Crack identification by ‘arrival time’ using XFEM and a genetic algorithm

A computational framework is developed in which cracks in two‐dimensional structures are identified, in conjunction with non‐destructive testing of specimens. As opposed to a previous study by the authors, which was based on time‐harmonic excitation with a single frequency, here the transient response of the structure to a short‐duration signal is measured along part of the external boundary. Crack detection is performed using the solution of an inverse time‐dependent problem. It is shown that the arrival time of the input signal to the points of measurement is a good criterion for crack identification in the time domain. The inverse problem of identification is solved using a genetic algorithm, while each forward problem is solved by the time‐dependent extended finite element method (XFEM). The XFEM scheme is efficient in that it allows the use of a single regular mesh for a large number of forward time response problems with different crack geometries. Numerical examples involving a crack in a flat membrane are presented. Identification based on ‘arrival time’ is shown to perform better than that based on time‐harmonic response. Copyright © 2008 John Wiley & Sons, Ltd.