Shaft design

Question 1

What is fatigue failure?

Answer 1

Weakness of a material caused by cycle loadings

Question 2

Describe the different types of stress

Answer 2

Tensile stress: pulltype of loading, passing through the axis
Compressive stress: pushtype of loading
Shear: Load is tangential to cross-section area
Crushing: local-comressions acting on pins/joints

Question 3

What does to SN-diagram shows?

Answer 3

Logaritmic curve, shows cycles to failure due to stress amplitud

Question 4

Why is the size factor important for the estimated endurance strength?

Answer 4

Large parts are more likely to fail than smaller parts because larger parts includes more links/more impurities (it only takes the smallest link to cause failure)

Question 5

Why is the stress type important for the estimated endurance strength?

Answer 5

It varies depending on stress.

Question 6

Why is the surface factor important for estimated endurance strength?

Answer 6

A rough surface can initiate cracks, which are not very likely with a smooth surface

Question 7

In the ANSI standard, explain the reason for using modified endurance strength in the first term, and yield strength in the second

Answer 7

First term: The moment causes pulsating stress –> endurance

Second term: Torsion causes constant stress –> design against yield