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Imposing a residual stress is simply a mechanism of changing the mean stress. Residual stress can be the result of a manufacturing process or an overload as in the case of this example. Prestress and offset stresses due to other effects such as gravity or centrifugal forces can be accounted for in the same manner. When these offset stresses vary over the model, generally an additional FE load case must define them. If the offset is constant, other methods of accounting for residual stress are possible in MSC Fatigue:
Accounting for Constant Residual Stress
1. Material Info... form. On this form, if you scroll the spreadsheet over you will see a column called Offset. Here you can impose a constant residual offset that will be applied to only the area of your model defined in Region (Group) with the specified combination of material, finish and treatment.
2. Loading Info... form. Aside from selecting an entire FE load case as a offset which varies from node to node, you can also set a constant offset for any specified FE load case. If you scroll the spreadsheet over on this form you will also see a column to specify an Offset.
3. FEFAT: Residual stress can be entered in the form of a loading or stress offset when performing analysis interactively using FEFAT. In the Design Optimization mode, Sensitivity analysis on residual stress is possible as well as in the Parameter optimization menu to back calculate a residual stress to meet the design life.
