A new technique for time-domain ultrasonic NDE of thin plates

A new time-domain ultrasonic NDE technique is reported in this paper for the measurement of the thickness (given the wavespeed) or wavespeed (given the thickness) of thin plates; by thin we mean the thickness is less than the wavelength. By introducing a retrieve function the incident field can be reconstructed from the transmitted (reflected) field by a two-term (three-term) summation. A systematic sensitivity analysis of this technique has been carried out. The new technique has been used to measure the thickness or the wavespeed of aluminum plates with thickness ranging from 0.089 to 6.426 mm using (low frequency) 1-MHz transducers: 0.014(thickness/wavelength)1.0. The measurement error was found to be about 1% for thickness and 3% for the wavespeed.