Signal enhancement in Rayleigh wave interactions using a laser-ultrasound/EMAT imaging system.

Enhancement of signal amplitudes from Rayleigh wave interaction at solid surface features has been investigated when signals were detected by an in-plane electromagnetic acoustic transducer (EMAT). A laser-ultrasound system was used to inspect surface-breaking slots, serving as artificial defects. Nd:YAG laser pulses were delivered onto a metal surface via an optical fiber and focused to a line source by a cylindrical lens. An in-plane EMAT receiver detected transient surface acoustic waves. A-scan signals and B-scan images from surface defects revealed increased signal amplitude up to 2.8+/-0.3 depending on the distance of the transducer from a slot. An explanation is based on the interaction of the EMAT sensor with the Rayleigh wave. A supporting computer model was derived to show that experimental signal enhancements were consistent with numerical predictions.

[1]  J. Spicer,et al.  Hybrid laser/broadband EMAT ultrasonic system for characterizing cracks in metals. , 2002, The Journal of the Acoustical Society of America.

[2]  G. A. Georgiou,et al.  Quantitative studies in ultrasonic wave-defect interaction , 1987 .

[3]  Anthony N. Sinclair,et al.  Improved finite element method for EMAT analysis and design , 2001 .

[4]  Vikram K. Kinra,et al.  Diffraction of Rayleigh waves in a half‐space. I. Normal edge crack , 1985 .

[5]  Richard J. Dewhurst,et al.  Further evidence for two-component surface acoustic wave reflections from surface breaking slots , 1986 .

[6]  A simple approach to estimate the size of small surface cracks with the use of acoustic surface waves , 1978 .

[7]  B. Auld.  General electromechanical reciprocity relations applied to the calculation of elastic wave scattering coefficients , 1979 .

[8]  Richard J. Dewhurst,et al.  A laser/EMAT system for thickness monitoring applications using shear and L-S mode-converted waves , 2001 .

[9]  Richard J. Dewhurst,et al.  Surface‐breaking fatigue crack detection using laser ultrasound , 1993 .

[10]  Jan Drewes Achenbach,et al.  Ultrasonic imaging of small surface-breaking defects using scanning laser source technique , 2002 .

[11]  J. Achenbach,et al.  Time‐domain boundary element analysis of elastic wave interaction with a crack , 1989 .

[12]  M. G. Silk,et al.  The transfer of ultrasonic energy in the diffraction technique for crack sizing , 1979 .

[13]  Jan Drewes Achenbach,et al.  Reflection and transmission of obliquely incident Rayleigh waves by a surface‐breaking crack , 1983 .

[14]  D. Thompson,et al.  Review of Progress in Quantitative Nondestructive Evaluation , 1982 .

[15]  J. Monchalin.  Optical Detection of Ultrasound , 1986, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[16]  Bernhard R. Tittmann,et al.  Finite element analysis of coupled electromagnetic acoustic systems , 1999 .

[17]  R. S. Sharpe,et al.  Research techniques in nondestructive testing , 1970 .

[18]  I. A. Viktorov.  Rayleigh and Lamb Waves: Physical Theory and Applications , 1967 .

[19]  David A. Hutchins,et al.  Quantitative measurements of laser‐generated acoustic waveforms , 1982 .

[20]  J. Achenbach,et al.  Elastodynamic Analysis of an Edge Crack , 1980 .

[21]  Leonard J. Bond,et al.  A computer model of the interaction of acoustic surface waves with discontinuities , 1979 .

[22]  R.B. Thompson,et al.  A Model for the Electromagnetic Generation and Detection of Rayleigh and Lamb Waves , 1973, IEEE Transactions on Sonics and Ultrasonics.

[23]  Richard J. Dewhurst,et al.  Noncontact detection of surface‐breaking cracks using a laser acoustic source and an electromagnetic acoustic receiver , 1986 .

[24]  R. Dewhurst,et al.  Optical remote measurement of ultrasound , 1999 .

[25]  Masahiko Hirao,et al.  Scattering of Rayleigh surface waves by edge cracks: Numerical simulation and experiment , 1982 .

[26]  O. Buck,et al.  Surface wave scattering from elliptical cracks for failure prediction , 1980 .

[27]  A. Gautesen.  Scattering of a Rayleigh Wave by an Elastic Quarter Space , 1985 .

[28]  E. Rivier,et al.  Influence of Elastic Properties on Rayleigh Wave Scattering by Normal Discontinuities , 1977, IEEE Transactions on Sonics and Ultrasonics.

[29]  Leon M Keer,et al.  Scattering of elastic waves by a surface-breaking crack , 1980 .

[30]  G. Kino.  The application of reciprocity theory to scattering of acoustic waves by flaws , 1978 .

[31]  S. Boonsang,et al.  Enhancement of laser-ultrasound/electromagnetic-acoustic transducer signals from Rayleigh wave interaction at surface features , 2003 .

[32]  Yves H. Berthelot,et al.  Detection of small surface-breaking fatigue cracks in steel using scattering of Rayleigh waves , 2001 .

[33]  V. Domarkas,et al.  Length and depth resonances of surface cracks and their use for crack size estimation , 1978 .

[34]  Sridhar Krishnaswamy,et al.  Mass spring lattice modeling of the scanning laser source technique. , 2002, Ultrasonics.

[35]  R. Dewhurst,et al.  Surface Acoustic Wave Interactions with Cracks and Slots: A Noncontacting Study Using Lasers , 1986, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[36]  Jan Drewes Achenbach,et al.  Laser ultrasonic detection of surface breaking discontinuities: Scanning laser source technique , 2000 .

[37]  R. J. Blake,et al.  Rayleigh wave scattering from surface features: wedges and down-steps , 1990 .

[38]  J. Achenbach,et al.  Ray Analysis of Surface-Wave Interaction with an Edge Crack , 1980, IEEE Transactions on Sonics and Ultrasonics.

[39]  M. G. Silk,et al.  Ultrasonic Transducers for Nondestructive Testing , 1984 .

[40]  P. R. Murray,et al.  Application of a laser/EMAT system for using shear and LS mode converted waves. , 2002, Ultrasonics.

[41]  Reinhold Ludwig,et al.  Numerical simulation of electromagnetic acoustic transducer in the time domain , 1991 .

[42]  C. Yew,et al.  An experimental study of interaction between surface waves and a surface breaking crack , 1984 .

[43]  William Veronesi,et al.  Finite element analysis of Rayleigh wave interaction with finite-size, surface-breaking cracks. , 2003, Ultrasonics.