Controlling the sequence of bolt pre-loads (SOL 401)

You can control the sequence of bolt pre-loads by either:

• Dividing bolt pre-loads over multiple pre-load steps

• Sequencing bolt pre-loads

The total axial strain on a pre-loaded bolt includes the axial strain defined by the bolt pre-load, along with the strain resulting from any other loads you apply, including pre-loads on neighboring bolts. When multiple bolts connect two bodies, the sequence in which the bolts are tightened affects the total axial strain of each bolt.

Dividing bolt pre-loads over multiple pre-load steps

You can divide bolt pre-loads over multiple pre-load steps in the solution. Pre-load steps have an end time of 0. Or, if they are sequentially dependent on a previous step, they inherit their end time from the previous step. You can add multiple pre-load steps to Simcenter 3D Multiphysics solutions.

Sequencing bolt pre-loads

Within each pre-load step, you can control whether all bolt pre-loads are applied at once, or if they are sequenced. To use sequencing, in the Solution Step dialog box, in the Time Step Definition tab, select the Enable Bolt Sequencing check box. When you enable bolt sequencing, the bolt pre-loads are applied in the order they appear in the Loads container of the preload step. To change the order, right-click the Loads container and select Sequence Bolt Loads. The order can combine individual bolt pre-loads, bolt load sets, and folders containing bolt loads. The bolt pre-loads in a load set or folder are applied simultaneously.

Tightening or loosening bolts

You can increase or decrease the bolt forces by including the same bolt pre-load in multiple steps. In the Step Association Manager dialog box, you can apply a scale factor to change the bolt forces. For example, to completely remove a bolt at a later time step, you can apply a scale factor of 0.

Corresponding Nastran Syntax

Selecting Enable Bolt Sequencing check box corresponds to defining the BOLTSEQ bulk data entry in Nastran. Each bolt load set corresponds to the BOLTLD bulk data entry.

Incrementing a preload and requesting output

A constant time subcase has an end time which is the same as the start time for that subcase. All bolt preload subcases have a constant time.

In the Time Step Definition group, you can use the Number of Increments to increment the loads, temperatures, and contact offsets for a constant time subcase or a bolt preload sequence. Incrementing a load can help convergence.

In addition, for a preload subcase that includes a bolt sequence, you can define the Number of Increments for each sequence in a Bolt Load Set. The Number of Increments defined for a bolt sequence overrides the value defined in the Time Step Definition for the subcase.

By default, the software outputs results for the intermediate load increments defined by the Number of Increments. This also occurs for the incremental load steps in a bolt preload sequence. In the Time Step Definition group, you can select Solution Step End Time for the Output Flag to request output for only the end of the subcase or for all sequences.

Where do I find it?

Enable Bolt Sequencing option

Application	Pre/Post
Prerequisite	A Simulation file as the work part and the displayed partSimcenter Nastran or Simcenter 3D Multiphysics as the specified solverStructural or Coupled as the specified analysis typeSOL 401 Multi-Step Nonlinear (Simcenter Nastran) or Multi-Step Nonlinear (Multiphysics) as the specified solutionPreload as the specified step type
Location in dialog box	Solution Step dialog box→Time Step Definition→ Enable Bolt Sequencing

Sequence Bolt Loads command

Application	Pre/Post
Prerequisite	A Simulation file as the work part and the displayed partSimcenter Nastran or Simcenter 3D Multiphysics as the specified solverStructural or Coupled as the specified analysis typeSOL 401 Multi-Step Nonlinear (Simcenter Nastran) or Multi-Step Nonlinear (Multiphysics) as the specified solutionPreload as the specified step type
Simulation Navigator	Right-click the Loads container→Sequence Bolt Loads

Learn more

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SOL 401 Multi-Step Nonlinear workflow

SOL 402 Multi-Step Nonlinear Kinematics

SOL 402 Multi-Step Nonlinear Kinematics workflow

Modeling thermal strain

Controlling plasticity and creep effects

Element Add/Remove (SOL 401)

Simcenter Nastran SOL 401 Co-simulation with Simcenter STAR-CCM+

Complex modes analysis (SOL 402)

Displaying graphs in the Solution Monitor using the Report simulation object

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Controlling the sequence of bolt pre-loads (SOL 401), Simcenter 3D 2021.1 Series

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