2022.4+26187-e1209cf7 Apr 14, 2022

6 U-splines

U-splines are a novel spline technology developed by Coreform which seeks to alleviate, if not eliminate, many longstanding limitations in prevailing spline representations, providing a smooth spline meshing technology for industrial-scale FEA applications.

In particular, U-splines can be seen as a generalization of the key innovations underlying both analysis-suitable T-splines (ASTS) and Bézier extraction. Bézier extraction is a method for providing a local Bernstein representation of a non-local smooth spline function, and is used widely in isogeometric analysis (IGA).

With this release, U-splines are now implemented in Coreform Cubit™, making it the world’s first general-purpose isogemetric analysis mesh-preprocessor.

    6.1 U-splines

      6.1.1 Current Limitations

    6.2 Basic CAD to U-spline workflow

      6.2.1 Building U-spline surfaces

      6.2.2 Building U-spline volumes

        6.2.2.1 U-spline volumes require swept input meshes

        6.2.2.2 Source surfaces must be contiguous in many-to-one swept meshes

        6.2.2.3 Entities cannot be creased using build crease group

      6.2.3 Commands

        6.2.3.1 set uspline

        6.2.3.2 build uspline

        6.2.3.3 build uspline optimized

        6.2.3.4 fit uspline

        6.2.3.5 draw uspline

        6.2.3.6 draw uspline projection_error

        6.2.3.7 remove uspline

    6.3 Automatic creasing of U-splines

      6.3.1 Creasing of extraordinary vertices

      6.3.2 Continuity grading near creased vertices

      6.3.3 Maintaining distance between perpendicular continuity transitions

      6.3.4 Global creasing options

      6.3.5 Automatic minimal creasing example on a Cubit mesh

      6.3.6 Automatic full creasing on a Cubit mesh

      6.3.7 Automatic full creasing with user-specified creased edges

      6.3.8 Automatic minimial creasing with user-specified creased edges

      6.3.9 U-spline creasing commands

        6.3.9.1 build uspline crease group

    6.4 Display U-spline projection error in Cubit

    6.5 Save and load U-splines with Cubit file

      6.5.1 Saving considerations

      6.5.2 History and snapshots

    6.6 Exporting U-splines

      6.6.1 Export formats

      6.6.2 Special options for BEXT U-spline export

        6.6.2.1 Exporting block-partitioned BEXT U-splines

        6.6.2.2 Exporting U-splines with LS-DYNA node sets

        6.6.2.3 Exporting block-partitioned U-splines with node sets

        6.6.2.4 Specifying node offsets to prevent node ID collision