Model Preparation using NX Nastran

Many time before analysis on a model, it is necessary to simplify that. After the simplification, the model become easy to meshing. For preparing model, we can use two type of process; geometry idealization and geometry abstraction.

The geometry idealization is the process to remove or suppress features from the model for proper defining a mesh. You can use the geometry idealization process to remove features such as bosses, fillet,  champhers, that are not significant in analysis.

The geometry abstraction operations can be perform on the geometry within the FEM environment. Using geometry abstraction operation you can remove small fillets as well as the small holes from the model.

Below the figure shows the master part with all its features and the next figure below it shows the prepared part for analysis after removing the small features that are not important for analysis.

Master Part in NX Nastran

The Idealized Part

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Creating Midsurface in NX Nastran

You can simplify your geometry for analysis by creating a midsurface. The midsurface tool generate an middle surface between pairs of surfaces selected. After generating the midsurface, you can use it to perform analysis directly and apply uniform shell meshing.

Below the figure shows the master part shown with default thickness, and the next figure shows the part after creating the midsurface.

Master Part

Master Part After Creating Midsurface

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Preparing model for Swept Meshing in NX Nastran

In Swept Meshing, the software create 2D (surface) element on one face of the model and then copy that mesh upto the target face. It then generates 3D (solid) elements connecting the two faces.

In case of complex and large model, it become difficult to create swept meshing. In NX Nastran you can use Split Body tool to split the model for preparing swept meshing. In splitting operation you divide the model using the geometry or planes.

For confirming the proper splitting, you can use Check for Sweepable Body check box of this dialog box, to verify whether the part is ready for swept meshing or not. If the model is in  Red color, that indicates you cannot currently generate a swept mesh on the part. For generating a swept mesh, you must split the part further. Yellow color indicates the ambiguity condition. It indicates, you may be able to generate a swept mesh on the part but that the software will show warning about mesh. However, you still need to divide the part further for successfully generate a swept mesh. While the Green color indicates that you are able to generate a swept mesh on the body without further splitting the body.

Below the figure shows the model before splitting and model after splitting operation.

The Model before Spliting                       The Model after Spliting

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