【新文速递】2024年2月4日固体力学SCI期刊最新文章

 

今日更新：International Journal of Solids and Structures 3 篇，Journal of the Mechanics and Physics of Solids 3 篇，Mechanics of Materials 1 篇，International Journal of Plasticity 3 篇，Thin-Walled Structures 9 篇

International Journal of Solids and Structures

MPNN based graph networks as learnable physics engines for deformation and crack propagation in solid mechanics

Xiao-Ping Zhou, Kai Feng

doi:10.1016/j.ijsolstr.2024.112695

基于 MPNN 的图网络作为可学习的物理引擎，用于固体力学中的变形和裂纹扩展

In this paper, the message passage neural networks (MPNN) based graph networks is proposed for learning and prediction of boundary loading problem in solid mechanics. As a learnable physics engine, the proposed model is designed to learn from historical data to understand the rules of the physical system behind the data, and then to make predictions. By learning the historical displacement field sampling data of 2D intact plate, the proposed model successfully realizes its continuous displacement field prediction. On this basis, the trained model also achieves a good prediction in a plate containing holes under the same loading condition but without training, which verifies the generalization ability of the proposed model. Finally, the crack propagation can be realized by learning the historical data of the plate with prefabricated cracks subjected to tension, which shows the excellent predict ability and exciting prospect of the proposed model.

本文提出了基于消息通道神经网络（MPNN）的图网络，用于学习和预测固体力学中的边界载荷问题。作为一个可学习的物理引擎，所提出的模型旨在通过对历史数据的学习来理解数据背后物理系统的规律，进而进行预测。通过学习二维完整板块的历史位移场采样数据，所提出的模型成功实现了连续位移场预测。在此基础上，经过训练的模型还能在相同加载条件下对含有孔洞但未经过训练的板材进行很好的预测，验证了所提模型的泛化能力。最后，通过学习预制裂缝板在拉力作用下的历史数据，可以实现裂缝扩展，这表明所提模型具有出色的预测能力和令人振奋的前景。

A deep difference collocation method and its application in elasticity problems

Z.M. Huang, L.X. Peng

doi:10.1016/j.ijsolstr.2024.112692

深差分配位法及其在弹性问题中的应用

Based on the coordinate transformation and difference scheme, a deep difference collocation method (DDCM) that solves the partial differential equations (PDEs) via a square domain is proposed in this paper. In most of deep learning-based methods such as physics-informed neural networks (PINNs), boundary losses and calculation of the items of PDEs in a physical domain using automatic differentiation will result in time-consuming training. DDCM utilizes a difference approximation approach to expedite the computation of neural network derivatives, enhancing training efficiency. It is adaptable to irregular physical domains via coordinate transformation and provides versatility in enforcing boundary conditions, enabling partial or total elimination of boundary losses. This research covers the analysis of 2D and 3D elastic problems along with the Kirchhoff plate bending problem. The validity of the introduced method is verified by comparing the obtained results to those from theoretical solutions, Finite Element Method (FEM), and Boundary Element Method (BEM). In comparison with PINN, the proposed methodology demonstrates a notably enhanced computational efficiency in solving PDEs, and exhibits commendable stability under a specified computational memory constraint.

本文基于坐标变换和差分方案，提出了一种通过方域求解偏微分方程（PDEs）的深度差分定位方法（DDCM）。在大多数基于深度学习的方法（如物理信息神经网络（PINN））中，边界损失和使用自动微分计算物理域中的 PDE 项将导致耗时的训练。DDCM 采用差分逼近方法，加快了神经网络导数的计算，提高了训练效率。它可以通过坐标变换适应不规则的物理域，并在强制执行边界条件时提供多功能性，从而可以部分或全部消除边界损失。这项研究涵盖了二维和三维弹性问题以及基尔霍夫板弯曲问题的分析。通过将获得的结果与理论求解、有限元法（FEM）和边界元法（BEM）的结果进行比较，验证了所引入方法的有效性。与 PINN 相比，所提出的方法明显提高了求解 PDE 的计算效率，并在特定的计算内存限制下表现出了值得称道的稳定性。

A strain-gradient elastic theory for special Cosserat rods

Vipin Kumar Yadav, Prakhar Gupta

doi:10.1016/j.ijsolstr.2024.112696

特殊 Cosserat 棒的应变梯度弹性理论

Micro-and nano-rods have been identified for various applications in actuators, sensors, and energy harvesters. This paper develops a general framework for micro-and nano-rods based on the one-dimensional strain-gradient theory for special Cosserat rods that considers large displacement and rotation of the cross section, chirality, and size effects. Initially, we obtain the linear momentum balance and angular momentum balance equations for rods utilizing the three-dimensional strain-gradient elasticity theory. Subsequently, we derive the constitutive relations for the strain-gradient elastic rods while considering material objectivity. We further identify the strain-gradient measures and their corresponding higher-order forces and higher-order moment terms. Using these constitutive relations, we show the applicability of our theory by deriving several closed-form solutions for geometrically nonlinear thin rods undergoing extension, shear, torsion, and bending deformation. Finally, we rigorously examine the effect of the length scale parameter on all these deformations of the strain-gradient elastic special Cosserat rod under classical and higher-order boundary conditions. Our analysis through these interesting examples can help in developing next-generation architected metamaterials using micro-and nano-rods.

