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Transient scattering of Rayleigh-Lamb waves by surface-breaking crack: comparison of numerical simulation and experiment
N DT Abstracts monitoring the change in transmissionratio with frequency may provide a means of defect sizing.
49939 Lmceleur, P.; de Betheval, J.F.; Mercier, N. Modeling of transient deformation of piezoelectric ceramics IEEE Transactions of Ultra:sonics, Ferroelectrics, and Frequency Control, Vol. 39, No. 2, pp. 293-301 (Mar. 1992) A method basedon a finite-element analysis is presentedthat permits the calculation and the visualization of deformationsof uhrasonictransducersin different configurations. The method uses a Fourier series synthesisgiving deformation of the free surface and electrical admittancefor wide frequency bands by the use of finite-element procedures previously developed at Universite de Technologie de Compiegne (WC). The method was originally developed for the monochromatic case. The work reported in the paper deals with the adaptation and validation of the method for the multifrequency excitation case, which is a more realistic approach used in the field of ultrasonic NDE. Several geometries were tested. In spite of the limitations of the method, due to the calculation requirements, the results show the role of the radial displacement behavior usually neglected in moncdimensionai analysis.
49893 Blake, R.J.; Bond, L J. Rayleigh wave scattering from surface features: up-steps and troughs Ultrasonics, Vol. 30, No. 4, pp. 255-265 (1992) The development of a melthod of sizing surface defects based on Rayleigh waves has been hampered by the lack of a theory to describe the scattering problem. In an earlier paper we described a new mixed finite element/finite difference model, which provides accurate and stable numerical solutions for faceted scattering geometries. This paper presents details of the interaction of Rayleigh waves with angled up-steps which, combined with our earlier discussionof angled down- steps, provides new insights into the scattering of pulsed surface waves from faceted troughs. Numerical visualizations, seismograms and spectral Rayleigh wave scattering coefficients provide a detailed description of the scattering process. The implications of the ~results for a non-destructivetesting method for surface feature characterization are discussed.
49688 Nouailhas; B.; Nguyen van Chi, G. Modelling study of ultrasonic propagation in bimetallic weld Ultrasonics International 91, Lc Touquet (France), l-4 Jul. 1991. pp. 563-566. Butterworth Heinemann (1991) Tbe in service inspection of French pressurized water reactor is performed by a robot (MIS) using immersed focussingtransducers.To avoid long and expensive tests on the capability of the transducers,the ultrasonic modelling is one solution. The Direction de Etudes et Recherches of Electricite de France has developed two codes : PROMANIS, a ray tracing code and ULTSON a 2-D finite element code, to respondsto this challenge
49405 Wagner, J.W.; Spicer, J.B.: Deaton, J.B. Laser source parameter selection and array considerations for enhancing detection sensitivity in laser ultrasonic systems Ultrasonics International 91, Le Touquet (France), 1-4 Jul. 1991, pp. 355-358. Butterworth Heinemann (1991). Recent work has demonstratedthat significant gains can be achieved in
developed at Universite de Technologie de Compiegne (UTC) for the monochromatic case. The work reported in this paper deals with the adaptation and validation of the method for the multi-frequency excitation case, which is a more realistic approach used in the field of ultrasonic NDE.
49393 Lord, W.; Hsu, D.; Ghorayeb, S.; Minachi, A.; You, Z. Finite element applications in NDE engineering Ultrasonics International 91, Le Touquet (France), l-4 Jul. 1991. pp. 463-466. But&worth Heinemann (1991). Domain methods of modeling ultrasonic wave propagation give a full displacement field solution which can be useful in studying physical phenomena associated with the nondestructive inspection of materials. A number of applications have been studied which make use of this attribute including the analysis of oblique echoes in thick composites,the simulation of SAFT reconstructions,the validation of a Gauss- Hermite beam model and the sensitivity of diffraction tomography algorithms to transducer aperture variations and anisotropy.
