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PROBLEM IN DESIGN OF MICROMETER DIMENSION SYSTEMS

Posted 18 janv. 2012, 08:35 UTC−5 Version 4.2 6 Replies

Saloni Chaurasia
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Hi all,
I am using COMSOL 4.2 and designed a square diaphragm pressure sensor of dimensions length=1000 micrometer thickness =10 micrometer.After analysis the result for displacement for applied pressure of 2000 Pa was about 6 meter which according to analytical results shud be 0.18 micrometer.Kindly help me out with dis difficulty.
6 Replies Last Post 5 févr. 2012, 05:30 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 18 janv. 2012, 09:22 UTC−5
Hi

if you could help us to understand your model perhaps we can come with some ideas, I would say there is < 1% chance that COMSOL is wrong and the complement that you have missed something in the model set up, such as:

geometry sizes & units
material data & units
BC set-up
mesh density
...
take a second look at your model ;)

--
Good luck
Ivar
Hi if you could help us to understand your model perhaps we can come with some ideas, I would say there is < 1% chance that COMSOL is wrong and the complement that you have missed something in the model set up, such as: geometry sizes & units material data & units BC set-up mesh density ... take a second look at your model ;) -- Good luck Ivar
Saloni Chaurasia
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Posted: 1 decade ago 20 janv. 2012, 06:02 UTC−5

Hi

if you could help us to understand your model perhaps we can come with some ideas, I would say there is < 1% chance that COMSOL is wrong and the complement that you have missed something in the model set up, such as:

geometry sizes & units
material data & units
BC set-up
mesh density
...
take a second look at your model ;)

--
Good luck
Ivar


Hi
thnx Ivar for ur valuable suggestion .It helped me to sort out my problem.I need another help regarding how to see node coordinates for maximum value of a specified field like stress or displacement except clicking at 1 point and other and repeating it until we get the result.Another is that if we know the coordinates then how to see result at that coordinate.I am attaching a snapshot of my model for ur reference.Kindly reply me ASAP.
[QUOTE] Hi if you could help us to understand your model perhaps we can come with some ideas, I would say there is < 1% chance that COMSOL is wrong and the complement that you have missed something in the model set up, such as: geometry sizes & units material data & units BC set-up mesh density ... take a second look at your model ;) -- Good luck Ivar [/QUOTE] Hi thnx Ivar for ur valuable suggestion .It helped me to sort out my problem.I need another help regarding how to see node coordinates for maximum value of a specified field like stress or displacement except clicking at 1 point and other and repeating it until we get the result.Another is that if we know the coordinates then how to see result at that coordinate.I am attaching a snapshot of my model for ur reference.Kindly reply me ASAP.

Attachments:

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 20 janv. 2012, 06:31 UTC−5
Hi

try to add a "Plot - More Plots - min/max " node and enter the variable you want to probe
You also have the Definition Probe items to follow a variable or a min max ...

--
Good luck
Ivar
Hi try to add a "Plot - More Plots - min/max " node and enter the variable you want to probe You also have the Definition Probe items to follow a variable or a min max ... -- Good luck Ivar
Saloni Chaurasia
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Posted: 1 decade ago 4 févr. 2012, 05:33 UTC−5
Hi,
As guided by you I was able to see desired results of displacements but found a problem while looking for max stress .The stress value shown is absurd and not matching with analytical results.I am sending the snapshot of the value shown by the software and couldnot make out wats wrong.Kindly sort it out ASAP.
Hi, As guided by you I was able to see desired results of displacements but found a problem while looking for max stress .The stress value shown is absurd and not matching with analytical results.I am sending the snapshot of the value shown by the software and couldnot make out wats wrong.Kindly sort it out ASAP.

Attachments:

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 4 févr. 2012, 15:41 UTC−5
Hi

are you sure about your dimensions and the loads (what about the units do they match ?,
You have gained a factor 1E6 in stress between your 2 images, that gives me the impression tat your model is 1000x smaller than expected. COMSOL has one caveat in my opinion w.r.t. graphics representation, it does not give the units by the X-Y-Z triedre so one are never shure about the sizes, and when you start to change the geoemtry units once the geoemtry is there, depending on how you apply the scale you get unexpected results, that is your logic might not be the one of COMSOL (I have been caught a couple of times with that. So far my suggestion to COMSOL to add the units "m" or mm or um orinch by the graphical triedre X-Y-Z has not been implemented, I hope they will once, as most graphs in COMSOL have now nits, except the geometry, and that has some importance ;)

Another thing one do quickly wrong: mix the absolute load and the pressure load (force by area)

--
Good luck
Ivar
Hi are you sure about your dimensions and the loads (what about the units do they match ?, You have gained a factor 1E6 in stress between your 2 images, that gives me the impression tat your model is 1000x smaller than expected. COMSOL has one caveat in my opinion w.r.t. graphics representation, it does not give the units by the X-Y-Z triedre so one are never shure about the sizes, and when you start to change the geoemtry units once the geoemtry is there, depending on how you apply the scale you get unexpected results, that is your logic might not be the one of COMSOL (I have been caught a couple of times with that. So far my suggestion to COMSOL to add the units "m" or mm or um orinch by the graphical triedre X-Y-Z has not been implemented, I hope they will once, as most graphs in COMSOL have now nits, except the geometry, and that has some importance ;) Another thing one do quickly wrong: mix the absolute load and the pressure load (force by area) -- Good luck Ivar
Saloni Chaurasia
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Posted: 1 decade ago 5 févr. 2012, 05:30 UTC−5
Hi,
I considered your suggestions and want to add that the dimensions are in nanometers this time. length =1000 nm and thickness of diaphragm = 10 nm.I applied pressure load of 1kPa.The problem is that result for max displacement calculations are right but as you can see in the image of the sensor that the result for max stress value is not matching with the one given on right side colored bar . A new geometry was created after changing dimensions settings to nanometers.There is no modification made to micro dimension geometry.Please suggest any feasible solution to this.
Hi, I considered your suggestions and want to add that the dimensions are in nanometers this time. length =1000 nm and thickness of diaphragm = 10 nm.I applied pressure load of 1kPa.The problem is that result for max displacement calculations are right but as you can see in the image of the sensor that the result for max stress value is not matching with the one given on right side colored bar . A new geometry was created after changing dimensions settings to nanometers.There is no modification made to micro dimension geometry.Please suggest any feasible solution to this.

Attachments:

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