Essay On Lubrication

CHAPTER 1

INTRODUCTION

1.1 Background of Study

Generally speaking, friction is happen every day and everywhere in our life. Friction helps us to make our life easier and when friction becomes a cycle in our life, wear will form over time. Examples of such scenarios are found in an internal combustion engine of vehicles, grinding operation, strip movement in metal rolling, control of chatter in a machine tool slide way, etc. The smoothness of movement is improved by reducing friction which is by using lubricant but this is not always the case and there may be instances in which it is more important to maintain steady friction than to obtain the lowest possible friction. Lubricant also acts to reduce wear, to prevent overheating and corrosion,

The lubrication parameters that can be plotted with coefficient of friction are viscosity, sliding speed, sliding distance and load. The coefficient of friction is at its lowest in the hydrodynamic and thin film zones. At this point, the oil film is thick enough to ensure that there is no contact between asperities on the pin and disc surfaces. Moving to the right of the graph, which is in hydrodynamic zone, the oil film thickness is increasing due to increasing viscosity, increasing sliding speed and decrease in load whereas the coefficient of friction increase gradually. Besides, on the left of the curve, the asperities will start to rub against each other because of the oil film thickness decreases. Thus, the friction increases due to decreases in oil film thickness. In the mixed film zone, oil film thickness has been reduced to zero and the load between pin and disc is being carried on asperity contacts. Finally, when move further left down the curve, the coefficient of friction is almost independent of load, viscosity and sliding speed. At this zone, it is being called as boundary lubrication