今日更新:Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇
Embedding strain-rate sensitivities of multiple deformation mechanisms to predict the behavior of a precipitate-hardened WE43 alloy under a wide range of strain rates
Weiss Jacob, Su Yanqing, McWilliams Brandon A., Beyerlein Irene J., Knezevic Marko
doi:10.1016/j.mechmat.2023.104843
嵌入多种变形机制的应变速率敏感性,预测沉淀硬化的 WE43 合金在各种应变速率下的行为
A rare earth Mg alloy, WE43, exhibits high strength, good ductility, low anisotropy, and moderately high strain rate sensitivity. As such, the alloy is a viable candidate for high strain rate applications. In this work, a comprehensive set of mechanical and microstructure data recorded during quasi-static, high strain rate split Hopkinson bar (SHB), and impact tests on specimens of WE43 Mg alloy reported in (Savage et al., 2020b) is simulated and interpreted using an advanced Taylor-type crystal plasticity finite element (T-CPFE) model. The T-CPFE model is formulated physically to embed two sources of strain-rate sensitivities inherent to each slip and twinning mode in WE43, one that occurs under constant structure and another that affects structure evolution. The model parameters are established for the alloy by achieving agreement in the stress-strain response and microstructure evolution under quasi-static and SHB tests. Density functional theory calculations of anti-phase boundary (APB) energy are carried out to explain origins of the unusually large initial slip resistance for basal dislocations, which shear precipitates in the alloy. The initial slip resistances of the prismatic and pyramidal dislocations are, instead, rationalized by Orowan looping around precipitates. After calibration and validation, the model is shown to successfully predict WE43 response at much larger strain rates than those used for model calibration. Specifically, mechanical response, specimen geometry changes, twin volume fractions, and texture evolution are predicted for different orientations of the Taylor cylinders. Details of the modeling framework, comparison between simulation and experimental results, and insights from the results are presented and discussed.
稀土镁合金 WE43 具有高强度、良好的延展性、低各向异性和适度的高应变速率敏感性。因此,该合金是高应变速率应用的可行候选材料。在这项工作中,使用先进的泰勒型晶体塑性有限元(T-CPFE)模型模拟和解释了(Savage 等人,2020b)中报道的 WE43 镁合金试样在准静态、高应变率分裂霍普金森棒(SHB)和冲击试验中记录的一整套机械和微观结构数据。T-CPFE 模型通过物理方法制定,嵌入了 WE43 中每种滑移和孪晶模式固有的应变速率敏感性的两个来源,一个是在恒定结构下发生的,另一个是影响结构演变的。通过在准静态和 SHB 试验下应力-应变响应和微观结构演变的一致性,为合金建立了模型参数。对反相边界(APB)能量进行了密度泛函理论计算,以解释合金中剪切析出的基底位错的初始滑移阻力异常大的原因。棱柱位错和金字塔位错的初始滑移阻力则是通过析出物周围的奥罗万循环而得到合理解释的。经过校准和验证,该模型可以成功预测 WE43 在比用于模型校准的应变速率大得多的应变速率下的响应。具体来说,预测了泰勒圆柱体不同方向的机械响应、试样几何形状变化、孪晶体积分数和纹理演变。本文介绍并讨论了建模框架的细节、模拟与实验结果的比较以及从结果中获得的启示。
Two-dimensional evolution of temperature and deformation fields during dynamic shear banding: In-situ experiments and modeling
Zeng Qinglei, Chen Manxi, Yu Xiaoqi, Qi Wei, Zhu Shengxin, Yang Heng, Chen Hao-Sen
doi:10.1016/j.ijplas.2023.103782
动态剪切成带过程中温度场和变形场的二维演变:现场实验与建模
Adiabatic shear band (ASB) is a significant failure mechanism observed in metals and alloys under impact loading. Though ASB formation has been widely assumed to be a one-dimensional thermo-mechanically-coupled instability problem, it is crucial to recognize that adiabatic shear banding is essentially a two-dimensional propagating event in space. However, it is challenging to perform in-situ characterization of temperature-deformation fields during ASB formation due to the extremely small spatial and temporal scales involved. To obtain the two-dimensional features of ASB evolution, a newly developed plane-array infrared imaging system and microspeckle-based digital image correlation (DIC) technique are synchronized with the Kolsky bar system. By incorporating interrupted tests, “quasi-synchronous” characterization of temperature-deformation-microstructure evolution during ASB formation in hat-shaped specimens of Ti-6Al-4V is achieved. A phase-field model incorporating energy-based shear banding criteria and independently calibrated model parameters is established to simulate the dynamic shear failure process, which is demonstrated to be able to well reproduce experimentally observed temperature and deformation evolution. Based on experimental characterization and simulation results, the two-dimensional features and thermo-mechanical aspects of ASB formation are presented. Energy dissipation of shear banding is estimated based on the measured temperature field, demonstrating good agreement with the calibrated values in the phase-field model. The “propagation” and “percolation” modes along the band are analyzed, which can be predicted by the introduction of a shear band process zone. The influences of thermal and microstructural softening on shear failure are also clarified through a comprehensive analysis of temperature and microstructure evolution.
