A method for determining changes in the average wall thickness or the mean radius of a pipe or tube using ultrasonic and/or magnetostrictive wave probes by analyzing the dispersive behavior of waves traveling in the tube wall volume. The method examines certain wave propagation modes and identifies a cut-off frequency that is characteristic for a particular wall thickness or tube diameter. This method permits the rapid and accurate inspection of a length of pipe or tube from a single location on the inside diameter of the pipe and permits a comparison of data gathered with similar data for the structure in its original condition. Changes in the cut-off frequency, indirectly determined by the method of the present invention are inversely related to changes in the wall thickness and/or the mean radius for the cylindrical structure. In this manner the method of the present invention provides a mechanism for determining the remaining service life for such pipes and tubes.
Joseph W. Brophy; Hegeon Kwun