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【新文速递】2024年12月26日固体力学SCI期刊最新文章

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

International Journal of Solids and Structures

Isolating the effects of deviatoric and hydrostatic stress on damage evolution using cold extrusion experiments

Robin Gitschel, Johannes Gebhard, Yannis P. Korkolis, A. Erman Tekkaya

doi:10.1016/j.ijsolstr.2024.113205

用冷挤压实验分离了偏应力和静水应力对损伤演化的影响

Ductile damage evolution is known to be dependent on stress triaxiality and Lode parameter. An experimental isolation of these two influencing factors is challenging, especially at large plastic strains, since a variation of the Lode parameter is usually accompanied by a variation in the triaxiality. In this study, forward rod extrusion and forward hollow extrusion are utilized to induce Lode parameters (L) of −1 and 0, respectively, while keeping the triaxiality and the plastic equivalent strain the same in both processes. For the triaxiality this is accomplished by superposing hydrostatic pressure by a counterpunch during forward rod extrusion. This allows for the first time, to the author’s knowledge, to experimentally study the isolated effect of the Lode parameter on void evolution at large plastic strains, and the resulting effects on product performance like impact toughness. Mass density measurements and scanning electron microscopy (SEM) on extruded samples of the case hardening steel 16MnCrS5 reveal an increased damage evolution under L = 0 as compared to L = −1. The SEM investigations show a distinct switch in void nucleation mechanisms from cracking of manganese sulphide inclusions for L = −1 to cracking and debonding of inclusions and surrounding matrix for L = 0. The debonding occurs in a preferred direction, leading to anisotropic void area fractions. The locations of inclusion-matrix-debonding are verified by evaluation of interface stresses between matrix and inclusion in representative volume element simulations. While the impact toughness of specimens extracted along different orientations is consistently different, this cannot be conclusively attributed only to the corresponding microscopic damage anisotropy.

已知延性损伤的演化取决于应力三轴性和Lode参数。在实验中分离这两个影响因素是具有挑战性的,特别是在大塑性应变下,因为Lode参数的变化通常伴随着三轴性的变化。本研究采用前向杆挤压和前向空心挤压分别诱导Lode参数(L)为- 1和0,同时保持三轴性和塑性等效应变相同。对于三轴性,这是通过在向前杆挤压过程中由反击器叠加静水压力来完成的。据作者所知,这允许首次通过实验研究Lode参数在大塑性应变下对空洞演化的孤立影响,以及由此产生的对产品性能(如冲击韧性)的影响。对16MnCrS5淬火钢挤压试样的质量密度测量和扫描电镜(SEM)结果表明,与L = −1相比,L = 0时损伤演化增加。扫描电镜研究表明,孔洞成核机制发生了明显的转变,从L = −1时硫化锰包裹体的开裂到L = 0时包裹体和周围基体的开裂和脱粘。脱粘发生在一个优先方向,导致各向异性空洞面积分数。在具有代表性的体元模拟中,通过评价基体与夹杂体之间的界面应力,验证了夹杂体-基体-脱粘的位置。虽然沿不同方向提取的试样的冲击韧性始终不同,但这不能完全归结为相应的微观损伤各向异性。


Journal of the Mechanics and Physics of Solids

Wavelength selection in the twist buckling of pre-strained elastic ribbons

Arun Kumar, Basile Audoly

doi:10.1016/j.jmps.2024.106005

预应变弹性带扭曲屈曲中的波长选择

A competition between short- and long-wavelength twist buckling instabilities has been reported in experiments on thin elastic ribbons having pre-strain concentrated in a rectangular region surrounding the axis. The wavelength of the twisting mode has been reported to either scale (i) as the width of the ribbon when the pre-strain is large (short-wavelength case) or (ii) as the length of the ribbon when the pre-strain is small (large-wavelength case). Existing one-dimensional rod or ribbon models can only account for large-wavelength buckling. We derive a novel one-dimensional model that accounts for short-wavelength buckling as well. It is derived from non-linear shell theory by dimension reduction and captures in an asymptotically correct way both the non-convex dependence of the strain energy on the twisting strain τ (which causes buckling) and its dependence on the strain gradient τ′. The competition between short- and long-wavelength buckling is shown to be governed by the sign of the incremental elastic modulus B0 associated with the twist gradient τ′. The one-dimensional model reproduces the main features of equilibrium configurations generated in earlier work using 3D finite-element simulations. In passing, we introduce a novel truncation strategy applicable to higher-order dimension reduction that preserves the positiveness of the strain energy even when the gradient modulus is negative, B0<0.

