In the last few years, considerable attention has been focused on using nonlinear ultrasonic properties for the nondestructive evaluation of materials. Some examples of important applications include: metal fatigue, micro cracking, bond strength of adhesives, metal embrittlement, and properties of coatings.
The Ritec SNAP incorporates a number of unique circuits designed to facilitate the determination of these properties using a variety of techniques:
- Harmonic generation in the sample can be monitored as a function of the driving sound amplitude.
- Acoustic resonances may be examined at high and low amplitudes.
- Beam mixing at two driving frequencies can be studied using two high-power, gated amplifiers.
- In some cases simple amplitude dependence may used to obtain valuable results.
Gated-amplifier, high-power outputs are obtainable over a frequency range far in excess of one decade. Typical high-power (5 KW) frequency ranges are 0.05 to 5 MHz and 0.5 to 7 MHz. At 1 kW these ranges are extended to ~5 and just under 20 MHz respectively. In the SNAP system, however, the superheterodyne receiver may be independently tuned up to 80 MHz without loss of phase coherency.