4918 1 Paffenholz, J.; Fox, J. W.; Gu, X.; Jewett, G.S.; Datta, S.K.; Spetzler, H.A. Experimental and theoretical study of Rayleigh-Lamb waves in a plate containing a surface-breaking crack Research in Nondestructive Evaluation, Vol. 1, No. 4, pp. 197-217 (1990). Scatteringof Rayleigh-Lambwaves by a normal surface-breakingcrack in a plate has been studied both theoretically and experimentally. The two-dimensionality of the far field, generated by a ball impact source, is exploited to characterize the source function using a direct integration technique. The scatteringof waves generated by this impact source by the crack is subsequently solved by employing a Green’s function integral expression for the scattered field coupled with a finite element representationof the near field. It is shown that theoretical results of plate response, both in frequency and time, are similar to those obtained experimentally. Additionally, implications for practical application are discussed.
49137 Liu, S.W.; Datt, S.K.; Ju, T.H. Transient scattering of Rayleigh-Lamb waves by surface. breaking crack: comparison of numerical simulation and experiment Journal of Nondestructive Evaluation, Vol. 10, No. 3, pp. 11 I-126 (Sep. 1991) Tbe transient scattering of Rayleigh-Lambwaves by a surface-breaking crack in a plate is investigatedin both time and ftequency domains by using the hybrid numerical method which combines the finite element discretization of the vicinity of the crack with the Green’s function integral representation of the exterior scattered field. The frequency domain responseis obtained by solving a set of large sparseunsymmetric complex matrix equations, elements of which are stored in a compacted dats structure,by the biconjugate gradient method. The time domain solution is then obtained by using FFT. The source function generated by a steel bag impact is extracted by a direct integration technique. It is then used to simulate some available experimental results. Good agreement has been obtained. Numerical and experimental results shown the effect of the crack more in the near field than far away.
laser ultrasonic signal generation efficiency and detection sensitivity by controlling the temporal and spatial source parameters as well as power density. In particular, temporal and spatial (array) modulation has been used to generate narrow band (toneburst) and directed ultrasound, thereby permitting useful reductions in electronic bandwidth of the detection system. The narrow band nature of the resulting ultrasonic signal permits filtering of the optically received waveform with dramatic improvementsin signal-to-noise ratio in some cases. A numerical processingalgorithm has been developed to permit modeling of the thermoelastic and ablative regimes for laser sourcesof finite element. This model has been usedto help predict the effects of altering source and array parameterswith very good agreement with experimental results.
49132 You, Z. Finite element study of ultrasonic imaging Dissertation Abstracts International, Vol. 52, No. 4, pp. 2230-E (Oct. 1991) (DA 9126275) This dissertationdescribes the development and use of finite elemen analysis to model ultrasonic wave propagation phenomena and to stud) diffraction tomography. Basic formulations are presented for genera three-dimensional(3-D) geometriesand verified by comparing to analytica solutions. To optimize computer resources, the combination of centra difference and forward difference schemes is chosen to approximate ti time derivatives and a lumped mass scheme is introduced to avoid thy expensive matrix inversion. The two-dimensional (2-D) and axisymmetric formulations discussedat length in this thesis effectively model problem! satisfying either plane strain or axisymmetric conditions. Absorbim boundary conditions are introduced for large geometries and applied tc some typical test situations.Using this infinite element model as a test bed the diffraction tomographic algorithm is studied with regard to finiu aperture effects and material anisotropy. Extensive comparisonof the fin& element results with analytic solutions proves the validity of the 2-D axisymmetric and 3-D models. Applications of the 2-D and axisymmetric formulations correctly predict useful phenomena associated wit1 wave/defect interactionsand the anisotropic property of the material.
