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- Jansson, Per-Åke, 1949, et al.
(författare)
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2D P-SV Wave Scattering by a Crack in a Cladding
- 2007
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Ingår i: Review of Progress in Quantitative Nondestructive Evaluation. - 9780735403994 ; 26A, s. 71-78
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Konferensbidrag (refereegranskat)abstract
- A situation that frequently occurs in the nuclear power industry is that of a thick plate or pipe with an austenitic cladding to reduce or prevent corrosion. A common method to apply the cladding on a ferritic base material is to use a welding process. From an ultrasonic testing point of view this leads to a number of complications. The interface between the cladding and the base material is usually corrugated, which may affect the scattering from the interface substantially. Furthermore, the cladding material is anisotropic with all the complications this may lead to.In this paper ultrasonic testing of a thick plate with a plane crack in a cladding is modelled analytically for a two-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, where an integral equation for the crack opening displacement is derived from integral representations for the displacement fields in the two media. A model for the ultrasonic transmitter and receiver is also included. Some numerical results for the change in signal response due to the presence of the crack are given.
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- Jansson, Per-Åke, 1949, et al.
(författare)
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Modeling of Ultrasonic Nondestructive Testing of Surface-breaking Cracks
- 2012
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Ingår i: Proceedings 18th World Conference of Non-Destructive Testing, 16-20 April 2012, Durban, South Africa. - 9780620528726
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Konferensbidrag (refereegranskat)abstract
- A complete model of ultrasonic nondestructive testing of defects in thick-walled components has been developed since more than a decade and has resulted in the computer program UTDefect. The program includes models of transmitting ultrasonic probes, and through a reciprocity argument also recieving probes. A number of simply shaped defects are included. Here the focus is on surface-breaking strip-like cracks, and a comparison of these with strip-like interior cracks. Both scattering problems are solved with a hyper-singular integral equation method, where the unknown crack-opening displacement (COD) is expanded into sets of Chebyshev functions. These expansions are different for the two cracks; whereas the interior crack has a COD that behaves as a square root at the tips, the surface-breaking COD has a finite value at the crack mouth, and these behaviours must be taken into account. Numerical comparisons are made between the two cracks, and it seems that the interior crack pushed to the surface behaves very much like the surface-breaking one, except at very low frequencies (crack size less than half a wavelength). Favourable comparisons with experiments are also made.
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- Jansson, Per-Åke, 1949
(författare)
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Rough Scatterers in Acoustics and Elastodynamics
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this thesis is to investigate the influence of roughness on wave scattering from finite-sized surfaces, in particular elastic wave scattering from cracks. Acoustic scattering from a sphere is considered using the null field approach. The ensemble averaged T matrix of the sphere is obtained as a perturbation series where the small parameter is the ratio of the RMS height to the wavelength. The scattered far field and the scattering cross section are calculated for an incident plane wave. The same method is applied to two-dimensional elastic wave scattering from an open nonplanar crack. The incident wave is taken to be a horizontally polarized shear wave. First an ordinary crack with zero volume is considered; then the solution is generalized to the case where the crack has a finite volume. The numerical results indicate that the influence of roughness is in most cases negligible compared to the effect of a finite volume. This is an expected result since roughness is a second order effect when ensemble averaged quantities are studied, while the volumetric effects are of first order. However, this does not necessarily mean that roughness is negligible for a specific crack of the ensemble. Acoustic scattering from a rough circular disc immersed in a nonviscous fluid of infinite extent is studied using an integral equation method. A number of deterministic surfaces are constructed using a numerical simulation technique and the T matrix is determined for each surface by a first order perturbation method. Some numerical results for the back-scattered far-field amplitude are calculated. Finally, the elastic wave scattering problem for a rough penny-shaped crack is solved using the same integral equation method. The stationary-phase approximation is used to determine the back-scattered far field. Numerical results are obtained for an incident plane longitudinal wave and a scattered longitudinal wave. For cracks with identical statistical properties there is a considerable spread in scattering data at oblique incidence except for low frequencies. Results are also given in the time domain, which means that pulse-echo testing is simulated.
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- Jansson, Per-Åke, 1949
(författare)
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Scattering from a rectangular crack in a cladding
- 2010
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Ingår i: IUTAM Symposium on Recent Advances of Acoustic Waves in Solids. - Dordrecht : Springer Netherlands. - 9789048198924 ; 26
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Konferensbidrag (refereegranskat)
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- Jansson, Per-Åke, 1949, et al.
(författare)
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Simulation of the 2008 Ultrasonic Benchmark Problems Using UTDefect
- 2009
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. - 9780735406292 ; 28B, s. 1968-1972
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Konferensbidrag (refereegranskat)abstract
- 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.
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- Jansson, Per-Åke, 1949, et al.
(författare)
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Ultrasonic benchmarking with UTdefect
- 2010
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735407480 ; 1211, s. 2149-2156
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Konferensbidrag (refereegranskat)abstract
- UTDefect is a program for simulation of ultrasonic testing with emphasis on applications within the nuclear power industry. The entire testing process, including the ultrasonic transmitter, the receiver, and scattering from various types of defects of simple shape, is modelled. The basic idea behind UTDefect is to use solutions to the elastodynamic wave equation that are esentially exact. For the 2009 benchmark problems the results obtained from UTDefect are in most cases in fairly good agreement with the experimental data from CEA. © 2010 American Institute of Physics.
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