Midas FEA interface elements and nonlinearities model relative displacement and traction across points, lines, or surfaces, including cracks, bond-slip, friction, and masonry-like joint behavior.
How It Works
The element-library side describes point, line, and surface interface elements and their finite element formulation in terms of relative displacement. The material-library side then assigns nonlinear laws such as discrete crack behavior, crack dilatancy, bond-slip, Coulomb friction, and combined cracking-shearing-crushing.
The manual emphasizes that normal and tangential interface behavior can be coupled. Crack dilatancy and frictional flow can introduce off-diagonal stiffness terms or nonsymmetric tangent behavior, which matters for solver selection and convergence.
Solver Development Notes
Store interface orientation and relative displacement components carefully.
Treat interface elements separately from general contact: an interface element has predefined connectivity, while contact often needs search and active-set updates.
Expect non-associated friction or dilatancy to produce nonsymmetric stiffness and slower convergence.
Include element-level tests for normal opening, tangential slip, coupled dilation, and unloading/reloading.
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