An Experimental and Numerical Investigation of Non-isothermal Cup Drawing of a 7XXX-T76 Aluminum Alloy Sheet

The 7000-series of aluminium alloys are an attractive material for anti-intrusion components in the car body-in-white due to their high specific strength and lower density. The limited room temperature formability of these alloys can be overcome through elevated temperature forming while controlling heat exposure to prevent changes to the microstructure such as over-aging. The present work details a comprehensive characterization of a developmental alloy, 7xxx-T76, for non-isothermal warm forming of a cylindrical deep drawn cup. Material anisotropy and a non-associated constitutive model were developed with the hardening response as a function of temperature and strain-rate. Friction was characterized at elevated temperature using a Warm Twist Compression Test apparatus developed at the University of Waterloo. Significant material anisotropy was observed in the tensile characterization results and during warm forming with the formation of eight ears in the deep drawn cups for a drawing ratio of 2.25. The predictions of the forming model were evaluated in terms of the earring profile, punch force, and surface strains from optical strain measurements using ARGUS.