example of optimization of the model using ansys

7/27/2019 Example of Optimization of the Model Using Ansys

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01.001

This is a good example of optimization of the model using

Ansys. Here we have to vary the input load P in Ansys and find

out the maximum value of P that can be applied to restrict thestress in the member to 340 MPa.

Here the length of the member is assumed to be equal to

10m.

Step 1:

Enter Keypoints in Ansys by path, Preprocessor-Modeling-Create-

Keypoints-In Active CS

Keypoint X Y


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1 0 0

2 0 10Step 2: Create line through keypoints by path Preprocessor-Modeling-

Create-Lines-Lines-In Active Coord. Following window will appear.

Use cursor to create line 1 between keypoint 1 and 2.

Step 3:- Define the Type of Element

Select: Element Type - Add/Edit/Delete. The following window willthen appear:


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Click on the 'Add...' button. The following window willappear:

Select 2D spar element and close the window.

Step 4: Define Geometric Properties

In the Preprocessor menu, select Real Constants > Add/Edit/Delete


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Click Add... and select 'Type 1 LINK1' (actually it is already selected).Click on 'OK'. The following window will appear:

Step 5: Element Material Properties

You then need to specify material properties:

o In the 'Preprocessor' menu select Material Props >Material Models


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Double click on Structural > Linear > Elastic > Isotropic

We are going to give the properties of Steel. Enter the following field:

EX

200000

Set these properties and click on 'OK'. Note: You may obtain the note'PRXY will be set to 0.0'. This is poisson's ratio and is not required forthis element type. Click 'OK' on the window to continue. Close the


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"Define Material Model Behavior" by clicking on the 'X' box in the upperright hand corner.

Step 5: Defining the Mesh attributes

Now we need to assign the area and Modulus we have defined to theline. Go to Meshing-Mesh Attributes-Picked lines and select the line

and following window will appear and click ok.

Step 6: Mesh Size

The last step before meshing is to tell ANSYS what size the elementsshould be. There are a variety of ways to do this but we will just dealwith one method for now.

In the Preprocessor menu select Meshing > Size Cntrls >ManualSize > Lines > All Lines


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In the size 'NDIV' field, enter the desired number of divisions per line.For this example we want only 1 division per line, therefore, enter '1'

and then click 'OK'. Note that we have not yet meshed the geometry,we have simply defined the element sizes.

Step 7: Mesh

Now the rod can be meshed.

In the 'Preprocessor' menu select Meshing > Mesh > Lines and click'Pick All' in the 'Mesh Lines' Window

Your model should now appear as shown in the following window


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Step 8: Saving your work

Save the model at this time, so if you make some mistakes lateron, you will at least be able to come back to this point. To do this, onthe Utility Menu select File > Save as.... Select the name andlocation where you want to save your file.

Step 9: Define Analysis Type

First you must tell ANSYS how you want it to solve this problem:

o From the Solution Menu, select Analysis Type > NewAnalysis.


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o Ensure that 'Static' is selected; i.e. you are going to do a

static analysis on the rod assemble as opposed to adynamic analysis.

o Click 'OK'.

Step 10 : Apply Loads

Select Define Loads > Apply > Structural > Force/Moment > onKeypoints.

Select Keypoint 1 and apply load of 200000 N in y direction as shownbelow.

Select Keypoint 2 and apply load of -200000 N in y direction as shownbelow.


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Your problem should look like this now.

Step 12: Solving the System


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We now tell ANSYS to find the solution:

In the 'Solution' menu select Solve > Current LS. This indicates thatwe desire the solution under the current Load Step (LS).

Once the solution is done the following window will pop up. Click'Close' and close the /STATUS Command Window..

Step 13: Result-Axial Stress

For line elements (ie links, beams, spars, and pipes) you will often needto use the Element Table to gain access to derived data (ie stresses,strains). For this example we should obtain axial stress to comparewith the hand calculations. The Element Table is different for eachelement, therefore, we need to look at the help file for LINK1 (Type helplink1 into the Input Line). From Table 1.2 in the Help file, we can seethat SAXL can be obtained through the ETABLE, using the item 'LS,1'

From the General Postprocessor menu select Element Table >Define Table

Click on 'Add...'


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o As shown above, enter 'SAXL' in the 'Lab' box. This specifiesthe name of the item you are defining. Next, in the'Item,Comp' boxes, select 'By sequence number' and 'LS,'.

Then enter 1 after LS, in the selection boxo Click on 'OK' and close the 'Element Table Data' window.

o Plot the Stresses by selecting Element Table > Plot ElemTable

o The following window will appear. Ensure that 'SAXL' isselected and click 'OK'

o List the Stresses From the 'Element Table' menu, select 'List Elem

Table'

From the 'List Element Table Data' window which

appears ensure 'SAXL' is highlighted

Click 'OK'


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We can see that for 200KN compressive stress in the member is

231.62 MPa. So we can still increase the load. Let us now check for 250KN.

For 250 KN stress value is 289.52 MPa. We are getting closer. Consider 300 KN for

next iteration.


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The value is more than limiting stress of 347 MPa. Let us reduce load to 293000 N.

We can see from above table that for 293000 N we are very close to the maximum

stress of 340 MPa. Therefore, maximum load that can be applied on the member is

293000 N.

example of optimization of the model using ansys

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