今日更新:Journal of the Mechanics and Physics of Solids 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 2 篇
On the effect of nuclear fission cladding stresses on Zirconium hydride orientation and dislocation strain energy fields via Discrete Dislocation Plasticity and Crystal Plasticity Finite Element modelling
Christos Skamniotis, Daniel Long, Mark Wenman, Daniel S. Balint
doi:10.1016/j.jmps.2024.105924
基于离散位错塑性和晶体塑性有限元模型的核裂变包层应力对氢化锆取向和位错应变能场的影响
The diffusion of hydrogen in Zircalloy fuel cladding components and its associated delayed hydride cracking (DHC) mechanism remain a bottleneck in nuclear fission. Through Crystal Plasticity Finite Element (CPFE) analysis at the grain scale (μm) and Discrete Dislocation Plasticity (DDP) at the hydride scale (nm), we explore how cladding stress history influences the dislocation network in a system of hydrides, and in turn, how this can impact hydrogen accumulation and embrittlement. CPFE indicates that high tensile stresses at service temperature can cause severe plasticity at a notch of a cladding component, leading to significant residual compressive stresses on service shutdown. As a result, hydrides evolve in this service scenario under a cyclic tensile-compressive background stress, which is found to enhance the ratchetting of dislocations compared to a typical constant background stress history and to eliminate the concentration of tensile residual hydrostatic stresses at the locations of dissolved hydrides. Since these tensile residual stresses drive the local accumulation of hydrogen during progressive precipitation-dissolution cycles, a key question is posed as to whether and how the sequencing of cladding stress-temperature reversals influences the growth rate of macro-hydride colonies. Simultaneously, we find that a large fraction of the total strain energy of hydrides is associated with the strain energy of dislocations and their interactions, posing the question of whether dislocation networks influence the energetically favourable hydride orientation. Our study provides a foundation for future studies of the DHC mechanism and drives the development of thermodynamically consistent dislocation-based models coupled with irradiation effects.
氢在锆合金燃料包壳组件中的扩散及其相关的延迟氢化物裂解(DHC)机制一直是核裂变研究的瓶颈。通过晶粒尺度(μm)的晶体塑性有限元(CPFE)和氢化物尺度(nm)的离散位错塑性(DDP)分析,我们探讨了包层应力历史如何影响氢化物体系中的位错网络,以及这如何影响氢的积累和脆化。CPFE表明,在工作温度下的高拉应力会导致包层部件缺口处的严重塑性,导致在工作关闭时产生显著的残余压应力。结果,氢化物在循环拉压背景应力下演化,与典型的恒定背景应力相比,这增强了位错的棘轮作用,并消除了溶解氢化物位置的拉伸残余静水应力集中。由于这些拉伸残余应力在渐进式沉淀-溶解循环中驱动氢的局部积累,因此提出了一个关键问题,即包层应力-温度逆转的顺序是否以及如何影响宏观氢化物菌落的生长速度。同时,我们发现氢化物总应变能的很大一部分与位错及其相互作用的应变能有关,这就提出了位错网络是否影响能量上有利的氢化物取向的问题。我们的研究为未来DHC机制的研究提供了基础,并推动了基于热动力学一致的位错耦合辐照效应模型的发展。
Dynamic deformation and fracture of brass: Experiments and dislocation-based model
E.S. Rodionov, V.V. Pogorelko, V.G. Lupanov, A.G. Fazlitdinova, P.N. Mayer, A.E. Mayer
doi:10.1016/j.ijplas.2024.104165
黄铜的动态变形和断裂:实验和基于位错的模型
In this work, we perform a comprehensive study of the dynamic deformation and fracture of brass, including Taylor tests with classical and profiled cylinders and ball throwing experiments reaching the strain rates of about (0.1−1)/μs, as well as atomistic and continuum-level numerical modeling. Molecular dynamics (MD) simulations are used to construct the equation of state (EOS) of brass and to study its fracture characteristics at shear deformation under negative pressure. An original model of fracture under combined tensile-shear loading is formulated, which takes into account both the accumulation of empty volume in the process of lattice loosening due to the lattice defect production in the course of plastic deformation and further mechanical growth of voids controlled by the dislocation plasticity. This atomic-scale model is transmitted to the macroscopic experiment-scale level and embedded into 3D dislocation plasticity model to describe the dynamic deformation and fracture of brass using the numerical scheme of smoothed particle hydrodynamics (SPH). A part of experimental data is used to find the optimal parameters of the dislocation plasticity model by means of the Bayesian global optimization method accelerated with the help of artificial-neural-network (ANN)-based emulator of the 3D model. Another part of experimental data is used to fit the fracture model parameter. The remaining experimental data, which are not used in the parameterization, are applied to verify the parameterized model. The developed physical-based model provides correct and meaningful description of the dynamic deformation and fracture of brass, while the developed formalized approach to its parameterization opens a way to wider use of this type of models in the engineering applications, including studies on dynamic performance and high-speed processing technologies.
