Learning Forum

[Puhia Qalaj]

Hi,

My simulations focus on asymmetric indentation with frictionless interaction, and I'm encountering a few problems. 

 

My first model works, but the issue appears when I change the height dimension of my model. 

 

Here is an example of the model 1 where the dimensions for the height of the rectangle is 500nm, the length of the rectangle is 1.5 micrometers and the tip radius is 200nm.

 

 

In terms of contact definition, I put these parameters:

 

For the steps, substeps I try these combinations: 

 

As regards my boundary conditions, I set a fixed support for the bottom left node of my rectangle, a blocked displacement in y for the nodes on the bottom face of the rectangle and a displacement in y = -50nm with x and z = 0 for the top face of the tip.

For this it works, but now if I increase the height of my model from 500nm to 3 micrometers it does not converge. 

 

 

It failed around 29nm of indentation depth.

 

Can you help please ?

 

Thank you ! 

 

Puhia

[Akshay Maniyar]

Hi Puhia,

It looks like that your model is undergoing an element distortion issue. What are the materials used for both parts? Please check the below video in 'handling element distortion issues' and see if it helps.

How to Handle Element Distortion Errors in Hyperelastic Materials — Lesson 3 - ANSYS Innovation Courses

Thanks,

Akshay Maniyar

[Puhia Qalaj]

Hi, 

 

Thank you for your response. For the definition of both materials: 

For the rectangle:

For the tip: 

I took the time to watch the video you suggested and have been experimenting with different approaches, unfortunately without success so far. I'm at a point where I'm not sure which direction to take to achieve the desired result.

 

In addition, I need clarification on the axisymmetric aspect. At the moment, I'm at a dead end because I haven't found an option that lets me specify the axis of rotation for this symmetry. My intention is to use the face on the left as the central axis for the axisymmetry operation.

 

Thank you.

 

Puhia

[Akshay Maniyar]

Hi Puhia,

Thank you for the description. It looks like you modeled both the part as linear material. Are you expecting any plastic strain or fracture in bone material? You will need to create a proper material model to get the correct results. 

Regarding the axisymmetric behavior, the Y-axis is considered as the axis of rotation and geometry should be in the XY plane.

Thanks,

Akshay Maniyar

[Puhia Qalaj]

Hi,

Thank you for your response!

My model is very simplified, focusing only on linear elastic deformation. My objective doesn't involve plastic strain or fracture.

Regarding the axisymmetric conditions, in my SpaceClaim design, the y-axis is positioned at the left edge and it is around this edge that I want my rotation. I'm unsure if this placement in SpaceClaim affects the rotation for axisymmetry. Could you clarify whether the rotation is centered around the left edge? Additionally, my model design is in the x-y plane but I do not know if there are additional restrictions, such as restricting it to positive values on both axes.

Thank you for your help!

Best regards,

Puhia

 

[Akshay Maniyar]

Hi Puhia,

Please check the below Ansys help link for more details on axisymmetry.

2.4. Finding Ways to Take Advantage of Symmetry (ansys.com)

For the convergence issue, please try below suggestions and see if it helps:

1. Try increasing the number of substeps
2. Try changing the contact formulation to program-controlled. 
3. Try using Non-linear adaptive remeshing for bone part(NLAD)

 

Thanks,

Akshay Maniyar