The accuracy of ultrasonic thickness measurement of distorted grain structure metal samples

Thickness measurement is one of the commonly used control measurements in sheet metal forming. Ultrasonic thickness measurement systems demand access to the ma terial only from one side which makes them very useful for this purpose. Distortion of grain structure of the workpiece influences ultrasonic velocity and in that way directly influences ultrasonic thickness measurement. Three different ultrasonic thicknes s measurement systems are examined on the same working sample. Two systems are defined by standard EN14127. The third system is not defined by the standard and includes previously measured ultrasonic velocity in specific direction of grain elongation. Stat istical analysis shows relations between measurement results obtained by all three systems and highlights the third system as the most accurate one