微型和纳米杆已被确定可用于致动器、传感器和能量收集器等多种应用领域。本文以特殊 Cosserat 棒的一维应变梯度理论为基础，考虑了横截面的大位移和旋转、手性和尺寸效应，为微型和纳米棒开发了一个通用框架。首先，我们利用三维应变梯度弹性理论获得了棒的线动量平衡和角动量平衡方程。随后，我们在考虑材料客观性的同时，推导出应变梯度弹性杆的构成关系。我们进一步确定了应变梯度量及其相应的高阶力和高阶力矩项。利用这些构成关系，我们推导出了几何非线性细杆在发生拉伸、剪切、扭转和弯曲变形时的几种闭式解，从而证明了我们理论的适用性。最后，我们严格研究了在经典和高阶边界条件下，长度尺度参数对应变梯度弹性特殊 Cosserat 杆件所有这些变形的影响。我们通过这些有趣的例子进行的分析有助于利用微纳米棒开发下一代架构超材料。

Journal of the Mechanics and Physics of Solids

Effective surface forces and non-coherent interfaces within the reduced relaxed micromorphic modeling of finite-size mechanical metamaterials

Leonardo A. Perez Ramirez, Félix Erel-Demore, Gianluca Rizzi, Jendrik Voss, Angela Madeo

doi:10.1016/j.jmps.2024.105558

有限尺寸机械超材料简化松弛微形态建模中的有效表面力和非相干界面

This paper introduces for the first time the concepts of non-coherent interfaces and microstructure-driven interface forces in the framework of micromorphic elasticity. It is shown that such concepts are of paramount importance when studying the response of finite-size mechanical metamaterials at the homogenized macro-scale. The need of introducing interface forces is elucidated through numerical examples comparing reduced relaxed micromorphic simulations to their full-microstructured counterparts. These results provide a milestone for the understanding of metamaterials’ modeling at the homogenized scale and for the use of micromorphic-type models to achieve an accurate upscaling towards larger-scale metamaterials’ structures.

本文首次在微形态弹性框架中引入了非相干界面和微结构驱动界面力的概念。研究表明，这些概念对于研究均质化宏观尺度下有限尺寸机械超材料的响应至关重要。通过对比简化松弛微形态模拟和全微形态模拟的数值实例，阐明了引入界面力的必要性。这些结果为理解超材料在均质化尺度上的建模以及使用微形态模型准确地升级到更大尺度的超材料结构提供了一个里程碑。

Design of origami structures with curved tiles between the creases

Huan Liu, Richard D. James

doi:10.1016/j.jmps.2024.105559

设计折痕间有弧形瓦片的折纸结构

An efficient way to introduce elastic energy that can bias an origami structure toward desired shapes is to allow curved tiles between the creases. The bending of the tiles supplies the energy and the tiles themselves may have additional functionality. In this paper, we present a basic theorem and systematic design methods for quite general curved origami structures that can be folded from a flat sheet, and we present methods to accurately find the stored elastic energy. Here the tiles are allowed to undergo curved isometric mappings, and the associated creases necessarily undergo isometric mappings as curves. These assumptions are consistent with a variety of practical methods for crease design. The h3 scaling of the energy of thin sheets (h=thickness) spans a broad energy range. Different tiles in an origami design can have different values of h, and individual tiles can also have varying h. Following developments for piecewise rigid origami Fan Feng et al. (2020), we develop further the Lagrangian approach and the group orbit procedure in this context. We notice that some of the simplest designs that arise from the group orbit procedure for certain circle groups provide better matches to the buckling patterns observed in compressed cylinders and cones than known patterns.

在折痕之间铺设弧形瓦片是引入弹性能量的有效方法，这种能量可以使折纸结构偏向所需的形状。瓦片的弯曲提供了能量，瓦片本身也可能具有额外的功能。在本文中，我们提出了一个基本定理和系统的设计方法，适用于可从平板折叠的一般曲面折纸结构，并介绍了精确计算所储存的弹性能量的方法。在这里，瓦片可以进行曲线等距映射，相关的折痕也必然进行曲线等距映射。这些假设与折痕设计的各种实用方法一致。褶皱

在折痕之间铺设弧形瓦片是引入弹性能量的有效方法，这种能量可以使折纸结构偏向所需的形状。瓦片的弯曲提供了能量，瓦片本身也可能具有额外的功能。在本文中，我们提出了一个基本定理和系统的设计方法，适用于可从平板折叠的一般曲面折纸结构，并介绍了精确计算所储存的弹性能量的方法。在这里，瓦片可以进行曲线等距映射，相关的折痕也必然进行曲线等距映射。这些假设与各种折痕设计的实用方法一致。薄片能量的 h3 比例（h= 厚度）跨度很大。折纸设计中的不同薄片可以有不同的 h 值，单个薄片也可以有不同的 h 值。根据范锋等（2020）对片状刚性折纸的研究，我们在此背景下进一步发展了拉格朗日方法和群轨道程序。我们注意到，某些圆组的群轨道程序所产生的一些最简单的设计与在压缩圆柱和圆锥中观察到的屈曲模式比已知模式更匹配。

Machine learning and sequential subdomain optimization for ultrafast inverse design of 4D-printed active composite structures

Xiaohao Sun, Luxia Yu, Liang Yue, Kun Zhou, Frédéric Demoly, Ruike Renee Zhao, H. Jerry Qi

doi:10.1016/j.jmps.2024.105561

机器学习和顺序子域优化用于 4D 打印活性复合材料结构的超快逆向设计

Shape transformations of active composites (ACs) depend on the spatial distribution and active response of constituent materials. Voxel-level complex material distributions offer a vast possibility for attainable shape changes of 4D-printed ACs, while also posing a significant challenge in efficiently designing material distributions to achieve target shape changes. Here, we present an integrated machine learning (ML) and sequential subdomain optimization (SSO) approach for ultrafast inverse designs of 4D-printed AC structures. By leveraging the inherent sequential dependency, a recurrent neural network ML model and SSO are seamlessly integrated. For multiple target shapes of various complexities, ML-SSO demonstrates superior performance in optimization accuracy and speed, delivering results within second(s). When integrated with computer vision, ML-SSO also enables an ultrafast, streamlined design-fabrication paradigm based on hand-drawn targets. Furthermore, ML-SSO empowered with a splicing strategy is capable of designing diverse lengthwise voxel configurations, thus showing exceptional adaptability to intricate target shapes with different lengths without compromising high speed and accuracy. As a comparison, for the benchmark three-period shape, the finite element and evolutionary algorithm (EA) method was estimated to need 219 days for the inverse design; the ML-EA achieved the design in 54min; the new ML-SSO with splicing strategy requires only 1.97s. By further leveraging appropriate symmetries, the highly efficient ML-SSO is employed to design active shape changes of 4D-printed lattice structures. The new ML-SSO approach thus provides a highly efficient tool for the design of various 4D-printed, shape-morphing AC structures.

