The 2004 Ultrasonic Benchmark Problem - SDH Response Under Oblique Incidence: Measurements and Patch Element Model Calculations
10 Mar 2006-Quantitative Nondestructive Evaluation (American Institute of Physics)-Vol. 820, Iss: 1, pp 1820-1827
TL;DR: In this article, the results of calculations based on the patch element model, recently developed at CNDE, to determine the response of an SDH in aluminum for specific oblique incidence angles are also presented.
Abstract: The 2004 ultrasonic benchmark problem requires models to predict, given a reference pulse waveform, the pulse echo response of cylindrical voids of various radii located in an elastic solid for various incidence angles of a transducer immersed in water. We present the results of calculations based on the patch element model, recently developed at CNDE, to determine the response of an SDH in aluminum for specific oblique incidence angles. Patch element model calculations for a scan across the SDH, involving a range of oblique incidence angles, are also presented. Measured pulse‐echo scans involving the SDH response under oblique incidence conditions are reported. In addition, through transmission measurements involving a pinducer as a receiver and an immersion planar probe as a transmitter under oblique incidence conditions are also reported in a defect‐free Aluminum block. These pinducer‐based measurements on a defect‐free block are utilised to characterize the fields at the chosen depth. Comparisons are made between predictions and measurements for the pulse‐echo response of a SDH.
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TL;DR: An explicit point spread function (PSF) evaluator in the frequency domain is described for an ultrasonic transducer operating in the pulse-echo mode and it is shown that the PSF can be obtained from a single-medium PSF model using an effective single- medium path length concept.
Abstract: An explicit point spread function (PSF) evaluator in the frequency domain is described for an ultrasonic transducer operating in the pulse-echo mode. The PSF evaluator employs the patch element model for transducer field determination and scattered field assessment from a small but finite "point" reflector. The PSF for a planar transducer in a medium has been evaluated in the near and the far field. The computed PSFs were used to deconvolve and restore surface images, obtained experimentally, of a single hole and a five-hole cluster in an Al calibration block. A calibration plot is arrived at for estimating, without the need for deconvolution, the actual diameters of circular reflectors from apparent diameters obtained experimentally for a single-medium imaging configuration. The PSF, when the transducer and the point reflector are in two media separated by a planar interface, was evaluated in the near and far field. The computed PSFs were used to deconvolve and restore subsurface images, obtained experimentally, of flat bottom holes (FBHs) in an Al calibration block. We show that the PSF, in the presence of a planar interface, can be obtained from a single-medium PSF model using an effective single-medium path length concept. The PSFs and modulation transfer functions (MTFs) are evaluated for spherical focused and annular transducers and compared with those for the planar transducer. We identify imaging distances to get better-resolved images when using planar, spherical focused, and annular transducers.
13 citations
Cites methods from "The 2004 Ultrasonic Benchmark Probl..."
...The PEM was also used to quantify the FBH response by treating the reflector as made up of patches [10]....
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...[10] have used the PEM to determine the transducer field characteristics....
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28 Mar 2007
TL;DR: In this paper, the authors present the results of calculations based on 2D FDTD to determine the response of rectangular shaped surface breaking defe... and show that FDTD is an explicit time domain tool that can simulate pulse propagation characteristics in acoustic and elastic media.
Abstract: The 2006 ultrasonic benchmark problem involves pulse‐echo angle beam scanning of a notch located on an inclined planar back surface. The response from a side‐drilled hole is to be used as a reference. The models are to simulate (a) the peak‐to‐peak B‐scan P‐ and SV‐ responses of the slots normalized by the appropriate SDH response and (b) the maximum peak‐to‐peak corner response of the slots (either mode‐converted or not). At CNDE, several simulation tools are being developed to assess/predict UT response for various geometries. The Finite‐Difference‐Time‐Difference (FDTD) scheme is one such simulation tool that has been under development in 1D, 2D and 3D. The FDTD is an explicit time domain tool that can simulate pulse propagation characteristics in acoustic/elastic media. The computational domain is limited by implementing Perfectly Matched Layers (PMLs) at the domain boundaries. We present the results of calculations based on 2D FDTD to determine the response of rectangular shaped surface‐breaking defe...
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TL;DR: In this article, the authors compared the predictions of four measurement models for the 2002 Ultrasonic Benchmark Problem, which involves the pulse-echo responses of spherical and cylindrical cavities.
