Defining Point Fasteners

You can define a point fastener to join two or more bodies with discrete connections at one or more points.

This task describes how to create the following types of point fasteners:

  • Fasteners modeled by beam or solid elements or modeled by connector elements.
  • Assembled fasteners that define complex fasteners with options for shear, pre-tension, and tension drill-through.

This task shows you how to:

See Also
About Point Fasteners
Detecting Point Fastener Locations and Applying Point Fasteners
Connections Section
Connection Manager
About Engineering Connections in Simulations
Defining Assembled Fasteners
In Other Guides
Creating Simulation Features
Support Selection
Entering Tabular Data
Material Behaviors

Create the Fastener

  1. From the Connections section of the action bar, click Point Fastener .
  2. From the Location options, select one of the following:
    OptionDescription
    Create default engineering connection Automatically creates a free engineering connection or selects the existing engineering connection if there is only one.
    Select existing engineering connection Allows you to pick an existing engineering connection from a list.
    Create in current FEM Creates the connection definition in the current finite element model.

    Note: If you select an existing connection, you must choose a support from the part instances used when the engineering connection was created.

  3. Optional: Enter a descriptive Name.
  4. Select the geometric or mesh Parts to fasten.

    Tip: You can click to clip the selection area to show only the smallest part, which can make it easier to pick the more detailed Fastener placement geometry you need. After you activate the clipping box, you can click to drag the box edges to resize it.

  5. Optional: To load fastener properties from a saved template file:
    1. Click .
      The Object Selection dialog box appears.
    2. Select one of the following options:

      • Search the available templates stored in the database, and select the template.
      • Click Import a file to import a file stored on your computer, and click the check mark in the object selection prompt that appears after the document has been imported.

    The parameters are applied to the current fastener definition.
  6. Optional: Click to save the parameters of the current fastener to a reusable template document, and specify a name for the document. For more information, see Template Files.
  7. Select the fastener Material.
  8. Enter the Fastener diameter; for example, the diameter of a bolt or rivet.

    The fastener diameter defines the radial influence distance from the center point of the fastener on each of the connected surfaces. If any portion of a mesh element lies within the radius, the fastener connects all nodes.

    Note: The fastener diameter is required only for Solid hex fasteners. If you enter a diameter for other construct types, this diameter is used to calculate the default influence radius. You can also specify the influence radius directly in the Realization options, as described below.

Define the Fastener Placement

  1. Specify the Fastener placement:
    OptionDescription:
    Select points

    Uses points or vertices to define the fastener locations. The selected points must be within reasonable proximity of the fastener placement—along or between the bodies connected the fastener. The app projects the positioning points onto the target surfaces along the surface normal vectors.

    Warning: There are no restrictions on the points that you can select to create the fastener. However, if you select an inappropriate point, the connection is likely to fail during or before simulation.
    Along lines

    Uses a line or edge to define the fastener placement. For example, you can use this method to distribute a number of spot welds along a line. The app distributes the fastener locations at equally spaced intervals along the placement line.

    Specify coordinates Uses X-, Y-, and Z-coordinates, which you enter directly or import, to locate the fasteners. For more information, see Specifying Coordinates for Point Fasteners.
    Flanges Determines the median axis of a face or set of faces that you pick and distributes the fastener locations at equally spaced intervals along this axis.

    You can also select a geometric set containing points and curves to define the fastener placement.

  2. If you selected to define the fasteners Along lines or with Flanges, do the following:
    1. Specify the Clearance, which is the spacing between the group of fasteners and either end of the line (or the inferred line for the Flanges method).

      The first and last fasteners are located at this distance from each end.

    2. Specify the Distribution method, which determines how the app locates the fasteners along the line. You can specify either the Number of fasteners or the Fastener spacing (distance between consecutive fasteners). For example, if you specify a 80 mm line, a clearance of 10 mm, and a distance between fasteners of 10 mm, the app creates seven fasteners.




      		Placement line


      		Clearance


      		Spacing

Define the Fastener Construct

  1. Specify the fastener Construct type.
    OptionDescription
    Rigid Defines the fastener as a rigid beam connector.
    Coupling Defines the fastener as fully rigid.