在对薄弹性带进行的实验中,已报道了短波长和长波长扭转屈曲不稳定性之间的竞争,这些薄弹性带的预应变集中在围绕轴的矩形区域内。据报道,扭转模式的波长要么(i)在预应变较大时与带的宽度成比例(短波长情况),要么(ii)在预应变较小时与带的长度成比例(长波长情况)。现有的一维杆或带模型只能解释长波长屈曲。我们推导出一种新的模型,它能解释短波长屈曲。该模型通过降维从非线性壳理论推导而来,并以渐近正确的方式捕捉了应变能对扭转应变τ的非凸依赖性(这会导致屈曲)以及对应变梯度τ'的依赖性。短波长和长波长屈曲之间的竞争被证明是由与扭转梯度τ'相关的增量弹性模量B0的符号所控制的。一维模型重现了早期使用三维有限元模拟生成的平衡构型的主要特征。顺便说一下,我们引入了一种适用于更高阶维度缩减的新型截断策略,即使梯度模量为负(B0<0),也能保持应变能的正性。


Mechanics of Materials

Identification for elastoplastic constitutive parameters of 316L stainless steel lattice structures using finite element model updating and integrated digital image correlation

Zhaozhen Huang, Caroline Antion, Franck Toussaint

doi:10.1016/j.mechmat.2024.105232

基于有限元模型更新和集成数字图像相关的316L不锈钢晶格结构弹塑性本构参数识别

Lattice structures are widely considered for industrial applications owing to their excellent energy absorption and mechanical properties. In this work, octet-truss lattice structures are manufactured from 316L stainless steel powder by selective laser melting (SLM). The geometrical information of lattice structures is captured by SEM and X-ray tomography. It reveals that realistic dimensions of struts differ slightly from CAD-designed ones. The mechanical behaviors are investigated both experimentally and numerically. Quasi-static uni-axial compression experiments with 2D digital image correlation (DIC) technology are conducted to measure displacement/strain fields. Finite element analysis based on an elastic and anisotropic plastic constitutive model is used to simulate mechanical behaviors. To improve the predictive accuracy, a finite element model updating approach is implemented to identify constitutive parameters. The results show that numerical simulation with optimized parameters match well with experiments in aspect of force-displacement curve at elastic-plastic stage and displacement fields.

晶格结构由于其优异的吸能性能和力学性能,在工业上得到了广泛的应用。本研究以316L不锈钢粉末为原料,采用选择性激光熔化(SLM)法制备八元桁架晶格结构。通过扫描电镜和x射线断层扫描捕捉到晶格结构的几何信息。结果表明,杆的实际尺寸与cad设计的尺寸略有不同。对其力学行为进行了实验和数值研究。采用二维数字图像相关(DIC)技术进行准静态单轴压缩实验,测量位移/应变场。采用基于弹性和各向异性塑性本构模型的有限元分析方法模拟其力学行为。为了提高预测精度,采用有限元模型更新方法识别本构参数。结果表明,优化后的数值模拟结果在弹塑性阶段的力-位移曲线和位移场方面与实验结果吻合较好。


Thin-Walled Structures

Energy dissipation of sand-filled TPMS lattices under cyclic loading

Na Qiu, Yuejing Ding, Jiayi Guo, Jianguang Fang

doi:10.1016/j.tws.2024.112848

循环荷载作用下填砂TPMS格架的能量耗散

A novel recoverable energy-absorbing structure for cyclic loading is introduced in this study: a sand-filled Triply Periodic Minimal Surface (TPMS) lattice. The mechanical properties of these lattices were systematically investigated across different architectures—Primitive (P), Gyroid (G), and Diamond (D)—along with varying filling ratios and sand particle sizes. Additionally, the effects of resting time and loading speeds were analyzed. It was demonstrated that sand-filled TPMS lattices significantly enhance energy dissipation compared to their hollow counterparts, showing improvements of 150% for P, 70% for G, and 30% for D. Notably, all sand-filled TPMS lattices perform similarly, although the P structure exhibits the lowest energy dissipation on its own. The damping capacity of both sand-filled and hollow TPMS lattices was found to improve with extended resting time. However, the sand-filled structures require longer recovery time due to complex interactions between sand particles and TPMS walls, along with the internal friction between sand particles and the resistance to rearrangement. As loading speed increased, the specific energy dissipation (SED) of the hollow P lattice was shown to improve by 98.2%, while that of the sand-filled P100% lattice increased by 41.8%, indicating greater sensitivity of the hollow structure to loading speed. This is because the solid-like P100% structure lacks the internal structure of porous P0% lattice that creates the inertia effects of the cell walls, more localized deformation and stress wave propagation, reducing the impact of higher speeds. Moreover, the structure filled with medium-sized sand particles has higher energy dissipation efficiency because they offer an optimal balance between inter-particle cohesion and flowability, allowing effective void-filling without excessive compaction or loss of mobility. Overall, the sand filling can alleviate the buckling of the walls and strain concentration, thus enhancing energy dissipation without sacrificing mechanical degradation. These findings provide valuable insights into the design of sand-filled TPMS lattices for improving energy dissipation and recoverability under cyclic loading conditions.

