Residual Stress Distributions in Elevator Guide Rail Straightening

Residual stresses that develop during the bending correction process of T-shaped elevator guide rails have become increasingly important. This paper reviews in various recent patents on elevator guide rail and rail straightening. The rail has a special cross section that is symmetrical in horizontal major axis of inertial direction but nonsymmetrical in vertical minor axis of inertial direction. In order to study the residual stress in straightening, considering the special cross section of the rail, an ideal elastic-plastic material model is used to analyze the residual stress distributions of the rail and the analytical expressions are obtained, and the possibilities of reverse yielding during the step of unloading are also analyzed. The results show that maximum of the residual stress can be found at the boundary of the elastic and plastic regions, but when the plastic deformation is further decreased, it is the highest at the outer surfaces which have the farthest distance from the neutral layer. Finite element analyses are also carried out to determine the accuracy of the mathematical model presented.