Fastener Definition Dialog Box—Connecting Solids
Click
Refine Model >
Fastener to open the
Fastener Definition dialog box.
The Fastener Definition dialog box displays the following items:
• Name—Specify a fastener name or use the default name.
• Connecting Shells or Connecting Solids—If you select Connecting Solids to create a fastener between solids the Fastener Definition dialog box displays the following items:
|  If you select Connecting Solids and create a fastener between two shells or between a solid and a shell , the fastener is ignored during meshing and when you run an analysis on the model. |
• Fastener Type—You can create either a bolt or screw fastener.
◦ Bolt—Select circular edges of the holes on each of the components you want to join with a bolt fastener. The first edge selected is the head of the bolt. The second edge selected is the nut end of the bolt.
◦ Screw—Select circular edges of holes on each of the components you want to join with a screw fastener. As with bolts, the holes you select must meet the prerequisites given in the section
“Fastener Modeling Prerequisites”. The hole associated with the first selected edge is designated as the head of the screw. The second edge or curve selected represents the opposite end of the screw.
• References—Selects geometric entities for your fastener. You must select circular edges of holes on each component to be fastened. All your previously selected valid geometric references for the fastener appear in the References collector. You can also select the required geometry after the dialog box opens. The first selected edge is designated as the head of the fastener.
• Properties—Defines the following fastener properties:
◦ Stiffness—Fastener stiffness can be defined using one of the following options:
▪ Using diameter and material—Defines the fastener stiffness using the fastener diameter and material. The fastener is modeled as a beam in this case.
◦ Fastener Head and Nut Diameter—Defines the head and nut diameter for the fastener. You can specify a head and nut diameter for screws as well as bolts. If the fastener is a bolt, the value of diameter is the value specified for both the head and nut. For screws, there is no nut, so the value applies to the head only.
◦ Fix Separation—Prevents interpenetration between fastened components. You should ensure that the fastened components do not interpenetrate each other. The most accurate method to prevent interpenetration is to define a contact interface between the components. The other method, which is not as accurate but requires less computing resources, is to select the Fix Separation check box. The selection you make affects the mesh as using a contact interface takes more solver time.
◦ Frictionless Interface—This check box is active only when you select the Fix Separation check box. When Frictionless Interface is selected the distributed spring between the two components will have zero tangential stiffness. When you do not select Frictionless Interface the distributed spring between the two components has a very large value.
◦ Separation Test Diameter—Defines an area within which normal stresses are tracked during analysis. The value you specify determines a sampling area about the fastener. This area is an annulus with an inner diameter equal to the hole diameter and an outer diameter equal to the specified separation test diameter. These annular areas are located on the inner surfaces of the fastener components.
During an analysis, normal stresses are checked at sampling points in the annular area to ensure that the stresses remain compressive (that is less than zero). Stress values that are zero or greater than zero imply that there is no compression between the components and the components are separating. This condition is reported in the analysis summary.
◦ Include Preload—Defines a preload for the fastener. A preload simulates the degree to which a bolt or a screw is tightened and allows you to determine whether the fastener compresses the components. You can define the tensile preload that results from the torque you expect the fastener to be tightened to. With this information, component compression and fastener tension are calculated. This allows a more realistic distribution of stresses between the fastener and the fastened components.
◦ Preload Force—Defines the tensile force in the fastener that results from tightening the bolt or screw. You must specify a positive value for preload force. This box is visible only if you select the Include Preload check box.