- Email: [email protected]
Numerical modelling of ultrasonic wave propagation using the efficient p-version finite element method
N DT Abstracts attention is devoted to the identification of those pillar geometries and distributions which may suppress unwanted lateral resonanceswithin the composite structure. The same approach is adopted to assess the nonresonant behaviour of such transducers, with particular attention to hydrostatic applications.
54480 Karunasena, W.M. Elastic waves in laminated composite plates for application in ultrasonic nondestructive evaluation Dissertation Abstracts International, Vol. 54, No. 3, p. 1552-B (Sep. 1993) (DANN 77849)
56013 Assaad, J.; Bruneel, C.; Decarpigny, J N.; Rouvaen. J M. Application of the finite element method to modelling transducer bars IEEE 1993 Ultrasonics Symposium, Baltimore, Maryland (United States), 31 Oct. - 3 Nov. 1993. Vol. 2, pp. 839-842. Edited by M. Levy and B.R. McAvoy. IEEE (1993) ISSN 1051-0117 Lithium Niobate (LiNbOsub(3)) bars are widely used in high frequency
A hybrid method is presented for analyzing scattering of waves by the flaws in laminated composite plates. The modeling is achieved by dividing the domain of the plate into two regions: an interior region that consistsof the flaws and a finite region of the plate around the flaw; and an unbounded exterior mgion. The hybrid method combinesa finite element formulation in the interior region with a wave function representationin the exterior region. The method is illustrated through solving the problems of scattering by a symmetric normal edge crack and a centrally located normal matrix crack that grows into delamination.
applications like ultrasonic imaging and non-destructivetesting. However due to strong material anisotrop:y,the modeling of such bar transducers,for the sake of optimisation, is quite difficult. This paper is focused on the two-dimensional modeling of LiNbOsub(3) bars using the finite element method with the help of the ATILA code. Mode dispersions curves are displayed for the (YZw)36sup(o) cut. For this cut bar the in-water far-field ditectivity patterns are shown, for several frequencies with width to thicknessratio (W/T) equal to 3.59.
55581 Ghorayeh, S.R.; Lord, W.; Udpa, S.S. Application of a beamforming technique to ultrasound imaging in nondestructive testing IEEE Transactions on Ultra.sonics, Ferroelectrics, and Frequency Control, Vol. 41, No. 2, pp. 119-208 (Mar. 1994) The data independent beamformer is studied as a potential method to reduce ultrasonic data acquisition time. The finite element method (FBM) is used as a testbed to mimic the ultrasound measurementsby simulating the action of a transducer array. Tests reveal that when the weights of the interpolating filters (beamformew) are adjustedproperly, they can indeed by used to predict A-scan signals from a data set produced by a transducer moving in a line-scan direction at nonuniform increments; hence, reducing the data acquisition time. The same filter weights also predict accurately A-scan signals from another data set produced by the same transducer moving at nonuniform increments for a different material geometry.
55523 Ishikawa, H.; Koimui, T.; Natsumara, T.; Funatogawa, 0. Experimental and analytical studies on impact damage in CFRP laminate Advanced Materials: Expanding the Horizons. 25th International SAMPE Technical Conference, Philadelphia, Pennsylvania (United States), 26-28 Oct. 1993. Vol. 25, ~~444-455. Edited by R. Trabocco and T. Lynch, SAMPE (1993) An experimental investigation is conducted to estimate the impact damage area of Carbon Fiber Reinforced Plastics (CFRP) laminates by the penetrative impact loading. For the design references to the typical aeroengine blade or vane, stacking sequences of the laminates am simplified. The effects of impact velocity and stacking sequencesof the laminates on the damage area are investigated. Numerical simulations are also conducted by using three-dimensional dynamic finite element analysis to clarify impact failure mechanisms. Some methodologies for impact resistancedesign am proposed.
