linear_static_simple_plate.pdf

Problem One: Linear Static Analysis

1. Problem One: Linear Static Analysis

1.1 Introduction

This example problem illustrates the use of NE/Nastran for a simple static analysis. You will

learn how to build the model using FEMAP, perform the analysis with NE/Nastran, and examine

the results with both the NE/Nastran Editor and FEMAP.

The model consists of a simple aluminum plate 10 inches long by 2 inches wide by 0.1 inch

thick. One end of the plate is firmly supported and the other end is loaded with a 60 pound

upward force. The goals of the analysis are to estimate the stresses in the plate and the

deflection when loaded.

The units used in this analysis are inches, pounds force, pounds force per square inch, and

pounds mass per cubic inch. The effects of gravity are not considered in this model.

1.2 Pre-Process the Model

You will first prepare the model geometry and then define the materials, define the properties of

the elements, mesh the geometry, and then apply the constraints and loads. These steps are

called pre-processing and will be done with the program FEMAP.

Because the plate has uniform thickness, the model is created as a two-dimensional surface.

The thickness is added later as a property of the elements into which the surface is divided.

1.2.1 Create the Geometry

In this step you will enter the coordinates of the two dimensional surface that characterizes the

shape of the aluminum plate.

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Problem One: Linear Static Analysis

Open FEMAP. From the FEMAP Main Menu select Geometry . Next, choose Surface and

then Corners… from the menus.

In the Locate – Enter First Corner of Surface dialog box verify that the X , Y , and Z fields

contain zeros. Choose OK .

Another dialog box will appear requesting the second corner of the surface. Enter the following

coordinates for the second corner:

Locate – Enter Second Corner of Surface :

enter:

X = 10 Y = 0 Z = 0

Then, click

OK .

For the third and fourth corners:

Locate – Enter Third Corner of Surface :

enter:

X = 10 Y = 2 Z = 0

Then, click

OK .

Locate – Enter Fourth Corner of Surface :

enter:

X = 0 Y = 2 Z = 0

Then, click

OK .

The surface you have drawn will appear off to the right side of your workspace. Since you will

not draw any other surfaces, click Cancel in the Locate – Enter First Corner of Surface dialog

box.

To center the image of the surface in your workspace, select View on the FEMAP Main Menu,

then from the menus, choose Autoscale and then Visible . You should have a surface in the

workspace that looks like this:

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The rectangles that appear in the surface are not the elements. The elements will be defined in

a later section.

1.2.2 Define the Material Properties

Here, you will define the physical properties of the material that composes the model.

From the FEMAP Main Menu select Model then choose Material… .

In the Define Isotropic Material dialog box enter the following values into their respective

fields:

ID 100

Title Aluminum

Youngs Modulus, E 1e7

Poisson’s Ratio nu 0.3

Mass Density 0.1

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Problem One: Linear Static Analysis

Select OK . The Define Isotropic Material dialog box will appear again expecting you to enter

another material. Since there is only one material in this model, choose Cancel to exit the next

material definition.

1.2.3 Define the Properties of the Elements

In this step, you will define the properties of the shell elements that will be used in the next step

to mesh the model.

From the FEMAP Main Menu select Model then choose Property… .

In the Define Property – PLATE Element Type dialog box click the Elem/Property Type…

button.

The Element / Property Type dialog box appears. Select Plate and verify that all other

settings are the same as illustrated.

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This last step will instruct NE/Nastran to use CQUAD4 quadrilateral plate or “shell” elements

with four nodes (grid points), one in each corner.

Select OK . In the Define Property – PLATE Element Type dialog box, fill the following values

into their respective fields:

ID 10

Title AluminumPlate

Thickness, Tavg or T1 0.1

Click the down arrow in the Material box and select 100..Aluminum .

Select OK . The Define Property – PLATE Element Type dialog box will re-appear. Click

Cancel because there are no further element types to define.

1.2.4 Mesh the Model

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