活性复合材料（AC）的形状变化取决于组成材料的空间分布和活性响应。体素级复杂材料分布为实现 4D 打印 AC 的形状变化提供了巨大的可能性，同时也为有效设计材料分布以实现目标形状变化带来了巨大挑战。在此，我们提出了一种集成机器学习（ML）和顺序子域优化（SSO）的方法，用于超快反向设计 4D 印刷交流电源结构。利用固有的顺序依赖性，循环神经网络 ML 模型和 SSO 实现了无缝集成。对于不同复杂程度的多种目标形状，ML-SSO 在优化精度和速度方面都表现出了卓越的性能，可在几秒内得出结果。与计算机视觉技术相结合后，ML-SSO 还能在手绘目标的基础上实现超快、简化的设计-制造范例。此外，采用拼接策略的 ML-SSO 还能设计出不同长度的体素配置，从而在不影响高速度和高精度的前提下，展现出对不同长度复杂目标形状的超强适应性。作为比较，对于基准的三周期形状，有限元和进化算法（EA）方法估计需要 219 天才能完成逆向设计；ML-EA 只需 54 分钟即可完成设计；而采用拼接策略的新型 ML-SSO 仅需 1.97 秒。通过进一步利用适当的对称性，高效的 ML-SSO 被用于设计 4D 印刷晶格结构的主动形状变化。因此，新的 ML-SSO 方法为设计各种 4D 印刷形状可变交流结构提供了高效工具。

Mechanics of Materials

On strength and toughness of soft staggered composites

Suhib Abu-Qbeitah, Mahmood Jabareen, Konstantin Y. Volokh

doi:10.1016/j.mechmat.2024.104935

关于软交错复合材料的强度和韧性

In the search of light yet strong and tough materials the nature produced soft composites with the staggered architecture. In such design, a soft protein matrix connects rigid mineral platelets similar to the cement connecting bricks in construction. In the present work, we examine strength and toughness (the total energy dissipated in fracture) of soft composites from the “first principles”. The latter means that we do not postulate material strength and toughness in advance — they become an outcome of numerical solutions of the initial boundary value problem. We formulate the boundary value problem on the basis of the material-sink approach enforcing the damage description in constitutive equations. In addition to the classical nature-made staggered architecture, we examine some alternative possible designs of platelets inside the soft matrix. Comparisons show that the classical staggered design is the best one (among considered). Nature wins at the moment.

为了寻找轻质而坚固的材料，大自然制造出了具有交错结构的软复合材料。在这种设计中，柔软的蛋白质基质连接着坚硬的矿物小板，就像建筑中连接砖块的水泥一样。在本研究中，我们从 "第一原理 "出发，研究软复合材料的强度和韧性（断裂时耗散的总能量）。后者意味着我们并不预先假定材料的强度和韧性--它们是初始边界值问题数值求解的结果。我们在材料沉降方法的基础上制定边界值问题，并在构成方程中强制进行损伤描述。除了经典的自然交错结构外，我们还研究了软基质内血小板的一些其他可能设计。比较结果表明，经典的交错设计是最好的设计（在所考虑的设计中）。目前，自然胜出。

International Journal of Plasticity

Shock Compression of Porous Copper Containing Helium: Molecular Dynamics Simulations and Theoretical Model

Bao Wu, XinXin Wang, HaoNan Sui, Qiang Bao, AnMin He, HaiQuan Sun, Qiang Wu, Pei Wang

doi:10.1016/j.ijplas.2024.103899

含氦多孔铜的冲击压缩：分子动力学模拟和理论模型

Shock compression of porous copper containing helium is studied via non-equilibrium molecular dynamic simulations. The results show that the shock propagation exhibits an elastic-plastic double-shockwave structure at low shock velocity. The shock Hugoniot elastic limit increases with higher gas concentration, and decreases with larger porosity, while almost independent of the shock velocity. The back-and-forth propagation of elastic shockwave between plastic shockwave and free surface leads to the occurrence of the special structure of “surface cap”, which can protect the porous metal in the vicinity of the free surface from collapse. The plastic shock propagates faster with higher gas concentration and gradually catches up with the elastic shockwave as shock intensity increases. Compared with porous copper without gas, the presence of helium significantly inhibits the post-shock temperature rising and the shock melting behavior. A new theoretical model was proposed to quantify the shock Hugoniot of porous materials containing gas. The model's predictions align well with MD simulations across a wide pressure range up to 100 GPa with different gas concentrations and porosities.

通过非平衡分子动力学模拟研究了含氦多孔铜的冲击压缩。结果表明，在低冲击速度下，冲击波的传播呈现出弹塑性双冲击波结构。冲击休格尼奥特弹性极限随气体浓度的增加而增加，随孔隙率的增大而减小，但几乎与冲击速度无关。弹性冲击波在塑性冲击波和自由表面之间的来回传播导致了 "表面帽 "这种特殊结构的出现，它可以保护自由表面附近的多孔金属免于坍塌。气体浓度越高，塑性冲击波传播速度越快，随着冲击强度的增加，塑性冲击波逐渐赶上弹性冲击波。与不含气体的多孔铜相比，氦的存在明显抑制了冲击后的温度上升和冲击熔化行为。研究人员提出了一个新的理论模型来量化含有气体的多孔材料的冲击休格尼奥。在高达 100 GPa 的宽压力范围内，该模型的预测结果与不同气体浓度和孔隙率的 MD 模拟结果非常吻合。

Investigation of failure mechanisms in dual-phase steels through cohesive zone modeling and crystal plasticity frameworks

