Abstract
Recently, many studies have investigated the friction, wear, and temperature characteristics of the interface between two relative movements. Such analyses often set the coefficient of friction as a fixed value and are analyzed in cases of two-body contact; however, the interface is often a three-body contact and the coefficient of friction varies depending on the operating conditions. This is a significant error in the analysis of contact characteristics, therefore, in this study, the actual interface and the change of the coefficient of friction were analyzed based on three-body micro-contact theory where the contact temperature was also analyzed and the difference between the generally assumed values were compared. The results showed that under three-body contact, the coefficient of total friction increased with an increase in particle size; and at a different particle size and area density of particles, the surface contact temperature increased with the plasticity index and load increases, and the particle contact temperature increased with the increasing particle size. The surface temperature rise was mainly affected by the ratio of the average temperature between surface 1 and surface 2 to the multiplication between the 100th root of the area density of particles and the square root of the equivalent surface roughness (Ts1s2_ave*/ηa0.01σ0.5) and the ratio of the 10th root of the mean particle diameter to the 100th root of the equivalent surface roughness (xa0.1/σ0.001). Particle temperature was mainly affected by the ratio of the 10th root of the mean particle diameter to the 100th root of the equivalent surface roughness (xa0.1/σ0.001) and the area density of particles ηa. Our study indicated that when the contact of surface with surface and the contact of the particles with the surface, the resulting heat balance was assigned to the particles and the surface in a three-body contact situation. Under this contact behavior, it could avoid a too high a rise in micro-contact temperature to achieve the material failure temperature.
Highlights
When the third bodies are present between the contact interfaces of two surfaces, there are two kinds of contact points, including surface-to-surface contact spots and particle-to-surface contact spots, in the roughness of the surfaces
D where An is the nominal contact area; Hs1 is the hardness of surface 1; Hs2 is the hardness of surface 2; Es1s2 is the equivalent elastic modulus of surfaces 1 and 2; Es1a is the equivalent elastic modulus of surfaces 1 and the particle; d is the separation based on asperity heights; ηa is the area density of particles; Xmax is the maximum particle size; and he is the maximum separation of two surfaces with particles that leads to plastic contact
The friction and contact temperature characteristics of different contact loads, particle diameters, and surface roughness were investigated when the moving elements were in contact, and they were compared with the contact temperature where the coefficient of friction was set to a fixed value of 0.1
Summary
When the third bodies (particles) are present between the contact interfaces of two surfaces, there are two kinds of contact points, including surface-to-surface contact spots and particle-to-surface contact spots, in the roughness of the surfaces. The real contact area is an important factor affecting the contact temperature rise in the interface, and this has been studied extensively between two rough surfaces, including the Greenwood and Williamson proposed GW model [8], the Pullen and Williamson proposed PW model [9], the Chang et al proposed CEB model [10], the Horng proposed H model [11], the Zhao et al proposed ZMC model [12], and the Kogut and Etsion proposed KE model [13]. This work combined the contact model, friction model, and contact temperature model to analyze the contact temperature rise characteristics in three-body contact situations at various particle sizes, area density of particles, relative speeds, surface roughness values, and applied loads
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