Researches on the Strength of Wheel Disc

Abstract

The strength of the wheel disc of a newly devised wheel in order to lighten rolling stock is discussed on the basis of an approximate bending theory for a flat spherical shell, since this wheel disc consists of two discs having the form of a flat spherical shell which is made up into a wheel together with boss and rim by welding. In this theory, unbalanced traction is supported only by the stresses deduced from the membrane theory and the boundary condition is satisfied by the sum of solutions of membrane and bending theories. Some approximations are utilized in order to derive the solution of bending theory. The stresses due to the force fit of axle and the shrinkage fit of tyre (i. e. initial stresses) and also those due to axle load and side thrust are considered. As the latter is a non-symmetrical problem, the boss and rim are assumed to be rigid, for simplicity. This assumption will entail larger errors than those due to approximations made in bending theory. A numerical example and comparisons with the experimental results and the other simple calculations are shown. The initial stresses are considerably large and the type of spherical shell is especially disadvantageous, as it causes very large bending stress. For the axle load, the calculation assuming the rigid rim and tyre does not agree with the experimental value which is concentrated in the direction of loading. But, the stresses due to the axle load will be small even if the load is unequally divided between discs. On the contrary, the assumption is reasonable for the side thrust and the calculated values agree with the experimental result. As the stresses due to axle load and side thrust are superimposed in the inside disc, the design is desirable in which the axle load is supported mostly by the other disc.