Hinge modeling through springs

I am modeling a mechanism which has two types of hinge joints:

A. which connects a set of three beams (solid to each other) to another set of three beams (solid to each other). The joint should allow for 1 DoF (rotation around local x of the hinge)

B. which connects a set of beams (solid to each other) to another set of beams (solid to each other); these two sets are initially co-planar. The joint should allow for 1 DoF (rotation on the plane which initially includes the sets of beams). In this case, the other two rotation should be allowed with stiffness, say 10-20 times bigger than the rotation within the plane - set close to 0).

In the files attached the joints are modeled by springs between the sets of elements, which, however, seem to not transfer bending moment at their ends. I am also not entirely sure if this is the correct way to process or maybe another approach could perform better.

Thank you

Claudio

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Replies to This Discussion

Permalink Reply by yousef anastas on August 21, 2017 at 1:17pm

Hi Claudio,

Did you try using normal
beams and adding a joint component with which you can set free degrees of freedom and apply a stiffness to others?

Permalink Reply by Claudio Campanile on August 21, 2017 at 6:51pm

Hi Yousef

Thank you for your reply. I tried the joint-agent component, and I think I should get back to my initial approach. For my understanding, the component creates a condition for which if the AtElemIds is linked to one of the ToElemIds, the joint is applied. This would simplify the case of having many beams which I might want to group in two different clusters which are joined through my joint condition.

However, I am having troubles in modeling joint B and anyway I am not sure about it. In the attached picture it is clear how the joint (red dashed line - representing two joint-agents and a beam) is a rough approximation of actual connection. However, I don't think that Karamba would be the best way to go so much into detail. The goal is to simulate which a good reliability the stiffness of the joint to cause the rigid element the rotation the actual joint causes.

For being more informative, there is a picture of the model showing the two plates being connected through that awkward rubber tube and the spring. As a last question, how would you translate the material properties (the joint will be something more controllable than that funny stuff)? I see that as the bending stiffness of the two plates and the bending stiffness of the rod which make the joint rotating out of the initial plane - I am not entirely sure of how reliable this can be.

Thank you

Claudio

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