Fastener-torque model to enhance reliability under cyclic load

A model and a FORTRAN program have been developed to determine the optimum torque required for various applications of threaded fasteners, considering design variables such as thread geometry, size, material, and friction coefficients. The model approach is useful in ensuring optimum torque for fasteners under cyclic load conditions. The optimum torque varies widely, and rules-of-thumb cannot consider the effects of all relevant variables adequately. Ultimately, the actual mean time to failure of a fastener under cyclic load will be a function of the proximity of the actual torque applied to the optimum required for an application, the load cycle, and the magnitude of the cyclic load