Connecting rod screw tribological response optimized by a proper choice of peening treatment parameters

This work deals with an experimental study on the frictional properties of connecting rod high strength screws. It is a follow-up of a previous work: at the initial stage, a careful microscope analysis of the previously tested screws under tribological tests was carried out. These observations suggested that the peening treatment could be optimized by either increasing the shot size or decreasing the Almen intensity, thus achieving a better impact load distribution, as well as a surface roughness reduction. The results indicate that the modified peening parameters are able to lead to a significant drop of friction and to its steady trend versus repeated tightenings even in dry conditions.