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Electromagnetic acoustic transducers: physical principles and finite element modeling
N DT Abstracts To improve the ultrasonic inspection of the safe ends connecting the nuclear vessel to the piping we m: conducting modelling studiesusing two models, PROMANIS a ray tracing code and ULTSON a 2D finite element code. The study has shown the great interest in combining modelling and experiments to improve the codes and react on the.experimental conditions. 47913
Lou, S.H.; Tsang, L.; Chan. C.H.
Application of the finite element method to Monte Carlo simulations of scattering of ‘waves by random rough surfaces: penetrable case Waves in Random Media, Vol. 1, No. 4, pp. 287-307 (Oct. 1991) The finite element method (FEM) of Monte Carlo simulationsof random rough surface scattering is extended to penetrable rough surface scattering. The. attraction of the method is the banded nature of the resulting matrix equation. Convergence and accuracy of the method is demonstratedand established by varying various input parameters such as the number of evanescent waves, the number of sampling points and the surface lengths. Results with incidence plane wave TE polarization are presented for both the mean reflected scattered intensity and the mean transmitted scattered intensity as a function of surface parameterssuch as RMS surface heights and correlation lengths. The numerical results are compared against the tapered wave integral equation (m7NIE) method. 47895 New inspection techniques urged for CF6-6 engines CSNDT Journal, Vol. 12, No. .4, pp. 30-34 (Jul. - Aug. 1991) Following an aircraft accident in Sioux City, Iowa 1989, the National Transportation Safety Board has made a number of amended recommendations about how rotor disks in aircraft engines should be inspected during statutory mainlenance programs. Ultrasonic tests are usually used to inspect these parts using contact techniques for on- wing inspection and immersion tests when disks are removed from the engine. These test have failed to detect cracks initiating from the surface of the Borea area of the rotor disk, and the curved surfaces and complex geometries involved make ultrasonic inspection difficult. Engines involved in manufacturing these parts have suggestedthe use of fracture mechanics and finite element computer models to estimate surface crack propagation. In future ultrasonic tests will be combined with surface inspectionmethods.
47220 Dai, X.-W. Electromagnetic acoustic transducers: physical principles and finite element modeling Dissertation Abstracts International, Vol. 5 1, No. 12, pp. 6023-6024 (Jun. 1991) In this dissertation. a complete set of governing equations and their boundary conditions are systematically derived from momentum conservationlaws, which provides a clear picture of the physical principles of an EMAT. Numerical analysis techniques are applied to solve the underlying electrodynamic equations for realistic magnetostaticand pulsed eddy current distributions in the specimen. Results field predictions from these elliptic and parabolic system models are then coupled into a hyperbolic description of the elastic wave equation to simulate transient ultrasonic waves in isotropic solidls. Both the electrodynamic and acoustic wave equations are solved in two dimensionsbased on hybrid implicit and explicit finite element and finite difference time stepping algorithms. In order to test the numerical simulatimons, analytical solutionsof both parabolic and hyperbolic systems are derived for certain canonical examples which permit direct comparison between1numerical and analytical predictions in the time domain. Having confirmed the correctnessof the overall numerical model, it is subsequentlyextended to simulate a generic two- wire transient EMAT configuration for an isotropic half-space with electric and acoustic material parametersequivalent to lhose aluminum.
47209 You, Z.; Lusk, M.; Ludwig, R.; Lord, W. Numerical simulation of ultrasonic wave propagation anisotropic and attenuative solid materials
in
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Vol. 38, No. 5, pp. 436-445 (Sep. 1991) An axisymmetric elastodynamic finite element code has been developed that is capable of predicting quantitatively accurate displacement fields for elastic wave propagation in isotropic and transversely isotropic materials. The numerical algorithm incorporates viscous damping by adding a time-dependent tensor to Hooke’s law. Amplitude comparisons are made between the geometric attenuation in the far field and the corresponding finite element predictions to investigatethe quality and validity of the code. In addition, through-transmissionexperimental measurementsmade with a l-MHz L-wave transducer attached to an aluminium sample support the code predictions.
46903
Xu, P.-C.; Datta, S.K.
Characterization of fiber-matrix interface by guided waves: axisymmetric case Journal of fhe Acoustical Society of America, Vol. 89, No. 6, pp. 2573- 2583 (Jun. 1991) A hybrid method combining the finite-element and eigenfunction expansionsis proposed lo study the guided waves in composite.cylinders. The object is to model uniaxial fiber-reinforced materials with interface zones between fiber (which is anisotropic) and the matrix (which is isotropic). Numerical results are presented for the axisymmetric case for a graphite in magnesium and epoxy matrices. In particular, the. measurable and analyzable effects of imperfect bonding are investigated.The reduction of bond stiffnessis found to have significant effect on the leaky waves.
