Nonlinear guided wave mixing in pipes for detection of material nonlinearity

Abstract

Pipes have multiple applications in daily life and they are subjected to different types of defects. Nonlinear guided wave has attracted significant attention in detecting microstructural change at early stage of material deterioration. Extensive research using wave mixing with different wave modes has focused on plate-like structures. However, limited experimental studies have been conducted on the detection of material nonlinearity in pipes using two interacting guided waves. This study investigates nonlinear features generated due to mixing of torsional guided waves and material nonlinearity in pipes at low frequency range. The nonlinear theory of elasticity is implemented in a three-dimensional (3D) finite element (FE) method to simulate the effect of material nonlinearity on torsional guided wave mixing. The phenomenon of nonlinear features generated due to torsional guided wave mixing is investigated by 3D FE models. There is good agreement between the data obtained in the laboratory and numerical simulation results. This study demonstrates the existence of the combinational harmonic generation experimentally and provides physical insight into the phenomenon of nonlinear wave mixing. The findings of this study can further advance the damage detection techniques based on material nonlinearity in wave mixing.