Estimating Cracking Behavior of Metallic Structures

Engineering design problems may include the need to estimate whether an observed or suspected crack or crack-like flaw in a metallic structure will extend slowly enough during service operations that structural integrity will not be compromised before repairs or replacement can be conveniently scheduled. This aspect of sub-critical cracking in metal structures can be usefully treated with methods derived from linear elastic fracture mechanics. With these available formulations, the experimental bases for estimating Model I sub-critical fatigue cracking are reviewed. The effects of differing material characteristics, loading variables, and environmental factors are analyzed. Within this framework, estimated solutions for three example problems of increasing complexity are demonstrated.