A study of surface breaking crack evaluating by using Scanning Laser Source-Dual Laser Source technique

A hybrid non-destructive surface breaking crack evaluation technique, combining a Scanning Laser Source (SLS) technique and Dual Laser Source technique is presented and studied by FEM method and experimentation. By using this technique, surface breaking crack information, such as location, depth and orientation can be measured in one measurement cycle. First, the SLS technique is employed to locate the crack, by detecting the characteristic changes in the amplitude content. Then the Dual Laser Source technique is utilised to quantify the crack depth and orientation. Numerical simulating results show good agreement with the experimental results. Furthermore, the diffracted and reflected ultrasonic wave modes are studied as a function of crack depth and orientation separately, in order to reveal the relationship between these ultrasonic wave components and the crack depth and orientation.