PERCENTAGE POROSITY MEASUREMENT BY A THROUGH-TRANSMISSION ULTRASONIC TECHNIQUE

Percentage porosity measurements are important in the cast metal indus try, due to the section thickness sensitivity. The pulse-echo techniqu e is normally used to measure the attenuation coefficient, which is ta ken as a measure of the percentage porosity. In this paper, the author s present experimental results relating to the measurement of porosity by a through-transmission ultrasonic technique. The frequency of the receiver probe was varied for a selected frequency of the transmitter probe and the height of the transmitted pulse was determined In additi on, attenuation coefficients were deter-mined. The results show that t he through-transmission technique can be used to assess the percentage porosity in cast metals of Al-4.5% Cu alloy where access to both side s of the casting is available. An added advantage of the technique is that the receiver frequency can be varied for a chosen transmitter fre quency.