ShapeBuilder

ShapeBuilder is a pre-processor to SectionBuilder. It enables the parametric definition of cross-sectional shapes that are used in mechanical and aerospace engineering. Two alternative definition approaches are available.

  1. The shape definition approach. In this approach, the configuration of the entire cross-section is parameterized. While various options might be available to modify details of the cross-sectional configuration and geometry slightly, its overall topology is prescribed. Simple shapes only can be defined with this approach.
  2. The component definition approach. In this approach, the cross-section is viewed as an assembly of interconnected components. This “building block” approach allows the definition of more complicated and realistic sections. Each component is of simple topology and geometry, but the assembly of a number of different components produces a realistic section.

1. The shape definition approach

A typical input to ShapeBuilder is of the following form, where the various entries depend on the specific shape being defined.

@SHAPE_BUILDER_ANALYSIS {
@SHAPE_BUILDER_NAME {ShbDefName} {
@SHAPE_GROUP {ShapeGroup}
@SHAPE_TYPE {ShapeType}
@OPTION_DEFINITION {o1, o2, ...}
@DIMENSIONS {
@DIMENSION_01 {d1}
...
}
@MATERIALS {
@MATERIAL_01 {Mat1}
...
}
@AIRFOIL_SHAPE_NAME {AirFoilName}
@NUMBER_OF_CONTROL_POINTS {Ncp}
@IS_DEFINED_IN_FRAME {FrameName}
@MESH_DENSITY {md}
@COMMENTS {CommentText}
}
}

NOTES

  • Parameters ShapeGroup and ShapeType define the type of shape to be defined. They can be chosen from the following options.
  • Shape Groups Shape Types Shape Types Shape Types Shape Types Shape Types
    SOLID Circular section Rectangular section Triangular section
    WALLED_OPEN C-Section I-Section L-Section T-Section Circular arc
    WALLED_CLOSED Rectangular box Double box Circular tube Tube with fins Flattened tube
    AIRFOIL No shear web One shear web IH-60 section High-lift device
    Table 1. ShapeBuilder cross-sectional shapes
  • For specific shape types, options are available. For instance, the top and bottom flanges of an I-section can be reinforced or not. The option flags, denoted o1, o2, etc., take values of 1 or 0, if a particular option is activated or not. If no options are available for this shape type, keyword @OPTION_DEFINITION should not appear.
  • The geometry of the shapes is parameterized and depends on a number of dimensions, d1, d2, ..., etc. These could represent the height of a web, the thickness of a reinforcement, or the inclination of a flange with respect to the horizontal.
  • The physical properties of the section must be defined as well. For homogeneous material, material properties can be defined and for heterogeneous, anisotropic materials, it is more convenient to define solid properties directly. A number of materials, Mat1, Mat2, .., etc., will be defined for the section.
  • Some of the cross-sections defined by ShapeBuilder are airfoil sections, such as those listed in the last line of table 1. The outer contour of these sections are defined based on aerodynamic considerations. The airfoil shape, AirSName, defines the shape of the aerodynamic contour precisely.
  • The definition of the geometry of the cross-section relies on the concept of NURBS curves. Ncp control points will be used for the definition of these NURBS curves. (Default: Ncp = 2,048)
  • Sectional shapes are defined in their own local coordinate system, which is assumed to coincide with the global coordinate system. If a fixed frame, FrameName, is specified, the local coordinate system coincides with this fixed frame.
  • The mesh density parameter, md, determines the level of mesh refinement. (Default: md = 4)
  • It is possible to attach comments to the definition of the object; these comments have no effect on its definition.

2. The component definition approach

The component approach involves the definition of two types of entities.

  1. A number of structural components such as wall or cores.
  2. A list of connections among these structural components.

2.1 Definition of the structural components

In the component definition approach, all the components that make up the complete cross-section must be defined first. Any number of components can be defined; the definition of each component is similar to that of a shape. A typical input to ShapeBuilder is of the following form.

@SHAPE_BUILDER_ANALYSIS {
@SHAPE_BUILDER_NAME {ComponentName1} {
@SHAPE_GROUP {COMPONENT}
@SHAPE_TYPE {ShapeType}
@OPTION_DEFINITION {o1, o2, ...}
@DIMENSIONS {
@DIMENSION_01 {d1}
...
}
@MATERIALS {
@MATERIAL_01 {Mat1}
...
}
@CURVE_NAME {CurveName}
@NUMBER_OF_CONTROL_POINTS {Ncp}
@IS_DEFINED_IN_FRAME {FrameName}
@MESH_DENSITY {md}
@COMMENTS {CommentText}
}
@SHAPE_BUILDER_NAME {ComponentName2} {
@SHAPE_GROUP {COMPONENT}
@SHAPE_TYPE {ShapeType}
...
}
@SHAPE_BUILDER_NAME {ComponentName3} {
@SHAPE_GROUP {COMPONENT}
@SHAPE_TYPE {ShapeType}
...
}
}
  • Parameters ShapeGroup and ShapeType define the type of component to be defined. They can be chosen from the following options.
  • Shape Groups Shape Types Shape Types Shape Types Shape Types
    COMPONENT Core Nose weight Spar Wall
    Table 2. ShapeBuilder structural components
  • The geometry is the components is defined by curve CurveName.
  • The interpretation of the remaining parameters is similar to that of the parameters associated with shapes, see above.

2.2 Definition of the connections

Once the components have been defined, the connections between these components must be established. A typical input to ShapeBuilder is of the following form.

@SHAPE_BUILDER_ANALYSIS {
@CONNECTION_NAME {ConnectionName1} {
@CONNECTION_TYPE {ConnectionType}
@COMPONENT_NAME {ComponentNameA}
@POINT_NAME {PointNameA1, PointNameA2}
@COMPONENT_NAME {ComponentNameB}
@POINT_NAME {PointNameB1, PointNameB2}
@COMMENTS {CommentText}
}
@SHAPE_BUILDER_NAME {ConnectionName2} {
@CONNECTION_TYPE {ConnectionType}
...
}
@SHAPE_BUILDER_NAME {ConnectionName3} {
@CONNECTION_TYPE {ConnectionType}
...
}
}
  • Connections are established along lines. The line joining points PointNameA1 and PointNameA2 of ComponentNameA is connected to the line joining points PointNameB1 and PointNameB2 of ComponentNameB. Points PointNameA1 and PointNameA2 must form an edge of ComponentNameA; points PointNameB1 and PointNameB2 must form an edge of ComponentNameB.
  • Connection Type Connection Type
    Adhesive Adhesive
    Table 3. ShapeBuilder connections