Bolt Pretension
Use the Bolt Pretension 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 Bolt Pretension node, a default Bolt Selection subnode is also automatically added. Use one such node to select each individual bolt.
The Bolt Pretension node is only available with some COMSOL products (see www.comsol.com/products/specifications/).
Bolt Label
Enter a name that will form the basis for the automatic generation of bolt labels when Bolt Selection 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.
Bolt Pretension
Select how to describe the pretension by selecting a Pretension type — Pretension force, Pretension stress, or Tightening torque.
•
For Pretension force enter a value or an expression for Fp, the pretension force in the bolt.
To compute the corresponding tightening torque, select the Compute tightening torque checkbox. Then, enter data as described below.
•
For Pretension stress enter a value or an 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 Compute tightening torque checkbox. Then, enter data as described below.
•
For Tightening torque, enter the following data:
-
The tightening torque, MT.
-
The Nominal bolt diameter. The default is From geometry, in which case the bolt diameters are derived from the cross section selections in the Bolt Selection subnodes. To use another value, select User defined, and enter the bolt diameter, d.
-
The Bolt hole diameter. The default is Automatic, in which case the bolt hole diameter is set to 1.1 times the nominal bolt diameter. To use anther value, select User defined, and enter the bolt hole diameter, dh.
-
The Bolt thread mean diameter. The default is Automatic, in which case the bolt thread mean diameter is set to 0.9 times the nominal bolt diameter. To use another value, select User defined, and enter the thread mean diameter, dt.
-
The Bolt head type — Circular or Hexagonal.
For a circular bolt head, enter the Bolt head diameter. The default is Automatic, in which case the bolt head diameter is set to 1.6 times the nominal bolt diameter. To use another value, select User defined, and enter the bolt head diameter, do.
For a hexagonal bolt head, enter the Bolt head width. The default is Automatic, in which case the bolt head width is set to 1.6 times the nominal bolt diameter. To use another value, select User defined, and enter the bolt head width, H.
-
The Half thread angle, α. The default is 30[deg], which is used in for example the ISO and UTS standards.
-
The Lead, l.
-
The Bolt head friction coefficient, 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 Bolt thread friction coefficient, μt. This is the friction coefficient between inner and outer thread. The default is 0.15.
See also
•
Modeling Pretensioned Bolts in the Structural Mechanics Modeling chapter for a complete description of how to model pretensioned bolts.
•
Bolt Modeling Theory.
•
Bolt Pretension Study for information about the Bolt Pretension study type.
Modeling of Pretensioned Bolts: Application Library path Structural_Mechanics_Module/Tutorials/bolt_pretension_tutorial
Location in User Interface
Context Menus
Solid Mechanics > Bolt Pretension
Solid Mechanics, Explicit Dynamics > Bolt Pretension
Beam > Bolt Pretension
Ribbon
Physics tab with Solid Mechanics; Solid Mechanics, Explicit Dynamics; or Beam selected in the Model Builder tree:
Global > Bolt Pretension