Estimation of uncertainty in measurement of ultrasonic wave attenuation

High sensitivity, high accuracy and almost no limitations on type of test material has made ultrasonic testing (UT) a desirable nondestructive testing method. Ultrasonic wave velocity and attenuation are two important parameters that affect an ultrasonic test. Attenuation is the loss of wave energy and reduction in wave amplitude during the propagation of waves through the material. In this paper, the attenuation coefficient is measured in an St37 specimen at a frequency of 1 MHz. The test is conducted in pulse-echo mode with immersion technique. The sources of error are identified, and the measurement uncertainty is calculated. In this measurement, the sources of error include errors due to measuring the length of the part and the amplitude of the echoes reflected from the back surface of the part. The attenuation coefficient is 39.33 dB/m and the measurement uncertainty is ±8.8 dB/m. The noise in the pulser-reciever system is found to be the main source of error in the measurement of amplitudes of reflected echoes from which the attenuation coefficient is calculated.