OPTIMUM DESIGN OF A ROTATING SHAFT FOR COMBINED FATIGUE-STRENGTH

A method is presented for the optimal design of a shaft in a general case of loading, time-variable stresses due to the rotation of the shaft taking place. The criterion being the minimum volume, the problem is essentially the ddetermination of the shape of equal fatigue strength. An effective solution for the general case is obtained by the small parameter method. Namely, small parameters take into account the influence of tension and shearing on the design of a shaft subject to simultaneous bending and torsion. The range of validity of the solution is analyzed. Conditions that the loading of the shaft must fulfill when the obtained formula determining the optimal cross-section is applied are stated as well. A simple example of the design of the shaft for a given scheme of loading is also given.