Showing papers by "Subhendu K. Datta published in 1997"

Axisymmetric Guided Wave Scattering by Cracks in Welded Steel Pipes

Abstract: 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.

Axisymmetric Guided Waves in Jointed Laminated Cylinders

Abstract: A combination of finite element formulation and wave function expansion is used to investigate the scattering of axisymmetric guided waves by an interphase region with bonding material between two laminated cylinders. The motivation of this study is to develop an effective numerical technique to characterize the material properties and the thickness of the bond region between two cylinders that are laminated and anisotropic. Numerical results of wave scattering are presented for a welded steel pipe with different weldment shapes and for two cross-ply symmetrically laminated composite cylinders that are bonded end to end. It is shown that as the frequency increases the reflection coefficients have resonance peaks while the transmission coefficients have sharp drops at the cutoff frequencies of higher guided modes in the cylinders. The resonance peaks of reflection coefficients become increasingly pronounced as the thickness of the joint increases. Another interesting feature is that the reflection coefficients have minimums at frequencies that depend on the thickness and the material properties of the joint. These features may be useful in quantitative nondestructive evaluation of joint properties.