Finite Element Simulation Of Laser Thermoelastically Generated Ultrasonic Guided Waves

Finite element method has been employed to simulate the generation of ultrasonic guided wave generated by the pulsed laser, which has been focused in the Point or ring Pattern. Through the analysis of the temperature field and stress field produced by interaction laser and material, research of the physical process of pulse laser generated Ultrasonic Guided Wave on the surface of aluminum plate and aluminum tubes.Based on the theoretical model of plane strain, Laser point or ring source irradiation on the aluminum material has been polarized in two dimensional plane, and laser-ultrasonic generated by point or ring laser in aluminum material is established using finite element method based on a theoretical model of thermo-elastic generation of laser-ultrasound. The transient temperature fields generated by a pulse laser radiating on the surface of aluminum material have been simulated. And the evolution curves of the temperature with time, radial variables and axle variables have been gotten. Furthermore, the formation and variation of temperature gradient in the interior of aluminum material have been analyzed.In order to improve the intensity of ultrasound signal, a laser-ultrasonic excited by ring array laser source is simulated using finite element method based on the theoretical model of laser-ultrasonic generated in aluminum plate.The optimum load model with high signal strength and high signal to noise ratio is obtained through the adjustment of the number of excitation source and spacing.Then,the frequency of ultrasonic signals is extracted by using FFT transform and the ultrasonic packet's group velocity is calculated.The results indicate that the laser-ultrasonic generated by our ring array laser source is the A0 mode of Lamb wave which has high energy, small dispersion, and always keeps sufficient vibration energy in the entire internal board meanwhile.The main Practical objective of the Present work is to develop a model of an ultrasonic technique for selecting laser excitation source and optimizing models in the test of laser-ultrasonic nondestructive.