Ultrasonic Measurement of Axial Stress Using High-Frequency Cylindrical Guided Wave

A new stress measurement method using single source high-frequency cylindrical guided waves is put forward to promote the efficiency and precision of the contact-type ultrasonic testing technique. The propagation patterns and acousto-elasticity of cylindrical guided waves, traveling in a loaded steel rod, are analyzed under the theoretical framework of the Pochhammer-Chree equation and nonlinear acoustics. According to the theoretical derivations, the ratio of the maximum group velocities of different modes is selected as the measurement criterion of stress. Then, a stress calibration/measurement experiment is conducted to prove the validity of the method. A single-source ultrasonic transducer driven with an impulsive excitation is introduced in the experiment and the generated multimode guided waves in the received signals are analyzed. It is observed from experimental results that the group speed ratio of two different modes is linearly proportional to the axial stress and the evaluation errors of the proposed method is less than 6%.