Ultrasonic testing of axial stress of bolt under the influence of temperature

The relationship between axial stress and the square of the ratio of longitudinal and transverse wave transit time is directly established by optimizing the axial stress detection model of bolt. The optimized model can correct the influence of temperature at the same time. The parameters in the model are only related to the changes of bolt material and temperature. Using various fitting parameters of the bolts of grade 8.8 M20×130, the stress detection accuracy and temperature correction of bolts of the same type and material at 0-300 MPa and 0-40 ℃ are verified. The results show that the errors of stress detection and temperature correction are 0-15.1 MPa and 3.31-10.22 MPa respectively, and the stress detection error of bolts of the same type is 1.1-24.3 MPa. The two errors of bolts with the same material are 1.9-26.9 MPa and 3.25-19.03 MPa respectively. The results show that the reliability of the optimized model is sufficiently high and it is suitable for axial stress evaluation and temperature influence correction of bolts of the same material, which can effectively improve the work efficiency in engineering application.