Numerical investigation of self-focused Lamb waves in anisotropic media

Abstract

Ultrasonic arrays are widely used in various fields including non-destructive testing and structural health monitoring (SHM) areas. Their application for inspection of anisotropic plates using guided waves is challenging, due to insufficient knowledge of angle-dependent wave velocity in the medium. Since time-reversal permits waves self-focusing without the knowledge about precise wave speed values, it seems to be a feasible solution for waves-steering in anisotropic media. In this paper performance of decomposition of the time-reversal operator (DORT) algorithm as well as its extended DORT-CWT method were studied on data from numerical simulations. The propagation of the guided ultrasonic waves in an anisotropic carbon fiber reinforced polymer (CFRP) plate was modelled using the local interaction simulation approach. Several application scenarios were investigated including different number and placement of the damage locations. In each case a number of simulations were performed to obtain the inter-element impulse responses for all the assumed transducers. The responses were decomposed to find the phase shifts and amplitudes necessary to focus on the scatterers. Accuracy of the estimated parameters for the DORT and DORT-CWT methods was verified by performing the backpropagation using all emitters in phased array mode. The presented approach produced accurate focusing on particular damage locations.Ultrasonic arrays are widely used in various fields including non-destructive testing and structural health monitoring (SHM) areas. Their application for inspection of anisotropic plates using guided waves is challenging, due to insufficient knowledge of angle-dependent wave velocity in the medium. Since time-reversal permits waves self-focusing without the knowledge about precise wave speed values, it seems to be a feasible solution for waves-steering in anisotropic media. In this paper performance of decomposition of the time-reversal operator (DORT) algorithm as well as its extended DORT-CWT method were studied on data from numerical simulations. The propagation of the guided ultrasonic waves in an anisotropic carbon fiber reinforced polymer (CFRP) plate was modelled using the local interaction simulation approach. Several application scenarios were investigated including different number and placement of the damage locations. In each case a number of simulations were performed to obtain the inter-elem...