J-integral method for fitness-for-service assessment

Development of a method for evaluation of material toughness requirements, allowable defect sizes, and sustainable stresses and strains is described. Yielding fracture mechanics and, specifically, the J integral are employed. The J integral is regarded as the crack driving force; applied J values above some critical value are predictive of material tearing. The applied J value is a function of applied stress and strain, crack length, and material tensile properties. The critical J integral value is measured in material fracture-toughness tests. The applied J integral is measured experimentally as a function of stress and strain in HY130 specimens with different crack lengths.