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346gnu13-Aquamarine
13-Aquamarine
June 13, 2012
Question

Creo Simulate Fasteners

  • June 13, 2012
  • 3 replies
  • 21173 views

Hello,

Can anyone share their experience of advanced fasteners in Creo Simulate, in particular when compared to an equivalent WF4/WF5 model?

Thanks


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    3 replies

    D
    danderson1-Visitor
    1-Visitor
    June 13, 2012

    I to would like some ensight related to the changes made in Creo Simulate version 1.0/2.0.
    My understanding that they made some changes to the internal software code related to how bolt preload is applied and how bolt tension is reported. Not sure if this is correct or not. My understanding is the issue of re-running the model to apply preload related to this document is no longer needed?
    http://www.ptc.com/cs/cs_26/howto/mst12163/mst12163.pdf

    Thanks,
    Don Anderson

    M
    MatsLindqvist1-Visitor
    1-Visitor
    June 18, 2012

    I prefer to model pre-loaded screws by using "hand-made" beam elements+links instead of the pre-defined fasteners. If I create them on my own, then there's no mystery as for how they work. Enter a material with zero coeff. of thermal expansion for the structure as a whole, and a large coeff. of therm. expansion for the screw. A -1 degree temp load will make the screw contract, and the structure will be pre-loaded. A -1 temp load, will cause an unloaded screw to contract with the same strain as the coeff. of thermal expansion. So you can make a rough hand calculation to get a ball-park figure for the pre-load, but for accurate pre-load, you will need two runs. Contact interface is needed between components obviously.

    /Mats Lindqvist/Econocap AB Sweden

    pre-load.jpg

      3
      346gnu13-AquamarineAuthor
      13-Aquamarine
      July 13, 2012

      Mats,

      I quite like what appears to be an ability to apply a temperature load to individual components (I have yet to play). The good old fashioned method you use required the whole model be shrunk/materials be applied with zero cte so only bolts shrink.

      My original question was regarding preloaded advanced fasteners and different answers between WF4 and Creo

      D
      DenisJaunin15-Moonstone
      15-Moonstone
      December 28, 2012

      Hello,
      Someone could still answer this question with details on the function of advanced assembly with two bolts on Creo Simulate.
      Possibly with a concrete example.
      With thanks.

      T
      TadDoxsee1-Visitor
      1-Visitor
      December 29, 2012

      Hi Dennis,

      We made several enhancement to the fastener functionality between Wildfire 5.0 and Creo 1.0. The most significant are:

      • In WF 5.0, the fastener was modeled internally as a spring, with axial and shear stiffness. In Creo 1.0, the fastener is modeled more accurately as a beam, with axial, shear, torsional and bending stiffness.
      • In WF 5.0, when "Fix Separation" was active, the separation between the two parts was maintained internally by a combination of springs and weighted links. In Creo 1.0, these are replaced by a distributed, surface-to-surface spring, which does a better job of modeling the real-life situation. (Note that using the Fix Separation option is a quick and easy approximation of the interface between the two parts. The most accurate method for modeling the interface is to create a true contact interface between the parts.)
      • Additional fastener measures were added in Creo 1.0, allowing you to more easily determine the forces that are transferred through your fasteners.
      • The user interface was enhanced in several ways. First, the automatic option was removed, making every control visible on the fastener definition dialog. Second, there is now a clear distinction between how fasteners are defined between parts modeled as solids versus parts modeled as shells. Finally, a single check-box specifies whether or not the interface between the parts is frictionless.

      In Creo 3.0 (but not in Creo 2.0, as suggested in some of the previous posts), it will be possible to model fastener pre-loads accurately with a single static analysis. (Creo Simulate runs the extra preliminary analysis automatically.)

      Tad Doxsee
      PTC R&D

      D
      DenisJaunin15-Moonstone
      15-Moonstone
      December 29, 2012

      Hello Lawrence,

      Thank you for the answer.

      When you want to connect two pieces together with a bolt, it works.

      Now when there are three pieces take them the simulation stops.

      In the examples, we always see a couple of pieces connected by a bolt but never three.

      It there a specific way to proceed when there are more than two pieces.

      Cordially.

      Denis

      D
      danderson1-Visitor
      1-Visitor
      January 2, 2013

      Denis,

      Have you added contacts between the plates along with 3 very light springs to ground?
      This should lock down the remaining degrees of freedom stabilizing the plates.
      Hope this helps,
      Don Anderson

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