55309 Fancher, N.B. Stress wave scattering in concrete: simple finite element model investigation International Conference on Nondestructive Testing of Concrete in the Infrastructure, Dearborn, Michigan (United States), 9-1 I Jun. 1993. pp. 256-266. Society for Experimental Mechanics, Inc., (1993) ISBN 109 12053429 This paper outlines a method to approximate the attenuation due to
scattering of a pulse stresswave in concrete-like, discrete inclusion models and presents the results of numerical experiments employing the method. The study usesa two-dimensional, dynamic finite element code to analyze models under bistatic and monostaticprobe spatial conligurations. A goal of the investigation with relatively simple, discrete inclusion models representing concrete without flaws or nonaggregate inclusions is to generate insights into attenuation that are applicable to subsequentstudies employing complex finite element model representations of concrete containing typical features for detection and characterization through ultrasonic nondestructiveevaluation (NDE). For a variety of parameters,the study provides approximations of scattering loss in a two-dimensional, concretelike composite material.
54456 McCann, D.R.; Jirinec, M.J.: Quinn, J.R. Low pressure turbine disk assessment a case study Proceedings: EPRI Steam Turbine and Generator NDE, Life Assessment, and Maintenance Workshop, Charlotte, North Carolina (United States), 16-19 Jul. 1991. pp. 34.1-34.12 EPRI-TR-101333 (1992) The shrunk-ondisks on two LP rotors from a 380 MW Allis-Chalmers crosscompoundunit were unstackedduring an outage in 1979 at&r I9 years of service. Keyway indications were found in 6 of I4 disks by magnetic particle inspection. The disk keyways and bore region were m-examined again in 1990 while the disks were assembledon the LP rotors utilizing an ultrasonic method (UDRPS). The examination was made from the hub and web sections of the disks; this technique has demonstrated detection of 0.020” deep flaws emanating from a keyway. A condition assessmentof the disks was conductedutilizing indication size, material propertiesdata, tinite element stressanalysis, and fracture mechanics analysis which considered stress corrosion and fatigue crack growth. It was concluded that the LP rotorscould be returnedto service without removing the disks. However, the disks must be inspected again within 5-7 years to determine the flaw size and propagationrate. It was estimated that a cost savings of $500,000 was realized from the ultrasonic disk inspectioncompared to unstacking.
54181
Wincheski, B.; Namking, M.; F&on, J.P.; Clendenin,
C.G.
Multi-mode excitation and data reduction for fatigue crack characterization in conducting plates IEEE 1992 Ultrasonics Symposium, Tucson, Arizona (United States), 20-23 Oct. 1992. Vol. 2, pp. 825-828 Edited by B.R. McAvoy. IEEE (1992) ISSN 1051-0117 Advances in the technique of fatigue crack characterization by resonant modal analysishave been achieved through a new excitation mechanismand data reduction of multiple resonance modes. A non-contacting electromagneticdevice is used to apply a time varying Lorentz force to thin conductingsheets.The frequencyand direction of the Lotentz force are such that resonancemodes are generated in the test sample. By comparing the changein frequency between distinct resonantmodes of a sample, detecting and sizing of fatigue cracks are achieved and frequency shifts caused by boundary condition changes can be discriminated against. Finite element modeling has been performed to verify experimental results. 54179
Varadan, V.V.; Varadan, V.K.
Smart structures - modeling and applications IEEE 1992 Ultrasonics Symposium, Tucson, Arizona (United States), 20-23 Oct. 1992. Vol. 2, pp. 833-841 Edited by B.R. McAvoy. IEEE (1992) ISSN 1051-0117 Smart structuresare expected to adapt to their environment and provide a useful response to changes in the environment. Piezcelectric ceramics have proved to be effective as both sensorsand actuatorsfor a wide variety of applications. A hybrid finite element method in conjunction with a boundary element technique is used to model the fields in and around a smart structurecontaining piezoceramic elements on an immersed structure. Experimental applications to the adaptive control of space and automobile structures, active sonar absorbers and vibration and radiated noise are reviewed. 54164
Issa, CA.; [yet-, KS.; Balasubramaniam, K.
