A new approach is presented to measure the static friction coefficient of a miniature bushing

What is it about?

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.

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Why is it important?

The principle of measurement, test rig, and test method are original and may contribute to the understanding of the friction phenomenon. The friction coefficient is the measure of the friction of a tribological system and not the measure of the friction of a pair of materials. The sliding of a cylindrical surface within a cylindrical surface is more representative of a tribological system formed by a shaft and a bushing.