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Harry_1-Visitor
1-Visitor
February 6, 2019
Question

Spring idealisation and contact interface

  • February 6, 2019
  • 1 reply
  • 4202 views
Hi Every one,
I am new to Creosim.
I am trying to simplify a connection using combination of spring idealisation and contact interface.
Two separate parts are assembled with these connections in parallel.
When the connection is under compression, we have contact and spring is compressed. When the connection is under tension the contact is released and there is no force for the spring.
1. I am not sure if is it possible to have contact between spring end and second part ? Ifound for the contact we need a surface, so do I need to define a surface between spring and second part or it is possible to have contact interface between a point and a body?

Because of number of conections I am looking for a quick and easy method. Only I am looking for the force at connection when it is under compression.

Any help is appreciated.

1 reply

S
SweetPeasHub17-Peridot
17-Peridot
February 6, 2019

A contact interface must be between surfaces.  I suggest a washer or disk part rigidly connected to the end of the idealized spring as representing the spring contact interface.  On the other hand since you say there are a number of these connections, maybe you can use non-linear spring definition instead because contacts will be much more difficult to run successfully.  I don't have time at the moment to mock up this type of model and prove what works but these are my initial suggestions.  I have not done any non-linear springs that I recall so I am not sure how to help that part be successful.  Use a low stiffness for extension lengths and normal spring stiffness for compression lengths.  You may need to keep the spring curve a smooth function near the break between T/C.  Hopefully someone in the community can enlighten on the possibility of using non-linear springs to model contact when you do not care about local contact areas/pressures.  Also keep in mind that point connections such as to a spring will generate very large stress so you may need to rigidize a small area right where the spring attaches or use weighted links to spread the load over a real area (the reason simply is a divide by zero problem.  Force/Area if A is zero = undefined/infinite stress)

good luck and welcome to the community!

 

    H
    Harry_1-VisitorAuthor
    1-Visitor
    February 7, 2019

    Thanks for your reply.

    I had already tested nonlinear spring. It is not an straight forward solution. I don't want to say it doesn't work but there is some difficulty with nonlinear spring which I havent been sorted it yet.

    When we define a nonlinear spring using a table in tension and compression region unfortunately it is not clear which number is deflection which one is force and which deflection positive or negative is related to compression mode of spring.

    I am trying to test its performance using some simple model. 

     

    H
    Harry_1-VisitorAuthor
    1-Visitor
    February 11, 2019

    I solved the problem with nonlinear spring. Now, there is another conflict between use of spring and shell idealization in single simulation. Creo has limitation.

    Is there any method to do an static analyses and after analyses to transfer displacement of a surface as input or boundary condition for the same surface in another analyses?

    I know for Ansys we have super element concept but I haven't found any thing similar in creo. 

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