A Quantitative Strain-and-Stress State Criterion for Failure in the Vicinity of Sharp Cracks

A quantitative strain-and-stress state criterion for failure has been developed which is applicable in the vicinity of sharp cracks. This criterion is applicable to any example which may be represented by finite element theory in the detail required to determine the strain-and-stress state for the crack tip region. The restriction of linear elastic fracture mechanics which defines a minimum crack length is removed, since the influence of the free boundary in the vicinity of the crack is included in the finite element solution. The development of the criterion includes an experimental base and demonstrates the applicability for the conditions of a “sharp” fatigue crack and for a “blunt” machined notch with an ∼0.001-in. tip radius.