Materials and Surface Engineering - Essay Example

Therefore, the mating surfaces should be accessible so that the lubricant can be applied at regular intervals. However, in many cases, the mating surfaces may be in radioactive or toxic zone or may be inaccessible due to design considerations. In such cases on cannot depend on liquid lubricants. At high load and low speed the liquid lubricant film is not thick enough to ensure effective separation of the mating surfaces and therefore, frictional force and wear loss increases. Therefore, one cannot rely on liquid lubricants under such operating conditions.

Liquid lubricants are not good for high temperature applications as viscosity decreases with increasing temperature and vapors may also be produced at higher temperature. Therefore, liquid lubricants are not suitable for application at higher temperatures. Liquid lubricants are not clean in itself in the sense that it gets spread on the workplace and also dirt and dust gets adhered to it deteriorating the cleanliness of the workplace further. Therefore, liquid lubricants are not preferred for clean applications. Q6. A steel ball of elastic modulus E1 and Poisson’s ratio 1 (figure, below) is pressing with load P onto a flat metallic surface of aluminum plate having elastic modulus E2 and Poisson’s ratio 2 and hardness H. (d) This equation gives a much larger value for the volume of wear than what is experimentally observed or what is observed in real life.

The difference is very high and is 4 to 7 order of magnitude higher than that observed in the experiments. This is because not all but only a very small fraction of the asperity contacts result in wear of the material and therefore, in stead of the equality sign in the Archard’s wear equation, there should be a proportionality sign. When this is done a constant is introduced in the equation whose value is determined experimentally. Thus the revised equation