Numerical modelling of ultrasonic wave propagation using the efficient p-version finite element method Ultrasonics, Vol. 32, No. 1, pp. 13-20 (Jan. 1994) In this paper, the new p-version of the finite element method has been used for the numerical modelling of ultrasonic wave propagation in solid media. The p-method involves increasing the polynomial order of the the interpolation functions to achieve convergence. Illustrative examples of wave propagation through an isotropic aluminium block, including a case
245
N DT Abstracts
with a built-in defect in the form of a crack have been discussed.Also, a convergence criterion has been developed for dynamic problems. The potential to extend this model to other applications such as medical ultrasonics of to a more complex anisotropic medium is significant.
good agreement in the vicinity of the central ray, and that the deviation increasesas one moves away from the axis. Also, as the beam propagates through multiple interfaces, the accuracy of the Gauss-Hem& solution decreases.
53983 B.
53423 Guo, N.; Cawley, P. The interaction of Lamb waves with delaminations in composite laminates Journal of the Acoustical Society of America, Vol. 94, No. 4, pp.
Assaad, J.; Bruneel, C.; Decarpigny. J.-N.; Nongaillard,
Electromechanical coupling coefficients and far-field radiation patterns of lithium niobate bars (Y-cut) used in high-frequency acoustical imaging and nondestructive testing Journal of the Acoustical Society of America, Vol. 94, No. 5, pp. 2969-2978 (Nov. 1993) The use of the finite element method, with the help of the ATILA code, is proposed to compute resonance frequencies, coupling coefficients, electrical impedance and in-water far-field directivity patterns. (YZw)36 and YXl)36 cuts with different Wn ratios have been analyzed and numerical results have been carefully and successfully compared with measurements. Main results concern the (YZw)36 cut for which symmetrical directivity patterns are obtained. In this case, a quite constant value is found for the thickness mode coupling coefficient K in the ranges Wn < 0.8 (kapprox 50%) and 1.2 < Wlr < 1.7 (kapprox 40%). For the (YX1)36 cut, the directivity pattern is non-symmetrical. In all the cases, a clear physical interpretation of transducer radiation characteristics is provided in terms of vibration modes.
53961 Powell, D J.; Hayward, G. A novel ultrasonic array incorporating composite transducer technology Proceedings of the IEEE 1992 Ultrasonics Symposium, Tucson, Arizona (United States), 20-23 Oct. 1992. Vol. 1, pp. 527-534. Edited by B.R. McAvoy. IEEE (1992). ISSN 10510117. This paper presents a new type of ultrasonic array transducer that incorporates the high bandwidth reception properties of PVDF with the greater transmissionsensitivity of a composite transducer.Through careful choice of epoxy phase for the composite polymer matrix and a novel electmding technique, the composite maintains its normal transmission sensitivity but with the added advantage of practical flexibility. This paper considersthe theoretical and practical design of the array structurewith the piezo-electric process within the composite and choice of ceramic pillar Width to Height (W/H) ratio being based upon a series of finite element modelling results.
53940 Sullivan, J.M.; Ludwig, R.; Grimes, WJ. An effkient FEM approach for the study of ultrasonic wave propagation in solids Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 19-24 Jul. 1992. Vol. 12A, pp. 131.138. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1993). ISBN O-306-44483-6. This work presents plane strain and axisymmetric finite element formulations which include viscous damping and anisotropic material capabilities that reduce by orders of magnitude the memory storage and execution time traditionally encountered. The time integration is accomplished using the explicit central difference method. The finite element spatial discretization employs a lumped mass matrix. The resulting decoupled equations are solved on a node by node basis at each time step. The code was verified as accurate by comparing the displacements qualitatively for the expected wave motion and by comparing the displacementhistoriesat specific nodesto both analytical solutionsbasedon the Cagnaird de-Hoop method and experimental pulse-echo piezoelectric transducerdata.
