Notch Effect on Plastic Deformation of Metallic Glass: A Numerical Study by Revised Free-Volume Theory

J F Yan,X G Yan,W J Meng,H Guo,Z Chen

doi:10.1155/2020/7872815

Abstract

By means of a revised free-volume theory, the notch effect on metallic glass was systematically investigated by the numerical method. Simulations on specimens without notches demonstrated that the parameters being determined in this work could reasonably describe the strength asymmetry of tension and compression. Moreover, four samples with different notches were used to numerically investigate the notch effect on global strength and plasticity. A better agreement could also be achieved between current simulations with existing experimental results, compared with another free-volume model. Combined with the free-volume distribution during deformation process, it was proven that the intersection of two major shear bands is the cause for the strength and plasticity enhancement found in sample with two symmetric notches. Besides, strength asymmetry between tension and compression was also found for notched samples. Compressive strengths are accordingly higher than tensile ones. Moreover, with the augment of the aspect ratio, the plasticity for specimens with two symmetric notches was found to increase firstly and then decrease afterwards.

Highlights

Metallic glass has received loads of attentions because of its unique properties such as high strength, large elastic limit, and high hardness [1,2,3]
Since notch could result in stress concentration leading to stress triaxiality, it is necessary to investigate the shear banding process in metallic glass when different notches are installed and eventually to understand dependence of notch configuration on the global plasticity. erefore, according to a recent constitutive law considering hydrostatic stress [21], systematic simulations are performed to understand the dependence of the global plasticity on the notch configurations and geometry by means of a user material subroutine (UMAT) in ABAQUS software
For the metallic glass Zr52.5Ni14.6Al10Cu17.9Ti5 [7], its measured tensile and compressive strengths are 1.66 GPa and 1.84 GPa, respectively [27]. It demonstrates an obvious tensile and compressive asymmetry, and the compressive strength is higher than tensile strength, which is consistent with our previous description on hydrostatic stress

Summary

Introduction

Metallic glass has received loads of attentions because of its unique properties such as high strength, large elastic limit, and high hardness [1,2,3]. A few models have been developed to analyze the shear banding process under complex stress states, few approaches have been reported on the notch effect of metallic glass when hydrostatic stress is considered. Since notch could result in stress concentration leading to stress triaxiality, it is necessary to investigate the shear banding process in metallic glass when different notches are installed and eventually to understand dependence of notch configuration on the global plasticity. Erefore, according to a recent constitutive law considering hydrostatic stress [21], systematic simulations are performed to understand the dependence of the global plasticity on the notch configurations and geometry by means of a user material subroutine (UMAT) in ABAQUS software. It is anticipated that the current work could broaden the understanding of deformation mechanism for metallic glass under complex stress states

Constitutive Laws considering Hydrostatic Stress Contribution

Results and Discussion

Deformation Behavior of Notched and Unnotched Samples