基于晶体塑性的辐照金属材料局部化颈缩和吕德斯带的模拟研究  

Simulations of the localized necking and Lüders band in irradiated metals by crystal plasticity

作　　者：付家琪 刘文斌 隋昊男 程杨洋 段慧玲 Jiaqi Fu;Wenbin Liu;Haonan Sui;Yangyang Cheng;Huiling Duan(State Key Laboratory for Turbulence and Complex System,Department of Mechanics and Engineering Science,The Beijing Innovation Center for Engineering Science and Advanced Technology,College of Engineering,Peking University,Beijing,100871,China;Key Laboratory of High Energy Density Physics Simulation,Center for Applied Physics and Technology,and Inertial Fusion Sciences and Applications,Collaborative Innovation Center of Ministry of Education,Peking University,Beijing,100871,China)

机构地区：[1]State Key Laboratory for Turbulence and Complex System,Department of Mechanics and Engineering Science,The Beijing Innovation Center for Engineering Science and Advanced Technology,College of Engineering,Peking University,Beijing,100871,China [2]Key Laboratory of High Energy Density Physics Simulation,Center for Applied Physics and Technology,and Inertial Fusion Sciences and Applications,Collaborative Innovation Center of Ministry of Education,Peking University,Beijing,100871,China

出　　处：《Acta Mechanica Sinica》2023年第4期132-146,共15页力学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.11988102,91848201,and 12002005).

摘　　要：金属材料中,颈缩失稳通常由表面缺陷或材料不均匀性等潜在扰动引起并随着微结构的演化进一步发展.本文将构型扰动法与考虑辐照效应的晶体塑性本构关系相结合,模拟了辐照前后局部化颈缩和吕德斯带等现象.通过考虑模拟局部化变形中扰动的必要性,发现了外在的几何缺陷和内禀的微结构演化在颈缩过程中的竞争关系.此外,以纯金属铜和奥氏体不锈钢为例研究了辐照硬化效应对颈缩失稳的影响.结果表明,流动应力的增加和功硬化能力的降低是均匀延伸率下降的原因,辐照效应导致的织构软化作用可以忽略.为了解释辐照后低碳钢下屈服点和吕德斯应变同时增加的现象,一种位错脱钉扎和位错与辐照缺陷的交互作用相耦合的塑性变形机制被提出并结合修正的流动方程,很好地模拟出包含屈服下降、应力平台、应变扩展和应变硬化等特征的吕德斯带现象.其中,位错与辐照缺陷的相互作用也可以解释辐照后纯金属材料中发现的扩散颈缩现象.我们的模拟结果既阐明了几何缺陷在颈缩失稳中的重要作用,也为辐照金属中常见的宏观塑性失稳现象提供了清晰的物理图像.In metallic materials,necking instability is initiated by underlying perturbations including surface imperfections or material inhomogeneity,and further facilitated by microstructural evolution.In this paper,the geometrical perturbation method and irradiation-dependent constitutive relationship are combined to simulate the occurrence of localized necking and the Lüders band with and without irradiation effects.Considering the necessity of perturbation in the simulation of deformation localization,the competition between extrinsic geometrical imperfections and intrinsic microstructure evolution on the necking process is revealed by a series of simulations with different perturbation coefficients.Moreover,face center cubic(FCC)metals including copper and austenitic stainless steel are taken as examples to correlate the irradiation hardening with the irradiation-advanced necking instability.The increase of flow stress and the decrease of work hardening capacity take responsibility for the limited ductility whereas the potential irradiation-accelerated texture softening is not observed.Then,a coupled mechanism of dislocations unpinning followed by the hindrance of movement is proposed to explain the increase of both lower yield point and Lüders strain in the irradiated mild steels,and a modified power law is used to depict the evolution of the Lüders band by simulations in which yield drop,stress plateau,strain transfer and strain hardening can be produced.The irradiation-induced diffuse necking is also present in pure metals for the first time by simulations.Our findings elucidate the important roles of geometry on necking instability and better reveal the clear physical picture of macroscopic deformation instability commonly observed in irradiated metals.

关 键 词：吕德斯带 金属材料 奥氏体不锈钢 晶体塑性 下屈服点 流动应力 几何缺陷 均匀延伸率 

分 类 号：TG142[一般工业技术—材料科学与工程]