Experimental Relationship Between Equivalent Plastic Strain and Constraint for Crack Initiation
SourceThe applicability of fracture mechanics data generated from standard fracture toughness specimens in predicting structural integrity is often a concern. For elastic-plastic conditions, a second parameter identified as “constraint” (hydrostatic stress divided by the equivalent stress) is being used to link different specimen/flaw configurations, thus providing a mechanism for using data generated from standard fracture toughness specimens to predict structural integrity. Much of the literature is concerned with the difference in constraint between specimens and a structure, while little effort is being given to investigating the sensitivity of the crack initiation process to constraint for a given material. This paper presents experimental results relating crack initiation processes to constraint for a ferritic steel and an aluminum-based alloy.