Plane Stress Field Measurement of Steel Members in Service Based on Acoustic Path Difference Method

Under complicated loads, the plane stress fields of steel members are unevenly distributed. The existing ultrasonic methods are limited by the size of the sensor, resulting in insufficient spatial resolution and failure to reveal the plane stress field of steel members. In this study, the acoustic path difference method is proposed to improve the spatial resolution of the plane stress field measurement. The innovation of this method is to decrease the acoustic path by calculating the acoustic time difference between two sets of acoustic paths. The measurement equation for the plane stress field is derived and the measurement system is designed. The signal processing system based on an interpolation algorithm and cross-correlation algorithm is established to capture the variations of acoustic time. The plane stress field of the H-beam is measured to verify the proposed method. The average deviations of measurement stresses between the proposed and strain gauges are less than 10 MPa, demonstrating the proposed method has high accuracy.