Bolt pre-loads with Simcenter Nastran and Simcenter 3D Multiphysics

If you are working with the Simcenter Nastran or Simcenter 3D Multiphysics solvers, you can use the Bolt Pre-Load command to apply a pre-load to a bolt modeled with certain types of 1D, 2D, and 3D elements.

Key Simcenter Nastran bolt pre-load concepts

Simcenter Nastran uses:

• The BOLT bulk data entry to define the beam elements to include in the bolt pre-load analysis.

• The BOLTFORC bulk data entry to define the actual bolt pre-load value. (SOLs 101, 103, 105, 107 through 112, 401, and 402)

• The BOLTFOR bulk data entry to define the actual bolt pre-load value. (SOL 601)

Simcenter 3D Multiphysics uses:

• The BOLT bulk data entry to define the elements to include in the bolt pre-load analysis.

• The BOLTFRC bulk data entry to define the actual bolt pre-load value.

In Pre/Post, when you define a bolt pre-load in the Simcenter Nastran or Multiphysics environments, you can use the options on the Bolt Pre-Load dialog box to both select the elements on which to define the load and specify the value of the load itself. When you solve your model, the software creates the appropriate BOLT and BOLTFOR or BOLTFRC bulk data entries in your Simcenter Nastran input file.

Bolt pre-load for Simcenter Nastran SOLs 101, 103, 105, 107 through 112

In the Bolt Pre-Load dialog box:

• Use the Force or Displacement on 1D elements option to define a pre-load on a bolt that is modeled with CBAR or CBEAM type beam elements. You select one CBAR or CBEAM element to define the bolt, even if you modeled the bolt as several elements.

• Use the Force or Displacement on 3D Elements - Cut Plane option to define a pre-load on a bolt that is modeled with CHEXA, CPENTA, or CTETRA elements. You select nodes that form a cross section through the bolt, and define the bolt axis.

For more information on bolt pre-loads in Simcenter Nastran linear solutions, see Bolt Preload in the Simcenter Nastran User’s Guide.

Bolt pre-load for Simcenter Nastran (SOLs 401, 402) and Simcenter 3D Multiphysics

The Bolt Pre-Load command is available only if your active step is a Pre-load type of step.

In the Bolt Pre-Load dialog box:

• Use the Force or Displacement on 1D elements option to define a pre-load on a bolt that is modeled with CBAR or CBEAM type beam elements. You must select all elements that model the shaft of the bolt.

• Use the Force or Displacement on 3D Elements - Cut Plane option to define a pre-load on a bolt that is modeled with CHEXA, CPENTA, or CTETRA elements. You select nodes that form a cross section through the bolt. You can define the axial force applied by the bolt or the axial displacement of the bolt.

• Use the Force or Displacement on 2D Elements - Cut Plane option to define a pre-load on a bolt that is modeled with the plane stress elements CPLSTS3, CPLSTS4, CPLSTS6, or CPLSTS8. You select nodes that form a cross section through the bolt. You can define the axial force applied by the bolt or the axial displacement of the bolt.

For SOLs 401 and 402, the bolt displacement is incremental. For example, if the first bolt pre-load subcase is set to displace the bolt by 0.5 mm, and the second and third bolt pre-load subcases are set to displace the bolt by 0.25 mm, the relative displacements are as follows:

• 0.5 mm at the end of bolt pre-load subcase 1.

• 0.75 mm at the end of bolt pre-load subcase 2.

• 1.0 mm at the end of bolt pre-load subcase 3.

You can also intersperse bolt pre-load force and displacement subcases. The displacement pre-load is added to the displacement in the previous subcase. For example, a force preload can generate an initial displacement which is then incremented by a displacement pre-load in the next subcase.

For more information on bolt pre-loads in SOL 401 or Multiphysics, see Bolt preload (SOL 401) in the Simcenter Nastran Multi-Step Nonlinear User’s Guide. For more information on bolt pre-loads in SOL 402, see Bolt preload (SOL 402) in the Simcenter Nastran Multi-Step Nonlinear User’s Guide.

Bolt pre-load for Simcenter Nastran SOL 601

In the Bolt Pre-Load dialog box:

• Use the Force or Displacement on 1D elements option to define a pre-load on a bolt that is modeled with CBAR or CBEAM type beam elements. You must select all elements that model the shaft of the bolt.

• Use the Force on 3D elements option to define a pre-load on a bolt that is modeled with CHEXA, CPENTA, CTETRA, or CPYRAM elements. You must select all elements that model the shaft of the bolt. You select a point to define a cross section through the bolt, and define the bolt axis.

For more information on bolt pre-loads in Simcenter Nastran SOL 601, see the Advanced Nonlinear Theory and Modeling Guide.

Bolt pre-load sign conventions for Simcenter Nastran (SOLs 401, 402) and Simcenter 3D Multiphysics

Shear forces and bending moments are evaluated on the lower part of the bolt, at the cut surface, where the lower part of the bolt is identified with respect to the direction of the bolt axis. The bolt axis can be either a global or a local axis.

In the following figure, the bolt axis is along the Y-axis, and the lower part of the bolt (1) is the lower segment in both bolts. The applied force (in red) generates an internal shear force at the bolt cut that is negative, with respect to the X-axis, in the first bolt, and positive in the second bolt. With respect to the generated bending moment, the sign is the same for the two bolts, and it is negative with respect to the Z-axis.

Bolt axes are along the Y-axis, and (1) the lower part of the bolts is the lower segment

Rotating the frame around the X-axis by 180 degrees results in the bolts in the following figure. In this case, the lower part of the bolt (1) is the upper segment for both bolts. This results in a positive shear force for the bolt on the left, and a negative shear force for the bolt on the right. The bending moment is positive around the Z-axis for both bolts.

Bolt axes are rotated 180 degrees around the X-axis, and (1) the lower part of the bolts is the upper segment

How do I

Define a bolt pre-load for a bolt modeled with beam elements (Abaqus)

Define a bolt pre-load (ANSYS)

Learn more

Bolt pre-load

Pre-loaded bolts modeled with beam elements (Nastran)

Pre-loaded bolts modeled with solid elements (Nastran)

Bolt pre-loads with Abaqus

Constraining bolts to their pre-loaded lengths (Abaqus)

Pre-loaded bolts modeled with solid elements (Abaqus)

Pre-loaded bolts modeled with beam elements (Abaqus)

Bolt pre-loads with ANSYS

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Bolt pre-loads with Simcenter Nastran and Simcenter 3D Multiphysics, Simcenter 3D 2021.1 Series

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