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# Bushing Modeling Problems

Experimenter

Hi,

I completed all of the motion training, and I understand how to model cylindrical bushings. The problem arises when I want to model a pin connection that acts like a bushing where the pin and housing are made out steel material. I want the pin to rotate inside the house but limit its translation in the other two axis in a way that is repentative of the clearance between the pin and the housing. Please see attached power point that depicts my problem. At this time I dont know to impose an stiffness in a way that for example allow a clearance of 0.1 inches but after this value is reach, then the pin is not allow translate any further. Any help will be greatly appreciate on this matter.

Regards,

MarcelM

3 REPLIES

# Re: Bushing Modeling Problems

Legend

hello MarcelM.

In order to take into account what you say you have to define a nonlinear spring.

You have to introduce a nonlinear stiffness curve, saying that after 0.1 inches the force you need to get displacement is very high (very high stiffness).

I hope I undestood the problem issue

# Re: Bushing Modeling Problems

Experimenter

Jon, you bring a good point, and based on how I'm interpreting your response, I think that the spring will control the rotation of the pin inside the bushing. Now, do you think that the spring will prevent the pin from only translating inside the cavity by +-0.1 inch for example?. It seem that the move I think abou it the more I arrived to the conclusion that 3D contact will be the only solution, which is not a good one. As 3D contact are slow to solve and depend highly on geometry charateristics. Let me know what you think. I'm also working with GTAC technical experts, I'm still waiting for an answer.

Regards,

Marcel

# Re: Bushing Modeling Problems

Legend

I try to answer the question of imposing some stiffness before you get 0.1 inches. And then very high stiffness. That is, the component moves until 0.1 inches under some kind of stiffness and then very high stiffness avoiding movement. Answering you question why not? If you define the bushing with a non linear function…. For example

disp 0  0.1    0.11        force 0 0.1  1,00E+08

In fact with cgap elements , I think , also you can do it. I think you can add initial gap (I do not remember). The problem of cgap /spring elements that you need that the nodes between parts are coincident (I mean at the same location with maybe some very small gap ). The point of cbush elment is that it has 6 dof and be careful the nodes you are joining (solid 3 elements have 3 dof …) Then, regards the problem definition, in this way, I think you will have a problem of solid rigid movement as the cylinder will be free to rotate about its axis (x in your figure). In my opinion I would try first with cgap not adding any clearance. And then adding initial gap. With cgap sol101 with bulk data options of gaps as contact. Remember nodes at the same locations