46688 Khair, K.R. Scattering of waves in an elastic half-space with applications of seismic ground motion amplification and ultrasonic to seismic ground motion amplification and ultrasonic nondestructive evaluation of surface-breaking cracks Dissertation Abstracts International, Vol. 51, No. 4, pp. 2021-B (Oct. 1990) (DA9024838) The problem of scattering of plane elastic waves by arbitrarily-shaped cylindrical inhomogeneitiesin an elastic half-space has been investigatedin this thesis.The inhomogeneityis modeled as an infinitely long cylinder with arbitrarily-shaped cross section. The incident of the. scatterer. Thus the motion is three-dimensional. This method combines the finite. element discretization and the boundary integral representation. The method has been applied to obtain three- dimensional ground motion on the surface of soft valleys and cavities in a half-space. Scattering of elastic waves by a surface-breakingcrack of different orientations has also been studied using the hybrid method. Numerical results for the scatteredsurfacedisplacements near the mouth of the crack and the.crack-opening displacementshave been presented. 46447
AI-Nassar, Y.N.
Scattering of Lamb waves in an elastic plate for ultrasonic nondestructive evaluation of weldments and cracks Dissertation Abstract International, Vol. 51, No. 6, pp. 122 (1990) (DA9032806) In this thesis we present a hybrid numerical technique for analyzing scatteringof time harmonic Lamb waves by normal rectangular weldments and surface-breaking cracks. This method combines the finite element discretization and modal representation. In this method, media inhomogeneitiesare enclosedin a finite region containing the defects. Three cases considered here are those of scattering by a normal rectangular weldment, normal surface-breaking cracks and normal surface-breaking cracks situated in a butt welded plate.. The reflection and transmission cceffkients are computed for the first two incident wave modes. The validity and accuracyof the.resultsare checked by satisfactionof the energy conservationprinciple. 46383
Imaino. W.
Electromagnetically delamination
generated
acoustic
determination
of
Journal of Applied Physics, Vol. 69, No. 7, pp. 3811-3815 (1 Apr. 1991) In fhis investigation, a finite-element calculation is used to provide a more detailed descriptionof the acoustic behavior of the delaminated plate.. The effects of source size relative to defect dimensions and acoustic properties of the substrate have been studied. The determination of the localized coupling is complicated by sbuctural resonancesof the substrate, which make single frequency measurements unfavourable. However, the analysis shows that the spectral acoustic behavior provides an indication of metallization to substratecoupling. A signal-processingalgorithm t#lsed on this analysis has been formulated and will be described. 46377
Nouailhas, B.; Nguyen, G.V.C.; Vermersch, S.
Ultrasonic modeling and experiments: bimetallic weld in nuclear power plant
an industrial
case:
Journal of Nondestructive Evaluation, Vol. 9, No. 2-3, pp. 145-153 (1990) To improve the ultrasonic inspection of the safe ends connecting the nuclear vessel to the piping, we are conducting modeling studies using two models: PROMANIS, a ray tracing code, and ULTSON, a 2-D finite element code. The study has shown a great interest in combining modeling and experiments to improve the codes and react to the experimental conditions.
251
Lou, S.H.; Tsang, L.; Chan. C.H.
Application of the finite element method to Monte Carlo simulations of scattering of ‘waves by random rough surfaces: penetrable case Waves in Random Media, Vol. 1, No. 4, pp. 287-307 (Oct. 1991) The finite element method (FEM) of Monte Carlo simulationsof random rough surface scattering is extended to penetrable rough surface scattering. The. attraction of the method is the banded nature of the resulting matrix equation. Convergence and accuracy of the method is demonstratedand established by varying various input parameters such as the number of evanescent waves, the number of sampling points and the surface lengths. Results with incidence plane wave TE polarization are presented for both the mean reflected scattered intensity and the mean transmitted scattered intensity as a function of surface parameterssuch as RMS surface heights and correlation lengths. The numerical results are compared against the tapered wave integral equation (m7NIE) method. 47895 New inspection techniques urged for CF6-6 engines CSNDT Journal, Vol. 12, No. .4, pp. 30-34 (Jul. - Aug. 1991) Following an aircraft accident in Sioux City, Iowa 1989, the National Transportation Safety Board has made a number of amended recommendations about how rotor disks in aircraft engines should be inspected during statutory mainlenance programs. Ultrasonic tests are usually used to inspect these parts using contact techniques for on- wing inspection and immersion tests when disks are removed from the engine. These test have failed to detect cracks initiating from the surface of the Borea area of the rotor disk, and the curved surfaces and complex geometries involved make ultrasonic inspection difficult. Engines involved in manufacturing these parts have suggestedthe use of fracture mechanics and finite element computer models to estimate surface crack propagation. In future ultrasonic tests will be combined with surface inspectionmethods.
47220 Dai, X.-W. Electromagnetic acoustic transducers: physical principles and finite element modeling Dissertation Abstracts International, Vol. 5 1, No. 12, pp. 6023-6024 (Jun. 1991) In this dissertation. a complete set of governing equations and their boundary conditions are systematically derived from momentum conservationlaws, which provides a clear picture of the physical principles of an EMAT. Numerical analysis techniques are applied to solve the underlying electrodynamic equations for realistic magnetostaticand pulsed eddy current distributions in the specimen. Results field predictions from these elliptic and parabolic system models are then coupled into a hyperbolic description of the elastic wave equation to simulate transient ultrasonic waves in isotropic solidls. Both the electrodynamic and acoustic wave equations are solved in two dimensionsbased on hybrid implicit and explicit finite element and finite difference time stepping algorithms. In order to test the numerical simulatimons, analytical solutionsof both parabolic and hyperbolic systems are derived for certain canonical examples which permit direct comparison between1numerical and analytical predictions in the time domain. Having confirmed the correctnessof the overall numerical model, it is subsequentlyextended to simulate a generic two- wire transient EMAT configuration for an isotropic half-space with electric and acoustic material parametersequivalent to lhose aluminum.
