Jaseung Lee presents his master’s thesis

Student: Jaseung Lee
Main Supervisor: Pär Söderström, Per Wessling
Examiner: Anders Ekberg
Opponent: Klara Matsson

Abstract of thesis

Due to improved quality control in wheel manufacturers and maintenance actions in railway operators, subsurface-initiated rolling contact fatigue rarely happens these days in passenger trains. However, in those cases it poses a risk to trigger accidents such as derailments. Therefore it requires careful monitoring in wheel maintenance.
There are two main methodologies in this study of subsurface-initiated rolling contact fatigue. First, fatigue initiating wheel defect size of a passenger wheel is estimated using Murakami’s theory. It uses the Dang Van stress as a fatigue index in the defect size estimation. Second, the influence of finite boundary effects on the subsurface stress field is studied by comparing stress from elastic Finite Element simulations with the analytical solution for semi-infinite bodies. The study includes an investigation of the influence of wheel reprofiling and lateral contact load position.
Based on measurements of wheel load detectors located in Sweden, this study predicts the initiation of subsurface-initiated rolling contact fatigue on passenger train wheels with wheel defects. A parametric study is conducted to investigate the effects of initial wheel defect size and wheel reprofiling. Finally, it establishes an equivalent Dang Van Wöhler curve (often called SN curve) for passenger train wheels, considering fatigue life reduction due to material defects.