Ilbilge Umay Aydiner, Berkehan Tatli, Tuncay Yalçinkaya

doi:10.1016/j.ijplas.2024.103898

通过内聚区建模和晶体塑性框架研究双相钢的失效机理

Dual-phase (DP) steels are characterized by their good formability and interesting material properties, which primarily originate from their unique composition, combining the ductile ferrite phase with the hard martensite phase. At the microscale, DP steels exhibit various fracture mechanisms that need to be investigated through proper plasticity and failure models. These mechanisms include interface decohesion between ferrite-martensite and ferrite-ferrite phases, as well as martensite cracking, depending on the steel’s microstructure. In this study, crystal plasticity and cohesive zone frameworks are employed together with a ductile failure model in 3D polycrystalline Representative Volume Element simulations to address the multiscale characteristics of the fracture mechanisms in DP steels. The analysis requires an extensive parameter identification procedure, which is presented in detail. The obtained results demonstrate the framework’s capability to effectively identify the primary failure mechanisms correlated with crucial microstructural features, including crystallographic orientation, morphology, volume fraction, and stress triaxiality. Findings indicate that an increase in the connectivity of the martensitic phase induces a shift from ferrite-ferrite decohesion to ferrite-martensite decohesion and martensite cracking. Similarly, as the volume fraction of martensite increases, decohesions become constrained, making martensite cracking the main failure mode. The numerical observations regarding triaxiality highlight that as stress triaxiality increases, the predominant failure mechanism is changed from martensite cracking and ferrite-martensite decohesion to ferrite-ferrite decohesion.

双相钢（DP）具有良好的成型性和有趣的材料特性，这主要源于其独特的成分，即韧性铁素体相与硬质马氏体相的结合。在微观尺度上，DP 钢表现出多种断裂机制，需要通过适当的塑性和失效模型进行研究。这些机制包括铁素体-马氏体相和铁素体-铁素体相之间的界面脱粘，以及马氏体开裂，具体取决于钢的微观结构。在本研究中，晶体塑性和内聚区框架与三维多晶代表体积元素模拟中的韧性破坏模型结合使用，以解决 DP 钢中断裂机制的多尺度特性问题。分析需要大量的参数识别过程，本文对此进行了详细介绍。获得的结果表明，该框架能够有效识别与关键微结构特征相关的主要断裂机制，包括晶体取向、形态、体积分数和应力三轴性。研究结果表明，马氏体相连接性的增加会导致从铁素体-铁素体解粘转变为铁素体-马氏体解粘和马氏体开裂。同样，随着马氏体体积分数的增加，解粘变得受限，使马氏体开裂成为主要的失效模式。有关三轴度的数值观测结果突出表明，随着应力三轴度的增加，主要的失效机制从马氏体开裂和铁素体-马氏体解粘转变为铁素体-铁素体解粘。

Plasticity Induced Anelasticity: The Atomistic Origin

Sanjay Manda, Saurabh Kumar, Namit N. Pai, Lokesh Soni, Ujjal Tewary, Pratyank Rastogi, Syed Asif, Ajay S. Panwar, Indradev Samajdar

doi:10.1016/j.ijplas.2024.103901

塑性诱导的无弹性：原子论起源

Plastic deformation is associated with developments in both dislocation density and residual strain. This study used multi-scale diffraction-based, X-ray as well as electron diffraction, measurements to quantify and relate them. Though both increased with progressive tensile deformation, an inverse orientation dependent relationship clearly emerged. In particular, higher elastically strained regions were accommodated by dislocation walls of lower residual strain. These experimental observations provided a combined perspective of elastic-plastic strain gradients in experimental plasticity. This study was then was then extended towards anelasticity, or internal friction, as induced by plastic deformation and elastic-plastic strains. Plastic deformation is known to enhance internal friction loss factor, tanδ, which then leads to the so-called dislocation enhanced Snoek (DES) peak. However, the atomistic origin of DES, role of elastic versus plastic strain, has never been established. Experimental nano dynamic mechanical analysis (nano-dma) measurements were used to bring out the plasticity induced DES of near-(001) grains. Experimental DES, however, scaled with both dislocation density and residual strain. This ambiguity necessitated use of numerical simulations to decouple respective contributions. Firstly, continuum finite element simulations indicated a stronger impact of residual stress, than the total stress, on the experimental DES. Further, atomistic modeling simulated (i) single-crystal nano-dma response and (ii) corresponding developments in residual stress as well as dislocation density. In particular, the DES emerged as an attribute of the non-uniform residual strain field(s) associated with dislocation(s). The corresponding change(s) in the anisotropies of local activation energy landscape, for interstitial diffusion of carbon, determined the enhanced Snoek response. Our experiments plus numerical modeling, thus brought out, and for the first time, a unique atomistic perspective towards anelasticity induced by plastic deformation.

塑性变形与位错密度和残余应变的发展有关。本研究利用基于 X 射线和电子衍射的多尺度衍射测量来量化这两者并将其联系起来。虽然二者都会随着拉伸变形的进行而增加，但明显出现了与取向相关的反向关系。特别是，弹性应变较高的区域被残余应变较低的差排壁所容纳。这些实验观察提供了实验塑性中弹性-塑性应变梯度的综合视角。随后，这项研究被扩展到由塑性变形和弹塑性应变引起的无弹性或内摩擦。众所周知，塑性变形会增强内摩擦损耗因子 tanδ，进而导致所谓的位错增强斯诺克（DES）峰。然而，DES 的原子论起源、弹性应变与塑性应变的作用尚未确定。实验性纳米动态机械分析（nano-dma）测量被用来揭示近（001）晶粒的塑性诱导 DES。然而，实验 DES 随位错密度和残余应变而变化。由于这种模糊性，有必要使用数值模拟来分解各自的贡献。首先，连续有限元模拟表明，残余应力比总应力对实验 DES 的影响更大。此外，原子模型模拟了 (i) 单晶纳米-dma 响应和 (ii) 残余应力以及位错密度的相应发展。特别是，DES 是与位错相关的非均匀残余应变场的属性。碳间隙扩散时，局部活化能景观各向异性的相应变化决定了斯诺克反应的增强。因此，我们的实验加上数值建模，首次以独特的原子论视角揭示了塑性变形引起的无弹性。