49400 Lunceleur, P.; de Belleval, J.F. Determination of transient deformations on the active surface of N.D.E. ultrasonic elements Ultrasonics International 91, Le Touquet (France), 1-4 Jul. 1991. pp. 4 19-422. Butterworth Heinemann ( 199 1). A method basedon a finite element analysis is presentedwhich permits the calculation and the visualization of deformations of uhrasonic transducers in different contigumtions. The method uses a Fourier series synthesis giving deformation of the tree surface and electrical admittance for wide frequency bandsby the luseof finite element procedurespreviously
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49939 Lmceleur, P.; de Betheval, J.F.; Mercier, N. Modeling of transient deformation of piezoelectric ceramics IEEE Transactions of Ultra:sonics, Ferroelectrics, and Frequency Control, Vol. 39, No. 2, pp. 293-301 (Mar. 1992) A method basedon a finite-element analysis is presentedthat permits the calculation and the visualization of deformationsof uhrasonictransducersin different configurations. The method uses a Fourier series synthesisgiving deformation of the free surface and electrical admittancefor wide frequency bands by the use of finite-element procedures previously developed at Universite de Technologie de Compiegne (WC). The method was originally developed for the monochromatic case. The work reported in the paper deals with the adaptation and validation of the method for the multifrequency excitation case, which is a more realistic approach used in the field of ultrasonic NDE. Several geometries were tested. In spite of the limitations of the method, due to the calculation requirements, the results show the role of the radial displacement behavior usually neglected in moncdimensionai analysis.
49893 Blake, R.J.; Bond, L J. Rayleigh wave scattering from surface features: up-steps and troughs Ultrasonics, Vol. 30, No. 4, pp. 255-265 (1992) The development of a melthod of sizing surface defects based on Rayleigh waves has been hampered by the lack of a theory to describe the scattering problem. In an earlier paper we described a new mixed finite element/finite difference model, which provides accurate and stable numerical solutions for faceted scattering geometries. This paper presents details of the interaction of Rayleigh waves with angled up-steps which, combined with our earlier discussionof angled down- steps, provides new insights into the scattering of pulsed surface waves from faceted troughs. Numerical visualizations, seismograms and spectral Rayleigh wave scattering coefficients provide a detailed description of the scattering process. The implications of the ~results for a non-destructivetesting method for surface feature characterization are discussed.
49688 Nouailhas; B.; Nguyen van Chi, G. Modelling study of ultrasonic propagation in bimetallic weld Ultrasonics International 91, Lc Touquet (France), l-4 Jul. 1991. pp. 563-566. Butterworth Heinemann (1991) Tbe in service inspection of French pressurized water reactor is performed by a robot (MIS) using immersed focussingtransducers.To avoid long and expensive tests on the capability of the transducers,the ultrasonic modelling is one solution. The Direction de Etudes et Recherches of Electricite de France has developed two codes : PROMANIS, a ray tracing code and ULTSON a 2-D finite element code, to respondsto this challenge
49405 Wagner, J.W.; Spicer, J.B.: Deaton, J.B. Laser source parameter selection and array considerations for enhancing detection sensitivity in laser ultrasonic systems Ultrasonics International 91, Le Touquet (France), 1-4 Jul. 1991, pp. 355-358. Butterworth Heinemann (1991). Recent work has demonstratedthat significant gains can be achieved in
developed at Universite de Technologie de Compiegne (UTC) for the monochromatic case. The work reported in this paper deals with the adaptation and validation of the method for the multi-frequency excitation case, which is a more realistic approach used in the field of ultrasonic NDE.
49393 Lord, W.; Hsu, D.; Ghorayeb, S.; Minachi, A.; You, Z. Finite element applications in NDE engineering Ultrasonics International 91, Le Touquet (France), l-4 Jul. 1991. pp. 463-466. But&worth Heinemann (1991). Domain methods of modeling ultrasonic wave propagation give a full displacement field solution which can be useful in studying physical phenomena associated with the nondestructive inspection of materials. A number of applications have been studied which make use of this attribute including the analysis of oblique echoes in thick composites,the simulation of SAFT reconstructions,the validation of a Gauss- Hermite beam model and the sensitivity of diffraction tomography algorithms to transducer aperture variations and anisotropy.
