Research and application of nodal stress correction at stiffness mutation position for fatigue life evaluation

Abstract

This paper proposes a two-level stress correction method to overcome the limitations of the element stress average method that is typically used to calculate the nodal stress in finite element analyses and increase the fatigue life evaluation accuracy at the stiffness mutation positions of large-scale structure. In the first stage, a standard-deviation-weighted stress smoothing method is used to address the high element stress dispersion at the stiffness mutation point. The second stage involves a stress gradient correction method established based on the theory that the nodal stress is affected by other nodal stresses on the stress gradient path. The nodal stresses of the key points of an 80-ton gondola car body are extracted using the two-level stress correction method, and the fatigue life of the key points is evaluated considering the load spectrum of the Daqin coal line. The fatigue lives corresponding to the measured stress spectrum at the key points are compared with the simulated values. Compared with that obtained by the traditional method, the fatigue life of the key joints obtained by the proposed method is closer to the actual fatigue life. Additionally, the nodal stress at the stiffness mutation position obtained by the proposed method is more accurate. Therefore, the two-level stress correction method is a promising platform for the fatigue life evaluation of large-scale structures.