Axisymmetric Guided Wave Scattering by Cracks in Welded Steel Pipes

Scattering of axisymmetric guided waves by cracks and weldments of anisotropic bonding material in welded steel pipes is investigated in this paper by a hybrid method employing finite element and modal representation techniques. The study is motivated by the need to develop a quantitative ultrasonic technique to distinguish flaws and bonding materials in welded cylindrical structures. Numerical results for reflection coefficients are presented for a steel pipe with cracks and V-shaped weldments with and without cracks at the interface between the weldment and the steel pipe. It is shown that as the frequency increases, the coefficients of reflection exhibit resonant peaks at the cutoff frequencies of higher guided modes. These peaks become increasingly pronounced as the slope and the length of the crack increase. Numerical results presented have important applications in quantitative nondestructive evaluation.