4918 1 Paffenholz, J.; Fox, J. W.; Gu, X.; Jewett, G.S.; Datta, S.K.; Spetzler, H.A. Experimental and theoretical study of Rayleigh-Lamb waves in a plate containing a surface-breaking crack Research in Nondestructive Evaluation, Vol. 1, No. 4, pp. 197-217 (1990). Scatteringof Rayleigh-Lambwaves by a normal surface-breakingcrack in a plate has been studied both theoretically and experimentally. The two-dimensionality of the far field, generated by a ball impact source, is exploited to characterize the source function using a direct integration technique. The scatteringof waves generated by this impact source by the crack is subsequently solved by employing a Green’s function integral expression for the scattered field coupled with a finite element representationof the near field. It is shown that theoretical results of plate response, both in frequency and time, are similar to those obtained experimentally. Additionally, implications for practical application are discussed.
49137 Liu, S.W.; Datt, S.K.; Ju, T.H. Transient scattering of Rayleigh-Lamb waves by surface. breaking crack: comparison of numerical simulation and experiment Journal of Nondestructive Evaluation, Vol. 10, No. 3, pp. 11 I-126 (Sep. 1991) Tbe transient scattering of Rayleigh-Lambwaves by a surface-breaking crack in a plate is investigatedin both time and ftequency domains by using the hybrid numerical method which combines the finite element discretization of the vicinity of the crack with the Green’s function integral representation of the exterior scattered field. The frequency domain responseis obtained by solving a set of large sparseunsymmetric complex matrix equations, elements of which are stored in a compacted dats structure,by the biconjugate gradient method. The time domain solution is then obtained by using FFT. The source function generated by a steel bag impact is extracted by a direct integration technique. It is then used to simulate some available experimental results. Good agreement has been obtained. Numerical and experimental results shown the effect of the crack more in the near field than far away.
laser ultrasonic signal generation efficiency and detection sensitivity by controlling the temporal and spatial source parameters as well as power density. In particular, temporal and spatial (array) modulation has been used to generate narrow band (toneburst) and directed ultrasound, thereby permitting useful reductions in electronic bandwidth of the detection system. The narrow band nature of the resulting ultrasonic signal permits filtering of the optically received waveform with dramatic improvementsin signal-to-noise ratio in some cases. A numerical processingalgorithm has been developed to permit modeling of the thermoelastic and ablative regimes for laser sourcesof finite element. This model has been usedto help predict the effects of altering source and array parameterswith very good agreement with experimental results.
49132 You, Z. Finite element study of ultrasonic imaging Dissertation Abstracts International, Vol. 52, No. 4, pp. 2230-E (Oct. 1991) (DA 9126275) This dissertationdescribes the development and use of finite elemen analysis to model ultrasonic wave propagation phenomena and to stud) diffraction tomography. Basic formulations are presented for genera three-dimensional(3-D) geometriesand verified by comparing to analytica solutions. To optimize computer resources, the combination of centra difference and forward difference schemes is chosen to approximate ti time derivatives and a lumped mass scheme is introduced to avoid thy expensive matrix inversion. The two-dimensional (2-D) and axisymmetric formulations discussedat length in this thesis effectively model problem! satisfying either plane strain or axisymmetric conditions. Absorbim boundary conditions are introduced for large geometries and applied tc some typical test situations.Using this infinite element model as a test bed the diffraction tomographic algorithm is studied with regard to finiu aperture effects and material anisotropy. Extensive comparisonof the fin& element results with analytic solutions proves the validity of the 2-D axisymmetric and 3-D models. Applications of the 2-D and axisymmetric formulations correctly predict useful phenomena associated wit1 wave/defect interactionsand the anisotropic property of the material.
49400 Lunceleur, P.; de Belleval, J.F. Determination of transient deformations on the active surface of N.D.E. ultrasonic elements Ultrasonics International 91, Le Touquet (France), 1-4 Jul. 1991. pp. 4 19-422. Butterworth Heinemann ( 199 1). A method basedon a finite element analysis is presentedwhich permits the calculation and the visualization of deformations of uhrasonic transducers in different contigumtions. The method uses a Fourier series synthesis giving deformation of the tree surface and electrical admittance for wide frequency bandsby the luseof finite element procedurespreviously
249