53490 Minachi, A.; Mould, J.; Thompson, R.B. Ultrasonic beam propagation through a bimetallic weld - a comparison of predictions of the Gauss-Hermite beam model and finite element method Journal of Nondestructive Evaluation, Vol. 12, No. 2, pp. 151.158 (Jun. 1993) Predictions of two models for the propagation of ultrasonic beams through a two-dimensional, bimetallic weld geometry are compared. The finite element method can predict beam propagation through quite general geometry with high accuracy. This model, however, requires significant computational time. On the other hand, the approximate Gauss-Hermite model offers considerably greater computational speed, but has lower accuracy in certain regions and cannot treat the most general geometriesand inhomogeneities in material properties. This paper compares the performances of the two models for the case of the two-dimensional, bimetallic weld consisting of multiple layers, some of which have anisotropic properties. It is found that the results of the two models are in
2240- 2246 (Oct. 1993) This paper discusses the interaction of the S Lamb mode with delaminations. The dispersion curves and the corresponding stress and displacement mode shapes of the lower order Lamb modes are obtained analytically and the interaction of the S mode with delaminations at different interfaces in a composite laminae is then studied both by finite element analysis and by experiment. It is shown that the amplitude of the reflection of the S mode from a delamination is strongly dependent on the position of the delamination through the thickness of the laminate and that the delamination locations corresponding to the maximum and minimum reflectivity correspond to the locations of maximum and minimum shear stressacrossthe interface in the.S mode.
53166 Minachi. A.: You, Z.; Thompson, R.B.; Lord, W. Predictions of the Gauss-Hermite beam model and finite element method for ultrasonic propagation through anisotropic stainless steel IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 40, No. 4, pp. 338-346 The predictions of the Gauss-Hermite beam model are compared to those obtained by the finite element method for a model problem. In the. model problem, a contact strip transducerradiates through an isotropic layer of ferritic steel into an anisotropic layer of austenitic stainless steel with various directions of the preferred axis of columnar grain alignment. Comparisonsare made of time-domain waveforms in a common observation axis in the austenitic material. The predictions of tbe two models ate found to be in good agreement near the center of the beam, with deviations developing as one moves away from the central ray.
52973 Minachi, A. Propagation of elastic waves through inhomogenous anisotropic materials Dissertation Abstracts International, Vol. 53, No. 7, p. 3537 (Jan. 1993) (DA9234836) In this dissertation, studies are presented evaluating the validity of the Gauss-Hermite model in a multilayered medium. First, a method of finding the elastic constants of anisotropic materials is presented. These elastic constantsare important inputs to the Gauss-Hermite model. To validate the Gauss-Herr&z beam model in multilayered media, comparisonshave been made between its predictionsand those found by the finite element method, which provides a more exact solution. The structures considered combine. both isotropic and anisotropic layers. The comparison of the model with the finite element method showed good agreement around the central ray direction.
5295 1 Jaleel, K.M.A.; Kishore, N.N.; Sunabrarajan, V. Finite-element simulation of elastic wave propagation orthotropic composite materials Materials Evaluation, Vol. 5 1, No. 7, pp. 830-838 (Jul. 1993)
in
In the present work, a plane strain finite-element model has been developed to study the elastic wave propagation and scattering in general anisotropic media. The interaction of pulsed compression waves and Rayleigh waves with cracks in isotropic material has been studied. The wave interaction with an interface crack in a layered graphite/epoxy composite structure has been investigated. It predicts the mode-conversion and diffraction of waves by cracks. It is found that for quasi-longitudinal waves the displacement along the fiber is prominent, whereas for quasi-transverse,that displacementperpendicular to the fiber is prominent. 52939
Lun, J.; Simoneau, MJ.; Boucher, S.G.
