Study on depth detection of surface notches using time-of-flight method with surface acoustic waves in viscoelastic media

Depth detection of surface notches using a time-of-flight method with surface acoustic waves in viscoelastic media is investigated.Based on the dynamic equilibrium equations in the frequency domain,the numerical models are established to simulate the laser-generated surface acoustic waves in the elastic and viscoelastic media with the surface notches by a finite element method.The influences of the variations of the velocity and dispersion of the surface acoustic waves,which are caused by the viscous property of the material,on the detection of the surface notches are studied. Besides,according to the propagation paths and arrival times of the reflected and transmitted surface acoustic waves,the surface notches in the viscoelastic media are detected by the time-of-flight method.The results show that the dispersion of the surface acoustic waves has little impact on the detection of the surface notches.The position and depth of the surface notches,which are detected by the time-of-flight method,agree well with the values used in the numerical models. It indicates that the effective theoretical method can be obtained for surface notches detections in viscoelastic media.