2 Replies Latest reply on Apr 30, 2018 12:03 PM by Ryan Dark

    Bonded v Allow Pen in Linear Dynamic Study?

    James Galliers

      Hi All,

       

      I was wondering if anybody could share some light into my query. I am running a random vibration analysis within an assembly. I have bolted joints which conventionally should be configured using "No Pen" local contact conditions. However the Radom study supports "Bonded" or "Allow Pen" local contact conditions only.

       

      I have the luxury of modelling a configuration that has failed real life MIL STD shaker testing and am getting comparable results with the actual failure using "bonded" local contact sets. The area that failed is an Aluminium 5251 Sheet metal component and the sim is showing approx. 93MPa of stress which exceeds the material endurance limit for fatigue.(3 hour vehicle mounted longitudinal profile).  When running the same study using "Allow Pen" my values for stress drop down to a negligible amount which I know is wrong!.

       

      My current situation is that I have replaced this component with a turned Aluminium 6082 T6 version and therefore removed unwanted stress concentrations, however I need to check to see if this stiffer/stronger part has translated the energy back down into another area of my assembly. I am comparing stress and displacement values in another known failure area but I could do with a bit more guidance on the correct use of contact sets for this Dynamic study.

       

      My question is

       

      1. What difference does applying a local bonded contact condition have over keeping with just the default global bonding?

       

      Also has anybody done any work on using Miners rule for Random Vibration Analysis. I have only used this for sine profile frequency stuff in the past.

       

      Many Thanks

       

      James

        • Re: Bonded v Allow Pen in Linear Dynamic Study?
          Jon Dahlgren

          It's generally no difference if you apply global or local bonded contacts.

           

          Global bonded connection will bond all surfaces in "contact". Local bonded connection will let you override the global (and component) connections and also let you select line & point selections.

          • Re: Bonded v Allow Pen in Linear Dynamic Study?
            Ryan Dark

            Hi James,

            Like Jon Dahlgren says, the definition of both a global and local bonded contact does not differ in behavior when placed between the same faces.  It is likely that your bonded version of your model is the accurate representation of the overall design.  When a bolted connection is made the objects behave as one.  Their vibrational modes of a bolted connection (with preload) and a bonded connection should be very similar.

             

            Now, if you are just using this connection as a force transmitter to the rest of the model to see if somewhere else fails you would absolutely want to bond this connection and see if other failures appear.