Development of an efficient transducer design tool: complete finite element modeling of transducer performance parameters on a PC New Developments in Ultrasonic Transducers and Transducer Systems, San Diego, California (United States), 21-22 Jul. 1992. pp. 57-71 Edited by F.L. Lizzi. SPIE Vol. 1733 (1992) The finite element method has been extended to the prediction of parameters more directly useful to the designer. A finite element program has been written in Fortran to compile and run on a 33MHz/386 PC. Eigenfrequencies, impedance, transmit and receive sensitivity, radiation
24 I6
54480 Karunasena, W.M. Elastic waves in laminated composite plates for application in ultrasonic nondestructive evaluation Dissertation Abstracts International, Vol. 54, No. 3, p. 1552-B (Sep. 1993) (DANN 77849)
56013 Assaad, J.; Bruneel, C.; Decarpigny, J N.; Rouvaen. J M. Application of the finite element method to modelling transducer bars IEEE 1993 Ultrasonics Symposium, Baltimore, Maryland (United States), 31 Oct. - 3 Nov. 1993. Vol. 2, pp. 839-842. Edited by M. Levy and B.R. McAvoy. IEEE (1993) ISSN 1051-0117 Lithium Niobate (LiNbOsub(3)) bars are widely used in high frequency
A hybrid method is presented for analyzing scattering of waves by the flaws in laminated composite plates. The modeling is achieved by dividing the domain of the plate into two regions: an interior region that consistsof the flaws and a finite region of the plate around the flaw; and an unbounded exterior mgion. The hybrid method combinesa finite element formulation in the interior region with a wave function representationin the exterior region. The method is illustrated through solving the problems of scattering by a symmetric normal edge crack and a centrally located normal matrix crack that grows into delamination.
applications like ultrasonic imaging and non-destructivetesting. However due to strong material anisotrop:y,the modeling of such bar transducers,for the sake of optimisation, is quite difficult. This paper is focused on the two-dimensional modeling of LiNbOsub(3) bars using the finite element method with the help of the ATILA code. Mode dispersions curves are displayed for the (YZw)36sup(o) cut. For this cut bar the in-water far-field ditectivity patterns are shown, for several frequencies with width to thicknessratio (W/T) equal to 3.59.
55581 Ghorayeh, S.R.; Lord, W.; Udpa, S.S. Application of a beamforming technique to ultrasound imaging in nondestructive testing IEEE Transactions on Ultra.sonics, Ferroelectrics, and Frequency Control, Vol. 41, No. 2, pp. 119-208 (Mar. 1994) The data independent beamformer is studied as a potential method to reduce ultrasonic data acquisition time. The finite element method (FBM) is used as a testbed to mimic the ultrasound measurementsby simulating the action of a transducer array. Tests reveal that when the weights of the interpolating filters (beamformew) are adjustedproperly, they can indeed by used to predict A-scan signals from a data set produced by a transducer moving in a line-scan direction at nonuniform increments; hence, reducing the data acquisition time. The same filter weights also predict accurately A-scan signals from another data set produced by the same transducer moving at nonuniform increments for a different material geometry.
55523 Ishikawa, H.; Koimui, T.; Natsumara, T.; Funatogawa, 0. Experimental and analytical studies on impact damage in CFRP laminate Advanced Materials: Expanding the Horizons. 25th International SAMPE Technical Conference, Philadelphia, Pennsylvania (United States), 26-28 Oct. 1993. Vol. 25, ~~444-455. Edited by R. Trabocco and T. Lynch, SAMPE (1993) An experimental investigation is conducted to estimate the impact damage area of Carbon Fiber Reinforced Plastics (CFRP) laminates by the penetrative impact loading. For the design references to the typical aeroengine blade or vane, stacking sequences of the laminates am simplified. The effects of impact velocity and stacking sequencesof the laminates on the damage area are investigated. Numerical simulations are also conducted by using three-dimensional dynamic finite element analysis to clarify impact failure mechanisms. Some methodologies for impact resistancedesign am proposed.