Thin-Walled Structures

Protection mechanism of liquid-filled welded square steel container with polyurea elastomer subjected to small-arms bullet

Chen Tao, Chong Ji, Jiangang Tu, Yuting Wang, Changxiao Zhao, Xin Wang

doi:10.1016/j.tws.2024.111668

聚脲弹性体充液焊接方钢容器在小武器子弹下的保护机制

The hydrodynamic ram (HRAM) caused by projectile impact would cause severe local damage to and overall deformation of a liquid-filled container. To prevent serious damage and rapid loss of an internal liquid in a thin-walled liquid-filled container upon high-velocity impact, a method involving spraying polyurea elastomer to enhance the impact protection performance of a container was proposed. A ballistic gun was used to launch small-arms bullet to impact a polyurea-coated liquid-filled square steel tube (PCST), and the macroscopic damage characteristics were obtained. The microscopic damage characteristics of polyurea were observed by scanning electron microscopy, the expansion process of cavity in water was photographed by high-speed photography, and the influence mechanism of polyurea layer on HRAM and container protection was further explained by numerical simulation. Results showed that the deflection deformation of the PCST initially increased and then decreased with increasing polyurea thickness. When the thickness of the polyurea was 4 mm, the maximum deflection deformation decreased to 76.3% of that in the bare container. Competition was observed between the restraint of the polyurea layer and the influence of projectile deceleration on the HRAM, and the protective effect was weakened when the polyurea layer was thin. The polyurea dominated the overall constraint of the structure, and the enhancement of the HRAM aggravated tearing damage at the weak corner-welded joint. When the protective effect was enhanced, the protective ability of the polyurea layer to enhance the liquid-filled container was manifested in two aspects. First, the “self-healing” of polyurea blocked the bullet hole on the steel plate and prevented internal liquid leakage. Second, the energy absorption and deceleration of polyurea weakened the water, thereby reducing damage to the container.

弹丸冲击造成的流体动力冲撞（HRAM）会对充液容器造成严重的局部损坏和整体变形。为了防止薄壁充液容器在受到高速撞击时内部液体的严重破坏和快速流失，提出了一种喷涂聚脲弹性体以提高容器撞击防护性能的方法。使用弹道枪发射小型武器子弹撞击聚脲涂层充液方钢管（PCST），获得了宏观损伤特征。利用扫描电子显微镜观察了聚脲的微观损伤特征，通过高速摄影拍摄了空腔在水中的膨胀过程，并通过数值模拟进一步解释了聚脲层对 HRAM 和容器保护的影响机理。结果表明，随着聚脲厚度的增加，PCST 的挠曲变形先增大后减小。当聚脲厚度为 4 毫米时，最大挠曲变形下降到裸容器的 76.3%。聚脲层的约束和弹丸减速对 HRAM 的影响之间存在竞争，当聚脲层较薄时，保护作用减弱。聚脲在结构的整体约束中占主导地位，而 HRAM 的增强加剧了薄弱的角焊缝处的撕裂破坏。当保护效果增强时，聚脲层对充液容器的保护能力增强表现在两个方面。首先，聚脲的 "自我修复 "功能堵住了钢板上的弹孔，防止了内部液体泄漏。其次，聚脲的吸能和减速作用削弱了水的作用，从而减少了对容器的损坏。

Buckling and Post-Buckling Behavior of Top Flange Coped I-Beams with Slender Web Panels

Abbas Ghadami, Akram Jawdhari, Ghazaleh PourMoosavi

doi:10.1016/j.tws.2024.111640

带细长腹板的顶部翼缘加坡工字钢的屈曲和屈曲后行为

In this work, a comprehensive parametric study, based on a robust finite element analysis validated by existing experimental results, was conducted to investigate the effects of plate slenderness, cope details, i.e. depth (dc), length (Lc), and initial geometrical imperfection, on the elastic, inelastic, and post-buckling behavior of top flange coped I-beams with slender web panel (CBSW). The analysis results showed that the primary failure mode is elastic/inelastic shear local buckling, resulting in the formation of an inclined tension field band on the coped web from the cope corner during the post-buckling stage. The ultimate resistance and failure mode of CBSWs are generally affected by both cope details and imperfection magnitude. A small cope (dc/D≤0.2 and Lc/D≤0.2, where D is beam depth) has a negligible effect on the elastic buckling mode shape and elastic local buckling resistance of CBSWs. Moreover, the failure mode of CBSWs generally shifts from inelastic local buckling to elastic local buckling (ELB) when decreasing the imperfection magnitude or increasing the web slenderness, cope depth, and cope length. The current design equations were found to accurately predict the ELB resistance of CBSWs with a maximum difference within 13%, but grossly overestimate (some cases up to 117%) the ultimate strength of CBSWs with small cope areas. To address this, a new equation was developed and significant improvement in the accuracy of the design prediction was obtained, particularly for CBSWs with small copes.

在这项工作中，我们基于稳健的有限元分析并通过现有的实验结果进行了验证，开展了一项全面的参数研究，以探讨板的细长度、锁口细节（即深度 (dc)、长度 (Lc)）和初始几何缺陷对带细长腹板的上翼缘锁口工字钢 (CBSW) 的弹性、非弹性和后屈曲行为的影响。分析结果表明，主要的破坏模式是弹性/非弹性剪切局部屈曲，导致在后屈曲阶段从斜角开始在连接腹板上形成倾斜的拉力场带。CBSW 的极限阻力和失效模式通常受拱缘细节和缺陷大小的影响。小拱度（dc/D≤0.2 和 Lc/D≤0.2，其中 D 为梁深度）对 CBSW 的弹性屈曲模式形状和弹性局部屈曲阻力的影响可以忽略不计。此外，当减小不完善度或增加腹板细长度、腹板深度和腹板长度时，CBSW 的破坏模式一般会从非弹性局部屈曲转变为弹性局部屈曲（ELB）。研究发现，目前的设计公式能准确预测 CBSW 的 ELB 抗力，最大差异在 13% 以内，但却严重高估了（某些情况下高达 117%）小坡口面积 CBSW 的极限强度。为了解决这个问题，我们开发了一个新的方程，大大提高了设计预测的准确性，尤其是对小拱顶的 CBSW 而言。

