Effect of Bushing Miniaturization on the Static Friction Coefficient

As machines become smaller, friction plays an increasingly important role in their performance. Although friction is a well-studied phenomenon, few studies have been performed on bushings and shafts with loads of a few tens of mN and dimensions of a few mm. In this work, the static friction coefficient is investigated for a miniature steel shaft rotating in bronze SAE 40 bushings. A new approach is presented to measure the static friction coefficient of a miniature bushing. The coefficient was evaluated without lubrication. It shows a linear dependence at loads higher than 152 mN and a nonlinear dependence at loads smaller than 152 mN.