Create Thread Pretension

Bolt Modeling > 3D Bolt > Thread Pretension

This tool is used to define thread pretension parameters of bolts in terms of bolt geometric data

Description

  1. Thread pretension can be defined for OptiStruct, Abaqus and Permas solvers.
  2. Pair identification tolerance is used to identify bolt-nut face pair.
  3. For OptiStruct and Abaqus, when thread pretension is created a contact is also created automatically between bolt-nut face pair.
    • OptiStruct and Abaqus thread pretension
  • The following parameters are common for both OptiStruct and Abaqus thread pretension,
    • Thread angle
    • Pitch
    • Bolt diameter
    • Mean diameter
    • Clearance
    • Bolt direction
  • For Abaqus thread pretension, "Surface interaction property" is to be defined.
  • For OptiStruct thread pretension, following parameters can be defined,
    • Search distance
    • Surface to surface
    • Friction coefficient
    • Separation
    • Gap Stiffness
  • For OptiStruct thread pretension when "Advanced Parameter" toggle is
    • OFF - "SLIDE" contact will be created.
    • ON - Contact will be created using advanced parameters. And the contact parameters will be written out in the deck using "contact property definition" (PCONT card).
  • Permas thread pretension

    • The following coupling types of thread pretension can be defined,
      • Surface to Surface node
      • Surface to node
      • Surface to Ground
    • The following parameters of Permas thread pretension are required,
      • Flank angle
      • Pitch
      • Pretension force
      • Pretension direction - Axis is required for Surface to Ground type only
      • Pretension direction based on PREDIR / SCREWDIR
    • For surface to surface node and surface to node coupling types a coordinate will be created automatically in the pretension direction. The Z axis of the coordinate will be the pretension direction. The pretension direction will point from the bolt head to the bolt bottom.
      • If there is an existing coordinate with Z axis in the pretension direction, then that coordinate can be used for pretension creation
      • This behaviour is controlled by the Preference > Analysis > "Create unique local coordinate system for each Permas thread pretension"
        • ON - It creates separate local coordinate for each Permas thread pretension
        • OFF - The thread pretension created will utilize the existing coordinate with the same Z axis orientation. If no coordinate is found then a new coordinate will be created, with Z axis pointing from bolt head to bolt bottom

Cards supported for various solvers

Solver Supported Cards
OptiStruct

CLRNC - {Thread angle, Pitch, Bolt major diameter, Bolt mean diameter, Clearance value, Bolt axis}

CONTACT -{Slide/PCONT}
Abaqus *CONTACT PAIR,INTERACTION={interaction name},ADJUST={value},SMALL SLIDING,TYPE=(SURFACE TO SURFACE/ NODE TO SURFACE)

*CLEARANCE,TABULAR,BOLT,MASTER = {master name},SLAVE = {slave name}
Permas $PRETENSION THREAD SURFACE TO SURFNODE/GROUND (SCREWDIR/PREDIR) = {Coordinate info/Vector} ALPHA = {value} PITCH = {value}

$PRETENSION LOAD LPAT=1 PREDIR = FORCE_LOCK