55309 Fancher, N.B. Stress wave scattering in concrete: simple finite element model investigation International Conference on Nondestructive Testing of Concrete in the Infrastructure, Dearborn, Michigan (United States), 9-1 I Jun. 1993. pp. 256-266. Society for Experimental Mechanics, Inc., (1993) ISBN 109 12053429 This paper outlines a method to approximate the attenuation due to
scattering of a pulse stresswave in concrete-like, discrete inclusion models and presents the results of numerical experiments employing the method. The study usesa two-dimensional, dynamic finite element code to analyze models under bistatic and monostaticprobe spatial conligurations. A goal of the investigation with relatively simple, discrete inclusion models representing concrete without flaws or nonaggregate inclusions is to generate insights into attenuation that are applicable to subsequentstudies employing complex finite element model representations of concrete containing typical features for detection and characterization through ultrasonic nondestructiveevaluation (NDE). For a variety of parameters,the study provides approximations of scattering loss in a two-dimensional, concretelike composite material.
54456 McCann, D.R.; Jirinec, M.J.: Quinn, J.R. Low pressure turbine disk assessment a case study Proceedings: EPRI Steam Turbine and Generator NDE, Life Assessment, and Maintenance Workshop, Charlotte, North Carolina (United States), 16-19 Jul. 1991. pp. 34.1-34.12 EPRI-TR-101333 (1992) The shrunk-ondisks on two LP rotors from a 380 MW Allis-Chalmers crosscompoundunit were unstackedduring an outage in 1979 at&r I9 years of service. Keyway indications were found in 6 of I4 disks by magnetic particle inspection. The disk keyways and bore region were m-examined again in 1990 while the disks were assembledon the LP rotors utilizing an ultrasonic method (UDRPS). The examination was made from the hub and web sections of the disks; this technique has demonstrated detection of 0.020” deep flaws emanating from a keyway. A condition assessmentof the disks was conductedutilizing indication size, material propertiesdata, tinite element stressanalysis, and fracture mechanics analysis which considered stress corrosion and fatigue crack growth. It was concluded that the LP rotorscould be returnedto service without removing the disks. However, the disks must be inspected again within 5-7 years to determine the flaw size and propagationrate. It was estimated that a cost savings of $500,000 was realized from the ultrasonic disk inspectioncompared to unstacking.
54181
Wincheski, B.; Namking, M.; F&on, J.P.; Clendenin,
C.G.
Multi-mode excitation and data reduction for fatigue crack characterization in conducting plates IEEE 1992 Ultrasonics Symposium, Tucson, Arizona (United States), 20-23 Oct. 1992. Vol. 2, pp. 825-828 Edited by B.R. McAvoy. IEEE (1992) ISSN 1051-0117 Advances in the technique of fatigue crack characterization by resonant modal analysishave been achieved through a new excitation mechanismand data reduction of multiple resonance modes. A non-contacting electromagneticdevice is used to apply a time varying Lorentz force to thin conductingsheets.The frequencyand direction of the Lotentz force are such that resonancemodes are generated in the test sample. By comparing the changein frequency between distinct resonantmodes of a sample, detecting and sizing of fatigue cracks are achieved and frequency shifts caused by boundary condition changes can be discriminated against. Finite element modeling has been performed to verify experimental results. 54179
Varadan, V.V.; Varadan, V.K.
Smart structures - modeling and applications IEEE 1992 Ultrasonics Symposium, Tucson, Arizona (United States), 20-23 Oct. 1992. Vol. 2, pp. 833-841 Edited by B.R. McAvoy. IEEE (1992) ISSN 1051-0117 Smart structuresare expected to adapt to their environment and provide a useful response to changes in the environment. Piezcelectric ceramics have proved to be effective as both sensorsand actuatorsfor a wide variety of applications. A hybrid finite element method in conjunction with a boundary element technique is used to model the fields in and around a smart structurecontaining piezoceramic elements on an immersed structure. Experimental applications to the adaptive control of space and automobile structures, active sonar absorbers and vibration and radiated noise are reviewed. 54164
Issa, CA.; [yet-, KS.; Balasubramaniam, K.
