Ductile fracture toughness evaluation at high strain rates using stretch zones and shear lips

摘要

Fracture studies of high strength low alloy steels, at very high loading (strain rates) of up to K equal to 10~6 MPa m sq root/s were conducted using a specially designed Split Hopkinson Bar (SHB) equipped with a swing arm mechanism capable of fracturing compact tension (CT) specimens with a thickness of 12.7 mm. While it was possible to reproduce the load-displacement curves for the specimens, evaluation of the fracture toughness was mostly obtained from post-test examination of the stretch zone ahead of the crack using scanning electron microscopy.