Bolt Pretension

Use the node to define the prestress force in pretensioned bolts. It is available for 3D and 2D axial symmetry only. Typically, the prestressed state is established in an initial study step, which is then followed by one or more steps in which the service loads are added.

When you add a node, a default Bolt Selection subnode is also automatically added. Use one such node to select each individual bolt.

The node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).

Enter a name that will form the basis for the automatic generation of bolt labels when subnodes are added. The label is used for identification during postprocessing. The default name is Bolt.

	If the base name is changed, it only affects how bolt labels are generated in Bolt Selection subnodes that are added later on. You may then, in particular, want to manually edit the default Bolt Selection subnode.

If the base name is changed, it only affects how bolt labels are generated in subnodes that are added later on. You may then, in particular, want to manually edit the default subnode.

Select how to describe the pretension by selecting a — , , or .

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For enter a value or expression for Fp, the pretension force in the bolt.

To compute the corresponding tightening torque, select the check box. Then, enter data as described below.

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For enter a value or expression for σp, the pretension stress in the bolt. The pretension force is computed through multiplication by the actual area of each selected bolt.

To compute the corresponding tightening torque, select the check box. Then, enter data as described below.

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For , enter the following data:

The . The default is in which case the bolt diameters are derived from the cross section selections in the subnodes. To use another value, select , and enter the bolt diameter, d.

The . The default is , in which case the bolt hole diameter is set to 1.1 times the nominal bolt diameter. To use anther value, select , and enter the bolt hole diameter, dh.

The The default is , in which case the bolt thread mean diameter is set to 0.9 times the nominal bolt diameter. To use another value, select , and enter the thread mean diameter, dt.

The — or .

For a circular bolt head, enter the . The default is , in which case the bolt head diameter is set to 1.6 times the nominal bolt diameter. To use another value, select , and enter the bolt head diameter, do.

For a hexagonal bolt head, enter the . The default is , in which case the bolt head width is set to 1.6 times the nominal bolt diameter. To use another value, select , and enter the bolt head width, H.

The , α. The default is 30[deg], which is used in for example the ISO and UTS standards.

The μh. This is the friction coefficient between the bolt head and the material under it, including the effect of, for example, washers. The default is 0.15.

The μt. This is the friction coefficient between inner and outer thread. The default is 0.15.

See also

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Modeling Pretensioned Bolts in the Structural Mechanics Modeling chapter for a complete description of how to model pretensioned bolts.

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Bolt Modeling Theory.

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Bolt Pretension Study for information about the study type.

	Modeling of Pretensioned Bolts: Application Library path Structural_Mechanics_Module/Tutorials/bolt_pretension_tutorial

Modeling of Pretensioned Bolts: Application Library path

	This section is present only in models created in versions prior to 5.3, in which the new Bolt Pretension study type was introduced. The purpose is to maintain backward compatibility for older models. Select Solve in bolt pretension study only check box to make the bolt pretension degrees of freedom behave as in a version 5.3 model, that is being solved for only in a study step of the Bolt Pretension type. By default, the check box is cleared, and then the bolt pretension degrees of freedom are solved for in any type of study step, unless you explicitly suppress that. The settings of the Solve in bolt pretension study only check box only affects new study sequences being generated. Existing study sequences will keep the current state for the bolt pretension degrees of freedom. Once you select the Solve in bolt pretension study only check box, the Solver Suggestion section will be hidden. Thus, it is not possible to clear the check box again. The degrees of freedom created under this Bolt Pretension node from now on assumes the version 5.3 behavior.

This section is present only in models created in versions prior to 5.3, in which the new study type was introduced. The purpose is to maintain backward compatibility for older models.

Select check box to make the bolt pretension degrees of freedom behave as in a version 5.3 model, that is being solved for only in a study step of the type. By default, the check box is cleared, and then the bolt pretension degrees of freedom are solved for in any type of study step, unless you explicitly suppress that.

The settings of the check box only affects new study sequences being generated. Existing study sequences will keep the current state for the bolt pretension degrees of freedom.

Once you select the check box, the section will be hidden. Thus, it is not possible to clear the check box again. The degrees of freedom created under this node from now on assumes the version 5.3 behavior.

Physics tab with or selected in the Model Builder tree: