Hope you help me find the mistakes I am making. I am trying to get the eigenmodes for a plate, my goal is to get it done with 'StressSolver', so as a benchmark, I've used the tutorial 4 : Eigenmodes of an elastic plate with SmitcSolver. I have attached the results of both solvers for eigenmodes 1 and 2, SmitcSolver results are the two plots on top while the two at the bottom come from StressSolver.

Here below is the Sif file with StressSolver I am getting troubles with:

Code: Select all

```
Simulation
Max Output Level = 5
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Simulation Type = Steady state
Steady State Max Iterations = 1
Output Intervals = 1
Timestepping Method = BDF
BDF Order = 1
! Solver Input File = case.sif
Post File = case_b.vtu
End
Body 1
Target Bodies(1) = 1
Name = "Body 1"
Equation = 1
Material = 1
End
Solver 1
Equation = Linear elasticity
Eigen System Values = 10
Procedure = "StressSolve" "StressSolver"
Variable = -dofs 3 Displacement
Eigen System Select = Smallest magnitude
Eigen Analysis = True
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-7
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 = Direct
Linear System Direct Method = Umfpack
End
Solver 2
Exec Solver = String "after timestep"
Equation = String "ResultOutput"
Procedure = File "ResultOutputSolve" "ResultOutputSolver"
Output File Name = "case2b"
Output Format = String "vtu"
End
Equation 1
Name = "Equation 1"
Active Solvers(2) = 1 2
Plane Stress = Logical True
End
Material 1
Name = "Ideal"
! Thickness = 0.001
Poisson ratio = 0.3
Tension = 0.0
Youngs modulus = 1e9
Density = 1000
End
Boundary Condition 1
Target Boundaries(5) = 1 2 3 4 5
Name = "fixed"
Displacement 3 = 0
Displacement 2 = 0
Displacement 1 = 0
End
```

Code: Select all

```
Simulation
Max Output Level = 5
Coordinate System = Cartesian
Coordinate Mapping(3) = 1 2 3
Simulation Type = Steady state
Steady State Max Iterations = 1
Output Intervals = 1
Timestepping Method = BDF
BDF Order = 1
Solver Input File = case.sif
Post File = case.vtu
End
Body 1
Target Bodies(1) = 1
Name = "Body 1"
Equation = 1
Material = 1
End
Solver 1
Equation = Elastic Plates
Eigen System Values = 10
Variable = -dofs 3 Deflection
Eigen System Select = Smallest magnitude
Procedure = "Smitc" "SmitcSolver"
Eigen Analysis = True
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-7
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 = Direct
Linear System Direct Method = Umfpack
End
Solver 2
Exec Solver = String "after timestep"
Equation = String "ResultOutput"
Procedure = File "ResultOutputSolve" "ResultOutputSolver"
Output File Name = "case2"
Output Format = String "vtu"
End
Equation 1
Name = "Plate Equation"
Active Solvers(2) = 1 2
End
Material 1
Name = "Ideal"
Thickness = 0.001
Poisson ratio = 0.3
Tension = 0.0
Youngs modulus = 1e9
Density = 1000
End
Boundary Condition 1
Target Boundaries(5) = 1 2 3 4 5
Name = "Fixed"
Deflection 1 = 0.0
Deflection 3 = 0.0
Deflection 2 = 0.0
End
```