Fatigue performance of Q345 structural steel after natural cooling from elevated temperatures

摘要

This paper reports a comprehensive investigation on the fatigue performance of Q345 steel after natural cooling from different elevated temperatures. First, the single-point group testing method for estimating S-N curves is improved by introducing the Pearson correlation coefficient. An implementation algorithm of the improved method is designed. After the parameters are determined by this algorithm, the corresponding expressions of S-N curves with reliability P and confidence level gamma are proposed. Second, fatigue tests are conducted on 40 specimens to investigate the fatigue performance of Q345 steel after natural cooling from the elevated temperatures of 20, 250, 500, and 750 degrees C. Finally, the effect of elevated temperatures on the fatigue performance of Q345 steel is discussed using the improved single-point group testing method. It is observed that the improved single-point group testing method can be used conveniently to estimate the parameters of the S-N curve expression based on the test data. After natural cooling from the elevated temperatures of 250 to 750 degrees C, the fatigue life of Q345 steel increases dramatically and then reduces significantly. The fatigue damage growth of Q345 steel is also significantly affected by the elevated temperature. Furthermore, significant differences are observed in the macro and micro fatigue fracture morphology of Q345 steel owing to the influence of the elevated temperature. (c) 2021 Elsevier Ltd. All rights reserved.