Study Of Detecting The Metal Surface Defects Based On Laser Ultrasound Technology

Laser ultrasound testing technology, an new non-destructive testing method, has emerged in recent years, which has advantages of non-contact, wide band width, high resolution and available for harsh environments. It is especially suitable for detecting metal surface defects. In this paper, the study of the detection of the metal surface’s defect based on the Laser ultrasound technology is demonstrated. The main contents of the research include the following aspects:The physical process of producing ultrasonic is simulated by the pulse laser in isotropic aluminum material in the finite element method. Then the influence of laser parameters on the ultrasonic field is analyzed. The results show that the change of laser spot radius and laser pulse rise time can have a greater influence on its ultrasonic field. Thus the ultrasonic field can be controlled by adjusting the parameters of the pulse laser. Also the propagation law and characteristics of various modal ultrasonic which are excited by Laser ultrasonic effect on non-defective aluminum plate is discussed. Further the interaction of the laser ultrasound and aluminum materials with surface defects and the influence of defect on the ultrasonic wave propagation are studied. The surface defect is detected and positioned by the surface wave roughly.The aluminum plates with artificial defects are detected by using a laser ultrasonic testing system. The causes and propagation characteristics of reflected wave and transmitted wave after laser ultrasonic interaction with defects are analyzed. Further the propagation rules of the reflected wave and transmitted wave are compared to make a further study. The results show that the signal-to-noise ratio of the reflected wave signal is stronger than transmission wave signal. Finally, the influence of defect size parameters to ultrasonic is studied. The influence law of defect size parameters and ultrasonic signals is obtained. The result provides some theoretical and experimental proofs for locating defects and analyzing defect size.