本文介绍了一种新的循环荷载可回收吸能结构:砂填充三周期极小表面晶格。系统地研究了这些晶格在不同结构下的力学性能——原始结构(P)、旋转结构(G)和菱形结构(D)——以及不同的填充比和砂粒度。此外,还分析了静置时间和加载速度的影响。结果表明,与空心TPMS晶格相比,填砂TPMS晶格的能量耗散能力显著增强,其中P晶格的能量耗散能力提高150%,G晶格提高70%,d晶格提高30%。值得注意的是,尽管P结构本身的能量耗散最低,但所有填砂TPMS晶格的性能都相似。随着静置时间的延长,填砂和空心TPMS格栅的阻尼能力均有所提高。然而,由于砂粒与TPMS壁之间复杂的相互作用,以及砂粒之间的内摩擦和重排阻力,填砂结构需要更长的恢复时间。随着加载速度的增加,空心P晶格的比能耗散(SED)提高了98.2%,填砂P100%晶格的比能耗散(SED)提高了41.8%,表明空心P晶格对加载速度的敏感性更高。这是因为固体状的P100%结构缺乏多孔的P0%晶格的内部结构,这种结构会产生细胞壁的惯性效应,更多的局部变形和应力波传播,减少了高速的影响。此外,填充中型沙粒的结构具有更高的能量耗散效率,因为它们提供了颗粒间凝聚力和流动性之间的最佳平衡,可以有效地填充空隙,而不会过度压实或失去流动性。总体而言,充砂可以在不牺牲力学退化的情况下,缓解墙体屈曲和应变集中,从而增强能量耗散。这些发现为在循环荷载条件下改善能量耗散和可恢复性的填砂TPMS格架设计提供了有价值的见解。


Research on the Bandgap and Flutter Suppression of Thin-Film Phononic Crystals for Satellite Honeycomb Panels

Zhiyu Ma, Yang Xu, Xiaowei Sheng, Guosheng Xie, Yixin Zhang

doi:10.1016/j.tws.2024.112865

卫星蜂窝板用薄膜声子晶体带隙及颤振抑制研究

Addressing the issue of satellite flutter suppression, a thin-film type localized resonant phononic crystal (FLRPC) is designed based on the satellite honeycomb sandwich panel, with the honeycomb cells filled with flexible materials. The band gap characteristics of FLRPC are explained through band structure and mode vibration mode, and the influence of structural parameters on the band gap characteristics is revealed. The research results show that FLRP forms a complete band gap in a specific frequency range, and the adjustment of structural parameters can adjust the bandwidth and range of the band gap. Subsequently, the measured flutter signal of the satellite cabin panel is collected to verify the flutter suppression ability of FLRPC. FLRPC sandwich panels show better flutter suppression performance than ordinary honeycomb sandwich panels. In addition, this paper proposes a scheme and preparation process for multi-scale FLRPC honeycomb sandwich panels and verifies its flutter suppression performance through flutter suppression simulation and experimental comparison. These results emphasize the application value of FLRPC in satellite flutter suppression and provide a reference scheme for future research.

针对卫星颤振抑制问题,在卫星蜂窝夹层板的基础上,采用柔性材料填充蜂窝单元,设计了一种薄膜型局部共振声子晶体(FLRPC)。从带结构和模态振动模态两方面解释了FLRPC的带隙特性,揭示了结构参数对带隙特性的影响。研究结果表明,FLRP在特定的频率范围内形成完整的带隙,调整结构参数可以调节带隙的带宽和范围。随后,采集卫星座舱面板的颤振实测信号,验证FLRPC的颤振抑制能力。FLRPC夹芯板的颤振抑制性能优于普通蜂窝夹芯板。提出了一种多尺度FLRPC蜂窝夹层板的方案和制备工艺,并通过颤振抑制仿真和实验对比验证了其颤振抑制性能。这些结果强调了FLRPC在卫星颤振抑制中的应用价值,并为今后的研究提供了参考方案。