绝热剪切带(ASB)是金属和合金在冲击载荷作用下出现的一种重要失效机制。尽管人们普遍认为 ASB 的形成是一个一维热机械耦合不稳定问题,但必须认识到绝热剪切带基本上是一个二维空间传播事件。然而,由于涉及的空间和时间尺度极小,在 ASB 形成过程中对温度-形变场进行现场表征具有挑战性。为了获得 ASB 演化的二维特征,新开发的平面阵列红外成像系统和基于微斑的数字图像相关(DIC)技术与 Kolsky bar 系统同步进行。通过结合间断试验,实现了对 Ti-6Al-4V 帽形试样 ASB 形成过程中温度-变形-微结构演变的 "准同步 "表征。建立了一个相场模型,其中包含基于能量的剪切带标准和独立校准的模型参数,用于模拟动态剪切破坏过程,该模型能够很好地再现实验观察到的温度和变形演变。基于实验表征和模拟结果,介绍了 ASB 形成的二维特征和热力学方面。根据测量的温度场估算了剪切带的能量耗散,结果表明与相场模型中的校准值十分吻合。分析了沿带的 "传播 "和 "渗流 "模式,这些模式可以通过引入剪切带过程区来预测。此外,还通过对温度和微结构演变的全面分析,阐明了热软化和微结构软化对剪切破坏的影响。
Fiber orientation and boundary stiffness optimization of laminated cylindrical shells with elastic boundary for maximum the fundamental frequency by an improved sparrow search algorithm
Chen Yugeng, Wang Qingshan, Zhong Rui, Shi Xianjie, Qin Bin
doi:10.1016/j.tws.2023.111299
用改进的麻雀搜索算法优化具有弹性边界的层叠圆柱壳的纤维方向和边界刚度,以获得最大基频
In this paper, a multivariate improved sparrow search algorithm (MCSSA) is proposed for maximizing the fundamental frequency of composite laminated cylindrical shells and preventing vibrational resonance. The mathematical model for analyzing the fundamental frequency of composite laminated cylindrical shells in free vibration is established based on the first-order shear deformation theory (FSDT). A fundamental frequency optimization model for composite laminated cylindrical shells with elastic boundary is formulated, considering the influence of fiber orientation and boundary stiffness, with the objective of maximizing the fundamental frequency. In the optimization process, in response to the shortcomings of the sparrow search algorithm, Piecewise Linear Chaotic Map (PWLCM), tracking learning strategy, opposition-based learning strategy (OBL) and elite retention strategy are introduced for improvement to obtain the MCSSA with better overall performance for model optimization. The effectiveness and applicability of the algorithm improvements are demonstrated by comparing MCSSA with the whale optimization algorithm (WOA), sparrow search algorithm (SSA), and pelican optimization algorithm (POA) using 13 standard test functions and 2 composite laminated cylindrical shell cases. The numerical calculation results show that the shells optimized with MCSSA have higher fundamental frequency. MCSSA is an effective candidate for solving such problems.
本文提出了一种多变量改进麻雀搜索算法(MCSSA),用于最大化复合材料层压圆柱壳的基频并防止振动共振。基于一阶剪切变形理论(FSDT),建立了分析自由振动中复合材料层压圆柱壳基频的数学模型。考虑到纤维取向和边界刚度的影响,建立了具有弹性边界的复合材料层压圆柱壳的基频优化模型,目标是使基频最大化。在优化过程中,针对麻雀搜索算法的缺点,引入了片断线性混沌图(PWLCM)、跟踪学习策略、基于对立面的学习策略(OBL)和精英保留策略进行改进,得到了整体性能更好的 MCSSA,用于模型优化。通过使用 13 个标准测试函数和 2 个复合层压圆柱壳案例,比较 MCSSA 与鲸鱼优化算法(WOA)、麻雀搜索算法(SSA)和鹈鹕优化算法(POA),证明了算法改进的有效性和适用性。数值计算结果表明,采用 MCSSA 算法优化的壳体具有更高的基频。MCSSA 是解决此类问题的有效候选算法。