problem 1: structural analysis of signs post university of puerto rico at mayagüez department of...
TRANSCRIPT
Problem 1:Structural Analysis
of Signs Post
University of Puerto Rico at Mayagüez Department of Mechanical Engineering
Modified by (2008): Dr. Vijay K. GoyalAssociate Professor, Department of Mechanical EngineeringUniversity of Puerto Rico at Mayagüez
Thanks to UPRM students enrolled in INME 4058 sections 2006-08
Scope
The purpose of this problem is to demonstrate how to solve the displacements of a homogeneous multiple section hollow bar using ANSYS.
Problem Description
A 20ft tall post is used to support advertisement signs at various locations along its height, as shown in the accompanying figure. The post is made of structural steel with a modulus of elasticity of E = 29X106lb/in2. Not considering wind loadings on the signs, (a) determine displacements of the post at the point of load application and (b) determine stresses in the post.
OD
T
1
2
3
100 lb
150 lb
200 lb
Set No. OD T
1 2.78125 0.390625
2 2 0.4375
3 1.125 0.3125
In inches
Start up
First, let’s start by opening ANSYS by: Click on:
Start > All Programs > ANSYS > Product Launcher.
The configuration window will appear: Here we will change the working directory and the
memory settings.
Working Directory
This is the
10.0 ANSYS
Product Launcher
main window. Select the Working
Directory and type
the name of work
shop on Job Name.
Memory Settings
This step is done for slow computers Click the button Customization/
Preferences. On the item of Use custom
memory settings type 128
on Total Workspace (MB):
and type 64 on
Database (MB):. Then click the Run
bottom.
Memory settings
ANSYS Main Window
This is the main window of ANSYS University Intermediate Utility Menu.
GUI Filtering
In order to maximize your workspace to meet your needs. Let’s filter out the GUI (Graphical User Interphase). Click on Preferences > Choose on GUI Filtering:
Structural > OK.
GUI Filtering
Setting Preferences:
1. Click on Preferences on the ANSYS Main Menu window
2. Select Structural and h-method and Click OK
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2
Element Type
For ANSYS to properly analyze the problem, we must choose well the appropriate element. We will choose Element Type Pipe Elastic straight16:
Element Type
1. On Main Menu window, click Preprocessor \ Element Type \ Add/Edit/Delete
2. Click Add… on The Element Types Window
1
2
Element Type
3. On the Library of Element Type window select Pipe Elastic straight16 \ click OK \ click Close on the Element Type window
3
Real Constants
The real constant are the dimensions that must remain constant during the design. These constants are: diameters, thickness, among others.
Real Constants
1. On the Main Menu Window select Preprocessor \ Real Constants \ Add/Edit/Delete.
2. On the Real Constants window, click add.
2
1
2
Real Constants
1. On the Real Constants window, input the values of outer diameter and wall thickness and click apply.
2. Then enter the new Set No. and repeat the step 1 for each Set No.
3. Finally click ok.
1
Set No. OD T
1 2.78125 0.390625
2 2 0.4375
3 1.125 0.3125
In inches
2
Real Constants
Change the Real Constant Set No.
Enter the New Outside Diameterand New Thickness
1
2
Then click Apply
3
Real Constants
Enter the New
Set No, Outside Diameter and Thickness
Finally Click ok
Real Constants
Click Close
Material Properties
1. On the Main Menu Window select Preprocessor \ Material Props \ Material Models.
2. On the Material Model Behavior window select Material Model Number 1 \ Structural \ Linear \ Elastic \ Isotropic
3. For EX enter 29e6 and in PRXY enter 0.30.
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1
Finally Click Ok and close the material Model Behavior window
Geometry
The strategy to create the desired geometry is by first creating the key points where the loads will be applied and then uniting these key points with lines.
