The influence of the friction coefficient on the clamping force of a bolted joint

Clamping force is the most important factor influencing the reliability and durability of a bolt connection. Therefore, it is important to form the correct clamping force when tightening the bolt joint. In connection with the above, the article reviews the literature in the aspect of factors influencing the tribological properties of fasteners. The research part focuses on, not discussed by the other authors, determining the influence of the material of counterpart on the value of the clamping force of the bolted joint, formed in the joint during tightening. Due to the requirements of the automotive industry, where manufacturers expect universal fasteners that can be used with both steel and aluminum counterparts, both of these counterparts' materials were selected for research. The influence of top coats on the value of the clamping force of the bolt joint during tightening was also studied. Using a top coat on fasteners reduces the coefficient of friction during tightening by more than 30%. If a top coat is not applied to electrolytically galvanized fasteners, the friction coefficient increases three times compared to the friction coefficient obtained with top-coated bolts. In this case, the clamping force of the bolted joint is reduced by more than 60% when tightening the bolts.