Numerical modelling of ultrasonic wave propagation using the efficient p-version finite element method Ultrasonics, Vol. 32, No. 1, pp. 13-20 (Jan. 1994) In this paper, the new p-version of the finite element method has been used for the numerical modelling of ultrasonic wave propagation in solid media. The p-method involves increasing the polynomial order of the the interpolation functions to achieve convergence. Illustrative examples of wave propagation through an isotropic aluminium block, including a case
245
N DT Abstracts
with a built-in defect in the form of a crack have been discussed.Also, a convergence criterion has been developed for dynamic problems. The potential to extend this model to other applications such as medical ultrasonics of to a more complex anisotropic medium is significant.
good agreement in the vicinity of the central ray, and that the deviation increasesas one moves away from the axis. Also, as the beam propagates through multiple interfaces, the accuracy of the Gauss-Hem& solution decreases.
53983 B.
53423 Guo, N.; Cawley, P. The interaction of Lamb waves with delaminations in composite laminates Journal of the Acoustical Society of America, Vol. 94, No. 4, pp.
Assaad, J.; Bruneel, C.; Decarpigny. J.-N.; Nongaillard,
Electromechanical coupling coefficients and far-field radiation patterns of lithium niobate bars (Y-cut) used in high-frequency acoustical imaging and nondestructive testing Journal of the Acoustical Society of America, Vol. 94, No. 5, pp. 2969-2978 (Nov. 1993) The use of the finite element method, with the help of the ATILA code, is proposed to compute resonance frequencies, coupling coefficients, electrical impedance and in-water far-field directivity patterns. (YZw)36 and YXl)36 cuts with different Wn ratios have been analyzed and numerical results have been carefully and successfully compared with measurements. Main results concern the (YZw)36 cut for which symmetrical directivity patterns are obtained. In this case, a quite constant value is found for the thickness mode coupling coefficient K in the ranges Wn < 0.8 (kapprox 50%) and 1.2 < Wlr < 1.7 (kapprox 40%). For the (YX1)36 cut, the directivity pattern is non-symmetrical. In all the cases, a clear physical interpretation of transducer radiation characteristics is provided in terms of vibration modes.
53961 Powell, D J.; Hayward, G. A novel ultrasonic array incorporating composite transducer technology Proceedings of the IEEE 1992 Ultrasonics Symposium, Tucson, Arizona (United States), 20-23 Oct. 1992. Vol. 1, pp. 527-534. Edited by B.R. McAvoy. IEEE (1992). ISSN 10510117. This paper presents a new type of ultrasonic array transducer that incorporates the high bandwidth reception properties of PVDF with the greater transmissionsensitivity of a composite transducer.Through careful choice of epoxy phase for the composite polymer matrix and a novel electmding technique, the composite maintains its normal transmission sensitivity but with the added advantage of practical flexibility. This paper considersthe theoretical and practical design of the array structurewith the piezo-electric process within the composite and choice of ceramic pillar Width to Height (W/H) ratio being based upon a series of finite element modelling results.
53940 Sullivan, J.M.; Ludwig, R.; Grimes, WJ. An effkient FEM approach for the study of ultrasonic wave propagation in solids Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (United States), 19-24 Jul. 1992. Vol. 12A, pp. 131.138. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1993). ISBN O-306-44483-6. This work presents plane strain and axisymmetric finite element formulations which include viscous damping and anisotropic material capabilities that reduce by orders of magnitude the memory storage and execution time traditionally encountered. The time integration is accomplished using the explicit central difference method. The finite element spatial discretization employs a lumped mass matrix. The resulting decoupled equations are solved on a node by node basis at each time step. The code was verified as accurate by comparing the displacements qualitatively for the expected wave motion and by comparing the displacementhistoriesat specific nodesto both analytical solutionsbasedon the Cagnaird de-Hoop method and experimental pulse-echo piezoelectric transducerdata.
