I have written a compendium for my fatigue-course at Aarhus University. It has been in draft state for the past 2.5 years and revised severely during this time. Now I think it has a quality such that it is worth sharing.
It introduces the basic concepts governing fatigue strength of metals and presents associated engineering approaches needed for practical application. Both machined components and welded (steel) structures are covered and similarities and differences are discussed.
The intention is to give insight into why things are as they are in the fatigue-business. Very often the answer is simply: “because of tradition”. Even so, the user deserves to know. Too often, rules are just stated; “this is how it is!”. In the compendium, I try to add some clarification or even justification.
An example is shown in the figure below, giving support to the FAT225 SN curve used for notch stress analysis of welded joints. It shows how most of the specimens agree nicely with the design SN curve, i.e. distributing as expected above it. There is one exception though – the joints tested in bending seems to be evaluated somewhat conservative.
It is far from perfect, but I hope someone will find it useful. Comments, suggestions and corrections are highly appreciated, please use the form below.
Mikkel M. Pedersen