Paper Title
Effect of Propagation Path and Frequency on Ultrasonic Wave

This paper presents the effect of variables affecting ultrasonic wave transmission in Ultrasonic Testing (UT), which is a non-destructive test method used to detect flaw within material. The principle is based on transmitting sound energy and receiving an echo signal reflected from the flaw in the material. The decision judging of the severity of the flaw is based on the height of the reflected signal. However, the height of this reflected signal is not only depended on the size and orientation of the flaw, it may effect by various variables which make the evaluation of result meet more complicate. In this paper, the variables which are frequency, surface roughness, types and ingredients of couplant, and time of inspection were studied. The reference point used to compare the variation is at 80% of full screen height receiving from back wall echo when using a probe frequency of 2.25 MHz at the grinding surface and by using glycerin as the couplant. The results show that the variables affecting the reflected signal height arrange in order are surface roughness, time of inspection, frequency, ingredients of couplant and the error from an operator. It makes the amplitude of the reflection signal reduceapproximately75, 50, 12, 12 and 6% respectively. The advantage of this paper is to know an impact level of the variables those influence the height of the reflected signal. It also recognizes the effects from ingredients of paste and the period of testing time. Index terms - Ultrasonic wave, Propagation path, Couplant, Frequency, Paste, Surface roughness