Learning Forum

[John Luke]

I'm doing a strength assessment for a mountain bike frame, my load and boundary conditions are;

1- a remote displacement with all 0 components  where the handler is attached to the bike frame
2- Symmetry region 
3- a Load tangential to the edge 

When I try to solve for equivalent stress it shows these messages.

 

I'm not sure whats the problem if someone could help I would appreciate it.

[Claudio Pedrazzi]

 

Where is the remote displacement located in the model? please post a screenshot of it too.  It seems likely that you are not constraining enough, but I would like to judge after having seen the remote displacement.  Is this a shell model?

 

[John Luke]

 

Its located in the middle of the handler where its attached the bike frame

 

yes it's a shell

[Claudio Pedrazzi]

Seems fine to me, though I do not really understand the symmetry, since you fix everything.  

But just for testing. If you substitute your remote displacement wiht a simple fixed constraint on that cylindrical surface, hopefully the problem disappears?  It would be a first hint.

[John Luke]

 

The handler is symmetrical in geometry and loads so I applied symmetry to simplify things, and I’ve tried fixed support instead of remote displacement the problem remains.

 

[Claudio Pedrazzi]

ok thank you for the clarification, at this point I have no other ideas.  My point about symmetry I need to explain it better.  That is, if I have understood the situation correctly.  In my sketch (I apologize for the bad quality) the two flags represent a symmetry condition. 

What I am saying is that if in the plane of symmetry every displacement and rotation is fixed (as I understood from your remote displacement), then the symmetry condition is not necessary, it is “implicit”.  Because no stress will get beyond your fixed point, no matter what type of loads you have.  But this does not answer your problem, I know.  It was just a side comment.  But I would delete the symmetry condition anyway. 

 

 

 

[John Luke]

[Erik Kostson]

 

Hi

Can you check as it says the load might be wrong (and in combination with material properties) – try and solve for 0.0001 N.

All the best

Erik

 

[wrbulat]

Here's something I always remember to forget to do in cases like this - duplicate the static structural system, convert it to a modal one, and solve for a few natural frequencies. Look for zero or near-zero natural frequencies and associated rigid body modes. This can be used to identify the motion that your presumably inadequate constraints allow and shine a light on what needs to be done to fix them. Also, please look closely at your mesh. From the forgoing discussion and images (thanks for these!) I frankly cannot see how this would be possible, but your model almost acts as if it isn't joined by nodal connectivity - like there is a dissimilar mesh at an interface and no bonded contact to structurally connect the meshes at the interface.

Cheers,

Bill

[John Luke]

It turned out that I had a simple mistake in the material assigment and when I gave the correct value for the young's modulus everything is behaving properly.

Thanks everyone for your help.

[Erik Kostson]

That is great - happy it helped.

Erik