Frictional catastrophe behaviors and mechanisms of brake shoe for mine hoisters during repetitious emergency brakings

Purpose - In order to improve the braking safety of mine hoisters, this paper aims to focus on the continuous repetitious emergency braking conditions to investigate an abnormal frictional phenomena called Frictional catastrophe (FC) and its mechanisms. Design/methodology/approach - The non-asbestos brake shoe of a mine hoister was selected as frictional material and its paring material is 16Mn steel. The tribological properties of the brake shoe were tested on the pad-on-disc friction tester by the simulation of continuous emergency braking conditions. The thermal analysis experiments, the temperature field simulations and the SEM analysis of the brake shoe were accomplished to reveal the mechanisms of the FC. Findings - It was found that the friction coefficient of the brake shoe sometimes falls suddenly during braking. This abnormal frictional phenomena is called Frictional catastrophe (FC). It is considered that the friction heat, which is accumulated rapidly by the braking on the surface of the brake shoe, makes the surface layer material qualitatively change from the solid state to a mixed state composed of gases, liquids and solid. The frictional modality of the braking changes accordingly from dry friction to lubrication with gases and liquids. The sudden lubrication makes the friction coefficient fall suddenly and induces the FC phenomena. Originality/value - An abnormal tribological phenomena called Frictional catastrophe (FC) was found in this paper. The investigations about the behaviors and mechanisms of the FC are considered helpful for improving the braking safety of mine holsters and other machines.