    This construct is similar to Rigid but uses only two couplings and no connector section. The couplings are joined at a common reference point.
    Spring Defines the fastener as a connector element with elastic behavior.
    Solid hex Defines the fastener using a 3D hexahedral element.

    By default, the app calculates the Cross section area based on the fastener diameter. However, you can specify a different value.

    The fastener uses C3D8 elements regardless of the global element types for the model.
    Beam Defines the fastener using 1D beam elements.

    Specify the Orientation geometry and Shape. For more information see, Defining Beam Sections and Defining Beam Profiles, respectively.

    The fastener uses B31 elements regardless of the global element types for the model.
    Assembled Defines a complex fastener with options for shear, pre-tension, and tension drill-through. For more information, see Defining Assembled Fasteners and About Assembled Fasteners.
  2. For Rigid and Spring constructs, specify the Axis system definition:
    OptionDescription
    Global Uses the global axis system.
    Implicit Aligns the fastener with respect to the normal projection of the point supports.
    Local Uses an axis system selected by the user. Local axis systems are defined by a displacement or rotation from the global system and can move with a portion of the model during deformation.
  3. If you are using the Spring construct, select the Spring type:
    OptionDescription
    Linear Axial Allows motion along the spring axis, with linear elastic behavior.
    Linear General Allows general motion, with linear elastic behavior.
    Nonlinear Axial Allows motion along the spring axis, with nonlinear elastic behavior.
    Nonlinear General Allows general motion, with nonlinear elastic behavior.

    The app applies axial connectors for axial spring definitions and bushing connectors for general spring definitions. For more information, see About Connectors.

  4. If you are using the Spring construct, do one of the following to define the spring behavior:
    • Define the Elasticity and Ref. Length parameters for the available motion components.
    • Select the Enable advanced behaviors option, and then click to define the elasticity using the Behaviors editor. With this option, you can define additional connection behaviors. For more information, see Connection Properties.

Specify the Realization Options

  1. From the Coupling type options, select one of the following:
    OptionDescription
    Kinematic Couples edge or face supports directly to the motion of a reference point.
    Continuum distributing Couples the displacement and rotation of the fastening points to the average displacement of the nodes.
    Structural distributing Couples the displacement and rotation of the fastening points to the average displacement and rotation of the nodes.
  2. If you are defining a distributing coupling, from the Weighting method options, select one of the following:
    OptionDescription
    Uniform Maintains an equal weight factor on all nodes within the influence radius.
    Linear Decreases the weight factor linearly with the distance from the fastening point.
    Quadratic Decreases the weight factor by a quadratic polynomial function of the distance from the fastening point.
    Cubic Decreases the weight factor by a cubic polynomial monotonic function of the distance from the fastening point.
    Tied Weights each node based on the shape of the mesh element face that contains the projected location.

  3. From the Coupled faces options, select one of the following:
    OptionDescription
    Nearest Limits the coupling to the nodes in the element containing the projected location.
    Within the radius Includes elements within the specified radius surrounding the projected location. The default is half the fastener diameter. This option is not available with the Tied weighting method.

    This option determines which element faces to include in the coupling. The coupling uses all nodes in the included element faces.

  4. Enter the value for Maximum projection distance, which is the maximum gap (distance) between the bodies bridged by a fastener.

    The fastener is not created at a point if the bodies are farther apart than this value.

  5. Enter the value for Maximum angle, which is the limit for the angle of inclination between the two surfaces being fastened.

    The fastener is not created at a point if the angle of inclination at that point exceeds this value.

  6. Enter the value for Maximum angle between adjacent faces, which is the limit for the angle between the normals of adjacent faces.

    The fastener is not created at a point if the normals exceed this angle.

  7. Enter the value for Adjust tolerance, which allows the simulation to move the center of the fastener by a specified distance when projecting the positioning point onto the connected surface.

    Adding a small tolerance can help avoid problems when the fastener point is very close to a hole in the surface (for example, on a flange) or even inside the hole. With the default tolerance of zero in this case, the projection of the positioning point might fail. Increasing the tolerance value allows the simulation to move the center of the fastener slightly so that the point projection avoids the hole.

  8. Optional: Click Update Mesh to see the mesh created for the point fastener.
  9. Click OK.