Proceedings of SerbiaTrib '13

fiber and glass fiber sliding against smooth mildsteel counterface is lower than that of gear fiber andglass fiber sliding against rough mild steelcounterface.Variations of wear rate with sliding velocity forgear fiber and glass fibre mating with smooth orrough mild steel counterfaces are presented in Fig.13. Curves show the variation of wear rate from1.167 to 1.778, 1.433 to 2.25, 1.258 to 1.95 and1.987 to 2.78 mg/min with the variation in slidingspeed from 1 to 3 m/s for gear fiber-mild steelsmooth, gear fiber-mild steel rough, glass fibermildsteel smooth and glass fiber-mild steel roughsliding pairs respectively. From these curves, it isobserved that wear rate increases with the increasein sliding speed for all types of materialcombinations. These findings are in agreement withthe findings of Mimaroglu et al and Suresha et al.[27,38]. This is due to the fact that duration ofrubbing is same for all sliding velocities, while thelength of rubbing is more for higher slidingvelocity. The reduction of shear strength of thematerial and increased true area of contact betweencontacting surfaces may have some role on thehigher wear rate at higher sliding velocity [51].Figure 13 also shows the comparison of thevariation of wear rate with sliding velocity fordifferent sliding pairs. From the obtained results, itcan also be seen that the highest values of the wearrate are obtained for glass fiber-mild steel roughpair and the lowest values of wear rate are obtainedfor gear fiber-mild steel smooth pair. The values ofwear rate of gear fiber-mild steel rough pair andglass fiber-mild steel smooth pair are found inbetween the highest and lowest values. It is notedthat the wear rates of gear fiber-mild steel roughpair are higher than that of glass fiber-mild steelsmooth pair.Wear rate (mg/min)3.02.52.01.51.00.5gear fiber-mild steel, smooth pairgear fiber-mild steel, rough pairglass fiber-mild steel, smooth pairglass fiber-mild steel, rough pair0.00.5 1.0 1.5 2.0 2.5Sliding velocity (m/s)Fig. 13. Wear rate as a function of Normal load for gearand glass fiber for different counterface surfaceconditions (normal load: 15 N, relative humidity: 70%).From this figure, it is also found that at identicalconditions, the values of wear rate of gear fiber andglass fiber sliding against smooth mild steelcounterface is lower than that of gear fiber andglass fiber sliding against rough mild steelcounterface. It is due to the fact that rough surfacesgenerally wear more quickly and have higherfriction coefficients than smooth surfaces.4. CONCLUSIONThe presence of normal load and sliding velocityindeed affects the friction force considerably.Within the observed range, the values of frictioncoefficient decrease with the increase in normalload while friction coefficients increase with theincrease in sliding velocity for gear fiber and glassfiber sliding against smooth or rough mild steel pin.Friction coefficient varies with the duration ofrubbing and after certain duration of rubbing,friction coefficient becomes steady for the observedrange of normal load and sliding velocity. Wearrates of gear fiber and glass mating with smooth orrough mild steel counterface increase with theincrease in normal load and sliding velocity. Thehighest values of the friction coefficient areobtained for glass fiber-mild steel rough pair andthe lowest values of friction coefficient are obtainedfor gear fiber-mild steel smooth pair. The values offriction coefficient of gear fiber-mild steel roughpair and glass fiber-mild steel smooth pair arefound in between the highest and lowest values.The friction coefficients of gear fiber-mild steelrough pair are higher than that of glass fiber-mildsteel smooth pair. At identical conditions, thevalues of friction coefficient of gear fiber and glassfiber sliding against smooth mild steel counterfaceis lower than that of gear fiber and glass fibersliding against rough mild steel counterface.As (i) the friction coefficient decreases with theincrease in normal load (ii) the values of frictioncoefficient increase with the increase in slidingvelocity (iii) wear rate increases with the increasein normal load and sliding velocity and (iv) themagnitudes of friction coefficient and wear rate aredifferent for smooth and rough counterface pins andtype of materials, therefore maintaining anappropriate level of normal load, sliding velocity aswell as appropriate choice of counterface surfacecondition and tested materials, friction and wearmay be kept to some lower value to improvemechanical processes.REFERENCES[1] Archard, J.F.: “Wear theory and mechanisms”,Wear Control Handbook, ASME, New York, NY,1980.72 13 th International Conference on Tribology – Serbiatrib’13