Re: Airscan transducer performance

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Re: Airscan transducer performance
Posted by: Bill Grandia , E-mail: wgrandia@aol.com, on September 08, 1996 at 00:49:38:
In Reply to: Airscan transducer performance posted by : Marvin Klein on September 06, 1996 at 22:46:55:
: A few questions about airscan transducer performance.
: (1) What kind of resolution can you obtain in 1/2 inch thick composite materials?
: (2) What is the frequency used and the signal-to-noise ratio?
: (3) What are the limitations in thickness?
: Have you looked at combining laser generation of ultrasound (very efficient, and still noncontact) with airscan detection?
:
: Marvin Klein
1) Please refer to our answers to R. Diederichs' questions.
2) Airscan instrumentation (Sonda 007) uses discrete frequencies of 200, 400, and 1000 kHz, 400 kHz being the most commonly used value. The S/N ratio depends on the overall gain level and and material attenuation. In general, S/N ratio better than 40:1 can be achieved.
3) Please consider that the losses due to the bulk absorption are negligible as compared to the reflection losses at the surfaces. Thickness limitations are therefore not critical. We have successfully inspected composite laminates of up to 6 inches thickness.
Yes. Preliminary experiments in detecting laser generated ultrasound with air-coupled acoustic receivers in composite laminates gave a S/N ratio of about 40:1. Further investigations are in progress.

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Comments:
: : A few questions about airscan transducer performance. : : (1) What kind of resolution can you obtain in 1/2 inch thick composite materials? : : (2) What is the frequency used and the signal-to-noise ratio? : : (3) What are the limitations in thickness? : : Have you looked at combining laser generation of ultrasound (very efficient, and still noncontact) with airscan detection? : : : : Marvin Klein : 1) Please refer to our answers to R. Diederichs' questions. : 2) Airscan instrumentation (Sonda 007) uses discrete frequencies of 200, 400, and 1000 kHz, 400 kHz being the most commonly used value. The S/N ratio depends on the overall gain level and and material attenuation. In general, S/N ratio better than 40:1 can be achieved. : 3) Please consider that the losses due to the bulk absorption are negligible as compared to the reflection losses at the surfaces. Thickness limitations are therefore not critical. We have successfully inspected composite laminates of up to 6 inches thickness. : Yes. Preliminary experiments in detecting laser generated ultrasound with air-coupled acoustic receivers in composite laminates gave a S/N ratio of about 40:1. Further investigations are in progress.

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