Laboratory tests, numerical simulations and design of austenitic stainless steel semi-oval hollow section columns

Shuai Li, Ou Zhao

doi:10.1016/j.tws.2024.111648

奥氏体不锈钢半椭圆空心截面柱的实验室测试、数值模拟和设计

Semi-oval hollow section is an innovative cross-section profile and consists of one semi-circular flange, one flat flange and two flat webs. While the semi-circular flange (exposed to fluid or wind) offers a low level of hydrodynamic or aerodynamic drag, the flat elements facilitate connections with other members. The flexural buckling behaviour and resistances of austenitic stainless steel semi-oval hollow section columns are investigated in this paper. An experimental programme was firstly conducted on two austenitic stainless steel semi-oval hollow sections, with six column specimens of varying member lengths adopted for each cross-section, and included tensile coupon tests, initial geometric imperfection measurements and pin-ended column tests. Both ‘C’-shaped flexural buckling (with failure specimens bowing towards semi-circular flanges) and ‘reverse C’-shaped flexural buckling (with failure specimens bowing towards flat flanges) were observed upon testing. The experimental programme was accompanied by a numerical modelling programme, with finite element models developed to simulate the test results and then adopted to conduct parametric studies to generate further numerical data. On the basis of the test and numerical data, the relevant buckling curves for austenitic stainless steel circular hollow section columns, as provided in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to austenitic stainless steel semi-oval hollow section columns. The evaluation results generally revealed that the codified buckling curves led to overall accurate and consistent flexural buckling resistance predictions when used for austenitic stainless steel semi-oval hollow section columns.

半椭圆形空心截面是一种创新的截面型材，由一个半圆形凸缘、一个扁平凸缘和两个扁平腹板组成。半圆形凸缘（暴露在流体或风中）提供了较低的流体动力或空气阻力，而扁平元件则便于与其他构件连接。本文研究了奥氏体不锈钢半椭圆形空心截面柱的挠曲屈曲行为和阻力。首先对两个奥氏体不锈钢半椭圆形空心截面进行了实验，每个截面采用六个不同长度的柱试样，包括拉伸试样试验、初始几何缺陷测量和针端柱试验。试验中观察到了 "C "形弯曲屈曲（失效试样向半圆形凸缘弯曲）和 "反 C "形弯曲屈曲（失效试样向扁平凸缘弯曲）。在开展试验项目的同时，还进行了数值建模项目，开发了有限元模型来模拟试验结果，然后采用有限元模型进行参数研究，以生成进一步的数值数据。根据试验和数值数据，对欧洲规范、美国规范和澳大利亚/新西兰标准中规定的奥氏体不锈钢圆形空心截面柱的相关屈曲曲线进行了评估，以确定其是否适用于奥氏体不锈钢半椭圆形空心截面柱。评估结果普遍表明，在奥氏体不锈钢半椭圆形空心截面柱中使用编纂的屈曲曲线时，可获得总体准确且一致的抗弯曲屈曲性能预测。

Seismic behavior of prefabricated thin-walled CFST double-column bridge piers

Chao Gu, Xuanding Wang, Xuhong Zhou, Xiang Li, Yue Liao, Nina Zheng

doi:10.1016/j.tws.2024.111654

预制薄壁 CFST 双柱桥墩的抗震性能

This paper investigates the seismic behavior of a prefabricated thin-walled concrete-filled steel tubular (CFST) pier system composed of circular thin-walled CFST double-column, I-shaped steel beam, and precast reinforced concrete (RC) cap beam. Hysteretic tests were conducted on two slender double-column pier systems: one with prefabricated connections (prefabricated pier system), and the other one with traditional embedded connections (traditional pier system). The test results indicated that, compared with the traditional pier system, the pier system with prefabricated connections demonstrating an 18% increase in lateral resistance and a 5% higher ductility coefficient, despite the weld of the steel beam cracked prematurely. Finite-element numerical models were established based on the OpenSees platform and validated by the cyclic loading tests. A comprehensive investigation involving a total of 12 cases, encompassing both CFST piers and RC piers, was conducted to evaluate their seismic performance and economic efficiency. The analysis results revealed that the proposed prefabricated pier system offers notable advantages in seismic performance for both tall and low piers.

本文研究了由圆形薄壁 CFST 双柱、工字形钢梁和预制钢筋混凝土（RC）盖梁组成的预制薄壁混凝土填充钢管（CFST）桥墩系统的抗震行为。对两种细长双柱桥墩系统进行了静力试验：一种是预制连接（预制桥墩系统），另一种是传统预埋连接（传统桥墩系统）。试验结果表明，与传统桥墩系统相比，尽管钢梁焊缝过早开裂，但采用预制连接的桥墩系统的抗侧能力提高了 18%，延性系数提高了 5%。基于 OpenSees 平台建立了有限元数值模型，并通过循环加载试验进行了验证。对 CFST 墩柱和 RC 墩柱共 12 个案例进行了综合调查，以评估其抗震性能和经济效益。分析结果表明，无论是高墩还是低墩，拟议的预制墩系统在抗震性能方面都具有显著优势。

Passive vibration control of subsonic thin plate via nonlinear capacitance and negative capacitance coupled piezoelectric shunt damping

Chao Wang, Guo Yao, Mingyu Liu

doi:10.1016/j.tws.2024.111656

通过非线性电容和负电容耦合压电分流阻尼实现亚音速薄板的被动振动控制

As part of the aircraft wing, the thin plate is always affected by external airflow and harmonic excitation to generate undesirable nonlinear vibration behaviors, which will produce fatigue and damage to the aircraft. Therefore, it is necessary to develop some schemes for vibration control of subsonic thin plates. This work proposes a nonlinear piezoelectric shunt damping for nonlinear vibration control of subsonic thin plates. The nonlinear motion equation of the electromechanical coupling system is established by the extended Hamilton principle. The subsonic aerodynamic model is introduced by linear potential flow theory. Three different piezoelectric control circuits made up of inductance, resistance, nonlinear capacitance, and negative capacitance are considered. The nonlinear dynamic equations are solved by the Matcont toolbox. The first four generalized coordinates before and after the piezoelectric vibration control of the system are discussed. It can be observed that piezoelectric control has significant vibration suppression effects. The vibration control effects of three different piezoelectric control circuits are compared under different external excitation amplitude and airflow velocities. This study provides a relatively perfect piezoelectric control scheme for the vibration control of thin plates in subsonic airflow.

