User Tools

Site Tools


feamesh

This is an old revision of the document!


Structural Modeling

OpenVSP allows a user to model aerospace structures for a geometry and generate a finite element mesh model. This model can then be exported to an FEA post-processing tool for further analysis. To begin, a geometry must first be created or loaded. The FEA Mesh GUI is accessed by clicking “FEA Mesh…” in the Analysis pull down menu.

VSP Terminology

Structure

A structure is defined as a collection of FEA Parts associated with a single geometry. A geometry is able to have multiple structures

FEA Part

An FEA part is any structural entity that is used to define a structure. This includes full-depth, zero-depth, and key-point types of entities.

FEA Element

A group of interconnected FEA nodes create an FEA element. All elements are assigned a single element property.

FEA Node

An FEA node is a 3D coordinate point used to build FEA elements. FEA nodes may be assigned to multiple elements. Key-points are FEA nodes that have been defined at a specific location.

Shell

Shells are full-depth FEA parts comprised of triangular FEA elements. In NASTRAN these elements are CTRIA6. In Abaqus and Calculix they are S6 elements.

Cap

A cap is a zero-depth FEA part made up of beam FEA elements. The beam elements are represented in NASTRAN as CBAR. In Abaqus and Calculix they are B32 elements.

FEA Mesh Screen

Visible on all tabs of the FEA Mesh GUI are the status window, currently selected structure output, and “Mesh and Export” button. The status window is mainly used to display the status of FEA mesh generation, which is run as a separate process. However, error messages and warning will also be displayed. The current structure output list which structure is selected in the structure browser on the Structure tab. This is the structure that willl be used to create the FEA mesh when “Mesh and Export” is selected.

Structure Tab

The main function of the Structures tab is the addition and removal of structures for the vehicle. At the top of the tab under “General”, there is a link to this wiki. Below, the unit system for the vehicle can be specified. All of the FEA export file formats are unitless, so the following options are available to ensure consist units:

  • Insert Unit System Chart

The structure browser lists all of the structures for the vehicle, along with their name, parent geometry, and surface index. Below the browser, all available geometries for which a structure may be added to are listed. The available surface indexes for each geometry are also listed. All geometry types, with the exception of Blank and Hinge, are available to add a structure to. In addition, more than one structure may be added to a geometry. The “Add Structure” button will create a new structure on the geometry and surface indicated in the above choices. “Delete Structure” will, as expected, delete the structure that is currently selected in the browser. The name of the currently selected structure may be edited below the add and delete buttons. When a structure is selected, the degenerate geometry preview can be displayed under “Orientation”. This feature is particularly useful for wing structural layups, where a top-down 2D view will be shown. The display options can also be changed in the Geom Browser under “Surface”.

Part Tab
Material Tab

The Material tab contains a library of linear, temperature-independent, isotropic materials. In NASTRAN, these are defined by the MAT1 keyword. Materials in the library are available to all structures and are saved with the vehicle, i.e. there is no need to recreate materials for different structures. The browser at the top of the Materials tab lists all materials in the library. The default materials available are Aluminum 7075-T6, Aluminum 2024-T3, Titanium Ti-6AI-4V, and AISI 4130 Steel. To add a material, simply select “Add Material” and adjust the parameters for mass density, elastic modulus, Poisson's ratio, and thermal expansion coefficient to the desired values.

Property Tab

Similar to the Material tab, the Properties tab contains a library of FEA element properties available to all structures.

Mesh Tab

The Mesh tab is available for controlling aspects of the solver used during the generation of an FEA mesh. The options available here are similar to those seen on the Global tab to the CFD Mesh GUI. Further insight into these settings can be found here: CFD Mesh Wiki.

Display Tab

FEA Part Types

Slice
Rib
Spar
Dome
Fixed Point
Sub-Surface
Array

API and Scripting

Best Practices

References and Further Reading

feamesh.1504828787.txt.gz · Last modified: 2017/09/07 16:59 by jgravett