Erdogan & Roberts method

In: local elastic-plastic strain methods->uniaxial methods

Because of the mean stress effect application is the same for all materials in the SWT criterion, Erdogan & Roberts tried to introduce a further parameter to be able to get better approximation:

Note that the mean stress effect projects only into the Basquin's part of the e-N curve (i.e. to the high-cycle fatigue above all). Negative mean stress is expected to be non-damaging and its value is reset to zero. The conversion to an equivalent value allows a use of the common uniaxial rain-flow decomposition. Dowling refers to the same method as to the Walker's method - see [Dow04]. This method leads to the best results in his comparison of different ways of the mean stress incorporation.

The choice of the appropriate decomposition method is the point in Calculation Methods window, where the way of the tensor's reduction is chosen.

Note: The results of the method are similar to the Bergmann method, where also another parameter was introduced to the SWT criterion.

Nomenclature:

Decomposition

- Rain-flow with von Mises reduction

- Rain-flow with Tresca reduction

- Rain-flow with von Mises (signed) reduction

Elasto-plasticity

- No

- Neuber elastic-plastic accommodation

- Glinka elastic-plastic accommodation

Material parameters

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