Ballistic impact behavior of AA6061 plates with different thicknesses impacted by hemispherical-nosed projectiles

Yu Wang, Buyun Su, Shaoying Zhang, Ruiqiang Ma, Hongwei Liu, Zhiqiang Li

doi:10.1016/j.tws.2024.112876

半弹头弹丸冲击下不同厚度AA6061板的弹道冲击性能

This research investigated the ballistic behavior of 6061 aluminum alloy with varying thicknesses subjected to hemispherical-nosed projectiles. It evaluated the necessity of incorporating nonlinear strain rate and temperature sensitivities in strength model for ballistic simulations, and analyzed the failure mechanisms of targets with two typical thickness. Ballistic tests were performed on 1.5-mm and 4-mm thick targets to determine ballistic resistance and failure modes. The Johnson-Cook (JC) failure model was employed, with simulations conducted using two strength models: the JC model and the modified JC (MJC) model. The experimental results revealed different failure modes for the two target thicknesses. The 1.5-mm target exhibited a disk-shaped plug and a short petal-like hole, whereas the 4-mm target displayed a mushroom-head plug and circumferential spalling at the rear hole. Numerical simulations showed that failure initiated as cracks on the rear surface, with tension dominating the failure process. Increased target thickness resulted in more complex failure paths, leading to variations in perforation and plug formation. Crack propagation and ductile perforation behavior significantly influenced failure modes, energy dissipation, and ballistic resistance. Simulations using the MJC strength model, which accounted for nonlinear strain rate and temperature sensitivities, showed better agreement with experimental results in terms of ballistic resistance, failure modes, and perforation mechanisms, particularly for the 4-mm target, compared to those using the JC model.

研究了6061铝合金不同厚度在半弹头弹丸作用下的弹道性能。评价了在弹道仿真强度模型中加入非线性应变率和温度敏感性的必要性,分析了两种典型厚度目标的失效机理。在1.5 mm和4 mm厚的目标上进行了弹道试验,以确定弹道阻力和破坏模式。采用Johnson-Cook (JC)破坏模型,采用JC模型和修正JC (MJC)两种强度模型进行模拟。实验结果表明,两种目标厚度下的破坏模式不同。1.5 mm靶具有盘状塞和短花瓣状孔,而4 mm靶具有蘑菇头塞和后孔圆周剥落。数值模拟结果表明,破坏的初始形式为后表面裂纹,破坏过程以拉伸为主。靶层厚度的增加导致了更复杂的破坏路径,从而导致射孔和桥塞形成的变化。裂纹扩展和延性穿孔行为显著影响破坏模式、能量耗散和弹道阻力。与JC模型相比,考虑了非线性应变率和温度敏感性的MJC强度模型在弹道阻力、破坏模式和射孔机制方面与实验结果更加吻合,特别是对于4mm靶材。



