JIAO Jingpin　 HE Cunfu WU Bin

(Department of Mechanical Engineering, Beijing University of Technology  Beijing 100124)

B.W.Drinkwater S.A.Neild P.D.Wilcox

(Department of Mechanical Engineering, University of Bristol Bristol, BS8 1 TR, UK)

Received Apr. 8, 2009

Revised Apr. 13, 2009

Abstract A nonlinear acoustic technique for detection of contact defects in plates was developed associating guided waves with vibro-modulation techniques.The low frequency vibration varies the interface area within the contact defect;then the amplitude and phase of high frequency guided waves reflected from the contact defect will be modulated.Due to the exiting of contact defects,there was obvious low frequency component in the time-frequency distribution of modulated guided wave series.Furthermore the nonlinear responses at frequency of vibration were extracted out and used for defect imaging.It was shown that the nonlinear guided wave imaging method based on vibration modulation can effectively characterize and locate the nonlinear contact defects.

PACS numbers: 43.25,43.35