Vickers Hardness testing simulation on ANSYS

[Libin20]

I have tried to simulate the Vickers hardness on a substrate with a coating on it. I am really struggling to get it to work as the deformation is far too big. I have added the pictures of my model. Is there anyone that can help me with this?

 

[Mech_Engineer]

If I had to guess the problem will be one of two things:

1. The model is under-constrained, and the parts are "flying away," or
2. The model doesn't have enough sub-steps during the solve, and so the contact surfaces pass right through each other

I see a fixed support in your model, I assume this is for your "anvil" in which case it's possible under-constraint isn't an issue, so that leaves contact conditions which is a common problem for new ANSYS users.

Let's try my standard response for any user with a contact condition problem and see if it works:

You don't mention what version of ANSYS you're using, but in any case you'll need to make sure you've got your settings right. Contact conditions are a pretty complicated topic, but in general here is some of the feedback I give every time. It's possible you don't need contact conditions at all; unless you expect to see a lot of movement at the bolts and washers I would seriously recommend you consider bonding them using a multi-body solid. Alternatively, consider deleting your washers altogether and then use a contact condition with just your bolts.

Contact condition guidelines:

1. Pay close attention to your mesh density in the contact conditions. The mesh should be of similar size on both sides of the contact, you can use a "contact condition mesh refinement" to make sure this happens. I'd also recommend using hex-dominant mesh where possible, tetrahedrons tend to make for rougher stress gradients.
2. Make sure you use an "Augmented Lagrange" formulation for the contacts between the components. This formulation tends to work best for me in most conditions.
3. As a start, make the contact condition between the parts frictionless. Once you get it to converge, then you can think about considering friction.
4. Make sure your contact condition forces update every substep, and split your problem into MANY substeps (on the order of 100).

Try this out and see what happens.

I also notice your mesh doesn't look very well optimized especially on the anvil. It's very dense on top out to the edges far away from the contact area; this will make your problem take a lot longer to solve. I'd recommend the following mesh settings:

1. Split your anvil geometry close to the contact condition so that you can set multiple mesh densities across the part; this will allow you to have a dense mesh near the contact without increasing the mesh density everywhere.
2. Use a multi-body solid when you split your geometry so you don't have extra contact conditions where they aren't needed
3. Use a hex-dominant meshing method where possible for better geometry coverage with fewer elements
4. Consider using a much lower density mesh until you can get your contact conditions to converge, then consider increasing density where appropriate

Good luck.

 

[Libin20]

I want to calculate the residual stress on a coating which has been spared on to a substrate. However, the only parameter I know about the coating is the young modulus, v and yield strength. I do not know the tangent modulus of the coating and I'm not sure how to add plasticity to the model. Is there anyone that can help?

 

[berkeman]

(Mentor Note -- Two threads on the same question merged into one thread)

 

[Mech_Engineer]

I want to calculate the residual stress on a coating which has been spared on to a substrate. However, the only parameter I know about the coating is the young modulus, v and yield strength. I do not know the tangent modulus of the coating and I'm not sure how to add plasticity to the model. Is there anyone that can help?

I'm getting the feeling you're over-thinking this; calculating residual stress should be pretty straightforward if you know the shrinkage of the coating after application.

Do you know any shrinkage factors associated with the coating? If so, getting a residual stress in ANSYS should be straightforward model.