Bolt Contact with Clearance (Abaqus)

When you are working with Abaqus as your solver, you can use the Bolt Contact with Clearance command to define precise clearance or overclosure (initial penetration) values when you model contact between a single-threaded bolt and a bolt hole. With Bolt Contact with Clearance, the initial clearance or overclosure value you specify overwrites the initial clearance or overclosure value that the software calculates at each slave node.

Contact with clearance for threaded bolts

The Bolt Contact with Clearance dialog box includes additional Clearance Definition options that let you model the thread characteristics of a bolt even if detailed thread geometry is not included in the model. These options let you specify details about the bolt threads, including the half thread angle (α), pitch (p, or the thread-to-thread distance), and major (d) and mean (md) bolt diameters. You also use the Bolt Axis options to define two points (a and b) along the bolt's axis. The software uses these points to generate the bolt's contact normal direction.

p = pitch, or the thread-to-thread distanceα = half thread angled= major bolt diameterdm = mean bolt diametera and b = two points along the bolt's axis used to define its contact normal direction	Abaqus threaded bolt geometry

Clearance or overclosure value can be uniform or spatially varying

In the Bolt Contact with Clearance dialog box, you can use the Clearance Definition options to define the clearance or overclosure value as either uniform or spatially varying for the contact pair. From the Value list:

• If you select Expression, you can specify a uniform clearance or overclosure value for the contact pair. A positive value indicates a clearance value, and a negative value indicates an overclosure value.

• If you select Field, you can specify spatially varying clearances or overclosures. With this option, you use a table field to specify the clearance at a single node or set of nodes on the slave surface. In the table field, the node ID is the independent variable, while the clearance or overclosure value is the dependent variable. You can also specify a Scale Factor to apply to the field. For more information, see Fields.

Contact with clearance is supported only in small-sliding contact analyses

You can only use the Bolt Contact with Clearance command when you use the small-sliding contact formulation in your analysis. In Abaqus, you use the *CONTACT PAIR keyword to specify the contact formulation. In Pre/Post, you use a Contact Pair modeling object to specify the parameters for the *CONTACT PAIR keyword:

1. In the Contact Pair dialog box, select Small from the Sliding Type list to use the small-sliding formulation instead of the finite-sliding formulation.

2. In the Bolt Contact with Clearance dialog box, use the Contact Pair option to associate the Contact Pair modeling object with the simulation object.

Associated Abaqus keywords

When you export or solve your model, the software uses the options you specify in the Bolt Contact with Clearance dialog box to define the *CLEARANCE keyword with the BOLT parameter as well as the *CONTACT PAIR keyword in your Abaqus input file. For more information, see Adjusting Initial Surface Positions and Specifying Initial Clearances in Abaqus/Standard Contact Pairs in the Abaqus Analysis User's Guide and *CLEARANCE and *CONTACT PAIR in the Abaqus Keywords Reference Guide.

Where do I find it?

Choose Home tab→Loads and Conditions group→Bolt Contact with Clearance .

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