来源:复合材料力学仿真Composites FEM
ACTMechanicalSystemSLMDeform振动非线性裂纹理论材料多尺度控制试验
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首次发布时间:2025-01-11
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【新文速递】2024年12月28日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,International Journal of Plasticity 3 篇,Thin-Walled Structures 2 篇International Journal of Solids and StructuresProgrammable wrinkling patterns of liquid crystal network bilayers on compliant substratesYifan Yang, Shichen Zhao, Zhijun Dai, Fan Xudoi:10.1016/j.ijsolstr.2024.113206 柔性基板上液晶网络双层的可编程起皱模式Smart soft materials have gained increasing attention in recent years because of their adaptive behaviors to external multi-physics stimuli, enabling diverse applications across multiple fields. Here, we show programmable wrinkling morphological patterns on liquid crystal network (LCN) bilayers bonded to compliant substrates under thermal load, by tuning the orientation of directors between LCN bilayers. We propose a solid-shell formulation that merges enhanced and natural assumed strain approaches to investigate the pattern formation and morphological transition of LCN bilayers. By introducing director-determined anisotropic spontaneous strains, we explore effects of director orientations determined by two angles θ (in-plane) and φ (out-of-plane) for each layer, on surface wrinkling pattern formation and evolution. When the directors are aligned in-plane, oblique angles of stripe wrinkles approximates to the average value of director angles in LCN bilayers, i.e., (θ_l+θ_u)/2. For more general spatial alignments of directors, phase diagrams on wrinkling modes indicate that diverse morphologies such as stripe, checkerboard, herringbone and parallel bead-chain modes, can emerge due to intricate nonlinear interactions between bilayers. Pattern selection is found to be primarily determined by the in-plane angle θ, rather than the out-of-plane angle φ. Our results could offer valuable insights into the functional design of smart surfaces related to wrinkling morphology.近年来,智能软材料因其对外部多物理刺 激的适应性行为而备受关注,这使其在多个领域拥有广泛的应用。在此,我们展示了在热载荷作用下,通过调节液晶网络(LCN)双层膜之间指向矢的方向,在与柔顺基底粘合的 LCN 双层膜上可编程形成褶皱形态图案。我们提出了一种将增强型和自然假设应变方法相结合的固体壳层公式,以研究 LCN 双层膜的图案形成和形态转变。通过引入由指向矢决定的各向异性自发应变,我们探讨了由每层的两个角度 θ(平面内)和 φ(平面外)决定的指向矢方向对表面褶皱图案形成和演变的影响。当指向矢在平面内对齐时,条纹褶皱的倾斜角度近似于 LCN 双层膜中指向矢角度的平均值,即(θ_l + θ_u)/ 2 。对于更普遍的双层膜中分子取向的空间排列,关于起皱模式的相图表明,由于双层膜之间复杂的非线性相互作用,会出现诸如条纹、棋盘格、人字形和平行珠链等多种形态。模式的选择主要取决于平面内角度θ,而非平面外角度φ。我们的研究结果可为与起皱形态相关的智能表面的功能设计提供有价值的见解。Journal of the Mechanics and Physics of SolidsCoupled large deformation phase-field and cohesive zone model for crack propagation in hard-soft multi-materialsAimane Najmeddine, Shashank Gupta, Reza Moinidoi:10.1016/j.jmps.2024.106016硬软复合材料裂纹扩展的大变形相场和内聚区耦合模型This work presents a unified large deformation constitutive framework that couples the phase-field approach for bulk fracture with the potential-based Park-Paulino-Roesler cohesive zone model (PPR CZM) to study crack propagation in multi-material systems that contain interfaces. The phase-field component captures crack initiation and propagation within bulk constituents, whereas the PPR CZM captures failure mechanisms at interface regions. The proposed unified framework is implemented via a user-element subroutine (UEL) within Abaqus and incorporates a large-deformation extension of the PPR CZM. It was used to examine fracture mechanisms in four scenarios: bi-layer hard-hard composite containing crack impinging on (1) a perpendicular interface and (2) an oblique interface, (3) tri-layer hard-soft multi-material composite containing crack perpendicular to interfaces, and (4) fiber-reinforced matrix composite. Results demonstrated that the unified framework successfully captured crack deflection and penetration in hard-hard bi-layers with dissimilar properties and both perpendicular and oblique interfaces, consistent with Linear Elastic Fracture Mechanics. Furthermore, the large-deformation component of the framework was shown to provide an effective numerical