在这项工作中,我们对黄铜的动态变形和断裂进行了全面的研究,包括经典圆柱体和轮廓圆柱体的Taylor试验和应变速率约为(0.1−1)/μs的抛球实验,以及原子和连续水平的数值模拟。采用分子动力学(MD)模拟方法建立了黄铜的状态方程(EOS),研究了黄铜在负压剪切变形下的断裂特征。提出了一种原始的拉伸-剪切复合加载断裂模型,该模型既考虑了塑性变形过程中由于晶格缺陷产生的晶格松动过程中空洞体积的积累,又考虑了位错塑性控制下空洞的进一步力学增长。将该原子尺度模型传递到宏观实验尺度,并嵌入到三维位错塑性模型中,采用光滑颗粒流体力学(SPH)数值格式描述黄铜的动态变形和断裂。利用部分实验数据,利用基于人工神经网络(ANN)的三维模型仿真器加速贝叶斯全局优化方法,找到位错塑性模型的最优参数。另一部分实验数据用于拟合断裂模型参数。其余未用于参数化的实验数据用于验证参数化模型。所建立的基于物理的模型为黄铜的动态变形和断裂提供了正确而有意义的描述,而所建立的形式化参数化方法为这类模型在工程应用中的广泛应用开辟了道路,包括动态性能和高速加工技术的研究。
An origami-wheeled robot with variable width and enhanced sand walking versatility
Jie Liu, Zufeng Pang, Zhiyong Li, Guilin Wen, Zhoucheng Su, Junfeng He, Kaiyue Liu, Dezheng Jiang, Zenan Li, Shouyan Chen, Yang Tian, Yi Min Xie, Zhenpei Wang, Zhuangjian Liu
doi:10.1016/j.tws.2024.112645
具有可变宽度的折纸轮式机器人,增强了沙地行走的多功能性
Robots inspired by origami that offer several benefits, including being lightweight, requiring less assembly, and possessing remarkable deformability, have drawn a lot of interest. However, the existing origami-inspired robots are usually of limited functionalities and developing feature-rich robots is very challenging. Here, we report an origami-wheeled robot (OriWheelBot) with exceptional mobility for sand walking and a changing width. Origami wheels created using Miura origami permit the OriWheelBot to alter wheel width over obstacles. We derive the variable-width and diameter analytical models of the origami wheel, assuming rigid-folding, which has been confirmed by testing. An enhanced variant, dubbed iOriWheelBot, is additionally being developed to autonomously determine the obstacle's breadth. Based on the width of the channel between the barriers, three actions will be executed: direct pass, variable width pass, and direct return. Sand-pushing is more suitable for walking on the sand than sand-digging, which is the other of the two motion mechanisms that we have identified. Many aspects of sand walking, including carrying loads, walking on a slope, climbing a slope, and negotiating sand pits, small rocks, and sand traps, have been methodically investigated. The OriWheelBot can climb a 17-degree sand incline, vary its width by 40%, and have a loading-carrying ratio of 66.7% on flat sand. Rescue operations in disaster areas and planetary subsurface exploration can benefit from the OriWheelBot.
受折纸启发的机器人有很多优点,包括重量轻、装配少、具有显著的可变形性,这些都引起了人们的兴趣。然而,现有的折纸机器人通常功能有限,开发功能丰富的机器人是非常具有挑战性的。在这里,我们报告了一种折纸轮式机器人(OriWheelBot),它具有特殊的沙子行走机动性和变化的宽度。使用三浦折纸技术创建的折纸轮子允许OriWheelBot在障碍物上改变轮子的宽度。在刚性折叠条件下,建立了折纸轮变宽度和变直径的解析模型,并通过试验得到了验证。另外,一款名为iOriWheelBot的增强版本正在开发中,可以自动确定障碍物的宽度。根据障碍物之间通道的宽度,将执行三种动作:直接通过、变宽通过和直接返回。推沙 比挖沙更适合在沙子上行走,这是我们已经确定的两种运动机制中的另一种。沙地行走的许多方面,包括负重、在斜坡上行走、爬坡、通过沙坑、小岩石和沙坑,都被系统地研究过。OriWheelBot可以爬上17度的沙坡,宽度可变化40%,在平坦的沙地上承载率为66.7%。在灾区的救援行动和行星地下勘探可以受益于OriWheelBot。
Oscillating laser-arc hybrid additive manufacturing of aluminum alloy thin-wall based on synchronous wire-powder feeding
Yunfei Meng, Qianxi Yu, Xu Wu, Xiaohan Guo, Ziheng Yang, Lidong Xu, Hui Chen
doi:10.1016/j.tws.2024.112665
基于同步送粉的铝合金薄壁振荡激光-电弧复合增材制造
Synchronous wire-powder feeding was adopted to overcome the poor mechanical properties of aluminum alloy thin-wall caused by limited filling composition in wire-based laser-arc hybrid additive manufacturing. The results showed that the optimized Mg powder feeding improved the droplet transfer into a fine spray mode with reduced transition time by 18%. Moreover, not only the effective width coefficient of thin-wall increased from 89% to 95%, but also the subsequent machining allowance reduced from 1.25 to 0.48 mm. The synchronous wire-powder feeding improved the formation accuracy by 61.6%. Although the deposition microstructure was mainly composed of dendrites with obvious direction and increased average grain size by 54%, a new Mg2Si strengthened phase was also found. The ultimate tensile strength of thin-wall was increased by 12% from 227.3 to 255.5 MPa. The related evolution mechanisms of deposition stability and mechanical properties by optimized powder feeding on the hybrid additive manufacturing were mainly discussed.
采用同步线粉进料的方法,克服了线基激光-电弧复合增材制造中填充成分有限导致铝合金薄壁力学性能差的问题。结果表明,优化后的Mg粉进料使液滴转变为细喷雾,转变时间缩短了18%。薄壁有效宽度系数由89%提高到95%,后续加工余量由1.25 mm减小到0.48 mm。同步送粉使成形精度提高了61.6%。虽然沉积组织主要由方向性明显的枝晶组成,平均晶粒尺寸增加了54%,但也发现了新的Mg2Si强化相。薄壁的极限抗拉强度由227.3 MPa提高到255.5 MPa,提高了12%。重点讨论了混合增材制造中优化进料对沉积稳定性和力学性能的影响机理。