Influence Of Initial Roughness Research Articles

Effect of initial roughness and oxidation on the running-in wear of machined surfaces under dry sliding

It is usually considered that initial roughness of a surface affects running-in wear. Oxidation of the surface is bound to occur during machining operation. The present investigation aims at understanding the influence of initial roughness and surface oxidation on the wear rate. Studies were conducted with a ball-on-flat geometry in a reciprocating tester at room temperature and at 100°C. Flat surfaces with initial roughness values of 0.42, 0.96 and 1.81 µm were used for dry tests of 120 minutes duration. It was observed that running-in wear rates were low and were inversely related to roughness. This phenomenon was explained on the basis of contact temperature rise and oxide thickness. After running-in, all the balls showed wear rates within a range of about 10% from 20 to 60 minutes. The roughness of the flats stabilised in the range of 0.04 µm to 0.06 µm at the end of the test.

The influence of initial roughness and circular axial run-out on friction and wear behavior of Si3N4–Al2O3 sliding in water

Recently, it has been shown that water-lubricated sliding of Si3N4 against Al2O3 can result in steady-state friction coefficient values as low as 0.004. However, most experiments were performed using extremely polished surfaces and did not consider the effect of circular axial run-out of the discs, which could be important in practical applications. In this paper it was investigated the influence of these parameters on the ultra-low friction coefficient (ULFC) phenomenon, including correlations with running-in. Greater initial surface roughness and circular axial run-out resulted in greater running-in duration and wear. In addition, the transition of wear mode from mechanical to tribochemical dominated as a function of sliding distance was clarified and it was proposed that a mixed lubrication regime is required for ULFC to occur.

Dynamic evolution of interface roughness during friction and wear processes

Dynamic evolution of surface roughness and influence of initial roughness (S(a) = 0.282-6.73 µm) during friction and wear processes has been analyzed experimentally. The mirror polished and rough surfaces (28 samples in total) have been prepared by surface polishing on Ti-6Al-4V and AISI 1045 samples. Friction and wear have been tested in classical sphere/plane configuration using linear reciprocating tribometer with very small displacement from 130 to 200 µm. After an initial period of rapid degradation, dynamic evolution of surface roughness converges to certain level specific to a given tribosystem. However, roughness at such dynamic interface is still increasing and analysis of initial roughness influence revealed that to certain extent, a rheology effect of interface can be observed and dynamic evolution of roughness will depend on initial condition and history of interface roughness evolution. Multiscale analysis shows that morphology created in wear process is composed from nano, micro, and macro scale roughness. Therefore, mechanical parts working under very severe contact conditions, like rotor/blade contact, screws, clutch, etc. with poor initial surface finishing are susceptible to have much shorter lifetime than a quality finished parts.

An Analysis on the Influence of Surface Characteristics and Operating Parameters on the Wear of Hardened AISI 52100

The objective of the research was to analyze the influence of initial roughness on the wear rate of component samples made of bearing steels. AISI 52100 samples were prepared with three different roughness values by varying the depth of cut and feed rate in milling process. Dry reciprocating wear tests were performed under the same laboratory conditions and at different loads and sliding speeds. A fractional factorial approach with one-third of 33 experimental design without replication was followed here. The overall wear rate was found out by mass loss method. The results were analyzed using contour plots between the factors influencing the wear rate as well as mean coefficient of friction. The results indicated that the wear rate and coefficient of friction was influenced by load, roughness and their interaction.