Ultrasonic Testing of Graphite Plates

Ultrasonic testing is one of the quite frequently used non destructive evaluation methods for detecting flaws in metals. However, the technique is not used regularly for non metals such as plastic. A need was felt for Ultrasonic testing of graphite plates in one of the critical applications. As no literature is found on such testing of graphite plate, the process had to be established as ab intio. This Ultrasonic testing was to be carried out before and after mandatory environmental tests of these plates. Significant changes, if any, are observed with respect to ultrasonic signal amplitudes, before and after environmental tests. If any failure occurs during any of the above testing, the graphite plate is liable to be rejected. For this test a probe is used to scan the entire area of the graphite plate. Ultrasonic probe is made out of Piezo-electric crystal having a frequency of 0.5 MHz. It is built with both transmitter and receiver (TR) probes. It generates the ultrasonic signals and passes over the cross sectional area along the thickness of the graphite plate, receives the pulse echo if any flaw is detected. The flaw will be detected by means of a pulse echo and the severity of the flaw shall be shown on amplitude reduction. This study established a methodology for first time for ultrasonic testing of graphite plates.