## ForceToStress Solver

### General Informations

• Solver Fortran File: `ForceToStress.f90`
• Solver Name: `ForceToStress`
• Required Output Variable(s): `Stress` (user defined)
• Required Input Variable(s): `Force`
• Optional Output Variable(s): None
• Optional Input Variable(s): None

### General Description

For a given boundary, this solver computes the nodal stress equivalent to a given nodal force. Force here means the result of a variable, named stress, which is of the same units than the force but per unit-area in 3D or unit-length in 2D. This can be used also to infer the flux from the value of a debit or to infer a tangential stress from the value of a tangential force.

### SIF contents

In the SIF example below, the normal stress on a boundary is inferred from the 3rd component of the Stokes residual.

```Solver 1
Equation = "Navier-Stokes"
Stabilization Method = String Stabilized
Flow Model = Stokes
...

Exported Variable 1 = Flow Solution Loads[Fx:1 Fy:1 Fz:1 CEQ Residual:1 ]
End

Solver 2
Equation = "ForceToStress"
Procedure = File "ElmerIceSolvers" "ForceToStress"
Variable = String "Stress"
Variable DOFs = 1

Force Variable Name = String "Fz"

Linear System Solver = Direct
Linear System Direct Method = umfpack
End

! Solve this for body Id 2 (=boundary 3 here)
Equation 2
Active Solvers(1) = 2
End

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Boundary Condition 3
Target Boundaries = 5
Body Id = 2
...
End```

### Examples

In the example found in `[ELMER_TRUNK]/elmerice/Tests/ForceToStress`, a pressure applied on a boundary is first integrated to get nodal force using the GetHydrostaticLoad Solver, and then the pressure is recovered using the `ForceToStress` Solver.

2 more tests were added on 15-12-2018:

[ELMER_TRUNK]/elmerice/Tests/ForceToStress_periodic: Test periodic conditions

[ELMER_TRUNK]/elmerice/Tests/ForceToStress_parallel: Test parallel solver 