Per-Åke Jansson

2D P-SV Wave Scattering by a Crack in a Cladding

The modeling of the ultrasonic NDT of a crack in a cladding is performed, this being of interest in the nuclear power industry. This problem is complicated by the anisotropy of the cladding and the wavy interface between the cladding and the base material. This waviness is approximated by a periodic boundary condition on a flat interface and the crack scattering problem is solved by a hypersingular integral equation technique. Some numerical examples show the importance of the interface.

Ultrasonic benchmarking with UTdefect

The computer program UTDefect has been developed during a decade and models the ultrasonic testing of a thick‐walled component with a single defect of simple shape. To solve the wave propagation and scattering problems Fourier representations, separation‐of‐variables, and singular integral equations are employed. The benchmarking problems with a side‐drilled hole in immersion testing with various angles and wave types are presented here. In general the correspondance between UTDefect and experiment is good with a difference of less than 2 dB in all but one case.

Scattering from a Rectangular Crack in a Cladding

Ultrasonic testing of a thick plate with a rectangular crack in a cladding is modelled analytically for a fully three-dimensional case. The effects of a corrugated interface and anisotropy are both taken into account. The wave scattering problem is solved by a hypersingular integral equation approach. A model for the ultrasonic transmitter and receiver is also included. Some preliminary numerical results for the change in signal response due to the presence of the crack are given.

SIMULATION OF THE 2008 ULTRASONIC BENCHMARK PROBLEMS USING UTDefect

The computer program UTDefect is used to solve some of the 2008 ultrasonic benchmark problems. UTDefect is a program for simulation of ultrasonic testing with applications within the nuclear industry in mind. Scattering from various types of defects, like a side‐drilled hole and a flat‐bottom hole, is modelled using solutions that are essentially exact. For the benchmark problems the results obtained from UTDefect are in fairly good agreement with the experimental data from CEA.

Ultrasound in an Anisotropic Cladding with Wavy Interface

The propagation of ultrasonic waves from a probe on a thick plate with a cladding is considered in the 2D case. The plate is made of two different materials, the base material and the cladding. Both materials can be anisotropic, and the interface between them is assumed to be wavy (sinusoidal), which is common for welded claddings. The null field approach is adopted and the starting point is thus the integral representations with the half‐space Green’s tensors. Numerical results in the form of field plots show the influence of the anisotropy and the wavy interface.

Anti-plane elastic wave scattering from a rough volumetric crack

Abstract The scattering of elastic waves from cracks is a field of study which has a number of important applications in nondestructive testing (NDT) and characterization of materials. So far most theoretical studies have concerned smooth cracks. There is reason to believe that the influence of roughness will scatter the energy in a more diffuse way, thus complicating the interpretation of test results. The problem considered here is the scattering of anti-plane waves, i.e. “horizontally” polarized shear waves, from a crack in an otherwise homogeneous, isotropic, elastic solid. The geometry is taken to be two-dimensional, and the scatterer is a curved volumetric crack with a small random roughness, which is characterized by the RMS height and a correlation length which is related to the average distance between the peaks of the irregularities. The term “volumetric” refers to the fact that the crack surfaces are slightly separated. Effects due to overall curvature as well as effects due to surface roughness and separation of the crack surfaces are thus included in the analysis. The method of solution can be described as an extension of the null field approach where certain matrix elements are expanded in terms of a small parameter describing the deviation from the smooth, nonvolumetric crack. The ensemble averaged amplitude of the scattered field for an incident plane wave has been computed numerically. Some results are given for various values of the frequency, the RMS height, the correlation length and the maximum gap between the crack surfaces.