Experimental and computational investigations of nonlinear frictional behavior in threaded fasteners

Abstract The conventional engineering design of threaded fasteners applies a linear model determining axial force from fastening torque and was found to be applicable only for vanishing inelastic deformations. Applications of the linear formula can result in a significant over-estimate of the axial force. Detailed experiments reveal that plasticity and wear damage in contact surfaces change frictional behavior and cause an over-proportional increment in tightening torque. A modified friction model was proposed based on the frictional dissipation energy and verified experimentally and computationally. The corresponding force-torque model shows good consistency with experiments and can be applied to predict plastic fastening processes.