Experimental Research Of The Laser Ultrasonic Surface Wave Detection

The subject which is based laser ultrasonic is an experimental of non-destructivetesting for laser ultrasonic surface wave detecting surface defects.Fist of all, the subject select the thermoelastic mechanism of low-energy laser lightexcitation of surface wave excitation source as a surface defect detection, beforelearning the mechanism of laser ultrasonic and according to detecting surface defects.The article selects no coupling agent and strong optical detection method forconcentrating energy in the two-wave mixing interferometer as a detection method,through the analysis of several electrical and optical detection of ultrasonic method.The sample substrate of the article is common in the field of aerospace7075aluminum alloy, based on the typical size of the fatigue defect, with wire-cuttingmethod in the production of artificial surface line defect on the substrate.The article researches the influence of process parameters on the measurement bythe experimental, which is the propagation characteristics of surface waves in thesurface, energy of the excitation source, the beam shape and focus of the optical probe.the article use SLLS(scanning laser liner source, the linear light source scanningtechnology) and change excitation source to the distance of the surface defects by1mmstep, and detect SAW signal of the reflection and transmission by surface defects, andgain consistent with the experimental results with theoretical expectations by selectingand controlling the appropriate process parameters.Studies have shown that the laser ultrasonic surface wave is effective and feasibleto detect surface defects. Testing process and testing methods for carrying out the laserultrasonic surface wave testing of materials surface fatigue defects have importantapplication value.