Inventor Stress Analysis force change problem

[Anonymous]

Hi friends.. I started to discover Inventor Pro 2017 Stress Analysis simulation, I have a tiny problem: why when changing force magnitude in stress simulation and re-simulate the part it doesn't change stress distribution? i.e. color distribution?, I noticed when viewing Safety Factor tab it does change and respond to the new load but Von Mise simulation doesn't change just the color scale changes it's values. 

Thanks for help.

Zeyad 

[TheCADWhisperer]

Attach *.ipt file here and images of what you are seeing. 

So simple!

[Anonymous]

Hi.. The file details are as follow:

Rectangular pipe of dimensions:

W=20 mm

H= 10 mm

Thick.= 1 mm inside

L= 200 mm (Extrude)

Material: Aluminum 6061

First image stress simulation with 100 N Force

Second image stress simulation with 500 N Force

Rest of sittings are default 

[Cris-Ideas]

Clearly it did react.

Look on the max values. 523 v 104 

Colours are only relative to values. So in case of your simulation they will not change.

Cris

[Anonymous]

I thought it would also change color distribution i.e stress. you see when applied force doesn't exceed critical stress or yield point there should be no red color in the simulation, in the pictures the red color still show up no matter how force magnitude is. why?

Thanks for reply.

[Cris-Ideas]

You can get that if you want.

You have to set equal scales for both simulations in graph settings.

Also you can have both of this simulations done in one file. This will make it easier to compare.

Cris.

[Cris-Ideas]

sorry,

remark of putting those simulations in a single file, is related to different thread. I was distracted obviously.

Cris.

[Anonymous]

Any directions (in details)  where to find Graph tools? as I said I am still a beginner in stress simulation. Thanks for being patient with me Cris. 

[Anonymous]

Thank you very much Cris, you made a great help for me in this video, I now can control the scale of stress range, but... there is one last question:

Why when changing force magnitude the stress scale changes automatically? I mean stress limits must be relevant to the part geometry, material and design, not the force magnitude so when apply force that exceeds these limits a failure indication will show up like red color.

[Cris-Ideas · Accepted solution]

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@Anonymous wrote:

Thank you very much Cris, you made a great help for me in this video, I now can control the scale of stress range, but... there is one last question:

Why when changing force magnitude the stress scale changes automatically? I mean stress limits must be relevant to the part geometry, material and design, not the force magnitude so when apply force that exceeds these limits a failure indication will show up like red color.

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Hi,

I think you must have miss understood stress colour scale. It is not to indicate failure but to present results only.

Whether something is a failure or not is for you to judge, as computer only does calculation for you.

FEA is just a tool like any other. Computer will not know if stress of 500MPa is big or small for your case.

For example. If I do FEA for elements made of S355 steel that has yield strength about 350 MPa. It is for me to judge  if stress of 5000MPa that come up is acceptable. And whether it is or not depends on the analysis I do. Sometimes I may decide it is OK because it is only present in parts of the model I am not interested in and have very cores mesh that combined with simplified boundary conditions gives very high local stress.

And in other cases I may decide that it is way to much as it concerns areas of the model I am analysing and result is not coming from numerical causes but from construction being overloaded.

Colour scale is there to let you judge and asses more easily.

But remember assessment and decision and responsibility is always yours.

FEA software is no a magic solution that tells you if you construction can withstand the load. It is only a method for calculations, and a method only. Depending on what you will put in to it it will produce results, but it cannot be ever allowed to think for you.

In my careerer I saw many times when engineers have trusted FEA not being able to asses the results. It is scary.

I also witness results of such approach on construction sites.  It easily costs lives.

When I than after was asked to do analysis of the causes I was devastated by lack of responsibility and basic knowledge in some designs.

So

Do not ever let computer judge. Use it as a brainless hummer.

If someone gets hurt it is YOU who has to live with this for the rest of your life.

Cris.

[Anonymous]

Well.. I am shocked of what you said... nevertheless it is a fact, I thought that FEA embedded in Inventor can at least predict failure not to mention exact results. 

Thanks a lot for your help, I appreciate the time you spent helping me.

Regards.