Measurement of small thicknesses by ultrasonic method

Abstract

The method of using ultrasonic devices beyond their passport capabilities is considered. The method is intended for measuring small thicknesses of thin-walled metal structures used in aviation and other equipment. This includes products of cellular or cellular construction: heat exchangers, hollow fan blades, metal pads for protecting parts made of composite materials. Existing methods for solving such problems require special equipment or complex mathematical analysis. The proposed method is based on the analysis of distortion of the shape of the ultrasonic signal by comparison with test samples. Distortion occurs as a result of a phase shift between the forward and reflected signals or as a result of modulation of the signal by vibrations of a thin wall. In particular, an example of measuring the thickness of thin-walled titanium alloy parts from 0.4 to 0.9 mm with an accuracy of 0.05...0.02 mm is shown. The measurement was performed using a serial ultrasonic thickness gauge at a frequency of 5 MHz. The proposed method can be useful when working out the technology of manufacturing thin-walled parts.