Page 75 - Analysis and Design of Machine Elements

Strength of Machine Elements
18 Johnson, K.L. (1987). Contact Mechanics. Cambridge, UK: Cambridge University 53
Press.
Problems

Review Questions

1 Distinguish the differences between static loads and variable loads, static stresses
and variable stresses. Give an example of variable stresses generated by a static load
in an element.

2 Describe fatigue fracture process in a machine element.

3 What is the difference between endurance strength rN and endurance limit ?
r
4 List factors that will affect fatigue strength of a machine element and give the rea-
sons.

5 Describe the linear cumulative damage rule and explain when to use it.

Objective Questions

1 Which of the following is not one of factors affecting endurance strength of an ele-
ment? _____
(a) stress concentration
(b) the size of the element
(c) the magnitude of the load the element carries
(d) materials and their heat treatments
2 Forces F and F are static loads. Which of the following in Figure P2.1 represents
a
thestressatpoint A with a stress ratio of −1 < r < 1? _____

(a) (b) (c)

Figure P2.1 Illustration for Objective Question 2.

3 Select the correct statement. ______
(a) Fluctuating stresses are only generated by fluctuating loads.
(b) Static loads cannot generate fluctuating stresses.
(c) Fluctuating stresses are generated by static loads.