A dynamic XFEM formulation for crack identification

Nelder–Mead (NM) and Quasi-Newton (QN) optimization methods are used for the numerical solution of crack identification problems in elastodynamics. Fracture is modeled by the eXtended Finite Element Method. The Newmark-β method with Rayleigh damping is employed for the time integration. The effects of various dynamical test loads on the crack identification are investigated. For a time-harmonic excitation with a single frequency and a short-duration signal measured along part of the external boundary, the crack is detected through the solution of an inverse time-dependent problem. Compared to the static load, we show that the dynamic loads are more effective for crack detection problems. Moreover, we tested different dynamic loads and find that NM method works more efficient under the harmonic load than the pounding load while the QN method achieves almost the same results for both load types.