Learning Forum

[Chinmay]

Hi,

I would like to explain the context first followed by the problem I am facing.

Following is Isometric View.

Now the Punch (1) is supposed to have downward motion while the die (4) is fixed as shown below.

As the punch displaces, the brass part (3) is supposed to plastically deform and take shape of punch while it enclose the copper wire strands (2) as shown in below image.

I gave plasticity (Bi-linear Isotropic Hardening) to copper as well as brass by adding their respective yield strength and tangent modulus = 0 but my solution stops at following step.

While I get following errors:

    

  

I know this is probably a silly question for advanced level users but I would really appreciate if your could help me with the issue.

Thanks,

[mille46]

Check for rigid body motion. Maybe your model is not sufficiently constraint?

Which boundary conditions do you have applied?

[Chinmay]

Hi, thank you for your reply.

I have 2 fixed supports as shown in figure while the punch has displacement.

And currently this is the result I am getting.

[mille46]

This is a rather advanced non-linear simulation from my point of view. I think you need to check that the contacts "see" each other in intial contact status at point 2. Probably apply the displacement in at least 2 loadsteps to close the contact between part 3 and the top of the punch. Also I think your mesh is pretty coarse for this type of simulation.Apart from this shouldnt part 3 be fixed but rather have a contact to part 4. But maybe it works for now to get the contact problem between part 3 and punch worked out.

 

[peteroznewman]

Hi Chinmay,

I agree with mille46 that the mesh is too coarse for this type of analysis. There should be a minimum of 8 elements through the thickness of the brass strand holder.

I strongly recommend you take this to a 2D Plane Strain model because it will solve (and fail) much faster so you will be able to fix more problems per hour than if you leave it as a 3D model.  The requirement for a 2D model is to place surfaces in the XY plane. You have to rebuild the Mechanical model from scratch. You can't reuse the existing Mechanical model.

Another way to make the model solve faster is to use a plane of symmetry, but that will enforce a symmetric solution, and the photograph shows a crimp that is not symmetric.

[Chinmay]

Thank you both for your valuable feedback. Firstly I converted the 3D into 2D using design modular as shown below.

Following is the contact type I used. I tried all other contact types, frictional, friction-less, rough but only bonded type solved to a limit.

   

As you both suggested, I refined the mesh so I get at least 8 elements through its thickness

This solved the problem within less time compared to last time but I encountered few issues as shown below.

  

This result is still better than what I got yesterday thank you, but in order to solve the other issues I am thinking of some ideas which I am not sure if they will work.

Firstly I will divide that edge into three parts as shown below.

The reason I think its not forming the required shape is because I have fixed the die (part 4) and the bonded contact is not letting the shape deform. So I'll use bonded contact on middle portion (2 marked in the image) of the whole edge this time.

As for the other issue, I think I should add another manual contact (friction-less) between the two merging parts so they would slide on each other rather than inserting in each other. Please kindly advice if its the right thought process for such problems ?

Thanks,

[peteroznewman]

Yes, you need to add a contact between the two tip faces that come into contact at the end. Make sure that the Contact Tool under the Connections folder shows that this new contact is Near Open, not Far Open, and use a Pinball Radius to make this happen if necessary.

You should have no Bonded Contact. It should all be Frictional Contact.

[Chinmay]

Hi, Thanks for your reply. I added frictionless contact between the two tips, now I am getting results what I expected when it comes to the tips but unfortunately I am not able to solve the issue of bottom part deformation.

  

I have attached .wbpz file here. Please kindly help.

Thanks,

[peteroznewman]

You need the wires in the center to push the corners down.