Crack-Propagation Sensitivity Index as a Tool to Promote Concepts of Fracture Mechanics

We consider basic parameters used for the evaluation of the reliability of engineering structures by the methods of fracture mechanics, namely, the geometry and location of cracklike defects, loading conditions, and crack-growth resistance of the material. It is indicated that the results of evaluation of reliability can be efficiently combined with the data of nondestructive diagnostics of structural elements. For this purpose, we introduce a notion of crack-propagation sensitivity index of a structural element. In the case of quasistatic loading, this parameter is introduced as the derivative of the stress intensity factor KI with respect to the crack length a: ∂KI/∂a. For cyclic loading, this parameter is defined as the slope of the log NR–a curve, where NR is the residual service life of the analyzed structural element. We also present examples of application of the proposed approach for the cases of a cylindrical pipe with corner crack and plates with central and edge cracks.