10.2.3.2. Generation of Input File
This section explains general processing to create MSC/NASTRAN input file with PATRAN and the method of modal analysis of MSC/NASTRAN using DMAP command. Moreover, some explanation is added such as meshing, imposing boundary condition, some required options of PATRAN and so on
10.2.3.2.1. Modal Analysis
The example model is 3D hexahedron model. This example creates mesh seed based on Hex8 contains eight nodes and meshed by CHEXA element with Number of element option. Material property set like as aluminum. It shows that when apply the DMAP command to the file generated from PATRAN
![../_images/image08914.png](../_images/image08914.png)
Figure 10.53 Target model
To create MSC/NASTRAN, run Patran and create new database
New database.
Specify the working directory and file name.
Figure 10.54 New Database
Create new geometric model
Move to Geometric entity
Geometric setting
Action: Create, Object: Solid, Method: XYZ.
Ref. Coordinate Frame: Coord0
Vector Coordinates Lists: <1 1 1>
Create
After set the above items, click Apply. You can get the new model.
Figure 10.55 Creation of model
Create Mesh seed on the model
Move to Elements
Mesh seed setting
Action: Create, Object: Mesh seed, Type: Uniform.
Number of Elements: 5.
Curve list: Select all curves by dragging window
Create
This method divides selected curves into Number of Element. It does not mean mesh. You can use another option that is Element Length to mesh seed.
Figure 10.56 Mesh Seed
Mesh based on mesh seed
Mesh options
Action: Create, Object: Mesh, Type: Solid
Mesher: IsoMesh
Element Topology: Hex8
Solid list: Solid1
Mesh
Element Topology means a kind of elements that has different node number in the element and solid list means geometric entity that performed mesh seed. After select model, click Apply.
You can get the result windows.
Figure 10.57 Mesh
Input Material properties
Move to Material
Material options
Action: Create, Object: Isotropic, Method: Manual Input,
Input material
Elastic Modulus: 70e9
Poisson’s Ratio: 0.33
Density: 2710
Figure 10.58 Material property
Input element property
Move to Property
Element property options
Action: Create, Object: 3D, Type: Solid.
Property set name: cubic.
Input Element properties
Click Alumin and OK. (Alumin is material property that created in above step.)
Select Members and Add. (Member is a set of created elements)
Figure 10.59 Element property
Perform analysis to export MSC/NASTRAN Input file
Move to analysis
Analysis options
Action: Analyze, Object: Entire Model, Method: Analysis Deck
Enter the jobname
After set the above options, select Solution Type
Solution Type: Normal Modes
Figure 10.60 Export
Edit exported file (jobname.bdf)
Refer DMAP command editing in 2.2.2 MSC/NASTRAN Interface.
Run MSC/NASTRAN
Run MSC/NASTRAN with exported file
Select Nastran Input file and open.
Run
You can get the punch file. (Jobname.pch).
Punch file contains mass and stiffness matrix, mode vector and frequency.
Figure 10.61 Analysis with MSC/NASTRAN
Note
When you generate RecurDyn/RFlex Input File (*.rfi) from Output file, you cannot include Stiffness matrix in option.