Abaqus user-defined elements let analysts implement custom element formulations through user subroutines rather than selecting a built-in element type.
How They Work
In Abaqus/Standard, user elements can be implemented through UEL; UELMAT can access Abaqus material behavior from inside the element. In Abaqus/Explicit, VUEL supplies the explicit user-element contribution. The user defines the element type key, active nodal degrees of freedom, number of nodes, coordinate requirements, properties, state variables, loads, mass behavior, and element contributions.
User-defined element output must generally be stored as solution-dependent state variables. User elements can use node-based surfaces in limited contact roles, but they do not behave like built-in elements in all contact and import workflows. Standard-to-Explicit or Explicit-to-Standard import does not transfer user-element state automatically.
Why It Matters
User-defined elements are the extension point for research formulations and specialized discretizations. They are powerful, but the analyst becomes responsible for element residuals, tangents or stable increments, state storage, loading, and numerical robustness.
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