Question

Which of the following method(s) can improve the fatigue resistance of a material if the loading stress is kept the same? OOO Select one or more: a. Making surface harder b. Making surface smoother c. Making surface larger d. Making surface flatter

Answer 1

We can improve the fatigue resistance of the material under constant stress by two methods of the given options.

1. Making surface harder

2. Making surface smoother

3. Making surface larger

The reasons are as follows.

In general engineering situations, the maximum stress occurs on the surfaces of the parts. Because surfaces have certain points called stress concentration or stress raiser sites. So a smoother surface has higher resistance to fatigue. During machining operations small scratches form the surface of the parts. These markings reduces fatigue life.

Case hardening operation increase hardness of the material. Hardeness can go in upto 1 mm. So outer surface is harder than core. This has significant effect on fatigue life. Hardnening helps to increase fatigue resistance.

Increasing the dimension of a part actually has a good effect og fatigue resistance. It improves the fatigue resistance.

So the first three options holds for the given question.