FINITE ELEMENT ANALYSIS OF CRACK PROPAGATION IN STRESS CORROSION CRACKING TEST SPECIMEN

Abstract

Most of the structural components these days require high strength to weight ratio. This has been made possible by use of high strength steels. But the susceptibility of high strength steels to stress corrosion cracking is a crucial problem. Components such as ship hulls, which are working in a corrosive environment and under stresses have been, reported to fail, by stress corrosion cracking. Here an attempt has been made to analyze the propagation of crack in a SCC test specimen of AISI 4340 steel. The data regarding the stress intensity factor at various crack lengths is available from Ph.D. thesis of V. K. Tewari and geometric modeling of the test specimen has been done using the ANSYS software. The model has been authenticated by comparing the stress intensity factor values available from the Ph.D. thesis with those obtained by using the ANSYS commands and they have been observed to be very close with little error. The ANSYS software was then used to obtain the stress contours in the geometric model and these stress contours were related to the fractographs available in the Ph.D. thesis. These stress contours confirm that with increasing stress intensity the stresses in the material are on a rise and relate well with the fracture mode which changes from intergranular -stress corrosion fracture with secondary intergranular cracks (at low stress intensity) to intergranular stress corrosion fracture with microvoid coalescence (at high stress intensity).