Abstract: In order to enhance the formability of aluminum alloy sheet, advanced forming technologies have been developed. Warm forming is an effective technology to realize high formability and high forming accuracy of aluminum alloy. The forming speed and temperature are important parameters of the warm forming technology and have significant effect on the formability of aluminum alloy sheet. A new approach for predicting forming limit of aluminum alloy sheet with comprehensive consideration of the influences of temperature and strain rate is presented. Response surface method is used to establish the mechanical property functional relationship between strain hardening index n, strain rate sensibility index m and forming temperature, strain rate condition. Based on M-K theory and by combining with Logan-Hosford yield function, the forming limit diagram calculation model of aluminum alloy sheet coupled with temperature and strain rate is derived. Model inspection shows that the response surface equation of mechanical properties has high precision. The calculation result of forming limit agrees well with the existing test value, which verifies the validity and reliability of the approach for predicting forming limit of aluminum alloy sheet coupled with temperature and strain rate.

Key words: Aluminum alloy sheet, Forming limit, Strain rate, Warm forming