Potential drop method for online crack length measurement during fracture testing: Development of a correction procedure

Though the potential drop method is included in testing standards for creep and fatigue crack growth, it is not used in fracture toughness tests because it overestimates the crack length during the initial loading due to crack tip plastic deformation. In the present paper, a procedure is proposed for correcting for this by using the blunting line equation and stretch zone width, a physical parameter as the reference. Compact tension samples of three different thicknesses were employed. The results after correction are compared with those from the standard methods, viz., elastic unloading compliance and normalization methods.