COMSOL 6.2 - Bolt Selection

Bolt Selection

The subnode is automatically added as a default node to the Bolt Pretension node. It is used for selecting the individual bolts. One node is required for each bolt.

Boundary Selection


	This section is only present in the Solid Mechanics interface. From the Selection list, choose the boundaries to define a cross section of a single bolt. This cross section must be an interior boundary. It is the section where the stress in the bolt is measured. In 2D axial symmetry, the cross section must be perpendicular to the Z-axis.

Point Selection


	This section is only present in the Beam interface. From the Selection list, choose a point to define a cross section of a single bolt. This cross section must be an interior point. It is the section where the stress in the bolt is measured.

Bolt Label

Enter a . The default is automatically generated based on the name given in the section of the parent node. The label is used for identification during postprocessing.

The automatic name generation is also active when a node is duplicated or copy-pasted.

Bolt Pretension

Select a — , , , or . In most cases, the input for the pretension force is given in the parent node. If, however, you need to modify the settings for individual bolts, you can do it here.

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

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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.

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For , enter a value or expression for MT, the tightening torque. All other values needed for computing the bolt force from the torque are taken from the parent node.

If you want to include a of the bolt pretension, enter a value or expression for r. The relaxation is an axial displacement, which is subtracted from the predeformation of the bolt. This value can, for example, be time-dependent in the case of a creep relaxation of the bolt stress.

If you want to model a process where the bolt forces are not applied simultaneously, select the check box. When selected, a new input field, , is accessible.

The is a Boolean expression, giving the parameter values at which the prestress is changed. Such an expression could, for example, be par==5 || par==10 if the bolt is tightened in two steps. If the tightening process is done stepwise, you also need to use a which is not the default . The expression for the pretension force in each individual bolt can then vary with the continuation parameter, and should match the steps at which the pretension force is changed.

Symmetry Detection

If a bolt is cut by a symmetry plane, the force in the modeled part is only half of the force in the real bolt. When is selected, this is compensated for. The program will then automatically detect when a bolt is located in a symmetry plane, and apply corrections.

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If the input of the pretension load in the parent node is by , the given force is interpreted as the force for the whole bolt.

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All results are given for the whole bolt.

When is cleared, the inputs and outputs are based on the modeled cross section area.


	The Symmetry Detection section is not present in 2D axial symmetry, since the bolt in that case always is axially symmetric.


	The Symmetry Detection section is not present in the Beam interface, since it is not possible to automatically determine the geometrical shape of the bolt.


	See also Modeling Pretensioned Bolts in the Structural Mechanics Modeling chapter.


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

Location in User Interface

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