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Applying constraints in stress analysis

5 REPLIES 5
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Message 1 of 6
Anthony
3485 Views, 5 Replies

Applying constraints in stress analysis

Could anyone give me a basic understandable breakdown of the meanings of the 3 constraint options when runing a stress analysis - pin, frictionless and fixed ?

 

It is difficult to tell if I am using the correct ones(s) and Inventor does not give a detailed enough description of how to apply them and which ones to use.

 

I have attached an image showing what I have done so far, the contraints in the drawings are 1 pin constraint to the bolt (only fix axial direction checked) and 1 fixed constraint on the I-beam surface.

 

Thanks in advance

Anthony Goodwin ~ Cad Manager/Senior Designer
Autodesk Inventor Professional 2013 SP2 64-Bit Edition
Windows 7 HP Z400, Intel Xeon W3550 3.07GHz
12.0GB RAM, ATI FirePro V4800 (FireGL)
5 REPLIES 5
Message 2 of 6
JDMather
in reply to: Anthony

Do you have this book?
http://www.amazon.com/Running-Autodesk-Inventor-Professional-2012/dp/1461066115/ref=sr_1_1?s=books&i...

 

Also see his online classes here http://au.autodesk.com

 


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Message 3 of 6
rhinterhoeller
in reply to: Anthony

Anthony:

 

In future could you please post images as a jpg since they are smaller and load faster.

 

The constraint names are quite self-explanatory.  For example if you have a linkage that hinges around a fixed (by an unmodelled structure) pin one would use the pinned constraint.

 

My question is "What are you trying to analyse?".  Are you analysing the big I-beam?  Are you trying to analyse the stand-off?  Are you trying to analyse the bracket as bolted to the attachment?

 

Once we know that we can try to answer your questions.

 

Also please tell us what version of IV you're using.

 

Richard

IV 2013 Product Design Suite 64 Bit
Win 7 64 bit
Message 4 of 6
Anthony
in reply to: rhinterhoeller

I am using Inventor 2012 Professional suite.

 

I am trying do a stress analysis on the bracket, you can see the top plate of the bracket in my image (where the colorization is), this is where the load is facing downward on the bracket.

 

Ideally I want to also see the stress on the bolt which is fixed through the CHS tube.

 

Thanks

Anthony Goodwin ~ Cad Manager/Senior Designer
Autodesk Inventor Professional 2013 SP2 64-Bit Edition
Windows 7 HP Z400, Intel Xeon W3550 3.07GHz
12.0GB RAM, ATI FirePro V4800 (FireGL)
Message 5 of 6
rhinterhoeller
in reply to: Anthony

In that case I would remove the beam from the simulation, it's sucking up resources with no benefit.  Constraining the left end of the stand-off using a fixed constraint would be just as effective and a more efficient us of resources.

 

Is this model symmetrical through the centre of the bolt?  If so I would only model the back half of the stand-off, the bracket and perhaps the bolt.  Apply a frictionless constraint to all of these cut surfaces.  Why?  Again you've cut the number of elements being analysed in half AND you get to see what's happening in the middle of the assembly.

 

Now ask yourself if the model represents reality.  My guess is it doesn't.  That pinned constraint you added to the bolt suggests that some magic force is holding the bolt from moving.  Remove that constraint and see what the result is.

 

Remove the whole bolt and re-analyse.  Do you get the same result as above?  If so come back and we'll talk some more.

 

Richard

 

 

IV 2013 Product Design Suite 64 Bit
Win 7 64 bit
Message 6 of 6
Anthony
in reply to: rhinterhoeller

Many thanks for the useful advise. Could you please clarify a few points.

 

I have removed the beam as you suggested and added a fixed constraint to the left end of the tube.

 

Yes the model is symmetrical through the bolt, could you clarify where the frictionless constraints you mentioned need to be added on the components ?

 

I also removed the pinned constraint from the bolt.

 

As I said before I need to see the stress on the bolt, tube and bracket, where would the best place be to add a constraint to the bolt so see this.

 

Sorry for asking you to suck eggs but I am new to stress analysis in Inventor.

 

Thanks

Anthony Goodwin ~ Cad Manager/Senior Designer
Autodesk Inventor Professional 2013 SP2 64-Bit Edition
Windows 7 HP Z400, Intel Xeon W3550 3.07GHz
12.0GB RAM, ATI FirePro V4800 (FireGL)

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