A computerised design aid for drive shafts with some fatigue considerations

Abstract

A method of designing power transmission drive shafts is described based on two interactive computer programs. The first program can model shafts of any configuration and under any system of loads and supports. The program is based on the finite element method. Reducing the size of the stiffness matrix by storing only the parameters in the matrix bandwidth and by overlaying the stiffness matrices, the problem of using finite element analysis on small memory microcomputers can be solved. A menu allows the designer to specify machine elements, such as spur or bevel gears or pulleys, to be positioned at any point along the shaft. The user can give information of the power transmitted, speed, and details of the physical dimensions of the machine elements which then enables the program to determine the force vectors and apply these to the shaft nodes. The second program determines the design factors of safety on the basis of both static and cyclic loads. For cyclic loads the factors of safety are based on infinite-life design, using Soderberg and Goodman criteria. The program contains extensive built-in data on endurance strengths, factors influencing the endurance limit, and stress concentration factors.