Proposal of the prediction method for fatigue strength of corroded rails with pitting corrosion by actual stress and stress gradient

Abstract

Rail corrosion is one of the causes of rail breaks. The relationship between rail corrosion state and fatigue strength is still unclear. Therefore, to accurately estimate the fatigue strength of corroded rails, the prediction method for fatigue strength of corroded rails with pitting corrosion by actual stress and stress gradient was investigated. Bending fatigue tests were performed on the rails with pitting corrosion on the bottom surface. At this time, models based on the shape of the rail bottom surface were created, and actual stresses and stress gradients generated at the rail bottom surface were evaluated by the finite element method. When the fatigue test results were evaluated by the actual stress, the bending fatigue strength appeared to be higher when the fracture origin position was inside of pitting corrosion than when it was outside. This was an apparent phenomenon due to the use of actual stress, which could be explained in terms of stress gradients. Furthermore, using the relationship between the correction factor of time strength q, which expresses the relationship between the fatigue strength of new rails and the apparent fatigue strength of the corroded rails, and the stress gradient χ, it is possible to estimate the number of loading cycles that the corroded rails break in the fatigue tests.

Keywords

• rail
• pitting corrosion
• bendeing fatigue test
• fem
• actual stress
• stress gradient