tool for probing the underlying toughening mechanisms in hard-soft multi-material assemblies relative to their monolithic counterparts. Toughening in these composites was characterized by crack bridging and post-peak hardening in the force–displacement response. Finally, the framework accurately predicted complex fracture phenomena in fiber-reinforced composites, involving fiber–matrix debonding (via PPR CZM) and matrix cracking (via phase-field). The framework can inform the design of dissimilar hard-hard brittle materials and hard-soft composites, offering insights into fracture behavior and toughening mechanisms.本文提出了一个统一的大变形本构框架,将相场方法与基于势的Park-Paulino-Roesler内聚区模型(PPR CZM)相结合,用于研究含有界面的多材料系统中的裂纹扩展。相场分量捕获了块体成分内部裂纹的萌生和扩展,而PPR CZM捕获了界面区域的失效机制。提出的统一框架是通过Abaqus中的用户元素子程序(UEL)实现的,并结合了PPR CZM的大变形扩展。研究了四种情况下的断裂机制:含裂纹撞击(1)垂直界面和(2)斜界面的双层硬-硬复合材料,含裂纹垂直界面的三层硬-软复合材料,以及(4)纤维增强基复合材料。结果表明,统一框架成功捕获了不同性能、垂直和倾斜界面的硬-硬双材料的裂纹挠曲和贯通,符合线弹性断裂力学。此外,框架的大变形组件被证明提供了一个有效的数值工具,用于探测硬-软多材料组件相对于其整体对应物的潜在增韧机制。复合材料的增韧表现为应力-位移响应中的裂纹桥接和峰后硬化。最后,该框架准确预测了纤维增强复合材料的复杂断裂现象,包括纤维-基体脱粘(通过PPR CZM)和基体开裂(通过相场)。该框架可以为不同的硬-硬脆材料和硬-软复合材料的设计提供信息,为断裂行为和增韧机制提供见解。International Journal of PlasticityNovel distortional anisotropic hardening model mediated by microstructure evolutions in polycrystalline metals: theory and validationSeonghwan Choi, Soo-Chang Kang, Jinwoo Lee, Myoung-Gyu Leedoi:10.1016/j.ijplas.2024.104227由多晶金属微观结构演变介导的新型畸变各向异性硬化模型:理论与验证In this study, we introduce a novel anisotropic hardening model designed to capture the macroscopic mechanical responses under complex loading paths while considering the mesoscopic evolutions of crystallographic structures. Based on the framework of homogeneous distortional anisotropic hardening, this model treats the plastic shear strain of each slip system as an internal variable. Utilizing the plastic work equivalence principle, the plastic shear rate within the slip system is determined, aligning with the evolution laws of rate-independent crystal plasticity (CP) theory. The model evaluates the Bauschinger effect and transient hardening at grain level and integrates it into the macroscopic yield function to describe phenomenological hardening responses. The model has been extensively validated against experimental and computational polycrystalline CP approaches, demonstrating its efficacy in capturing both the evolution of crystal textures and complex anisotropic hardening behaviors for both FCC and BCC materials. This proposed hardening model marks a significant advancement in material behavior modeling, effectively bridging the gap between microstructural mechanisms and macroscopic mechanical behavior in better practical way.在这项研究中,我们引入了一种新的各向异性硬化模型,旨在捕捉复杂加载路径下的宏观力学响应,同时考虑晶体结构的细观演变。该模型基于均匀变形各向异性硬化框架,将各滑移体系的塑性剪切应变作为内部变量。利用塑性功等效原理,根据速率无关晶体塑性理论的演化规律,确定了滑移体系内的塑性剪切速率。该模型评估了包辛格效应和瞬态硬化在晶粒水平上的影响,并将其整合到宏观屈服函数中来描述现象性硬化响应。该模型已经通过实验和计算多晶CP方法进行了广泛的验证,证明了它在捕获FCC和BCC材料的晶体结构演变和复杂的各向异性硬化行为方面的有效性。提出的硬化模型标志着材料行为建模的重大进步,有效地弥合了微观结构机制和宏观力学行为之间的差距,更切合实际。Bulging of grain boundaries and core-shell dislocation structures enhance mechanical properties of equiatomic high-entropy alloysJungwan Lee, Sun Ig Hong, Hyoung Seop Kimdoi:10.1016/j.ijplas.2024.104224 晶界胀形和核壳位错结构提高了等原子高熵合金的力学性能Regulating elemental compositions of structural materials has been at the heart of interests for metallurgists to ensure target properties under harsh environments. For instance, metastability engineering that exploits phase transformation or deformation twinning depends on a minor modification in atomic compositions. Distinct from the well-studied control of elemental compositions, this work centers on a straightforward thermomechanical process of hot rolling to induce bulging of grain boundaries and core-shell dislocation cell structures. During the hot rolling, the bulging of grain boundaries releases high-density dislocation walls and more dislocations are distributed around the grain boundaries in equiatomic CoCrFeMnNi, one of the most studied high-entropy alloys. Under the tensile deformation at cryogenic