Abstract: The fully plastic plane stress solutions of elastic-plastic fracture mechanics parameters such as J-integral, load-point displacement and crack-opening displacement were computed for a welded center-cracked specimen in monotonically loading with the fully plastic finite element method. The equivalent yielding stress and equivalent strain hardening exponent near the crack tip were introduced for estimating the fracture mechanics parameters with mechanical heterogeneity. The engineering approach for estimating the elastic-plastic fracture mechanics parameters of weldment was given.The accuracy of the approach was assessed by using elasticplastic finite element calculations for a specific configuration.