ex 4 beam plate meshing

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Exercise 4 – Beam/Plate Meshing

© UGS Corp. 2006. All rights reserved.Femap with NX Nastran 2-2

Exercise 4 -

Beam/Plate Meshing

In this example we will read in simplified wireframe geometry of the

following assembly

The top plate will be modeled with plate elements, and the underlying

support beams will be modeled with beam elements.


1. Import the geometry from a DXF file

a) Select the File, Import, Geometry command

b) Import GEOMMESH.DXF, located in the Training Files subdirectory of

the Femap Training folder on your desktop.

c) This geometry will be meshed with elements, whose properties and

materials we will now define.

Exercise 4 -

Beam/Plate Meshing


Exercise 4 -

Beam/Plate Meshing

2. Create the Material

a) Select the Model, Material command

or right-click on the Materials object

in the Model Info window and select

New.

b) In the Define Material – ISOTROPIC

dialog box, press Load.

c) Select the material, 7050-T651 Al

Plate .25 - .5 in the Select from

Library dialog box. Press OK to load

the material attributes into the

Define Material – ISOTROPIC

dialog box.

d) Press OK to create the material.

e) Press Cancel or use the esc key to

exit the command.


Exercise 4 -

Beam/Plate Meshing

3. Create the Plate Property

a) To create the plate property,

right-click the Properties

object in the Model Info

window and select New.

b) In the Define Property – enter

the Title

c) Select the material previously

created in the Material field.

d) Enter Thickness of 0.1.

e) Press OK to continue (Don’t

exit the command by pressing

Cancel the esc key).


Exercise 4 -

Beam/Plate Meshing

4. Create the Beam property

a) To change to a beam property,

press the Elem/Property Type

button, and change the

Elem/Property Type to Beam. OK

b) Instead of entering the beam

properties, press Shape button to

enter the cross-section data

directly

c) Select I-Beam or Wide Flange (W)

for the shape. Set H = 2.0, Width,

Top = 1.0, W Bot =1.0, Thick, Top

= 0.1, Thick, Bot = 0.1, Thickness

= 0.1.


Exercise 4 -

Beam/Plate Meshing

5. Continue to create Beam property

a) In addition to the cross-section

definition, be sure to change the

Orientation Direction to Up, this will

be useful in our example to align

the cross-section with respect to

the rest of the model.

b) Press OK when finished, and

Femap will return to the standard

Beam input with appropriate values

filled in.

c) Be sure to fill in a title, it will make

selecting properties later more

intuitive.


Exercise 4 -

Beam/Plate Meshing

6. Create Boundary Surfaces that will be

meshed with plates

a) Select the Geometry, Boundary Surface, From

Curves then six curves (curves 1-6) that make

up the left boundary in any order. Press OK to

create the boundary surface

b) Create another Boundary Surface using the

four curves (curves 2 and 7-9) in the right cell

7. Convert Boundary Surfaces to Parasolid

surfaces

a) Select Geometry, Surface, Convert command

b) Select all surfaces and press OK.

c) When prompted to “OK to delete original

surfaces?”, press OK.

d) Note how the two surfaces now appear in the

Model Info window as sheet solids.


Exercise 4 -

Beam/Plate Meshing

About Mesh Sizing

The default mesh spacing in a new Femap model is 1.0. By using the

tools available under the Mesh, Mesh Control command set, you can

customize the mesh spacing almost infinitely.

The figures below show meshes performed on boundary surfaces with

different mesh sizes specified for the various curves.


Exercise 4 -

Beam/Plate Meshing

8. Visualize the mesh size

a) To visualize the mesh spacing, select View

Options (F6) command,

b) Under the Labels, Entities and Color category,

select the Curve – Mesh Size option, and the

Show As option to Symbols (all curves) to turn on

the Mesh Size indicators on curves. Also, check

the Draw Entity option on.

c) Press OK to display the Mesh Size indicators.

d) If you cannot see the mesh size indicators, try

increasing the symbol size by choosing Tools and

View Style as the category, selecting Symbols

from the Options list, then selecting a larger

symbol size from the Symbol Size list.


Exercise 4 -

Beam/Plate Meshing

9. Turn off display of the surfaces

a) Using either Visibility icon on View toolbar or the Ctrl-Q hotkey

b) Press the Geometry Off button, then check the Curves option on.

c) Press Done to update the display.

10. Adjust the mesh size on the arc

a) Select Mesh, Mesh, Control Size Along Curve then select the arc, OK

b) Change the Number of Elements to 8, OK


Exercise 4 -

Beam/Plate Meshing

11. Model constraints

We will add boundary conditions to the geometry of the model before

meshing. Femap will automatically expand the boundary conditions out to

the nodes when exporting the analysis model to your solver.

a) To fix the edges of this model, select the Model, Constraint, On Curve

command, fill Title in the box as shown, and press OK to continue.

b) Select the five curves indicated.


