Bolt Thread Contact

Use the node to define a simplified model for the contact between two mating threads. The boundary between the internal and external thread is assumed to have a cylindrical shape. This feature is available for 3D and 2D axial symmetry only.

For each bolt, you have to add one Thread Boundary Selection subnode to select the contact pair describing each bolt and its matching thread. You can add such subnodes either from the context menu (right-click the parent node) or from the toolbar, menu.

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

Enter the , α. The default angle is 30[deg], which is used in for example the ISO and UTS standards. For 2D axial symmetry, this is the only input required to describe the bolt geometry. For 3D, you need also to provide the following settings:

Enter the , l. This is the axial distance a single thread travels after one full revolution of the bolt.

Select a — or . Most bolts are right- handed.

Select a — or . If the mesh on the boundaries selected for the contact between internal and external thread give a good representation of a cylinder, the diameter and centerline of the bolt can be determined automatically. If this is not sufficient, you can instead enter the data manually.

•

When using , the computed orientation of the beam axis, ea, is indeterminate with respect to its direction. If needed, you can control the direction by selecting the check box. Then, enter a vector giving an , ea,approx. The positive orientation of the bolt axis will be chosen so that

•

For , enter the bolt diameter, dp. Then enter the of the bolt axis, ea, and a , P.

Select a — , , or . In most cases, it is obvious that only one side of the thread will come into contact. It is then possible to decrease the size of the contact problem by considering only that direction. For a prestressed bolt, having the bolt axis orientation vector ea pointing toward the bolt head, it will usually be sufficient to check contact in the direction.

Enter a value or an expression for the , p. A smaller value will increase overclosure and sliding, but is in general more stable. The default value, (2*solid.btc1.Eequ)/solid.btc1.rd, is intended to supply a stiffness which gives a small elastic slip. This slip is related to the estimated bending stiffness of the threads.