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
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。
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。
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。
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。