ABSTRACT
We present a new laser prototype for laser ultrasonics excitation. The fundamental wavelength of a Q-switched Nd:YAG laser with a repetition rate of 1 kHz is converted to 3.3 µm with a KTiOAsO4 optical parametric oscillator. The achieved pulse energy at 3.3 µm is 1.7 mJ, and the pulse duration at the fundamental wavelength of 1.06 µm has been measured to be 21 ns. The ultrasonic excitation efficiency is about 3.5 times better compared to the application of state-of-the-art CO2 lasers.
ABSTRACT
A method based on pulsed digital holographic interferometry for the measurement of dynamic deformations of a surface by using a moving system is presented. The measuring system may move with a speed of several meters per minute and can measure deformation of the surface with an accuracy of better than 50 nm. The deformation is obtained by comparison of the wavefronts recorded at different times with different laser pulses produced by a Nd:YAG laser. The effect due to the movement of the measuring system is compensated for by digital processing of the different holograms. The system is well suited for on-line surveillance of a dynamic process such as laser welding and friction stir welding. Experimental results are presented, and the advantages of the method are discussed.
