Local elastic stress method
In: Local methods
This type of analysis initiated in nominal stress analysis. When the FEM started to be more widely used, the engineers got a better insight into precise description of local load states. A solution of nominal S-N curves looking for nominal cross-section, so that the nominal stress could be enumerated, became to be too cumbersome. There are other ways, how to describe the effect of shape and load changes. The most often method nowadays is to analyze the stress gradient around the node examined.
The local elastic stress analysis can be used in mid-cycle as well as high-cycle region, but its use below 50.000 cycles should be very cautious. It requires an elastic FE-calculation only.
There is a class of methods, which relate the actual local loading towards the fatigue limit only. There are many applications, as well as many research papers, who care about this one specific point. The methods manipulate only elastic stresses, thus they are incorporated here. The prime area for their use is multiaxial fatigue. The following methods are implemented in PragTic:
- Carpinteri & Spagnoli method v. SWT
- Carpinteri & Spagnoli method v. MD & SWT
- Fogue method (marked as Kenmeugne integral method in older versions of PragTic)
- Gonçalves, Araújo & Mamiya (GAM) method
- Robert method (marked as Kenmeugne critical plane method in older versions of PragTic)
Be aware, that even here the incorporation of a stress gradient or of other method for inclusion of the load state around the point examined is necessary. All the methods given above are implemented for a use on smooth unnotched specimens. The stress gradient effect is not evaluated.
There is another method, which already takes care of stress gradient effect, but it is purely uniaxial now. This is the LESA method.
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