STRAIN RATE DEPENDENCE OF DYNAMIC FLOW STRESS OF 2017 ALUMINUM ALLOY AT VERY HIGH STRAIN RATES.

To estimate the strain rate dependence of the dynamic flow stress of aluminum alloys, 2017-O and - T4, high strain rate and rate reduction tests are performed at strain rates ranging from about 1000/sec to 30000/sec. A steep increase in the flow stress is observed for 2017-O at the strain rate of about 3000/sec. For 2017-T4, the above phenomenon is observed at the strain rate above about 10000/sec. A simplified model for dislocation kinetics under dynamic plastic deformation is employed which can represent a transition in the rate controlling mechanism of dislocation motion from a thermally activated process to a viscous drag. It is expected that the steep increase in the flow stress observed at high strain rates is attributed to the rate dependence of the viscous drag on the dislocation motion. [ABSTRACT FROM AUTHOR]