Extracting guided waves from cross-correlations of elastic diffuse fields: applications to remote structural health monitoring.

Due to their apparent complexity, diffuse fields are not commonly used by conventional structural health monitoring methodologies. However, recent theoretical and experimental studies have demonstrated that local Green's functions (GFs) can be estimated from the cross-correlation of elastic diffuse fields (CDFs) recorded between any points of a sensor grid and generated by sources located remotely from the monitoring area. Hence, this CDF technique effectively transforming each measurement point into a virtual elastic source, thus allowing to measure the local structural response (or GF). Theoretical and experimental studies are conducted to assess the broadband performance of the CDF technique for the extraction of low-frequency coherent Lamb waves (4-90 kHz) propagating in a thin aluminum plate of complex geometry using a scanning laser Doppler vibrometer. The coherent signal-to-noise ratio and the accuracy of the phase and group velocity measurements of the coherent A(0) mode obtained from CDF are also measured to quantify the influence of the spatio-temporal characteristics of the recorded diffuse field, the number and spatial configuration of the remote ultrasonic sources, and the influence of incoherent measurement noise (e.g., sensor noise). In addition, a criterion to assess the emergence rate of late coherent coda arrivals from CDF is also formulated.

[1]  W. Kuperman,et al.  Ambient noise cross correlation in free space: theoretical approach. , 2005, The Journal of the Acoustical Society of America.

[2]  Peter Cawley,et al.  Measurement and prediction of diffuse fields in structures , 1999 .

[3]  M. Fink,et al.  Imaging from one-bit correlations of wideband diffuse wave fields , 2004 .

[4]  Richard L. Weaver,et al.  Diffuse fields in open systems and the emergence of the Green’s function (L) , 2004 .

[5]  Richard L. Weaver,et al.  On diffuse waves in solid media , 1982 .

[6]  Diffuse waves in finite plates , 1984 .

[7]  R. Snieder.  Extracting the Green's function from the correlation of coda waves: a derivation based on stationary phase. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[8]  Philippe Roux,et al.  Arrival-time structure of the time-averaged ambient noise cross-correlation function in an oceanic waveguide. , 2005, The Journal of the Acoustical Society of America.

[9]  David R Dowling,et al.  Using cross correlations of turbulent flow-induced ambient vibrations to estimate the structural impulse response. Application to structural health monitoring. , 2007, The Journal of the Acoustical Society of America.

[10]  Peter Gerstoft,et al.  Surface wave tomography from microseisms in Southern California , 2005 .

[11]  Richard L. Weaver.  Laboratory studies of diffuse waves in plates , 1986 .

[12]  M. Fink,et al.  Ultrasonic pulse compression with one-bit time reversal through multiple scattering , 1999 .

[13]  Eric Larose,et al.  Passive correlation imaging of a buried scatterer , 2006 .

[14]  R. Weaver,et al.  Generalized Berry conjecture and mode correlations in chaotic plates. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[15]  Philippe Roux,et al.  Stability of monitoring weak changes in multiply scattering media with ambient noise correlation: laboratory experiments. , 2009, The Journal of the Acoustical Society of America.

[16]  Ivan Bartoli,et al.  Structural health monitoring by extraction of coherent guided waves from diffuse fields. , 2008, The Journal of the Acoustical Society of America.

[17]  A. Derode,et al.  Empirical synthesis of time-asymmetrical Green functions from the correlation of coda waves , 2005 .

[18]  C. Farrar,et al.  SYSTEM IDENTIFICATION FROM AMBIENT VIBRATION MEASUREMENTS ON A BRIDGE , 1997 .

[19]  W. Kuperman,et al.  Emergence rate of the time-domain Green's function from the ambient noise cross-correlation function , 2005 .

[20]  Richard L. Weaver,et al.  The mean and variance of diffuse field correlations in finite bodies , 2005 .

[21]  K. van Wijk,et al.  On estimating the impulse response between receivers in a controlled ultrasonic experiment , 2006 .

[22]  R. Weaver,et al.  Ultrasonics without a source: thermal fluctuation correlations at MHz frequencies. , 2001, Physical review letters.

[23]  Roel Snieder,et al.  Extracting the Building Response Using Seismic Interferometry: Theory and Application to the Millikan Library in Pasadena, California , 2006 .

[24]  Fluctuations of correlations and Green's function reconstruction : Role of scattering , 2008, 0805.0195.

[25]  R S Langley,et al.  On the diffuse field reciprocity relationship and vibrational energy variance in a random subsystem at high frequencies. , 2007, The Journal of the Acoustical Society of America.

[26]  Eric Larose,et al.  Reconstruction of Rayleigh-Lamb dispersion spectrum based on noise obtained from an air-jet forcing. , 2007, The Journal of the Acoustical Society of America.

[27]  Michel Campillo,et al.  High-Resolution Surface-Wave Tomography from Ambient Seismic Noise , 2005, Science.

[28]  Jan Drewes Achenbach,et al.  Quantitative nondestructive evaluation , 2000 .