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Name of Experiment：application of power amplifier in dry coupled ultrasonic testing system

Research Direction：study on sound pressure gain at focal point of high efficiency Fresnel acoustic lens in water

Experiment Contents：firstly, a set of dry coupling ultrasonic testing system was constructed, and a dry coupling probe with a special structural form of piezoelectric oscillator and sound transmission rod was designed.Then a dry coupled ultrasound imaging method based on time reversal was proposed, and the principle of dry coupled ultrasound time reversal focusing was analyzed. The transient fluctuation map at the focusing time was established through the extraction, time reversal and secondary loading of the damage scattering signal. Finally, the defects were imaged by summing and multiplying the amplitudes of structural elements.

Experiment Objective：to solve the problem that the coupling agent can not be applied on the surface of solid rocket motor shell during ultrasonic testing.

Experiment Equipment:dry coupling probe, ultrasonic pulse generator receiver, preamplifier, digital storage oscillocard, probe tool, ATA-4051 power amplifier, signal generator, oscilloscope, computer

Experiment Process:

(1)Time reversal method for dry coupled ultrasound

dry coupled ultrasonic time reversal process

The time-reversal focusing process of dry-coupled ultrasound is shown in the figure. First, the piezoelectric vibrator in the dry-coupled emission probe is excited by the inverse piezoelectric effect to generate ultrasonic waves, which are transmitted to the composite material specimen through the sound transmission rod. Then, multiple dry-coupled probes are used to receive the scattered signals from the defects in the receiving plates at different positions on the specimen. Secondly, the received signal is processed by time reversal, amplification and delay, and the original receiving probe is used as the transmitting probe to reload the processed signal for transmission. Finally, the received signal is acquired twice, and the signal produces a focusing and amplification effect at the wave source.