About FKM Assessments

You can define FKM assessments for performing either static or fatigue strength assessments of weld strength. You can specify parameters from the FKM Guideline in the FKM assessment; some parameters apply only to static or fatigue assessments, and some parameters are included in both types of assessment.

Prerequisites

Before you define an FKM assessment for your durability simulation, you should perform the following prerequisite steps:

Set up one or more structural analysis cases to compute the stresses needed for fatigue assessments.
Ensure that the welds have been modeled and that the materials assigned to the welds have the required FKM material properties.
Ensure that the interfaces between the welds and plates have compatible meshes with nodal condensation (nodes shared between the weld and plate).
If you plan to use surface stress extrapolation to compute the local structural stresses, use a relatively fine mesh on the plates near the weld toes. The elements should be approximately one quarter of the plate thickness.
If you plan to use through-thickness stress linearization to compute the local structural stresses, use a relatively fine mesh around the weld toe on the plates and on the weld fillet itself. The elements at these locations should be less than one tenth the size of those on the plate thickness.
For both stress linearization methods, you should confirm the accuracy of the mesh using mesh convergence studies.
Create an FKM durability analysis case. Static or fatigue assessments and weld fillets and lines are specific to an FKM durability case. You cannot share them between cases.

Propagation of Parameters in FKM Assessments

Static and fatigue FKM assessments are similar to steps in structural analysis cases. The parameters propagate from assessment to assessment until you modify their values, and you can duplicate or delete FKM assessments using the same commands available for duplicating or deleting steps.

You can enable the propagation of parameter values from assessment to assessment by selecting a parameter's Use Default option. This option is not available for the first FKM assessment in which the parameter is valid because there is no preceding FKM assessment from which to derive the value. The parameter value will be derived from the preceding FKM assessment iteratively until either:

The first FKM assessment (for which the parameter is valid) in the FKM analysis case is reached, or
The value for the FKM assessment is specified directly, from table or by calculation.

Where a derived parameter depends on one or more independent parameters—for example, when the first parameter is read from a table cell, and the second parameter value specifies the relevant table column—the independent parameter values are taken from the same FKM assessment as the dependent parameter.

Information on the parameter value and how it was obtained is presented alongside the parameter option.