Nonlinear Elastic Integrator

[larsson4]

This PR adds a nonlinear elastic DG integrator to scaleupROM.

Tasks:

Stage 1: linear elastic integrators

• Declare classes for integrators except interface
• Implement (linear) integrators except interface
• Unit tests for integrators (Compare them to linear elasticity integrators)

Stage 2: Solver structure with linear elastic integrators

• Declare classes for solver (copy paste from linear elasticity)
• Implement solver structure (copy paste from linear elasticity)

• Write tests for the nonlinear solver (equality to linear solver) (didn't do this because too trivial)

Stage 3: Nonlinear Boundary, Domain and Dirichlet BC integrators

• Implement nonlinear domain integrator by copy paste from hyperelasticnlfintegrator
• Implement linear material model
• Test nonlinear domain integrator against linear integrator
• Implement nonlinear boundary integrator (merging DG and hyperelasticnlfintegrator)
  • Implemented the boundary version
  • Interface version
  • Add gradient calculation for both versions
• Test nonlinear boundary integrator against linear
  • Test for boundary version
  • For interface version
• Implement nonlinear Dirichlet BC integrator following linear example
• Test nonlinear Dirichlet BC integrator formulation
• Deal with Kappa term
• Test solver with linear material model against linear DG

Stage 4: Geometric nonlinearity

• Implement class following Linear Elastic model
• Eval P
• Derivative function

Stage 5: Interface integrator (maybe next step)

• Declare interface integrator class
• Implement interface integrator functions
• Unit test interface integrator against boundary integrator
• Test subdivided solver against MFEM implementation / non subdivided solver.

Future steps

• Implement moment boundary condition for linear elasticity and hyperelasticity
• Make tip moment example
• Add NIPG version
• Add HyperelasticDG tip moment example to MFEM