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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
    Where that 9kN goes depends on the relative stiffness of the bar to the plate (aka the load path). (Remember, the R in RBE == Rigid, so there is no flexibility in this connection. The center and edges move together.) The bar/bolt carried 1620N, the remaining 7380N went into the spider, then to the solid elements, and was eventually reacted at constraints. Without seeing the geometry and other loads, it's hard to comment on the load path. I suspect you have a lot more load of the 9kN load going into the plate than you realize.
    To diagnose, request MPC Forces, or Grid Point Balance Table if you want to visualize the load path in Patran (with the Freebody tool).
    Also, if you want to correctly model a preload, your need more than 1 CBAR to do it. You need at least 2 CBARs plus the BOLT entity. Input the preload force, then lock the bolt to hold. (You can still use RBE2 or 3 for the spider.)
     
    The rigidity of the RBE2 spider is the reason some prefer to use RBE3 to model this type of connection (it has flexibility).
     
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  • 0
    Where that 9kN goes depends on the relative stiffness of the bar to the plate (aka the load path). (Remember, the R in RBE == Rigid, so there is no flexibility in this connection. The center and edges move together.) The bar/bolt carried 1620N, the remaining 7380N went into the spider, then to the solid elements, and was eventually reacted at constraints. Without seeing the geometry and other loads, it's hard to comment on the load path. I suspect you have a lot more load of the 9kN load going into the plate than you realize.
    To diagnose, request MPC Forces, or Grid Point Balance Table if you want to visualize the load path in Patran (with the Freebody tool).
    Also, if you want to correctly model a preload, your need more than 1 CBAR to do it. You need at least 2 CBARs plus the BOLT entity. Input the preload force, then lock the bolt to hold. (You can still use RBE2 or 3 for the spider.)
     
    The rigidity of the RBE2 spider is the reason some prefer to use RBE3 to model this type of connection (it has flexibility).
     
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