Linear & Non-Linear.

[Supituki]

Hi Everyone,

I am new to Elmer and even though I have read the guides available at the elmer pages, I couldn't understand how to really use them.

Now i am trying to analize a simple estructure both with a linear procedure and a non-linear one. The ElmerSolver starts without problems, but after 20 iterations it says that the system didn't converge for both of them. I am afraid that i am defining something wrong since the structure is not very complicated and the node number isn't extremely high. There is a very thin part but the mesh overthere is thick enough to get a rough solution at least.

The lines written at the .sif file are:

file 1: Linear Analysis

Code: Select all

Solver 1
Equation = Linear elasticity
Procedure = "ElasticSolve" "ElasticSolver"
Variable = -dofs 3 Displacement
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-8
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-8
Linear System Preconditioning = ILU0
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End

Equation 1
Name = "Equation 1"
Active Solvers(1) = 1
End

File2: Non-Linear

Code: Select all

Solver 1
Equation = Nonlinear elasticity
Procedure = "StressSolve" "StressSolver"
Variable = -dofs 3 Displacement
Exec Solver = Always
Stabilize = True
Bubbles = False
Lumped Mass Matrix = False
Optimize Bandwidth = True
Steady State Convergence Tolerance = 1.0e-5
Nonlinear System Convergence Tolerance = 1.0e-8
Nonlinear System Max Iterations = 20
Nonlinear System Newton After Iterations = 3
Nonlinear System Newton After Tolerance = 1.0e-3
Nonlinear System Relaxation Factor = 1
Linear System Solver = Iterative
Linear System Iterative Method = BiCGStab
Linear System Max Iterations = 500
Linear System Convergence Tolerance = 1.0e-8
Linear System Preconditioning = ILU0
Linear System ILUT Tolerance = 1.0e-3
Linear System Abort Not Converged = False
Linear System Residual Output = 1
Linear System Precondition Recompute = 1
End

Equation 1
Name = "Equation 1"
Active Solvers(1) = 1
End

Are the Linear and Non-Linear Parameters well defined? Are the Procedure variable and the Equation Variable correctly defined?
I got the lines from the tutorials and as the parameters suit me too, i left them unmodified.

Thanks in Advance

Supituki

[raback]

Hi

StressSolver is the linear one and ElasticSolver the nonlinear one. The first should converge immediately since there is no nonlinearity. The second one may be more difficult, you could try setting nonlinear relaxation to 0.5, for example.

-Peter