Investigation of nonlinear torsional guided wave mixing in pipes buried in soil

Abstract

Pipes have been widely applied in different engineering areas, such as drainage and the conveyance of chemical products and they are usually installed underground. This makes the structural integrity inspection becomes challenging. Numerous studies investigated the phenomenon of guided wave propagation in buried pipes and the wave interaction with different types of damage, e.g. corrosion and thermal damage. However, very limited studies focused on studying guided wave mixing in embedded pipes, which has recently attracted significant research interest for damage detection. This study develops a three-dimensional (3D) finite element (FE) model incorporating strain energy function to analyse wave mixing phenomena in pipes embedded in the soil. To characterise nonlinear features, such as combinational harmonic generation, due to guided wave mixing, the 3D FE model is used to simulate two torsional guided waves interacting with each other. The numerical results are then verified by experimentally measured data and the results show that the amplitude in the frequency-domain exhibits a sharp drop due to the energy leakage in the existence of soil medium at fundamental frequencies, second and combinational harmonics.