Guided wave propagation and focusing in multi-layer pipe with viscoelastic coating and infinite soil media

A semi-analytical finite element (SAFE) algorithm was developed to investigate the wave propagation possibilities in coated pipes. An experiment was carried out on a 203 mm schedule 40 steel pipe coated with 4 mm fibrous coal tar material at 272 K (-1 °C). The application of the coated pipe focusing parameters brought an enhancement up to 44% compared with axisymmetric inspection, and up to 360% compared with the bare pipe focusing parameters, which is additional evidence of the benefit of improving penetration power using the real-time phased array focusing technique for pipe inspection. The soil influence on the penetration power of guided waves is another major concern for pipe inspection since many pipelines are buried in soil. A novel hybrid SAFE technique was developed to tackle the real-time phased array focusing in buried pipe. The parameters calculated by the hybrid SAFE technique were compared to the parameters calculated by the SAFE and analytic techniques, resulting in a significant enhancement of the penetration power and potentially excellent signal-to-noise ratio.