Frictional behavior of selective laser melted brake discs under high-speed braking

Abstract

Selective laser melting (SLM) is a promising technique for achieving function-driven design as well as unique performances of parts. This article focuses on the frictional behavior of the SLMed brake disc under high-speed conditions, aiming to reveal the inherent wear mechanisms. A bench test of the SLMed disc was conducted using a full-scale flywheel brake dynamometer. The initial braking speed ranged from 50 km/h to 380 km/h, and the clamping force was from 18 kN to 37 kN. The relationship between instantaneous friction coefficient and multiple variables was explored, including clamping force, initial braking speed, and temperature. With rising temperature, the wear mechanism shifted from abrasive wear to adhesive wear. Compared to a cast disc, SLMed disc is better for high-speed conditions, as it exhibits a more stable friction coefficient, shorter braking distance, and higher braking energy efficiency. The average friction coefficient distribution of the SLMed disc is relatively more concentrated, ranging from 0.333 to 0.417, while it is from 0.277 to 0.426 for cast disc. The braking distance of the SLMed disc is 20% shorter when clamping force is 37 kN. Moreover, the braking amplification factor is proposed to enhance the accuracy of brake performance evaluation. Additionally, a preliminary utilization principle is established for SLMed discs.