Experimental mechanics at velocity extremes —Very high strain rates

Abstract

The early experimental work of Clark and Wood with regard to von Karman's theory on the effect of material flow and fracture at high strain rates has led to many controversial issues on these effects. Interest has been greatly revived in recent years because of the increased emphasis on such high-velocity forming processes as explosive and capacitor discharge. Considerable new work has been performed by Ling-Temco-Vought, Inc., for the Air Force, the results of which are presented in this paper. Data have been accumulated on tensile and compression specimens, spherical bulging and cylindrical bulging for a wide variety of materials. This high-speed information has been generated with the use of a special projectile impact machine and special presses utilizing various combinations of explosive and capacitor-discharge energy, with strain rates to 101/sec. The effect of velocity on ductility is discussed for total strain distribution, uniform strain, double necking and critical impact velocity. The modes of failure for various part shapes are presented and related to the forming velocity.