The paper presents a numerical technique to estimate the critical value of J integral, of a ductile metal (Aluminum alloy). Cracked, Single Edge Notch Bend (SENB) specimen of the alloy is modeled by finite element method. Load over the specimen is chosen such that the process or fracture zone is generated at the crack tip. The load is subsequently increased for the process zone size to go up. Process zone sizes and displacements under loads are measured from post processor solutions. Resistance curve and blunting line are plotted. Intersection of the two provides the value of. equals upon fulfillment of the plane strain condition. Various thickness values of the specimen are tried. The value of KIC obtained from is found to be in close agreement with the reported value obtained from experiments.Nomenclature