Date of Award
Master of Science
In recent decades, non-asbestos organic (NAO) brake pads have been used in automotive industry due to concerns of health hazards of asbestos. Typically, friction materials are chosen as brake pad materials, they must have good thermal stability, high friction performance, and high wear resistance. Heat generation during a braking process decreases friction performance. Modifiers like metal wool, ceramics wool are added to improve thermal stability and wear resistance. In addition, humidity plays a significant role in increasing or decreasing the coefficient of friction by a generation of menisci, which may lead to an increased contact area and adhesion or serve as a lubricant. Noise is another concerned issue in the automotive industry. It is a vibration phenomenon while vehicles are braking. Vibration typically produces a loud noise and often causes complaints from customers. It is generally believed that nanoadditives can alter friction performance of brake pads and provide favorable tribological properties. This paper, friction tests were performed with Universal Mechanical Tester (UMT), discusses kinetic coefficient of friction and friction performance at different humidity levels and concentrate on nanoadditives and how affect brake pads. Moreover, surface topography measured by 3D optical microscope and SEM/EDX analysis after friction tests are discussed as well. Real contact areas between two approaching particles are much smaller than the apparent areas. Thus, a research of surface topography by measuring surface roughness helps understand the mechanism of friction. SEM/EDX is a good technique to investigate the surface structure and the chemistry on the surfaces. By studying chemical components on the surface, the effects of additives on friction performance can be further understood.
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