A method for cracked body J-integral estimation

For medium strength metals, research is still underway to formulate methods of estimating crack growth. One of the complications for this type of material is significant plastic yielding around the crack tip before fracture commences. One parameter which has been proposed for estimating crack growth is the J-integral. Calculating this parameter for an elastic-plastic stress field is complicated. A method proposed by Sumpters, for estimating the J-integral of a cracked body with significant but constrained plastic yielding, uses elastic field values thus reducing the order of complexity. Assuming the J-integral to be a useful fracture criterion this method might be employed for design and assessment. An investigation has been made and the method has been extended to cover cases more complex than those originally studied. (author)