Name :Hemamalini Rawindran
Group: ACB (A2)
In materials science, the terminology wear simply means, the disintegration of material from a solid surface by the movement of another solid. Wear may result whenever there is sliding. A potential wear situation occurs when there is relative motion between two solids under load. Motion can be unidirectional or reciprocating either sliding or rolling. There may be a combination of rolling and sliding of wear which may occur due to oscillary movement at small amplitudes. The investigation of the techniques of wear is some piece of the control of tribology.
Depending on the nature of the movement or of the media involved in an interaction under load, the following types of wear have been classified;
1. Adhesive wear
2. Abrasive wear
3. Corrosive wear
4. Surface fatigue
There are few types of wear mechanisms that can be found in automobile components. The components that are involved includes the accumulator, rolling bearings, piston rings, brake pads, gears and etc whereby different type of wears can be identified from each components.
2.0 Wear materials in automobiles
2.0.1 Ball and roller bearings
The ball and roller bearings is made up of several components such as two rings, rolling bodies, a cage (steel or bronze) to separate and guide the rolling balls, lubrication(oil or grease), protection (steel baffle) that is always lubricated. There are three types of roller bearings such as cylindrical, taper and spherical bearings.
Rolling, compared to sliding requires less effort and rolling bearings give the some order of low friction as encountered under fluid film lubrication in journal bearings. In a typical assembly, the shaft is fixed to the inner race which rotates while an outer race is located in a housing. In the space between these races, the rolling elements are dispersed which may be in the form of balls or cylinders. The rolling elements are separated from one another by means of a cage, which is also referred as a separator (Figure 1).
Figure 1: Principle of a roller bearing (schematic)
The primary factor in determining the lives of ball and roller bearings is the fatigue of the surfaces of the raceways due to the repeated high stresses at the points of contact. In determining the B10 life, a group of apparently identical bearings are run under the same conditions. B10 is the measurement of life span of a machine before they malfunction. The number of running hours at which 90% of the group can be expected to reach or exceed before the signs of fatigue appear is taken to be the bearing life.
2.0.2 Causes of wear in ball and roller bearings
Common cause of wear is due to lack or loss of lubrication. Two surfaces, upon being in contact and slide against each other without lubrication, the particles tend to tear off, and the surfaces do not adhere. These particles will then rejoin to either surface, and creates a smear. There is a type of smear called skidding that occurs when...