Dynamic Fracture Toughness versus Crack Tip Speed Relationship at Lower than Room Temperature for High Strength 3239var Structural Steel

A transient _nite element analysis is carried out to provide insight into the low temperature dynamic material toughness versus crack tip relationship for high strength structural steels under intense stress pulse loading[ The problem analyzed here is plane strain fracture of an edge cracked specimen under plane wave loading conditions[ The _nite element formulation employed accounts for the e}ects of _nite geometry changes\ material inertia\ and heat conduction[ The material is characterized as an isotropically hardening and thermally softening elastic!viscoplastic von!Mises solid[ To model crack initiation and crack advance various crack!tip equations of motion based on elastodynamic modelling of crack growth are used[In particular\ relatively simple forms for the crack tip equation of motion corresponding to crack growth at either constant energy release rate\ or a constant stress intensity factor\ or a constant crack tip speed\ along with more complicated forms involving a sharp upturn in fracture resistance at a limiting crack tip speed are employed[ The results of these models emphasize the existence of a sharp upturn in dynamic fracture toughness in high strength structural steels at a material characteristic limiting crack tip speed at test temperatures as low as −79>C and with crack tip loading rates of the order of KþI 1⁄4 09 7 MPa zm:s[ Þ 0887 Elsevier Science Ltd[ All rights reserved[