Investigation on the effect of pressure and radius of contact surface curvature on the friction coefficient in contact surfaces of interference fit joints

Interference fit joints are widely used in the industry to produce tight joints. These type of connections have produced more beautiful and smaller joints by eliminating other joints such as keys which are defected with stress concentration. Interference fit joints could be applied under dynamics and statics design loads, successfully. Interference fit joints are always imperfect, such as other industrial products and also affected by some parameters which directly affect the operation of these joints. For instance, contact surface of every manufactured joint parts are not a perfect cylinder and always there are some form defects. The variation of these parameters could affect the performance and strength of interference joints, so these parameters should be considered. Some effective parameters on the strength of interference fit joints are friction coefficient, roughness, materials properties, dimensions and geometric irregularities of contact surfaces. In this study the effect of diameter of shaft and interference value variation on the friction coefficient in contact surface and strength of joints are investigated. Finite element results are interacted with experimental ones to estimate friction coefficients. Also, factorial method, which is a statistical method for design of experiments, are used to analysis the effects of pressure, which is vary by variation of interference, and radius of contact surface curvature on friction coefficient and strength of joints. Results indicate that the friction coefficient changes with diameter of interference surface, inversely and increase of interference and consequently, pressure leads to growth of friction coefficient.