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• Publicado : 3 de febrero de 2012

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Introduction
This tutorial was created using ANSYS 7.0 to solve a simple 3D space frame problem.

[pic]Problem Description

The problem to be solved in this example is the analysis of a bicycle frame. The problem to be modeled in this example is a simple bicycle frame shown in the following figure. The frame is to be built of hollow aluminum tubing having an outside diameter of 25mm and awall thickness of 2mm.
[pic]
[pic]

[pic]Verification

The first step is to simplify the problem. Whenever you are trying out a new analysis type, you need something (ie analytical solution or experimental data) to compare the results to. This way you can be sure that you've gotten the correct analysis type, units, scale factors, etc.
The simplified version that will be used for thisproblem is that of a cantilever beam shown in the following figure:
[pic]

[pic]Preprocessing: Defining the Problem

1. Give the Simplified Version a Title (such as 'Verification Model').
Utility Menu > File > Change Title
2. Enter Keypoints
For this simple example, these keypoints are the ends of the beam.
o We are going to define 2 keypoints for the simplifiedstructure as given in the following table
|keypoint |coordinate |
| |x |y |z |
|1 |0 |0 |0 |
|2 |500 |0 |0 |

o From the 'ANSYS Main Menu' select:
Preprocessor > Modeling > Create > Keypoints > In Active CS
3. Form Lines
The two keypoints must now be connected to form a bar using astraight line.
o Select: Preprocessor > Modeling> Create > Lines > Lines > Straight Line.
o Pick keypoint #1 (i.e. click on it). It will now be marked by a small yellow box.
o Now pick keypoint #2. A permanent line will appear.
o When you're done, click on 'OK' in the 'Create Straight Line' window.
4. Define the Type of Element
It is now necessary tocreate elements on this line.
o Click on the 'Add...' button. The following window will appear:
[pic]
o For this example, we will use the 3D elastic straight pipe element as selected in the above figure. Select the element shown and click 'OK'. You should see 'Type 1 PIPE16' in the'Element Types' window.
o Click on the 'Options...' button in the 'Element Types' dialog box. The following window will appear:
[pic]
o Click and hold the K6 button (second from the bottom), and select 'Include Output' and click 'OK'. This gives us extra force and moment output.
o Click on 'Close' in the 'Element Types' dialog box and close the 'ElementType' menu.
5. Define Geometric Properties
We now need to specify geometric properties for our elements:
o Click Add... and select 'Type 1 PIPE16' (actually it is already selected). Click on 'OK'.
o Enter the following geometric properties:
o Outside diameter OD: 25o Wall thickness TKWALL: 2

This defines an outside pipe diameter of 25mm and a wall thickness of 2mm.
o Click on 'OK'.
o 'Set 1' now appears in the dialog box. Click on 'Close' in the 'Real Constants' window.
6. Element Material Properties
You then need to specify material properties:
o In the 'Preprocessor' menu selectMaterial Props > Material Models...
o Double click Structural > Linear > Elastic and select 'Isotropic' (double click on it)
o Close the 'Define Material Model Behavior' Window.
We are going to give the properties of Aluminum. Enter the following field:
| |EX 70000 |
| |PRXY 0.33 |

o Set these properties and click on 'OK'.
7. Mesh Size...