An effective crack identification method in viscoelastic media using an inverse meshfree method

Abstract

In the present study, a numerical approach is proposed for identification of straight cracks in two-dimensional linear viscoelastic media. The identification procedure is based on the wave propagation in cracked viscoelastic media. The forward wave propagation problem in viscoelastic media is solved using the meshfree radial point interpolation method (RPIM), which allows the crack boundary to be easily modelled at any part of the domain. In the meshfree approach, the crack position can be changed freely during the iterations of the identification procedure. A modified higher-order incremental method is implemented for modelling dynamic behaviour of linear viscoelastic materials. Also, the integration points are determined using the background decomposition method (BDM). Firstly, the wave propagation behaviour in viscoelastic media is studied, and the effect of crack on wave propagation is investigated. Then, the inverse identification task is formulated as a nonlinear optimization problem to determine the unknown crack parameters. The optimization problem is solved by a gradient-based inverse method. Several numerical tests are simulated with different number of sensors, crack size, and various initial guesses, to demonstrate the capability of the proposed techniques in obtaining accurate results. Also, it is shown that the proposed method is robust to tackle reasonable levels of measurement error. In addition, the method is investigated for different placement patterns for several sensors and the effect of number of sensors on identification of the crack is studied.