Exercise 4 -

Beam/Plate Meshing

12.Complete constraining the model

a) Choose Fixed under Standard

Types to fix the model at all nodes

on the curves that were selected.

By associating the constraints with

the geometry, the model can be

re-meshed without having to

redefine the constraints.

Note: Advanced Types allows you to

create constrains based upon any

or all six degrees of freedom on

an existing coordinate system, or

by specifying the constraint type

based on a surface or

cylinder/hole.


Exercise 4 -

Beam/Plate Meshing

13.Apply a 100 lb/inch load to the model

a) Select Model, Load, On Curve command and start with a new load set,

entering the Title 100 lb Load.

b) Select the arc, and press OK.

c) In the Create Loads on Curves dialog box, set the load type as Force Per

Length and set the value to FZ = 100.

d) Press OK to create the load.


Exercise 4 -

Beam/Plate Meshing

14. Mesh the surfaces

a) Select the Mesh, Geometry, Surface command. Since we are going to

mesh all the surfaces in this model (the two boundary surfaces), use the

Select All button and then press OK.

b) Change the Property reference to the plate property we created, by

selecting it in the Property drop down menu. Use the default values for

Mesher and Mapped Meshing, press OK to mesh


Exercise 4 -

Beam/Plate Meshing

15.Add the support beams

a) Select Mesh, Geometry, Curve then four curves as indicated

b) Select the property of the I-Beam. Press OK to continue.

c) Femap will now ask for a vector to orient the Y-Axis of the beam

elements, align the beam Y-Axis with the Global Z-Axis (base: 0,0,0

tip: 0,0,1).


Exercise 4 -

Beam/Plate Meshing

16.Modify the beam offsets (offset the Neutral Axis and Shear Center).

a) Select the Modify, Update Elements, Line Element Offsets command.

b) Select Method as Type, and scroll to Type 5. L Beam. Select All, then press

OK to continue.

c) Now check the options for Update End A and Set End B=End A and OK

d) This will open the Vector Locate dialog box.

Note: You can also

graphically select one

of the beams to

specify the type.

© UGS Corp. 2006. All rights reserved.Femap with NX Nastran

17.Continue to modify the beam offsets

a) Press on Methods, and change the vector location method to Global Axis.

b) Set the Direction to Negative Z Axis and the Length to 1.05.

c) Press OK to modify the Beam offsets.

17.Clean up the display by removing unnecessary entities

a) Press Ctrl+Q to bring up Visibility dialog box

b) Select Geometry Off, and then toggle off the Nodes. Press Done.

18.Rotate the model

a) Select View, Rotate, Model command from the menu (Ctrl+R) or F8,

choose a Dimetric View.

2-18

Exercise 4 -

Beam/Plate Meshing


Exercise 4 -

Beam/Plate Meshing

Change the visualization of the elements to

display the beam shape(s)

a) Select the View Options (F6) command.

b) Set Category to Labels, Entities and Color.

c) Set Options to Element –

Orientation/Shape, and Element Shape to

3..Show Cross Section, Press OK

d) Or go to View Style icon and select

Thickness/Cross Section


Exercise 4 -

Beam/Plate Meshing

Run final checks on the model

When you mesh different portions of a model at different times, there are

invariable, coincident nodes, sections of your model that overlap.

a) Select Tools, Check, Coincident Nodes. Select All of the nodes

b) Toggle on Merge Coincident Entities and List Coincident Entities

c) Press OK to merge the nodes


Exercise 4 -

Beam/Plate Meshing

20.The model is ready to analyze, using NEiNastran solver follow the

below steps

a) Select the Model, Analysis command or right-click on the Analyses

object in the Model Info window and select Manage to open the

Analysis Set Manager dialog box.

b) Press on New to create a new analysis set.

c) Give it a title, set the Solver to NEiNastran, the Analysis Type to

1..Linear Statics, and press OK to accept the default analysis options.

d) Press on Analyze to start the analysis, save the Nastran input (.NAS)

and press F5 in NEiNastran Editor

e) Press Continue for any Information and Warning Messages and close

Editor


Exercise 4 -

Beam/Plate Meshing

21.Display the deformed model, displacement and stress results using

View, Select

22.Using the View, Select, turn off stresses and deformation and display

the Free Body display using the Freebody Display option in the Select

Postprocessing Data dialog box

ex 4 beam plate meshing

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