Guided wave attenuation due to deposits on the pipe wall

Abstract

Our interest is taken in the reflection and the attenuation of longitudinal waves caused by a circular shape deposit placed on the pipe wall. The reflection of the S0 mode by the deposit is experimentally shown. The experimental results are compared with the theoretical results obtained from a finite element method (FEM). The attenuation of modes is determined and analyzed for five widths of deposit. In the case of a tube filled with water, only the symmetrical waves, S0 in low frequency and S1 (f=2.56 MHz), are considered because of their strongly axial nature. A viscous deposit (epoxydic resin) characterized by different widths and placed on the surface of a pipe is the defect considered in this article. Our interest is taken in the attenuation of the longitudinal waves at particular frequencies. Theoretically and experimentally, the propagation of guided waves is considered in a stainless steel tube (length L=3 m) with an outer radius a = 19 mm, an inner radius b = 17.5 mm (thickness d = 1.5 mm). The mechanical parameters are CL = 5823 m/s (longitudinal wave speed), CT = 3210 m/s (transverse wave speed), ρ = 8027kg/m 3 (density), filled or not with water (Fig.1).