Geometry
1. On the Main Menu Window select Preprocessor \ Modeling \ Create \ Keypoints \ In Active CS.
2. Enter the locations for all the nodes in the table. Then click OK.
Note that all dimensions were converted to inches
12
Keypoint X Y Z
1 0 0 0
2 0 120 0
3 0 180 0
4 0 240 0
Then Click Apply
Geometry
Enter the New Key Point and It Location
Then Click Apply
Geometry
Enter the New Key Point and It Location
Then Click Apply
Geometry
Enter the New Key Point and It Location
Finally click apply and then ok
Geometry
3. On the Main Menu Window select Preprocessor \ Modeling \ Create \ Lines \ Lines \ Straight Line.
4. Pick point 1 and then point 2.
5. Repeat process until all three lines are finished.
3
4
Geometry
Pick First point 1 and then point 2
1
2
Geometry
Pick Point 2 and then Point 3
Geometry
Pick point 3 and then point 4
Finally Click Ok
Geometry
6. The final model should look like this:
6
Meshing
To make the finite element analysis we must first divide the object into small elements, this is called meshing.
Meshing
1. On the Main Menu window, select Preprocessor \ Meshing \ MeshTool
2. On the MeshTool window Click on Smart Size \ Select 4 \ Select Mesh: Lines \ Click on Mesh.
1
2
2
2
Meshing
3. Click on the material # 1 and then OK
Material # 1
Click OK
Meshing
4. Click on: Plot > Lines to see the element.
Meshing
5. Click on: Set > Real Constant Set No. enter 2 > OK > Mesh Set
Select 2
Mesh
Meshing
6. Click on the material # 2 and then OK
Material # 2
Click OK
Meshing
7. Click on: Plot > Lines to see the element.
Meshing
8. Click on: Set > Real Constant Set No. enter 3 > OK > Mesh Set
Select 3
Mesh
Meshing
9. Click on the material # 3 and then OK
Material # 3
Click OK
Meshing
10. Close the “Mesh Tool” window
Close
Loads & Displacements
Now we are able to apply the loads at the key points and the boundary conditions of the element
Displacements
1. On Main Menu Window select Preprocessing \ Loads \ Define Loads \ Apply \ Structural \ Displacement\On Keypoints
2. Select the Keypoint Number 1 and click OK.
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3. Select All DOF, and Apply as Constant Value with a Value of 0.
Displacements
3
Loads
1. On Main Menu Window select Preprocessing \ Loads \ Define Loads \ Apply \ Structural \ Force/Moment \ On Keypoints
2. Select the Keypoint Number 2 , choose FY and enter a value of -200 and then click OK.
1Pick Point 2 and then click ok
Enter the corresponding Values for the force
Loads
3. Repeat the previous procedure for the loads applied at the key points three and four.
Keypoint Load Direction
2 -200 FY
3 -150 FY
4 -100 FY
Loads
4. The Model should look like this:
FEM Solution & Plotting Results
Now we already developed the geometry, Loads & Displacements and the meshing. We will start with the finite element analysis and obtain the displacements on the key points.
After make the FEM solution we are able to plot the results, in this case the displacements.
FEM Solution
1. On ANSYS Main Menu window select Solution \ Solve \ Current LS
1
Then click OK
FEM Solution
Then a window will appear indicating that the solution is done. Next close the window.
Plotting Results
1. On Main Menu Window select General Postproc \ Plot Results \ Deformed Shape.
2. Select Def + undeformed
3. Click ok
2
1
3
Plotting Results
3. On Main Menu Window select General Postproc \ Plot Results \ Contour Plot \ Nodal Solu
4. Then DOF Solution \ Y-Component of displacement \ OK.
Uy
Plotting Results
5. The plot for the Y-displacements should look like this:
Plotting Results
Plotting Results for Stresses
1. On Main Menu Window select General Postproc \ Element Table \ Define Table
2. Click Add.
2
1
Plotting Results
Plotting Results for Stresses
3. Select Stress \ von Mises Stress SEQV
4. Click OK.
4
3
Plotting Results
Plotting Results for Stresses
5. On Main Menu Window select General Postproc \ Element Table \ Plot Elem Table.
6. Select SEQV and No – do not avg and click OK.
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6
Plotting Results
Plotting Results for Stresses
7. The plot for the Von Misses stresses should look like this: