Detection of Internal Defects in Engineering Components by Laser Ultrasonics

Detection of Internal Defects in Engineering Components by Laser Ultrasonics

In this paper, laser ultrasonic testing is used for detection of internal defects in engineering components. An aluminum test piece is prepared with embedded defects with known sizes and locations. By irradiation of a Q-Switched Nd:YAG laser on one side of the test piece, longitudinal, shear, and surface waves are generated in the material. Laser energies of 55 mJ and pulse duration of 12 ns are used for generating the ultrasonic pulses in thermo-elastic regime. The receiver is a piezoelectric transducer. All experiments are performed using through transmission ultrasonic technique. A finite element model (FEM) is also developed for modelling the propagation of lasergenerated ultrasonic waves in the specimen. The experimental and FEM results are compared. Using this method, the size and location of defects are measured with high accuracy.