On the dynamics of localization and fragmentation-IV.Expansion of Al 6061-O tubes

摘要

In this series of papers, we investigate themechanics and physics of localization and fragmenta-tion in ductile materials. The behavior of ductile met-als at strain rates of about 4,000-15,000 per secondis considered. The expanding ring experiment is usedas the vehicle for examining the material behavior inthis range of strain rates. In Parts I–III, we examinedthe response of rings with cross-sectional aspect ratiosin the range of 1-10, exhibiting a transition from dif-fuse necking to sheet-mode localization. In the presentpaper we report on experimental observations of highstrain-rate expansion of Al 6061-O tubes. Through aninnovative use of high-speed imaging aided with a con-ical mirror we determine the sequence of deformationand failure in the expanding tube. In particular, the con-ical mirror provides information of surface deforma-tion on the tube. Forming limit diagrams at high strainrates are obtained from post-mortem measurement ofthe deformed tubes or fragments and are compared withanalysis from quasi-static analysis. Numerical=simula-tions are used to explain the experimental observations.