47209 You, Z.; Lusk, M.; Ludwig, R.; Lord, W. Numerical simulation of ultrasonic wave propagation anisotropic and attenuative solid materials
in
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, Vol. 38, No. 5, pp. 436-445 (Sep. 1991) An axisymmetric elastodynamic finite element code has been developed that is capable of predicting quantitatively accurate displacement fields for elastic wave propagation in isotropic and transversely isotropic materials. The numerical algorithm incorporates viscous damping by adding a time-dependent tensor to Hooke’s law. Amplitude comparisons are made between the geometric attenuation in the far field and the corresponding finite element predictions to investigatethe quality and validity of the code. In addition, through-transmissionexperimental measurementsmade with a l-MHz L-wave transducer attached to an aluminium sample support the code predictions.
46903
Xu, P.-C.; Datta, S.K.
Characterization of fiber-matrix interface by guided waves: axisymmetric case Journal of fhe Acoustical Society of America, Vol. 89, No. 6, pp. 2573- 2583 (Jun. 1991) A hybrid method combining the finite-element and eigenfunction expansionsis proposed lo study the guided waves in composite.cylinders. The object is to model uniaxial fiber-reinforced materials with interface zones between fiber (which is anisotropic) and the matrix (which is isotropic). Numerical results are presented for the axisymmetric case for a graphite in magnesium and epoxy matrices. In particular, the. measurable and analyzable effects of imperfect bonding are investigated.The reduction of bond stiffnessis found to have significant effect on the leaky waves.
46688 Khair, K.R. Scattering of waves in an elastic half-space with applications of seismic ground motion amplification and ultrasonic to seismic ground motion amplification and ultrasonic nondestructive evaluation of surface-breaking cracks Dissertation Abstracts International, Vol. 51, No. 4, pp. 2021-B (Oct. 1990) (DA9024838) The problem of scattering of plane elastic waves by arbitrarily-shaped cylindrical inhomogeneitiesin an elastic half-space has been investigatedin this thesis.The inhomogeneityis modeled as an infinitely long cylinder with arbitrarily-shaped cross section. The incident of the. scatterer. Thus the motion is three-dimensional. This method combines the finite. element discretization and the boundary integral representation. The method has been applied to obtain three- dimensional ground motion on the surface of soft valleys and cavities in a half-space. Scattering of elastic waves by a surface-breakingcrack of different orientations has also been studied using the hybrid method. Numerical results for the scatteredsurfacedisplacements near the mouth of the crack and the.crack-opening displacementshave been presented. 46447
AI-Nassar, Y.N.
Scattering of Lamb waves in an elastic plate for ultrasonic nondestructive evaluation of weldments and cracks Dissertation Abstract International, Vol. 51, No. 6, pp. 122 (1990) (DA9032806) In this thesis we present a hybrid numerical technique for analyzing scatteringof time harmonic Lamb waves by normal rectangular weldments and surface-breaking cracks. This method combines the finite element discretization and modal representation. In this method, media inhomogeneitiesare enclosedin a finite region containing the defects. Three cases considered here are those of scattering by a normal rectangular weldment, normal surface-breaking cracks and normal surface-breaking cracks situated in a butt welded plate.. The reflection and transmission cceffkients are computed for the first two incident wave modes. The validity and accuracyof the.resultsare checked by satisfactionof the energy conservationprinciple. 46383
Imaino. W.
Electromagnetically delamination
generated
acoustic
determination
of
Journal of Applied Physics, Vol. 69, No. 7, pp. 3811-3815 (1 Apr. 1991) In fhis investigation, a finite-element calculation is used to provide a more detailed descriptionof the acoustic behavior of the delaminated plate.. The effects of source size relative to defect dimensions and acoustic properties of the substrate have been studied. The determination of the localized coupling is complicated by sbuctural resonancesof the substrate, which make single frequency measurements unfavourable. However, the analysis shows that the spectral acoustic behavior provides an indication of metallization to substratecoupling. A signal-processingalgorithm t#lsed on this analysis has been formulated and will be described. 46377
Nouailhas, B.; Nguyen, G.V.C.; Vermersch, S.
Ultrasonic modeling and experiments: bimetallic weld in nuclear power plant
an industrial
case:
Journal of Nondestructive Evaluation, Vol. 9, No. 2-3, pp. 145-153 (1990) To improve the ultrasonic inspection of the safe ends connecting the nuclear vessel to the piping, we are conducting modeling studies using two models: PROMANIS, a ray tracing code, and ULTSON, a 2-D finite element code. The study has shown a great interest in combining modeling and experiments to improve the codes and react to the experimental conditions.
251