Ansys
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Revision as of 11:49, 12 January 2007
Effect of Modelling on Ansys
Ansys is a finite element analysis software used for numerically solving static/dynamic structural problems, thermal, electromagnetics, acoustics and fluid problems. The results that are obtained reflect how the model was generated, loaded and meshed. When performing a geometry optimization using Ansys, users must take into account all of these factors. By exploring a case study, the sensitivity of Ansys to these changes can be visualized. Modelling
There are multiple ways to generate geometry in Ansys.
[[[Image:bracket.JPG]]] ...
Figure 1. Angle Bracket
Using log files obtained from a CMU undergrad mechanical engineering course, there were two main methods in which users approached this problem. Method 1
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1. [[[Image:1_1.JPG]]] o
Figure 2. Created two rectangles
2. [[[Image:1_2.JPG]]] o
Figure 3. Rounded corners
3. [[[Image:1_3.bmp]]] o
Figure 4. Filleted with lines
4. [[[Image:1_4.bmp]]] o
Figure 5. Filleted with lines
5. [[[Image:1_5.bmp]]] o
Figure 6. Subtracted area of hole
Method 2
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1. [[[Image:2_1.bmp]]] o
Figure 7. Created arcs
2. [[[Image:2_2.bmp]]] o
Figure 8. Created arcs
3. [[[Image:2_3.bmp]]] o
Figure 9. Created lines
4. [[[Image:2_4.bmp]]] o
Figure 10. Created area
5. [[[Image:2_5.bmp]]] o
Figure 11. Subtracted area of hole
Modelling Path
[[[Image:modellingpath.JPG]]]
Figure 12. Meshing
[[[Image:meshing.JPG]]] 2/15 used an element mesh size of .25 while 13/15 used an element mesh size of .5. Figure 13. Loading
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6/15 users accounted for depth and applied 80 psi *
8/15 used 10 psi from the diagram *
1/15 did not use either *
All users applied 0 displacement
Results
[[[Image:meshingerror.JPG]]]
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With constant pressure, average difference due to modelling is 19.94% *
WIth constant pressure and constant mesh size, average difference is 23% *
Meshing affected the results by 3%
[[[Image:pressurediff.JPG]]]
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Same model given two different pressures *
Percent difference due to pressure difference is 87.5%
Conclusion
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The greater the difference in modelling, the greater the difference in Ansys results. *
By setting a tighter criterion for convergence, the difference due to meshing should go to zero. *
The same loading will produce the same results.
Links
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http://en.wikipedia.org/wiki/ANSYS *
http://computing.ee.ethz.ch/sepp/ansys-6.0-bo/structural_tut.html