和流体动力应力，机械地破坏和松动血栓，促进血栓的破碎和去除。由此产生的碎片连同一群碎片一起被磁引导回导管进行回收，确保有效清除并最大限度地降低栓塞风险。该跨尺度系统在心脏血管模型中得到验证，证明了在复杂血管结构中安全、可控和微创的血栓清除。该方法建立了微创血栓清除的力学驱动平台，为生物医学应用中多功能微/纳米机器人系统的设计提供了新的范例。

{"title":"Cross-scale magnetic catheter-magnetic swarm strategy for precise thrombus clearance","authors":"Yunqi Xu , Congcong Lou , Ken Cham-Fai Leung , Xinglong Gong , Shouhu Xuan","doi":"10.1016/j.eml.2025.102411","DOIUrl":"10.1016/j.eml.2025.102411","url":null,"abstract":"<div><div>Thrombotic vascular occlusion presents a critical clinical emergency requiring rapid and precise intervention to restore blood flow and prevent tissue necrosis. Current therapies are constrained by poor accessibility to deeply seated thrombus and a lack of controlled navigation. Here, we propose a cross-scale thrombus removal strategy based on an integrated \"magnetic catheter-magnetic swarm\" system that couples a steerable magnetic catheter (macro-scale) with dynamically assembled Fe<sub>3</sub>O<sub>4</sub>@PDA swarm (micro-scale). Anisotropic Fe<sub>3</sub>O<sub>4</sub>@PDA nanoparticles were synthesized and magnetically actuated to form dynamic swarm under a rotating magnetic field. The swarm exhibited excellent maneuverability, deformation, and transport in complex and confined environments, while the magnetic catheter enabled precise macroscopic delivery. Driven by external magnetic fields, the swarm generated localized shear forces and hydrodynamic stresses to mechanically disrupt and loosen thrombus, promoting fragmentation and removal. The resulting debris, together with the swarm, was magnetically guided back to the catheter for retrieval, ensuring efficient clearance and minimizing embolism risk. This cross-scale system was validated in a cardiac vascular model, demonstrating safe, controllable, and minimally invasive thrombus removal in complex vascular structures. The proposed approach establishes a mechanics-driven platform for minimally invasive thrombus removal and offers a new paradigm for designing multifunctional micro/nanorobotic systems in biomedical applications.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"80 ","pages":"Article 102411"},"PeriodicalIF":4.5,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145333146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0