Optimization of a Railway Freight Car Wheel by Use of a Fractional Factorial Design Method

Abstract

The performance of a ‘low-stress wheel’ exposed to vertical and lateral contact forces and to thermal braking loads is investigated. Based on finite element calculations, a two-level fractional factorial design method is used to quantify the influences of rim thickness, disc thickness and hub-rim offset on thermal and mechanical stressses, on axial rim displacement, and on wheel mass. A number of approximating linear empirical formulas have been obtained. They offer a powerful tool in designing and optimizing railway wheels. The most effective measure to reduce thermal and mechanical stresses is found to be a hub-rim offset but the penalty is a thermoelastic axial rim displacement during heating. This displacement can be minimized by using as large an offset as possible within geometrical limits. In contrast to the standard type of wheel, no residual deformations and large stresses are induced in the offset wheel after heavy block braking. Full-scale dynamometer brake tests performed on a new prototype wheel are reported. The test results support the calculation model used.