Modeling initial imperfections (Simcenter Samcef)

Typically, when you create an FE model, the model geometry has:

• Perfect form where planar surfaces are flat, cylinders are free of runout, and so on.

• Dimensions at their nominal values, or at the maximum or least material condition.

For many engineering applications of FEM, you can use such ideal geometry because the slight dimensional differences between the actual structure and the model of the structure have little consequence on the analysis results.

However, when you perform a buckling analysis, the analysis results can be sensitive to these slight differences.

To estimate the influence of the initial geometric imperfections, you solve a standalone buckling analysis, followed by a nonlinear or a linear static analysis, depending on whether you want to include nonlinearities (plasticity, contact conditions, and so on).

In general, the critical imperfection is the one that, for a given magnitude, produces the smallest buckling load.

This critical imperfection is evaluated in the following way:

• The first bifurcation analysis is carried out with a perfect structure in a Standalone Buckling Analysis.

• The model is then changed by adding a buckling mode weighted by a scale factor to the nodes' coordinates, and a second bifurcation analysis is done.You do this by chaining a Nonlinear Analysis or a Linear Static Analysis to a Standalone Buckling Analysis.In the Chaining page of this new analysis:In the Mode Shape Number property, you select the buckling mode to use.In the Mode Shape Amplitude property, you set the weight factor to apply to that mode.Note: The buckling mode that you select is usually the one that matches the lowest buckling load. This mode is sometimes called the modal default.You may need to repeat this procedure for weight factors on that modal default.

For more information, see Post-buckling analysis (Simcenter Samcef).

Where do I find it?

Application	Simcenter 3D
Prerequisite	A Simulation file or a FEM file as the work part and displayed partSimcenter Samcef as the specified solver
Simulation Navigator	In an active Linear Static Analysis or Nonlinear Analysissolution, right-click the solution → Edit
Location in dialog box	Chaining page → Activate Chaining check box

Look up more details

Solution dialog box (Simcenter Samcef Linear Static Analysis)

Solution dialog box (Simcenter Samcef Nonlinear Analysis)

Modeling initial imperfections (Simcenter Samcef), Simcenter 3D 2021.1 Series

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