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Convergence Error in Parameter Sweep study

Posted Sep 12, 2022, 6:12 a.m. EDT General, Studies & Solvers, Structural Mechanics Version 6.0 2 Replies

Shyam Kishor
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Hi Everyone, In my model large plastic defromation of metel occurs I done it using auxillary sweep using large study steps (range(0,0.1,1)) and perform a parameteric study using parametric sweep.My answers are correct.

Now when I use more study steps (range(0,0.01,1)) it creats problems. It showing following errors-

Failed to find a solution for all parameters, even when using the minimum parameter step. No convergence, even when using the minimum damping factor. Returned solution is not converged. Not all parameter steps returned.

Why? Can someone help me in find out the reason behind this error, There is only one change of study steps in two model.

2 Replies Last Post Sep 15, 2022, 2:32 a.m. EDT
Temesgen Kindo
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Posted: 2 years ago Sep 13, 2022, 7:33 p.m. EDT

One possibility is your boundary conditions. If you have an input which oscillates for step sizes greater than 0.01 but less than 0.1 then taking the big steps may miss that oscillation giving you a false smooth input. Your solution converges. Then you take small steps and the fast variability in your input shows up, leading to difficulty diverging.

Similar effects can happen if your constitutive behavior has sharp changes. What is the hardening law you are using in plasticity? For the solution that converges, at what value of the parameter does yielding happen? Does your second solution diverge before that? That may help you diagnose if the constitutive behavior is the culprit.

One possibility is your boundary conditions. If you have an input which oscillates for step sizes greater than 0.01 but less than 0.1 then taking the big steps may miss that oscillation giving you a false smooth input. Your solution converges. Then you take small steps and the fast variability in your input shows up, leading to difficulty diverging. Similar effects can happen if your constitutive behavior has sharp changes. What is the hardening law you are using in plasticity? For the solution that converges, at what value of the parameter does yielding happen? Does your second solution diverge before that? That may help you diagnose if the constitutive behavior is the culprit.
Shyam Kishor
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Posted: 2 years ago Sep 15, 2022, 2:32 a.m. EDT

Thanks for your reply,

Actually in my simuation If I donot use parameter sweep ( do simulation for a set of parameters) then there is no problem on both conditions (0.01 and 0.1). but when I use parameter sweep then this error is occur. For hardening I use simple linear isotropic hardening by giving a tangent modulus. I am new on COMSOL so still working on the suggestions as you suggest. Thanks

Thanks for your reply, Actually in my simuation If I donot use parameter sweep ( do simulation for a set of parameters) then there is no problem on both conditions (0.01 and 0.1). but when I use parameter sweep then this error is occur. For hardening I use simple linear isotropic hardening by giving a tangent modulus. I am new on COMSOL so still working on the suggestions as you suggest. Thanks

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