作为飞机机翼的一部分，薄板总是受到外部气流和谐波激励的影响，产生不良的非线性振动行为，从而产生疲劳并损坏飞机。因此，有必要开发一些亚音速薄板振动控制方案。本研究提出了一种用于亚音速薄板非线性振动控制的非线性压电分流阻尼。机电耦合系统的非线性运动方程由扩展汉密尔顿原理建立。亚音速空气动力学模型由线性势流理论引入。考虑了由电感、电阻、非线性电容和负电容组成的三种不同的压电控制电路。非线性动态方程由 Matcont 工具箱求解。讨论了系统压电振动控制前后的前四个广义坐标。可以看出，压电控制具有显著的振动抑制效果。比较了三种不同压电控制电路在不同外部激励振幅和气流速度下的振动控制效果。这项研究为亚音速气流中薄板的振动控制提供了一种相对完美的压电控制方案。

Highly Stretchable, Sensitive and Healable Polyurethane-urea/Graphene Nanocomposite Sensor for Multifunctional Applications

Yin Yu, Zhaoyang Xu, Lisheng Xu, Yikuan Li, Tianqing Liu, Qingshi Meng, Xiao Su, Hsu-Chiang Kuan, Jiabin Dai, Jun Ma

doi:10.1016/j.tws.2024.111660

用于多功能应用的高拉伸性、灵敏性和可愈合性聚氨酯尿素/石墨烯纳米复合材料传感器

Flexible wearable electronic devices offer promising potential for monitoring physiological signals. However, creating a single sensor that integrates high tensile strength, sensitivity, self-healing capabilities, and a wide working range presents a significant and multifaceted challenge. This study reports a novel nanocomposite consisting of polyurethane-urea elastomer (PUU) and graphene nanoplatelets (E-GNPs) that are mechanochemically modified with diethyltoluene diamine ethacure 100. A low electrical percolation threshold was observed at 4.17 vol% E-GNPs. The sensor based on the PUU nanocomposite at 7 vol% of graphene has revealed a gauge factor up to 17.57 and a wide working range of 361.76% with high tensile strength of 19.73 MPa. It can withstand 20,000 cycles at 50% strain. The sensor exhibits negative temperature dependence at 20–100 °C, with a resolution of 0.01/°C at 36–40 °C. Treatments with solvents and heat enable a healing efficiency for sensitivity of up to 70.46%. The healable sensor enables real-time monitoring of temperature and strain signals, making it ideal for wearable devices in human health and sports monitoring.

柔性可穿戴电子设备具有监测生理信号的巨大潜力。然而，创建一个集高拉伸强度、高灵敏度、自愈能力和宽工作范围于一体的传感器是一项重大而多方面的挑战。本研究报告介绍了一种新型纳米复合材料，它由聚氨酯尿素弹性体（PUU）和石墨烯纳米片（E-GNPs）组成，并用二乙基甲苯二胺乙醯化物 100 对其进行了机械化学修饰。在 4.17 Vol% 的 E-GNPs 中观察到了较低的电渗阈值。基于石墨烯含量为 7 Vol% 的 PUU 纳米复合材料的传感器的测量系数高达 17.57，工作范围宽达 361.76%，抗拉强度高达 19.73 MPa。在 50%应变下，它可以承受 20,000 次循环。该传感器在 20-100 °C时呈负温度依赖性，在 36-40 °C时分辨率为 0.01/°C。使用溶剂和热处理可使灵敏度的愈合效率高达 70.46%。这种可愈合传感器能够实时监测温度和应变信号，是人体健康和运动监测领域可穿戴设备的理想选择。

Investigations on Low-Velocity Ballistic Impact behaviour of Kevlar / Epoxy Composites Reinforced with Chopped Wet Spun Fibers Intruded with Nanofillers

Nitin Mathusoothanaperumal Sukanya, Suresh Kumar Sundaram

doi:10.1016/j.tws.2024.111665

用纳米填料填充的切碎湿法纺丝纤维增强的 Kevlar / 环氧树脂复合材料的低速弹道冲击性能研究

The low-velocity ballistic behaviour of chopped fiber-reinforced Kevlar Epoxy composites has been investigated. The chopped fibers of ‘Poly Vinyl Alcohol’ were fabricated using a wet spinning machine and intruded with functionalised Carbon Nanotubes and reduced Graphene Oxide (rGO) both individually and synergistically. The characterisation performed on the spun fibers indicated that the addition of fillers improved the properties owing to the increase in the surface interactions. The tensile strength was seen to increase with the addition of fillers and a maximum improvement of 214.74 % was observed for the fiber with both CNT and rGO filler addition. These fibers were chopped and incorporated into the composites prepared by the ‘hand layup’ process. Tensile and Inter Laminar Shear Strength tests conducted on the prepared composite samples revealed that the hybrid samples had the maximum values. The chopped fiber with both the filler addition had an improvement of 15.02 % in tensile strength, 17.45 % in modulus and 67% in Inter Laminar Shear Stress (ILSS). This combination had the highest resistance to the projectile's motion under low-velocity ballistic impact also. All the targets were able to ‘ricochet’ the projectile with large Depth of Penetration values. The lowest DoP, lowest strike face cracking and no delamination was observed for the optimum reinforced composite target. The presence of chopped fiber improves the toughness by crack bridging, load sharing and creating prestressing in the composite.

