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International Journal of Automotive Technology > Volume 20(S); 2019 > Article
International Journal of Automotive Technology 2019;20(S): 31-37.
ON THE CONSTITUTIVE MODELS FOR ULTRA-HIGH STRAIN RATE DEFORMATION OF METALS
Hossein Sedaghat, Weixing Xu, Liangchi Zhang, Weidong Liu
The University of New South Wales
PDF Links Corresponding Author.  Liangchi Zhang , Email. liangchi.zhang@unsw.edu.au
ABSTRACT
Ultra-high strain rate deformation (> 104 s-1) is common in high speed manufacturing and impact engineering. However, a general constitutive model suitable for describing the material deformation at ultra-high strain rates is still unavailable. The purpose of this study is of two-folds. The first is to systematically evaluate the performances of four typical constitutive models, Johnson-Cook (J-C), Khan-Huang-Liang (KHL), Zerilli-Armstrong (Z-A), and Gao-Zhang (G-Z), in predicting the dynamic behaviors of materials. The second is to obtain an improved constitutive model to better describe the deformation of materials under ultra-high strain rates. To this end, high strain rate tests were carried out on different crystalline structures, i.e., BCC, FCC, and HCP over a wide range of strain rate from 102 s-1 to 1.5 × 104 s-1. It was found that before the critical strain rate, around 104 s-1, all of the previous models can predict the flow stresses. When the strain rate passes a critical point, however, these models fail to predict the sudden upsurge of the flow stresses. The improved model developed in this paper, by considering the dislocation drag mechanism, can successfully characterize the dynamic behaviours of materials over the whole range of strain rates.
Key Words: Ultra high strain-rate, Constitutive model, Dislocations, Drag mechanism
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