Testing and optimization of ultrasonic pulse locating antenna by laser vibrometer

摘要

Ultrasonic pulse propagation along locating antenna and ultrasonic wave radiation efficiency depend on material and shape of antenna. Some errors and mistakes can be made during designing and manufacturing of the main element of ultrasonic location meter. These errors can be detected by testing antenna after production. No additional optical elements can be attached to the usually curved fragile and optically rough sound wave radiating surface. Semiconductor laser short distance home made interferometer was used for pulse propagation investigation. Distance along radius between measurement points was chosen taking into account shift pulse wavelength on the surface. There was a possibility to adjust amplitude during the optimization process and to measure real amplitudes of completed antenna in working conditions. It was found that the pulse amplitude and velocity was decreasing with distance from the center. This result was in accordance with theoretical prediction. Pulse energy is distributed on wider surface and therefore pulse amplitude is decreasing. The edge of antenna is less rigid because of it's shape and velocity of pulse should be smaller than it is near to the center. The shift pulse average velocity should be 1.5 times as high as velocity of ultrasound in surrounding medium. Comparison of velocity of shift pulse propagation on the surface of ultrasonic antenna and velocity of acoustic wave in environment material allowed optimizing thickness and parabolic shape of antenna's body.