temperatures with decreased stacking fault energy, the less stable grain boundaries promote the emanation of partial dislocations and the consequent formation of deformation twinning. As a result, the hot-rolled alloy exhibits an enhanced combination of yield strength of ∼941 MPa and uniform elongation of ∼54% at –196 °C, which is counterintuitive to low ductility of as-rolled metallic materials. This lies at the upper bound in comparison with tensile responses of precipitation-strengthened high-entropy alloys and high-strength steels. The higher propensity of deformation twins in hot-rolled alloy compared to that of cold-rolled and annealed one enhances strain hardening despite the hot-rolled state. Regarding the benefits of the streamlined thermomechanical history, this study validates the academic and industrial worth of hot-rolled metallic materials to develop the alloy science and fabricating technology.调节结构材料的元素组成一直是冶金学家感兴趣的核心,以确保在恶劣环境下的目标性能。例如,利用相变或变形孪晶的亚稳态工程依赖于原子组成的微小改变。不同于已被充分研究的元素成分控制,这项工作集中在一个直接的热轧热力学过程中,以诱导晶界膨胀和核-壳位错细胞结构。等原子CoCrFeMnNi是研究最多的高熵合金之一,在热轧过程中,晶界的胀形释放出高密度的位错壁,晶界周围分布着更多的位错。在低温拉伸变形下,层错能降低,晶界不稳定,促进了部分位错的发散,从而形成变形孪晶。结果表明,热轧合金在-196℃时屈服强度达到~ 941 MPa,延伸率达到~ 54%,这与轧制时金属材料的低延展性相反。与析出强化高熵合金和高强钢的拉伸响应相比,这是上界。与冷轧和退火合金相比,热轧合金的变形孪晶倾向较高,在热轧状态下强化了应变硬化。考虑到热轧金属材料在热轧过程中所带来的好处,本研究验证了热轧金属材料在合金科学和制造技术发展中的学术和工业价值。Influences of dislocation configuration and texture optimization on obtaining exceptional cryogenic strength-ductility synergy in a dynamic-recovered heterogeneous high-manganese steelHao Xiong, Yu Li, Chun Xu, Wei Li, Xiaoshuai Jiadoi:10.1016/j.ijplas.2024.104225 位错结构和织构优化对动态回收非均相高锰钢获得超常低温强度-塑性协同效应的影响In this study, an innovative strategy of dislocation configuration and texture optimization is employed to achieve a heterogeneous dynamic-recovered (DRV) high-manganese steel via successive cold-warm-rolling (CWR). Compared with single-step warm-rolling (WR) treatment, the imposed cold deformation of CWR process not only results in more and finer dislocation cells in DRV grains, but also leads to texture optimization with intensity weakening and component changing. Hence, the CWR sample shows a higher yield strength (YS, ∼1.35 GPa) and ultimate tensile strength (UTS, ∼1.6 GPa) without sacrificing the tensile elongation (TEL, ∼57%) at LNT (liquid nitrogen temperature), accompanied with a significantly lower mechanical anisotropy. The exceptional cryogenic strength-ductility synergy can be attributed to following: i) the difference of YS comes from the additional Taylor hardening effect (∼150 MPa); ii) the prefer-orientated DRV grains with a high Schmid factor (SFR) of twinning induces the twin deflections or kinks at the dislocation boundary in the early deformation stage; and iii) the refined cell structure can increase the critical resolved shear stress (CRSS) of twin, act as twin nucleus and impede its growth, leading to the occurrence of high-density of nano-twin segment (thickness: ∼15 nm, number density: ∼1.1*108 m-3) at a high stress and strain level. Thus, the cooperative forest dislocation hardening (∼870 MPa) and dynamic Hall-Petch strengthening (∼220 MPa) effects can provide continuous strain hardening capacity. In contrast, the high ductility of the WR sample primarily originates from the abundant microband-induced plasticity correlated with limited twinning- (TWIP) and transformation-induced plasticity (TRIP) due to a coarse twin (∼22.5 nm) and martensite thickness (∼55 nm).在本研究中,采用一种创新的位错构型和织构优化策略,通过连续冷温轧制(CWR)实现了高锰钢的非均质动态恢复(DRV)。与单步温轧(WR)处理相比,CWR工艺的冷变形不仅使DRV晶粒中出现了更多更细的位错细胞,而且使织构优化,强度减弱,成分变化。因此,CWR样品在LNT(液氮温度)下表现出更高的屈服强度(YS, ~ 1.35 GPa)和极限抗拉强度(UTS, ~ 1.6 GPa),而不牺牲抗拉伸长率(TEL, ~ 57%),同时力学各向异性显著降低。特殊的低温强度-延性协同作用可归因于以下原因:1)YS的差异来自额外的泰勒硬化效应(~ 150 MPa);ii)高施密德因子(SFR)的择优取向DRV晶粒在变形初期在位错边界处诱发孪晶挠曲或扭结;精细的胞元结构增加了孪晶的临界分解剪切应力(CRSS),起到孪晶核的作用,阻碍孪晶的生长,导致在高应力应变水平下出现纳米孪晶段高密度(厚度:~ 15 nm,数密度:~ 1.1*108 m-3)。因此,协同森林位错硬化(~ 870 MPa)和动态Hall-Petch强化(~ 220 MPa)效应可以提供连续应变硬化能力。相比之下,WR样品的高延展性主要源于丰富的微带诱导塑性,这与有限的孪晶(TWIP)和由粗孪晶(~ 22.5 nm)和马氏体厚度(~ 55 nm)引起的相变诱导塑性(TRIP)有关。