The United States of America as Represented by the Administrator of the

Jerry M Saunders

James M Beggs

John W Redmon, Jr

Garland D Johnston

Joseph N Portwood

Archie D Coleman

Allen C Porter

A method and a system for testing the bonding of foam insulation (22) attached to metal. The system involves the use of an impacter (10) which has a calibrated load cell (12) mounted on a plunger (14) and a hammer head (16) mounted on the end of the plunger (14). When the impacter (10) strikes the insulation (22) at a point to be tested, the load cell (12) measures the force of the impact and the precise time interval during which the hammer head (16) is in contact with the insulation (22). This information is transmitted as an electrical signal (20) to a load cell amplifier (28) where the signal (20) is conditioned and then transmitted to a Fast Fourier Transform (FFT) analyzer (34). The FFT analyzer (34) produces energy spectral density curves (power plotted against frequency in Hertz) which are displayed on a video screen (39). An operator, by observing the frequency point at which the curve terminates, may determine the quality of the bond. Specifically, the termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a high quality bond, good bond, or debond is present at the point of impact. For future reference and use, data from the FFT analyzer (34) are recorded on a magnetic disk (41) and/or a hard copy is produced by a printer (43).

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Huntsville, AL, United States of America

Jerry M Saunders