Flow and fracture characteristics of aluminium alloy AA5083-H116 as function of strain rate, temperature and triaxiality

摘要

This paper presents a part of an on-going study of light-weight shelters made of aluminium alloy AA5083-H116. A necessary prerequisite for numerical simulations of impact behaviour of such shelters is a calibrated numerical model. Slightly modified versions of the two Johnson-Cook models describing flow stress and fracture strain are applied. In addition to ordinary quasistatic tests with smooth specimens, these models demand tests at elevated temperatures and strain rates, and different triaxiality ratios. All tests to be presented in this paper are uniaxial tension tests performed in servohydraulic test machines or a Split-Hopkinson bar. The test programme involves approximately 100 specimens, and includes coupons from three different directions of the plate material, thereby taking account for the anisotropy. The AA5083 alloy is susceptible to dynamic strain ageing, and this phenomenon is shown to result in serrated stress-strain curves and negative strain rate sensitivity for a rather wide range of strain rates. In particular, the specimen geometry seems to have a strong influence on the serrated curves. The calibration shows that the Johnson-Cook-type models represent most of the observed material behaviour reasonably well, although the negative strain rate sensitivity is not adequately described.