Computerized Ultrasonic Testing System (CUTS) for in-process thickness determination

A Computerized Ultrasonic Testing System (CUTS) was developed to measure, in real-time, the rate of deposition and thickness of chromium plated on the inside of thick steel tubes. The measurements are made from the outside of the tubes with the ultrasonic pulse-echo technique. The resolution of the system is 2.5 micron. (0.0001 in.) and the accuracy is better than 10 micron (0.0004 in.). The thickness is measured using six transducers mounted at different locations on the tube. In addition, two transducers are mounted on two reference standards, thereby allowing the system to be continuously calibrated. The tube temperature varies during the process, thus the input from eight thermocouples, located at the measurement sites, is used to calculate and compensate for the change in return time of the ultrasonic echo due to the temperature dependence of the sound velocity. CUTS is applicable to any commercial process where real-time change of thickness of a sample has to be known, with the advantage of facilitating increased efficiency and of improving process control.