Thin-Walled StructuresCrashworthiness analysis of bio-inspired multi-order self-similar polymer honeycomb under axial quasi-static and dynamic loadingChenghao Guo, Xueyu Cheng, Lixin Lu, Liao Pandoi:10.1016/j.tws.2024.112877 仿生多阶自相似聚合物蜂窝轴向准静态和动态载荷下的耐撞性分析At present, making the improvement of load-bearing capacity in polymer honeycombs under multi-conditional loading is a critical engineering challenge. To enhance the crashworthiness of polymer honeycomb configurations subjected to quasi-static compression and dynamic impacts, this study proposes a hierarchical strategy, inspired by the cross-sectional structures of horsetail grass and muscle tissue. The hierarchical honeycombs were fabricated using toughened polylactic acid through fused deposition modeling. The load-bearing enhancement mechanism of the hierarchical honeycombs was analyzed using numerical simulations. This strategy reduces the folding wavelength during honeycomb compression, significantly improving cell wall utilization and enhancing energy absorption capacity and stability. Notably, the mean crushing force (MCF) and specific energy absorption (SEA) of the second-order hierarchical honeycomb demonstrate significant enhancements compared to regular honeycomb at the same relative density, with increases of 50.45% and 43.78%, respectively. The third-order hierarchical honeycomb exhibits the excellent energy absorption stability. Under dynamic impacts, the hierarchical honeycombs display an increasingly stable load-bearing process and superior crashworthiness properties with higher hierarchy orders. The MCFs of the hierarchical honeycombs increase significantly with the increase of cell wall thickness. Furthermore, theoretical calculation models incorporating the strain rate effect of the hierarchical honeycombs were developed. The discrepancy between theoretical and experimental results is within 7.5%, confirming the models’ reliability.目前,如何提高聚合物蜂窝在多条件载荷下的承载能力是一个关键的工程难题。为了提高聚合物蜂窝结构在准静态压缩和动态冲击下的耐撞性,本研究提出了一种分层策略,灵感来自马尾草和肌肉组织的横截面结构。采用增韧聚乳酸熔融沉积模型制备了分层蜂窝。通过数值模拟分析了分层蜂窝的增强承载机理。该策略减少了蜂窝压缩过程中的折叠波长,显著提高了细胞壁利用率,增强了能量吸收能力和稳定性。值得注意的是,在相同相对密度下,二级分层蜂窝的平均破碎力(MCF)和比能吸收(SEA)比普通蜂窝有显著提高,分别提高了50.45%和43.78%。三阶分层蜂窝具有优异的吸能稳定性。在动力冲击下,分层蜂窝结构的承载过程越来越稳定,且随着分层阶数的增加,其耐撞性能也越来越好。分层蜂窝的mcf随细胞壁厚度的增加而显著增加。在此基础上,建立了考虑分层蜂窝应变率效应的理论计算模型。理论与实验结果的偏差在7.5%以内,验证了模型的可靠性。Pre-compressed beam-based multistable mechanical metamaterials with programmable loading and unloading deformation sequencesJian Hua, Yuan Zhou, Zhiqiang Meng, Chang Qing Chendoi:10.1016/j.tws.2024.112879具有可编程加载和卸载变形序列的基于预压缩梁的多稳定力学超材料In this work, we propose four types of pre-compressed beam-based multistable mechanical metamaterials and use a combination of theoretical, simulation and experimental methods to systematically explore the effects of pre-compression and initial configurations on their mechanical properties. We found that curved beams with identical initial configurations but different pre-compressions have the same negative stiffness value, but their peak forces differ. Furthermore, the results demonstrate that applying pre-compression is a more effective programming strategy than geometric modulation for altering the stability of the beams. We also demonstrate that pre-compressed multistable mechanical metamaterials can robustly program unloading deformation sequences while maintaining consistent loading orders, thereby enabling the concealment of certain stable configurations. The proposed pre-compressed beam-based mechanical metamaterials offer potential benefits in mechanical computing and information encryption, paving the way for expanding the design concepts and application prospects of multistable mechanical metamaterials.在这项工作中,我们提出了四种基于预压缩梁的多稳态力学超材料,并采用理论、模拟和实验相结合的方法系统地探索了预压缩和初始配置对其力学性能的影响。研究发现,初始结构相同但预压不同的弯曲梁具有相同的负刚度值,但其峰值力不同。结果表明,采用预压缩比几何调制更有效地改变梁的稳定性。我们还证明了预压缩的多稳定力学超材料可以鲁棒地编程卸载变形序列,同时保持一致的加载顺序,从而实现某些稳定构型的隐藏。提出的基于预压缩梁的机械超材料在机械计算和信息加密方面具有潜在的优势,为扩展多稳态机械超材料的设计理念和应用前景铺平了道路。来源:复合材料力学仿真Composites FEM

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