2 Replies Latest reply on Jun 8, 2008 4:00 AM by Anthony Botting

    Help with Connectors/Forces

    Mike Hissong
    Mike Hissong Jun 5, 2008 2:44 PM
      Trying to do a COSMOSWorks analysis of this 3-piece assembly. Actual assembly is connected with pins at both ends to upright components - I'm using Fixed restraints on the larger thru holes at both ends. Would Immovable restraints be more appropriate?

      Second image shows how I am applying Pin Connectors and Force.
      Do I need to put Pin connectors on both ends of each of 4 thru holes, or is one side adequate for each?
      Whole assembly needs to support a certain amount of weight. Is it OK to apply force just to middle component as shown or should I also select top faces of the 2 main parts?
      Let's say I want to test assy @ 100 lbs - if I choose all 3 components COSMOS input box says I'm applying 100 lbs "Per Entity" - does this make force 300 lbs?

      I'll probably have more questions, but let's start here. Thanks.
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        • Help with Connectors/Forces
          Basil Gello
          Basil Gello Jun 6, 2008 4:43 PM (in response to Mike Hissong)
          Mike,

          I will try answering your questions in the order you are asking them:

          1. Actually, you need the straight pin through a pair of holes. If you can not do that, use 4 pins - all holes attached in reality should be attached in model too.

          2. Load of 100 lbs per entity * 3 entities = exactly 300 lbs.

          Regards,Basil
          • Help with Connectors/Forces
            Anthony Botting
            Anthony Botting Jun 8, 2008 4:00 AM (in response to Mike Hissong)
            I agree with Basil. Regards the first question about fixed or immovable - the question I believe you're asking is "Should the ends be allowed to pivot?". A "least-stiff", and perhaps conservative approach would be to allow the ends to pivot. You'll see the most deflection in the structure with the ends allowed to pivot. You can do that with a "Hinge" restraint. The question regarding "fixed" or "immovable" comes into play when you're using shell elements, and is a local phenomenon. For solid elements, "fixed" and "immovable" mean the same thing - nodes cannot move. For shell elements, the term "fixed" means all nodes are prevented translation AND rotation. The term "immovable" on a shell element means only translation is restrained, but nodes are allowed to rotate individually. This issue arises because solid element nodes only have three degrees of freedom - in translation. However, shell element nodes have six degrees of freedom. Each node on a shell element can rotate about three axes and translate along each axis. I hope this helps. Regards, Anthony Botting