Analysis of dispersion characteristics of elastic wave in sandwich pipeline

The dispersion characteristics of the elastic wave in pipeline wall, the acoustic wave in pipeline and the wave propagation of acoustic-solid coupling between elastomer and fluid are studied. Based on Timoshenko beam model, the wavenumber analytical formula of elastic pipeline is derived. Considering the acoustic-solid coupling effect, the wave numbers and mode shapes of the coupling between the elastic wave of pipeline wall and the acoustic wave of fluid in the unlimited length sandwich pipeline are solved. The dispersion relation, guided wave modes, and the cut-off frequencies of different orders under coexistence of water and air in the pipeline are calculated by parametric scanning. From the analysis results, the analytical solution and numerical solution of the dispersion curves of different media in the sandwich pipeline are basically consistent. Over a certain frequency, the numerical solution of bending mode produces deviation, and the elastic wave mode will experiences mode interference. The analysis of the elastic wave dispersion characteristics of sandwich pipelines provides a theoretical basis for acoustic detection of fault in sandwich pipelines.