Identification of crack positions and crack loading quantities from strain gauge data by inverse problem solution

Abstract

A method for the detection of cracks in finite and semi-infinite plane structures is presented. This allows both the identification of crack position parameters such as length, location and inclination angles with respect to a reference coordinate system and the calculation of stress intensity factors (SIFs). The method is based on strains measured at different locations on the surface of a structure and the application of the dislocation technique. Cracks and boundaries are modelled by continuous distributions of dislocation densities. This approach gives a set of singular integral equations with Cauchy kernels, which can be solved using Gauss-Chebyshev numerical quadrature [Erdogan et al. (1973)]. Once knowing the dislocation densities, the strain at an arbitrary point can be calculated. The crack parameters as well as external loads are parameters which are determined by solving the inverse problem with a genetic algorithm. Once knowing loading and crack parameters, the SIFs can be calculated.