First it helps to understand the difference between loadsteps and steps/substeps the solver takes in each loadstep:
https://www.padtinc.com/2011/11/08/you-dont-wanna-step-to-this-breaking-down-loadsteps-and-substeps-in-ansys-mechanical/
For nonlinear convergence,
See the below – you can search also for nonlinear convergence and quite a few posts will come up that should help.
Some resources that might help.
Some additional links from external sources:
Overcoming Convergence Difficulties in ANSYS Workbench Mechanical, Part I: Using Newton-Raphson Residual Information
Overcoming Convergence Difficulties in ANSYS Workbench Mechanical, Part II: Quick Usage of Mechanical APDL to Plot Distorted Elements
Nonlinear Convergence Tips
https://www.ansystips.com/2018/06/non-linear-convergence.html
1. Align nodes between contact and target if possible in the sliding direction (link)
2. Save Newton-Raphson Residuals & Identify Element Violation before analysis starts (link)
3. Use MPC for bonded contacts if needed (link).
4. Set small initial time steps. Here is my default setting for difficult problems:
The first step would thus be 1/100= 0.01s with a minimum time step of 1/1000= 0.001s. Apply this to all “Current Step Number” of interest.
5. Have similar size mesh at contacts. If not, Contact has finer mesh while Target is coarser.
6. Slice and dice geometry such that the volumes adjacent to contacts can be Hexahedron elements.
– Starting with pretty mesh by the contacts reduces the distortion during the analysis.
– Hexahedron elements are less distorted when capturing curved geometries (e.g. holes).
7. Drop Contact Normal Stiffness Factor (i.e. FKN) to 0.01. Watch out for excessive penetration.
8. Use Contact Tool to see if any contacts are open. Pinball radius may need tweaking.
9. Switch model to Displacement driven instead of Force driven for better stability.
10. Avoid over-constrained model whenever possible (e.g. symmetry and bonded contacts)
11. Move the body to be just in contact so that it doesn’t ‘fly’ a small distance before touching.
For metal plasticity:
https://www.youtube.com/watch?app=desktop&v=OZbKnxKTd_0
All the best
Erik
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