Abstract: The predictions of four measurement models are compared for the 2002 Ultrasonic Benchmark Problem. The problem involves the pulse‐echo responses of spherical and cylindrical cavities. The ultrasonic waves are considered to be generated and detected by either a planar or spherically focused probe, each of finite diameter and positioned to produce normally incident or refracted waves (longitudinal or shear) of the desired angle. Among the results are a new expression for the response of the cylindrical cavity and a quantitative comparison of the various models. Noteworthy is the differences in the predictions of the beam models, for refracted angles near critical angles and for focused probes.
22 citations
04 May 2005
TL;DR: In this article, a conceptually simple yet reliable numerical technique to determine these internal fields in any region of interest within the elastic solid for the specified angles made by the transducer in water is presented.
Abstract: The ultrasonic benchmark problem requires models to predict, given a reference pulse waveform, the pulse echo response of cylindrical voids of various radii located in an elastic solid for various incidence angles of a transducer immersed in water. We present a conceptually simple yet reliable numerical technique to determine these internal fields in any region of interest within the elastic solid for the specified angles made by the transducer in water. The technique, equivalent to evaluating the Rayleigh‐Sommerfeld integral but through a computationally less demanding procedure, regards the transducer as made of elemental rectangular/square patches and uses the well‐known expression for the radiation pattern of an elemental patch to obtain the total transducer radiation field. A ray‐based method is adopted to propagate the elementary radiation field across a fluid‐solid interface. The FBH is treated in terms of explicit patch element reflectors, its response is evaluated and validated with measurements. The P‐wave scattering charactieristics of spherical voids are evaluated using the exact separation of variables method and the patch model for the transducer is used to determine their response. The advantages of the patch model for the transducer in the context of the benchmark problems in particular and non‐destructive evaluation in general are indicated.
5 citations
TL;DR: In this article, three transducer beam models are developed for obtaining the bulk waves generated by a plane piston transducers radiating through a planar fluid-solid interface, and the limitations of these models for simulating inspections near critical refracted angles and near the interface are discussed.
Abstract: Three types of transducer beam models are developed for obtaining the bulk waves generated by a plane piston transducer radiating through a planar fluid—solid interface. The first type, called the surface integral model, is based on a Rayleigh—Sommerfeld-like integral that requires a two-dimensional surface integral to be evaluated. The second model, called the boundary diffraction wave (BDW) paraxial model, simplifies the two-dimensional integration of the surface integral model to a one-dimensional line integration. The third type of model, called the edge element model, is shown to be a novel way of efficiently evaluating the two-dimensional surface integration of the surface integral model. The limitations of these models for simulating inspections near critical refracted angles and near the interface are discussed.
4 citations
TL;DR: In this paper, the backscatter from cylindrical voids of 0.125, 0.5, 1.0, 2.0 and 4 mm radii in an aluminum block for an incident plane longitudinal elastic wave has been numerically evaluated using one exact and one approximate solution and compared.
Abstract: Measurements and numerical experiments are reported for a sub‐set of the problems defined as the Ultrasonic Benchmark 2002 by the World Federation of Nondestructive Evaluation Centers. The backscatter from cylindrical voids of 0.125, 0.5, 1.0, 2.0, and 4 mm radii in an Aluminum block for an incident plane longitudinal elastic wave has been numerically evaluated using one exact and one approximate solution and compared. The exact solution is based on the separation of variables method. The approximate solution is based on Kirchoff’s approximation. Within the Thomson‐Gray measurement model and the paraxial approximation for the transducer beam, the peak‐to‐peak voltage is computed as a function of void radius using the exact and approximate backscatter solutions. Using a prescribed reference RF signal waveform, the backscattered RF flaw signals are predicted. Within the Kirchoff’s approximation, the backscatter from partially illuminated cylindrical voids is evaluated as a function of the fractional area illuminated. RF signal waveforms were measured for cylindrical voids of 0.5, 1.0, 2,0 and 4.0 mm radii in an Aluminum block under a normal incidence immersion method. The RF signals were also measured, as the transducer was scanned perpendicular to the cylindrical void axis. Measurements were also carried out to obtain the backscatter from solid cylinders of various radii immersed in water. Comparisons between predicted peak‐to‐peak voltages and measurements are made. Attention is drawn to the transition from 2D backscatter to 3D backscatter encountered when seeking comparisons between predictions and measurements.
2 citations