Skip to content

Multi-Material Interface

While further details will be covered in upcoming publications and in the Theory Manual, the multi-material interface was originally developed to enable the treatment of multi-material bodies with perfectly bonded interfaces (i.e., no external patch separating different cellZones) in OFFBEAT.

This treatment is inspired by the original work of Tukovic et al. 1 (as well as of the implicit contact boundary condition developed by Scolaro et al. 2), extending their approach within the mesh and

It has been observed that the multiMaterialInterface correction also enhances accuracy in single-material domains, particularly in cases with significant temperature gradients, variable material properties, or additional strain components such as creep. Indeed, when force conservation is applied fully between adjacent cells with such non-uniformities, it results in the derivation of a different stress discretization (both for the implicit and explicit component) as well as of a different internal face displacement interpolation (thus a different gradient scheme). This correction is not activated by default, but it is recommended to activate it in most cases, if convergence permits.

In brief, without delving into the mathematical details, the multiMaterialCorrection, when used in a mechanicsSubSolver, employs custom gradient and Laplacian schemes that enforce full conservation at cell interfaces. Consequently, the schemes indicated in fvSchemes for the gradient and Laplacian for the displacement fields are disregarded in favor of this corrected approach.

The multiMaterialInterface correction is activated automatically when the multiMaterialCorrection dictionary is defined in the mechanicsOptions dictionary, which in turn is located within the solverDict. The type of multiMaterialInterface class must then be selected with the type keyword.

Classes

Warning

Although the reasons are not entirely understood, it has been found that applying the full multi-material correction for every internal face may negatively impact convergence. For this reason, the multiMaterialInterface classes uses a system of weights to allow for a partial use of the correction.

Currently, OFFBEAT supports the following mechanics solvers:

  • uniform - It applies the multi material correction uniformly in the mesh (good choice for standard fuel performance simulatoins where there are no multi-material bodies).
  • uniform2D - It applies the multi material correction uniformly in the mesh but only in the x-y plane (good choice for standard fuel performance simulatoins that are quite coarse along the axial direction where there are no multi-material bodies).
  • cellZone - The user can select defaultWeights for the correction on internal faces (within a cellZone) and a interfaceWeight for the interface faces, defined as the faces between two different cellZones.
  • faceSet - The user can select defaultWeights for the correction on internal faces (within a cellZone) and a interfaceWeight for the interface faces, defined using faceSet.
  • topoSet- The user can select defaultWeights for the correction to be applied to internal faces (within a cellZone) and a interfaceWeight for the interface faces, defined using topoSet.

  1. Ž. Tuković, A. Ivanković, and A. Karač. Finite-volume stress analysis in multi-material linear elastic body. International Journal for Numerical Methods in Engineering, 93(4):400–419, 2013. URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/nme.4390, arXiv:https://onlinelibrary.wiley.com/doi/pdf/10.1002/nme.4390, doi:https://doi.org/10.1002/nme.4390. ↩

  2. Alessandro Scolaro, Carlo Fiorina, Ivor Clifford, and Andreas Pautz. Development of a semi-implicit contact methodology for finite volume stress solvers. International Journal for Numerical Methods in Engineering, 123(2):309–338, 2022. URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/nme.6857, arXiv:https://onlinelibrary.wiley.com/doi/pdf/10.1002/nme.6857, doi:https://doi.org/10.1002/nme.6857. ↩