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Max. Von Misses stesses do not match.
Posted Aug 10, 2012, 10:34 a.m. EDT Version 4.2a 2 Replies
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Hello,
I am using COMSOL 4.2a version. I am investigating a simple compression problem on pillars. My aim is to find a maximum stress. This is the following procedure I used looking for the maximum stress.
Definitions-->Model Couplings-->Maximum-->Specify boundaries of interest
Then when the solution is obtained:
Derived Values-->Global Evaluation-->maxop1(solid.mises)
The problem is that the value obtained using the above method does not match the maximum value that I read from the COMSOL Von Mises Stress plot.
Now I am confused which is correct. For example the Von Mises stress plot gives me 2.7MPa, while the maxop1(solid.mises) gives me 3.3MPa. As you can see the difference is substantial.
Thank you for your help
Mantas
I am using COMSOL 4.2a version. I am investigating a simple compression problem on pillars. My aim is to find a maximum stress. This is the following procedure I used looking for the maximum stress.
Definitions-->Model Couplings-->Maximum-->Specify boundaries of interest
Then when the solution is obtained:
Derived Values-->Global Evaluation-->maxop1(solid.mises)
The problem is that the value obtained using the above method does not match the maximum value that I read from the COMSOL Von Mises Stress plot.
Now I am confused which is correct. For example the Von Mises stress plot gives me 2.7MPa, while the maxop1(solid.mises) gives me 3.3MPa. As you can see the difference is substantial.
Thank you for your help
Mantas
2 Replies Last Post Aug 10, 2012, 11:28 a.m. EDT
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Posted:
1 decade ago
Hi
it is always delicate to study stress values, as often these are maximum very locally at some numerical singularities, therefore you should analyse in detail where these maximum are and their shape, plots are often smoothed by 2nd or higher order polynomials, maxop() might be too but with another order, this can easily give large differences.
I usually use average values in critical regions the be sure I'm not getting a peak stress value for only one node/mesh element that most probably comes from a numerical issue. And I compare the see how sensitive this value is w.r.t. my local mesh density
--
Good luck
Ivar
it is always delicate to study stress values, as often these are maximum very locally at some numerical singularities, therefore you should analyse in detail where these maximum are and their shape, plots are often smoothed by 2nd or higher order polynomials, maxop() might be too but with another order, this can easily give large differences.
I usually use average values in critical regions the be sure I'm not getting a peak stress value for only one node/mesh element that most probably comes from a numerical issue. And I compare the see how sensitive this value is w.r.t. my local mesh density
--
Good luck
Ivar
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Posted:
1 decade ago
Hello Ivar,
Thank you for your quick repsonse. I will try using your suggestion to calculate average values at high stress concentration sites. This should smoothen the values.
Thank you
Mantas
Thank you for your quick repsonse. I will try using your suggestion to calculate average values at high stress concentration sites. This should smoothen the values.
Thank you
Mantas