Fatigue Restart in Optistruct

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Fatigue analysis restart can be performed in Optistruct utilizing Linear Static, Global-Local (Submodelling) model and Frequency Response Analysis results from a different run. The restart feature can be broken down into the following steps:

1. Input the .h3d results with ASSIGN,H3DRES,ID,(results_filename).h3d
2. Create a dummy subcase (linear static, frequency response) and import the corresponding results of the specific subcase with IMPORT (SUB= SUBID) = ASSIGN_ID

Fatigue Restart from Linear Static results

An .h3d file containing results from a linear static analysis can be imported into a dummy linear static subcase. A subsequent fatigue analysis subcase can be defined based on the linear static analysis results.

Below the basic steps for Fatigue Restart from Linear Static results are highlighted in an example.

Figure 1 Hyperworks setup

Figure 2 Optistruct’s deck setup

(Example attached: linear_static_results.fem, linear_static_fatigue.fem)

  

Fatigue Restart from Random Response results

An .h3d file containing results from a frequency response analysis (modal/direct) can be imported into a dummy frequency response subcase. The frequency response results are used to obtain the random response in a subsequent random subcase which is then used in the Fatigue analysis loadcase.

 

Below the basic steps for Fatigue Restart from Random Response results are highlighted in an example.

Figure 3 Hyperworks Setup

  

Figure 4 Optistruct’s deck setup

 

(Example attached: FRF_results.fem, Random_Fatigue.fem)

 

Fatigue Restart from Global model results

An .h3d file containing results from the global model can be imported into a dummy local static subcase which contains the corresponding global-local interface setup via SPC/SPCD with the M option for mapping. The SPC/SPCD’s will be applied to a grid set containing the interface/transfer zone nodes (local side). The mapped enforced displacements on this grid set are calculated and applied internally by OptiStruct through point cloud interpolation. A subsequent fatigue analysis subcase can be defined based on the results coming from the local model.

Below the basic steps for Fatigue Restart from Global model results are highlighted in an example.

 

Figure 5 Hyperworks setup

Figure 6 Optistruct’s deck setup

(Example attached: submodel_static_results.fem, submodel_static_fatigue.fem)

 

If STRESS/STRAIN/FORCE output, energy output (ESE/EKE/EDE), and/or rotational output of DISPLACEMENT/VELOCITY/ACCELERATION is required in the subsequent analysis, then rotation output is required during the initial analysis that generates the .h3d file too. See above example, we request rotational displacement via DISPLACEMENT(H3D,ROTA)=ALL output.