静水应力对金属玻璃变形和破坏的影响

EFFECT OF HYDROSTATIC STRESS ON THE DEFORMATION AND FAILURE OF BULK METALLIC GLASSES

论文考虑自由体积、热和静水应力等因素对材料变形和破坏的影响,推导了块体金属玻璃的三维热力耦合本构模型,并引入临界自由体积浓度的材料破坏准则.将相应本构模型和破坏准则写入LS-DYNA软件的用户自定义材料子程序(UMAT)中,开展了针对金属玻璃在不同变形条件下的有限元模拟研究,分析材料内部物理参量的演化特性及其所导致的材料宏观表象.分析显示,静水应力对金属玻璃的力学行为具有重要影响,导致材料的变形和破坏呈现出显著的拉压不对称特征.

A modified coupled thermo-mechanical constitutive model for bulk metallic glasses(BMGs),which is generalized to the multiaxial stress state and considers all the effects of free volume,heat and hydrostatic stress,has been deduced in the present paper.Besides,a failure criterion of critical free volume concentration is introduced.The constitutive model as well as the failure criterion is implemented into the LS-DYNA commercial software through the user material subroutine(UMAT).Then FEM simulations for different deformation conditions are conducted,and the evolutions of material parameter as well as corresponding macroscopic mechanical behavior of material are analyzed.Related analysis shows that the hydrostatic stress effects the deformation and failure of BMGs significantly,and it will lead an obvious asymmetry between the deformation or failure under tension and compression.