Combination of transverse and longitudinal ultrasonic waves for plane stress measurement of steel plates

The measurement and monitoring of plane stress is important for the safety, reinforcement and maintenance of steel structures. In this study, a new method for plane stress measurement was developed theoretically and experimentally. Based on transverse wave birefringence, we deduced the stress-acoustic relations for plane stress separation by introducing longitudinal waves to increase the number of equations. In signal processing, we used the phase spectra of echoes to measure the polarized transverse wave phase velocity difference and the longitudinal wave phase velocity. The processed steel plate was regarded as a slightly orthotropic component and five stress coefficients need to be determined. Experiments were conducted on a total of four specimens. Strain gauge method was applied to confirm the validity of the proposed method. The results show that the proposed method can realize the direct separation of plane stress and has good accuracy on the laboratory scale.