Determining plane strain fracture toughness and the j-integral for solid

Abstract

A method of determining the mechanical behavior of solid materials by using stress field modified miniature specimens. The method is an improvement in the method of determining mechanical behavior information from specimens only so large as to have at least a volume or smallest dimension sufficient to satisfy continuum behavior in all directions. Mechanical behavior of the material is determined from the measurements taken during the loading of the specimen resulting in the formation of cracks and/or the further propagation of cracks in the miniature specimen. The specimens include construction features for applying additional stress field modifying loads upon the specimens during the test. These additional loads result in a desired stress state in the specimen which could not be achieved otherwise. A particular example is the introduction of a transverse tensile load during a bend test to increase the transverse stress field to achieve plane strain conditions in a thin specimen. The methods are useful in determining plane strain fracture toughness, dynamic plane-strain crack initiation and arrest fracture toughness, the J-Integral for the material, and the fracture mode transition behavior when the specimen thickness and volume is smaller than previously thought necessary.