Study of fracture resistance of a weldment with a propagating crack

The overall fracture resistance of a weldment with a propagating crack across the weld, HAZ and base material has been evaluated for a AISI type 316LN stainless steel (SS), based on coupled experimental-finite element analysis. Compact type (CT) specimens with initial crack tip in the weld, heat affected zone (HAZ) and base material have been tested to evaluate J-integral resistance curve (J-R curve) across the weldment. Towards evaluating the J-integral for a heterogeneous material, elastic component of J was determined using equivalent Young's modulus (Eeq) in terms of instantaneous compliance and crack depths. Simultaneously, finite element (FE) analyses have been carried out to estimate J-integrals for various contours across the weldment and for nodal singularities along interfaces, leading to a modified J-integral for overall weldment. The reasonable agreement among experimental J values from different regions with the modified J-integral values gives credence to this procedure to predict overall fracture resistance across the weldment over a heterogeneous microstructural gradient.