DYNAMIC STRESS-STRAIN RELEASE PATHS FOR ALUMINIUM AND MAGNESIUM MEASURED TO 200-KB

Measurements are presented of the variation of stress and strain in metals as they are subjected to shock impulses of up to 200 kb and released. Results have been obtained for a magnesium alloy and for two grades of aluminium of very different yield strengths. The release characteristics of these metals are shown to be broadly consistent with a simple elasto-plastic model for metal behaviour. Elasto-plastic Hugoniots are fitted to published shock data for the metals used; a revised calibration is given for the manganin stress transducer employed, and a new method of construction is illustrated. Stress relaxation is observed in magnesium and is associated with the easy slip on the basal plane in hexagonal close-packed materials.