Applying pretension to bolted and screwed connections allows a more complete understanding of the behavior of a structure.

Often, these preloads are of a significant magnitude and can influence design decisions.

Typical examples are clamping structures, such as bearing housings or bicycle handlebars and seat-posts. In engines, cylinder bore distortion can be a critical design requirement highly influenced by the loads generated by the bolt down of the cylinder head.

Pretension can be enabled on a fastener or multiple fasteners by selecting them, enabling pretension in the Property Editor, and entering a pretension force. This pretension is then included as a load in all load cases.

Figure 1. Enabling and defining pretension in the Property Editor
A load case with no other external loads will apply the pretension loads only. When running any model that includes pretension, Inspire automatically creates and runs a load case with only pretension loads.

Figure 2. Results showing automatically generated load case: Subcase 1

Pretension Properties

Following is a list of pretension properties and the types of objects to which they apply (indicated in parentheses).

  • Press F3 to open the Property Editor.
  • Use Enable (fasteners)
    1. Select the checkbox to allow entry of a pretension force for fasteners.
  • Use Force (fasteners)
    1. Enter a magnitude for the pretension force.