I had an interesting problem to solve last week. It was concerning fatigue failure. A simple element after sucessive stress solicitations breaks apart (nothing new). It starts with a small scratch/crack and after a few million cycles and voilá the part breaks.

I initially made the traditional fatigue analysis but discovered that it is possible to go one step ahead! Using crack analysis directly in my model. Well I know this is around since at least 2014 so says Ansys.

My traditional approach involved a two way analysis where I calculated my maximum stresses for a dynamic input load measured through lab tests. After this I used standard fatigue analysis techniques to calculate the fatigue strenght. To do this I also required a wohler curve.

An alternative way is to include the crack into the finite element model and calculate what happens after a few cycles. Some software packages allow this type of calculation making our lives simpler.

I will go more indeph on fracture mechanics and fatigue in the future but for now I just want to give some good references to get started fast in this subject.

A good example of what to do, to give you a guide for your first steps on fracture mechanics can be seen in the following link.

https://caeai.com/resources/fracture-mechanics-workbench-v145-e-learning-presentation

A good example of a fatigue fracture can be seen in the Wikipedia

https://commons.wikimedia.org/wiki/File:Pedalarm_Bruch.jpg

https://en.wikipedia.org/wiki/Fatigue_(material)

https://en.wikipedia.org/wiki/Fatigue_(material)#The_S-N_curve

https://commons.wikimedia.org/wiki/File:Strain-N.png