53490 Minachi, A.; Mould, J.; Thompson, R.B. Ultrasonic beam propagation through a bimetallic weld - a comparison of predictions of the Gauss-Hermite beam model and finite element method Journal of Nondestructive Evaluation, Vol. 12, No. 2, pp. 151.158 (Jun. 1993) Predictions of two models for the propagation of ultrasonic beams through a two-dimensional, bimetallic weld geometry are compared. The finite element method can predict beam propagation through quite general geometry with high accuracy. This model, however, requires significant computational time. On the other hand, the approximate Gauss-Hermite model offers considerably greater computational speed, but has lower accuracy in certain regions and cannot treat the most general geometriesand inhomogeneities in material properties. This paper compares the performances of the two models for the case of the two-dimensional, bimetallic weld consisting of multiple layers, some of which have anisotropic properties. It is found that the results of the two models are in
2240- 2246 (Oct. 1993) This paper discusses the interaction of the S Lamb mode with delaminations. The dispersion curves and the corresponding stress and displacement mode shapes of the lower order Lamb modes are obtained analytically and the interaction of the S mode with delaminations at different interfaces in a composite laminae is then studied both by finite element analysis and by experiment. It is shown that the amplitude of the reflection of the S mode from a delamination is strongly dependent on the position of the delamination through the thickness of the laminate and that the delamination locations corresponding to the maximum and minimum reflectivity correspond to the locations of maximum and minimum shear stressacrossthe interface in the.S mode.
53166 Minachi. A.: You, Z.; Thompson, R.B.; Lord, W. Predictions of the Gauss-Hermite beam model and finite element method for ultrasonic propagation through anisotropic stainless steel IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 40, No. 4, pp. 338-346 The predictions of the Gauss-Hermite beam model are compared to those obtained by the finite element method for a model problem. In the. model problem, a contact strip transducerradiates through an isotropic layer of ferritic steel into an anisotropic layer of austenitic stainless steel with various directions of the preferred axis of columnar grain alignment. Comparisonsare made of time-domain waveforms in a common observation axis in the austenitic material. The predictions of tbe two models ate found to be in good agreement near the center of the beam, with deviations developing as one moves away from the central ray.
52973 Minachi, A. Propagation of elastic waves through inhomogenous anisotropic materials Dissertation Abstracts International, Vol. 53, No. 7, p. 3537 (Jan. 1993) (DA9234836) In this dissertation, studies are presented evaluating the validity of the Gauss-Hermite model in a multilayered medium. First, a method of finding the elastic constants of anisotropic materials is presented. These elastic constantsare important inputs to the Gauss-Hermite model. To validate the Gauss-Herr&z beam model in multilayered media, comparisonshave been made between its predictionsand those found by the finite element method, which provides a more exact solution. The structures considered combine. both isotropic and anisotropic layers. The comparison of the model with the finite element method showed good agreement around the central ray direction.
5295 1 Jaleel, K.M.A.; Kishore, N.N.; Sunabrarajan, V. Finite-element simulation of elastic wave propagation orthotropic composite materials Materials Evaluation, Vol. 5 1, No. 7, pp. 830-838 (Jul. 1993)
in
In the present work, a plane strain finite-element model has been developed to study the elastic wave propagation and scattering in general anisotropic media. The interaction of pulsed compression waves and Rayleigh waves with cracks in isotropic material has been studied. The wave interaction with an interface crack in a layered graphite/epoxy composite structure has been investigated. It predicts the mode-conversion and diffraction of waves by cracks. It is found that for quasi-longitudinal waves the displacement along the fiber is prominent, whereas for quasi-transverse,that displacementperpendicular to the fiber is prominent. 52939
Lun, J.; Simoneau, MJ.; Boucher, S.G.
Development of an efficient transducer design tool: complete finite element modeling of transducer performance parameters on a PC New Developments in Ultrasonic Transducers and Transducer Systems, San Diego, California (United States), 21-22 Jul. 1992. pp. 57-71 Edited by F.L. Lizzi. SPIE Vol. 1733 (1992) The finite element method has been extended to the prediction of parameters more directly useful to the designer. A finite element program has been written in Fortran to compile and run on a 33MHz/386 PC. Eigenfrequencies, impedance, transmit and receive sensitivity, radiation
24 I6