QUANTIFYING THE CONSTRAINT OF THREE-DIMENSIONAL BIAXIALLY LOADED SPECIMENS CONTAINING SEMI-ELLIPTICAL CRACKS USING THE J-A2 METHOD

Fracture toughness is an important material property used to. assess the structural integrity of mechanical components containing cracks. Often, the fracture toughness depends upon the geometry of the component as well as the applied loading. This dependence is referred to as the constraint effect in fracture. The two parameter J-A(2) method can be used to quantify the constraint effect. The J-A(2) method is a more accurate representation of the stress fields near the crack compared to the classical HRR solution, as additional terms from the series solution are used. The subject of the current study is to apply the J-A(2) method to published fracture toughness data of three-dimensional, flat plates containing semi-elliptical cracks and subjected to both uniaxial and biaxial loading to determine the constraint effect and also to determine if the method can be used to predict fracture. The J-A(2) results of the flat plates are compared to those of 3PB specimens to determine if loss of constraint exists. Finite element analysis models were developed for each specimen to determine the constraint parameter A(2) for each applied loading. The results of the current study reveal that both the uniaxial and biaxial loaded plates exhibit loss of constraint relative to the 3PB specimen and biaxial load increases the constraint of the uniaxially loaded specimen. Further, the J-A(2) method shows potential as a tool to predict failure with different constraint level.