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Modeling of Bolts

ron.kunz
Dear all,
I have a big assembly and want to model bolts in the complete assembly. What is the best and accurate way to model this.
Cbar analysis is accurate enough to analyse the bolt forces. Boltstress is of secundair interest.
Are there examples for these bolts?
In addition bar orientation for this CBAR property, how can this best be modeled?
 
Thanks in advance
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  • 0
    You need 3 nodes to define the preload condition on the BOLT entity (or as an MPC). Review the figures on page 4 of the attachment (labeled pg 427) for the details. How you do this is up to you. You can split the beam into 2 elements with coincident nodes at the split. Or you can have coincident nodes at the end of one beam and the center of your RBE2 spider. Create a control node at a convenient location (coordinates don't matter) and use it when you create the BOLT between all 3 nodes. You apply the preload (as a force or displacement) to the Control Grid: GRIDC (the first one).
     
    To demonstrate the behavior, I created (and attached) a simple example w/ 4 four subcases:
    SC 1: Preload bolt only with a force
    SC 2: Preload bolt only with a SPC (determined from SC 1 displacement)
    SC 3: Pressure only (no bolt preload)
    SC 4: Pressure plus SPC preloaded bolt
    (My example doesn't have any contact bodies - just a preloaded bolt connected to a flat plate.)
     
    The Bolted Plates PDF example shows preload tension in the bolt creating compression on the plate faces. I always use contact bodies to model contact. There is no need for linear gaps. Model the assembly however you wish.
    Attached Files (1)
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  • 0
    You need 3 nodes to define the preload condition on the BOLT entity (or as an MPC). Review the figures on page 4 of the attachment (labeled pg 427) for the details. How you do this is up to you. You can split the beam into 2 elements with coincident nodes at the split. Or you can have coincident nodes at the end of one beam and the center of your RBE2 spider. Create a control node at a convenient location (coordinates don't matter) and use it when you create the BOLT between all 3 nodes. You apply the preload (as a force or displacement) to the Control Grid: GRIDC (the first one).
     
    To demonstrate the behavior, I created (and attached) a simple example w/ 4 four subcases:
    SC 1: Preload bolt only with a force
    SC 2: Preload bolt only with a SPC (determined from SC 1 displacement)
    SC 3: Pressure only (no bolt preload)
    SC 4: Pressure plus SPC preloaded bolt
    (My example doesn't have any contact bodies - just a preloaded bolt connected to a flat plate.)
     
    The Bolted Plates PDF example shows preload tension in the bolt creating compression on the plate faces. I always use contact bodies to model contact. There is no need for linear gaps. Model the assembly however you wish.
    Attached Files (1)
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