A method for determining mixed mode stress intensity factors using strain gage data

An experimental method for determining mixed mode stress intensity factors, crack tip location, and crack tip orientation using strain gage data near the crack tip is developed. From the strain gage data and the relative location of the strain gages to each other the location of the crack tip and its orientation relative to the strain gages is derived along with the mixed mode stress intensity factors. The method is based on an iterative linear least squares fit to generalized Westergaard equations that describe the strain field near a crack tip;The method is applied to numerical data generated from finite element models of a compact tension specimen and a mixed mode specimen. The method is also applied to experimental data from the same specimens. Theoretical, numerical, and experimental results are compared. Limits on the applicability and accuracy of the method are developed