Effect of thermal and residual stresses on the J-integral elastic-plastic fracture analysis

Abstract

This paper presents a comprehensive finite element study using the ADINA code with an objective towards developing a procedure for incorporating the effect of thermal/residual stresses in the J-integral elastic-plastic estimation method. Thermal-elastic-plastic finite element studies have been carried out for several two-dimensional crack geometries including the center-cracked plate, single-edge cracked plate and cylinders containing axial and circumferential flaws. Analyses are based on the J 2 flow theory of plasticity and include material strain hardening. Results are obtained for various fracture parameters of interest such as J, COD and mouth-opening displacement (MOD). The J-integral is calculated by a virtual crack extention method, modified for thermal-elastic-plastic crack problems. It is shown that the effect of thermal/residual stresses is negligibly small when fully plastic conditions are achieved. Based upon these observations and using the superposition principle for the stress intensity factor K 1 under small-scale yielding, a modified procedure for estimating fracture parameters under thermal-elastic-plastic conditions is formulated. The results thus obtained are compared against detailed finite element calculations, with an observed excellent agreement between the two sets of results. Various aspects of the crack-tip behavior under the conditions of thermal-elastic-plastic deformation are also discussed.