Virtual Thread Contact dialog box

Use this dialog box to define the bolt casing and bolt cylinder contact pair, thread, orientation, and contact parameters necessary to model bolt threading with a Virtual Thread Contact simulation object.

Type	Specifies the method for creating the contacting surfaces on the bolt hole and bolt cylinder.ManualLets you create the bolt face pairs manually by selecting the bolt casing and the bolt cylinder.Automatic PairingLets the software create the face pairs. The software uses the same process to pair the faces as it uses for contact and glue simulation objects, so the face pairing is not limited to cylindrical faces. Therefore, check the pairing to ensure that only the bolt casing hole and bolt cylinder faces are paired.
Name
Name	Sets the name of the virtual thread contact simulation object.
Destination Folder
Simulation Object Container	Specifies the folder in the Simulation Navigator in which the boundary condition is stored. The list includes the root container and existing folders that you created using the New Folder command. Examples of a root container include Load Container, Constraint Container, and Simulation Object Container.
Folder Manager	Displays a hierarchical list of existing folders. To create a new folder, right-click any level of the hierarchy and choose New Folder.
Automatic Face Pair Creation
Face Pairs	Appears when Type is set to Automatic Pairing.Opens the Create Automatic Face Pairs dialog box, where you can select the bolt casing and cylinder and set other options to determine how the surfaces are identified. Note: After the face pair is created, ensure that the outer and inner surfaces are correctly identified.The outer surface is the inner face of the bolt casing (hole).The inner surface is the outer face of the bolt cylinder.
Outer Surface
Outer Surface	Appears when the face pair creation method is set to Manual.Lets you select the face of the bolt casing.
Inner Surface
Inner Surface	Appears when the face pair creation method is set to Manual.Lets you select the face of the bolt cylinder.
Swap Regions
	Appears when the face pair creation method is set to Manual.Reverses the contacting surfaces.
Thread Definition
Thread Shape	Specifies how the thread should be modeled, which determines how the software computes the contact normals.Single-Sided ContactModels the thread using only a defined angle. The contact normals are all in the same direction, but you can represent the bolt in tension or compression depending on the order in which you select the nodes or points to define the bolt orientation.(1) bottom and (2) top nodes selected to represent the bolt in tension(1) top and (2) bottom nodes selected in reverse to represent the bolt in compression****Double-Sided ContactModels the thread using a defined angle and pitch. The contact normals alternate for the top and bottom of the thread.(1) bottom node; (2) top node; (3) alternating normalsFor more information, see the THDOPT parameter on the BVTPAR bulk entry in the Simcenter Nastran Quick Reference Guide.	(1) bottom and (2) top nodes selected to represent the bolt in tension	(1) top and (2) bottom nodes selected in reverse to represent the bolt in compression
(1) bottom and (2) top nodes selected to represent the bolt in tension	(1) top and (2) bottom nodes selected in reverse to represent the bolt in compression
Half-thread Angle	Sets the half-thread angle (α), as shown below.
Pitch	Appears when Thread Shape is set to Double-Sided Contact.Sets the pitch (P), as shown below. The pitch is the thread-to-thread distance.
Bolt Axis
Selecting the correct bottom and top nodes or points is critical in determining the vector of the bolt. The first node or point must be at the bottom, and the second node or point must be closer to the head of the bolt.Be sure to select the nodes or points in the correct order. If you select the nodes in reverse, that is, if you select the node for the top face first and then the bottom, you need to change the sign of the thread angle unless you set Thread Shape to Single-Sided Contact and want to represent the bolt in tension or compression. To represent the bolt in tension or compression, see the description for Thread Shape above.Be sure to select the nodes or points at the center of the face (on the axis of symmetry) for both the top and bottom bolt faces. Selecting the center node or point ensures that the bolt is correctly aligned.
Bottom	Specifies whether you are identifying the center of the bottom bolt face by a node or point.Note: If you are modeling large displacements, you must first create an RBE2 or RBE3 element on the bottom face of the bolt as explained in Bolt orientation in Modeling bolt threads (SOL 402).To model large displacements or rotations, select Node, and then select the center node of the RBE2 or RBE3 element.You can use this same method to model small displacements or rotations.To model only small displacements or rotations, you can select Node, or you can select Point and set the coordinates for each point.
Bottom Point	Appears when Bottom is set to Point.Lets you create or select a point on the bottom face of the bolt. The point must be located in the center of the bolt face.
Select Bottom Node	Appears when Bottom is set to Node.Lets you select an existing node on the bottom face of the bolt. The node must be located in the center of the bolt face, on the axis of symmetry. If you created an RBE2 or RBE3 element for modeling large displacements or rotations, select the center node of the element.If you are modeling small displacements or rotations and a node does not exist at the center of the bolt face, you can create a point instead, or you can close the dialog box, create a node at the center of the bottom bolt face, and then define the Virtual Contact Thread simulation object.
Top	Specifies whether you are identifying the center of the top of the bolt by a node or point.
Top Point	Appears when Top is set to Point.Lets you create or select a point at the center of the top face of the bolt.
Select Top Node	Appears when Top is set to Node.Lets you select an existing node at the center of the top face of the bolt. The node must be located in the center of the bolt face, on the axis of symmetry. If it is not, you can create a point instead, or you can close the dialog box, create a node at the center of the top bolt face, and then define the Virtual Contact Thread simulation object.
Contact Parameters
Coefficient of Static Friction	Sets the static coefficient of friction for the virtual thread contact. The direction of the frictional force is parallel with the thread. When contact is detected, the software uses this value to calculate any tangential contact forces by multiplying the normal contact force by the value you specify.You can override this value in the Virtual Thread Parameters modeling object (Virtual Thread Parameters dialog box, Tangential Behavior page).
Contact Parameters	Specifies the Virtual Thread Parameters modeling object whose contact parameters you want to apply to this bolt.Select an existing modeling object from the list or click Create Modeling Object to create a new one.Click Edit to edit the selected modeling object.

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Modeling bolt threads (SOL 402)

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Virtual Thread Contact dialog box, Simcenter 3D 2021.1 Series

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