1. Two Dimensional Truss.pdf

(892 KB) Pobierz
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
University of Alberta ANSYS Tutorials - www.mece.ualberta.ca/tutorials/ansys/BT/Truss/Truss.html
Two Dimensional Truss
Introduction
This tutorial was created using ANSYS 7.0 to solve a simple 2D Truss problem. This is the first of four
introductory ANSYS tutorials.
Problem Description
Determine the nodal deflections, reaction forces, and stress for the truss system shown below (E = 200GPa, A =
3250mm 2 ).
(Modified from Chandrupatla & Belegunda, Introduction to Finite Elements in Engineering, p.123)
Preprocessing: Defining the Problem
1.
Give the Simplified Version a Title (such as 'Bridge Truss Tutorial').
In the Utility menu bar select File > Change Title :
The following window will appear:
Enter the title and click 'OK'. This title will appear in the bottom left corner of the 'Graphics' Window
once you begin. Note: to get the title to appear immediately, select Utility Menu > Plot > Replot
2.
Enter Keypoints
The overall geometry is defined in ANSYS using keypoints which specify various principal coordinates
Copyright © 2002 University of Alberta
839154859.017.png 839154859.018.png 839154859.019.png 839154859.020.png
 
839154859.001.png 839154859.002.png
University of Alberta ANSYS Tutorials - www.mece.ualberta.ca/tutorials/ansys/BT/Truss/Truss.html
to define the body. For this example, these keypoints are the ends of each truss.
{ We are going to define 7 keypoints for the simplified structure as given in the following table
coordinate
x
keypoint
y
1
0
0
2
1800
3118
3
3600
0
4
5400
3118
7200
0
5
6
9000
3118
7
10800
0
(these keypoints are depicted by numbers in the above figure)
{ From the 'ANSYS Main Menu' select:
Preprocessor > Modeling > Create > Keypoints > In Active CS
The following window will then appear:
{ To define the first keypoint which has the coordinates x = 0 and y = 0:
Copyright © 2002 University of Alberta
839154859.003.png 839154859.004.png 839154859.005.png
 
839154859.006.png
University of Alberta ANSYS Tutorials - www.mece.ualberta.ca/tutorials/ansys/BT/Truss/Truss.html
Enter keypoint number 1 in the appropriate box, and enter the x,y coordinates: 0, 0 in their
appropriate boxes (as shown above).
Click 'Apply' to accept what you have typed.
{ Enter the remaining keypoints using the same method.
Note: When entering the final data point, click on 'OK' to indicate that you are finished entering
keypoints. If you first press 'Apply' and then 'OK' for the final keypoint, you will have defined it
twice!
If you did press 'Apply' for the final point, simply press 'Cancel' to close this dialog box.
Units
Note the units of measure (ie mm) were not specified. It is the responsibility of the user to ensure that a
consistent set of units are used for the problem; thus making any conversions where necessary.
Correcting Mistakes
When defining keypoints, lines, areas, volumes, elements, constraints and loads you are bound to make
mistakes. Fortunately these are easily corrected so that you don't need to begin from scratch every time an
error is made! Every 'Create' menu for generating these various entities also has a corresponding 'Delete'
menu for fixing things up.
3.
Form Lines
The keypoints must now be connected
We will use the mouse to select the keypoints to form the lines.
{ In the main menu select: Preprocessor > Modeling > Create > Lines > Lines > In Active Coord .
The following window will then appear:
{ Use the mouse to pick keypoint #1 (i.e. click on it). It will now be marked by a small yellow box.
Copyright © 2002 University of Alberta
839154859.007.png 839154859.008.png 839154859.009.png
University of Alberta ANSYS Tutorials - www.mece.ualberta.ca/tutorials/ansys/BT/Truss/Truss.html
{ Now move the mouse toward keypoint #2. A line will now show on the screen joining these two
points. Left click and a permanent line will appear.
{ Connect the remaining keypoints using the same method.
{ When you're done, click on 'OK' in the 'Lines in Active Coord' window, minimize the 'Lines' menu
and the 'Create' menu. Your ANSYS Graphics window should look similar to the following figure.
Disappearing Lines
Please note that any lines you have created may 'disappear' throughout your analysis. However, they have
most likely NOT been deleted. If this occurs at any time from the Utility Menu select:
Plot > Lines
Define the Type of Element
4.
It is now necessary to create elements. This is called 'meshing'. ANSYS first needs to know what kind of
elements to use for our problem:
{ From the Preprocessor Menu, select: Element Type > Add/Edit/Delete . The following window
will then appear:
Copyright © 2002 University of Alberta
839154859.010.png 839154859.011.png 839154859.012.png
University of Alberta ANSYS Tutorials - www.mece.ualberta.ca/tutorials/ansys/BT/Truss/Truss.html
{ Click on the 'Add...' button. The following window will appear:
{ For this example, we will use the 2D spar element as selected in the above figure. Select the
element shown and click 'OK'. You should see 'Type 1 LINK1' in the 'Element Types' window.
{ Click on 'Close' in the 'Element Types' dialog box.
5.
Define Geometric Properties
We now need to specify geometric properties for our elements:
{ In the Preprocessor menu, select Real Constants > Add/Edit/Delete
Copyright © 2002 University of Alberta
839154859.013.png 839154859.014.png 839154859.015.png 839154859.016.png

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin