绝热剪切破坏的超弹-塑性本构与多尺度方法研究

Adiabatic shear band failure and fracture is a dominate damage mode in the structure of key component for metals subjected to shock loading. The dynamic behavior and mechanism remains one of the most important fundamental issues in the fields of material science and weapon physics. This program aims to establish a microstructure characterized anisotropic hyperelastic-plastic constitutive model, and develop a multiscale method that coupling the strain enhanced finite element and the particle calculations, for simulating the initiate nucleation, evolution development, interaction and the growth into macroscopic damage of shear bands subjected to ballistic loading. Based on the crystal plasticity theory, we derive the hyperelastic-plastic constitutive model within a thermodynamically admissible framework, and incorporate the microstructure evolution and heterogeneous deformation effects that related to the material macroscopic property into the computation of plasticity. The essential technique points in the simulation of shear band fracture 1) The effect of strain softening is added to the flow stress based on the large deformation gradient theory, to address the pathological mesh-dependence issue; 2) Considering the shear localization resulting “stress collapse” phenomenon, multiple physical models are presented to describe the different dynamical behaviors inside and outside the shear band, respectively; 3) The multiscale method that coupling a strain enhanced finite element with a meshfree particle simulation is proposed to capture the material damage evolution and fragmentation will be investigated and developed. Cooperating with the study of experimental group, we aim to deepen the understanding of nucleation and evolution of micro-defects and reveal the underlying micro-mechanism for macro adiabatic shear band fractures.

强冲击下金属绝热剪切带失效和破坏模式在关键部件结构损伤和断裂过程中占主导地位，其动力学行为和机理是材料科学、武器物理领域长期以来关心的基本问题之一。本项目旨在建立微结构表征的各向异性超弹-塑性本构模型，发展耦合应变增强型有限元和粒子模拟的多尺度方法，实现爆轰加载下剪切带从损伤形核、发展演化、相互作用至贯穿汇合成宏观断裂的全过程数值模拟。在热力学相容框架下基于晶体塑性理论推导超弹-塑性本构模型，将影响材料宏观性能的微结构演化和非均匀形变效应包含在塑性计算中。发展模拟剪切带破坏的关键技术：利用梯度理论增加流应力的应变软化效应，解决长期以来剪切带计算中的网格依赖问题；针对剪切局部化引起的“应力坍塌”现象发展多物理模型分别描述剪切带内和带外的不同动力学行为；研究耦合应变增强型有限元和粒子模拟的多尺度方法以描述材料断裂破碎过程。结合相关实验研究，探讨微缺陷成核演化规律以及宏观损伤的微观机理。

本项目针对关键部件中金属绝热剪切带失效和损伤断裂数值模拟中的难点问题开展研究，通过推导热力学相容的超弹-塑性本构关系，建立了微结构表征的各向异性超弹-塑性本构模型，将位错、空洞等微缺陷演化效应包含在塑性计算中。探讨了冲击加载下绝热剪切带等损伤结构网格依赖性的物理和数学原因，利用形变梯度理论解决网格依赖问题。发展了耦合塑性-损伤机制的相场变分模型，分析了本构关系与引发剪切局部化应变软化机制之间的关系以及解决方案。基于以上绝热剪切失效及损伤演化数值模拟研究，发展了耦合粒子模拟和有限元计算的多尺度方法，建立了相关数值模拟程序，对典型结构绝热剪切失效及后续演化破坏开展了研究，结合实验研究探讨宏观剪切破坏的微观机理。工程应用方面，本项目建立的多尺度程序模拟了熔石英材料从微观缺陷受热膨胀、损伤成核到裂纹生长直至宏观破坏过程。结合相场方法与热-力耦合本构模型对损伤起始与演化开展了数值模拟研究，为深入理解熔石英损伤机制提供了一个有力工具。