研究了短切纤维增强凯夫拉环氧树脂复合材料的低速弹道性能。聚乙烯醇 "短切纤维是用湿法纺纱机制造的，并单独或协同添加了功能化碳纳米管和还原氧化石墨烯（rGO）。对纺出的纤维进行的特性分析表明，由于表面相互作用的增加，填充物的添加改善了纤维的特性。拉伸强度随着填料的添加而增加，添加了 CNT 和 rGO 填料的纤维的拉伸强度最大提高了 214.74%。这些纤维被切碎并加入到通过 "手糊 "工艺制备的复合材料中。对制备的复合材料样品进行的拉伸和层间剪切强度测试表明，混合样品的拉伸和层间剪切强度值最大。同时添加两种填料的切碎纤维的拉伸强度提高了 15.02%，模量提高了 17.45%，层间剪切应力提高了 67%。在低速弹道冲击下，这种组合对弹丸运动的阻力也最大。所有目标都能以较大的穿透深度值 "弹射 "弹丸。最佳增强复合材料靶材的穿透深度最低，打击面裂纹最少，且无分层现象。切碎纤维的存在通过裂缝桥接、负载分担和在复合材料中产生预应力来提高韧性。

Experimental and numerical study on the protective mechanism of the full helmet subjected to blast loadings

Yongqiang Li, Jun Lin, Sheng Liu, Hengyi Zhu, He Zhang, Hualin Fan

doi:10.1016/j.tws.2024.111666

爆炸荷载下全头盔保护机制的实验和数值研究

The efficacy of full helmets in ballistic protection is well established. However, their effectiveness against blasts remains uncertain. The study combines free-field blast tests and numerical simulations to comprehensively investigate the protective mechanism of the full helmet under blast shock waves. Four blast tests are conducted on a hybrid III dummy head model with various helmet configurations. Simultaneously, finite element (FE) models are developed to explore full helmet protection. Five blast scenarios are simulated, including bare head, helmet-head, helmet-mandible guard-head, helmet-visor-head, and full helmet models. The experimental results indicate that wearing the full protective helmet can effectively mitigate overpressure at the eyes and forehead, and the sealing of the helmet significantly affects the attenuation of the peak overpressure. The simulation results reveal that the full helmet can dramatically attenuate the head overpressure in the frontal blast but cause localized overpressure amplification due to the underwash effect. Meanwhile, shock wave propagation heavily relies on the gap between the head and foam pads. The effect of blast loading directions and helmet-mandible guard gap on the head overpressure are investigated. The findings indicate that the mandible guard and visor can cause localized overpressure amplification. The overpressure on the eyes and forehead regions has a linear relationship with the gap between the helmet and mandible guard.

全盔在防弹方面的功效已得到公认。然而，它们对爆炸的防护效果仍不确定。本研究结合自由场爆炸试验和数值模拟，全面研究了爆炸冲击波下全头盔的防护机制。在混合三代假人头部模型上进行了四次爆炸试验，头盔配置各不相同。同时，还开发了有限元（FE）模型，以探索全头盔的保护机制。模拟了五种爆炸场景，包括裸头、头盔-头、头盔-易碎护板-头、头盔-遮阳板-头和全头盔模型。实验结果表明，佩戴全防护头盔能有效缓解眼睛和前额处的过压，头盔的密封性对峰值过压的衰减有显著影响。模拟结果表明，在正面爆炸中，全防护头盔可显著减弱头部超压，但由于下冲效应会导致局部超压放大。同时，冲击波的传播在很大程度上依赖于头部和泡沫垫之间的间隙。研究了爆炸加载方向和头盔与下颚护板间隙对头部超压的影响。研究结果表明，下颚护板和面罩会导致局部过压放大。眼睛和前额区域的过压与头盔和下颚防护罩之间的间隙呈线性关系。

Hierarchical design and coupling deformation of lattice structures with variable unit cells manufactured by laser powder bed fusion

Dongming Li, Bingzhi Chen, Deyu Yue, Tongyuan Sun, Xu Zhang

doi:10.1016/j.tws.2024.111667

通过激光粉末床熔融技术制造的具有可变单元格的晶格结构的分层设计和耦合变形

With the development of additive manufacturing technology, lattice structures with complex topological shapes can be manufactured. In order to combine the advantages of stretch dominance and bend dominance, a hierarchical lattice structure composed of variable unit cell is proposed. The hierarchical lattice structures are manufactured by laser powder bed fusion (LPBF). Five different cell arrangement combinations are designed based on face centered cubic (FCC) with octet truss structure (OTS) at the macro scale. The mechanical performance and deformation behavior of the hierarchical lattice was investigated systematically through compressive experiments and numerical simulations. The deformation modes were captured with a digital camera. Then, the crashworthiness design on the Row layered structure parametric analysis was performed to discuss the effect of geometrical parameters including component ratio and size ratio. The results indicated that the hierarchical structure exhibits a mixed deformation mode among those the Row layered structure has the best energy absorption characteristics. And the specific ratios of these geometrical parameters significantly enhance the energy absorption of hierarchical structure. Overall, this work not only provides a novel solution for designing hierarchical structures, but also highlights the advantages of additive manufacturing techniques for manufacturing complex structures.

随着增材制造技术的发展，具有复杂拓扑形状的晶格结构可以被制造出来。为了结合拉伸优势和弯曲优势，本文提出了一种由可变单元格组成的分层晶格结构。分层晶格结构是通过激光粉末床熔融（LPBF）制造的。在宏观尺度上，基于面心立方（FCC）和八元桁架结构（OTS）设计了五种不同的单元排列组合。通过压缩实验和数值模拟，系统地研究了分层晶格的机械性能和变形行为。用数码相机捕捉了变形模式。然后，对行列式分层结构进行了耐撞性设计参数分析，讨论了几何参数（包括部件比和尺寸比）的影响。结果表明，分层结构表现出混合变形模式，其中，Row 分层结构具有最佳的能量吸收特性。而这些几何参数的特定比例能显著提高分层结构的能量吸收能力。总之，这项工作不仅为分层结构的设计提供了一种新的解决方案，而且凸显了增材制造技术在制造复杂结构方面的优势。