Learning Forum

[m.caragiuli]

Hi,

I'd like to have your opinion about how to couple two solid bodies which are slightly far away, but should be connected to each other at least virtually meaning that a force should be transmitted through them.

Diving into the details, there are two splints (oral appliances) bonded to the teeth. One is for the upper arch and the other is for the lower one.

There should be two lateral arms to join the lower splint left screw (fixed laterally) to the lateral left  screw of the upper splint and the same for the right side. These arms are not physically modelled, thus I'm thinking about a way to couple the two splint simulating these arms in order to transmit a force applied to the inferior splint to the upper splint.

If I use a general joint body body, keeping as reference the upper splint screws and as mobile the lower splint screws in order to allow translation and rotation of the lower splint, could it be ok? Can you suggest other strategies?

Hope to be clear. Thanks for the attention. 

[peteroznewman]

Yes, a Joint is required if you want relative motion between the two bodies. If you just wanted them fixed to prevent relative motion, then there are more choices.

[m.caragiuli]

ok, I want the upper splint to be fixed so it receives the force but doesn't move, whilst the lower splint will be able to move according to the force applied.

Probabily,  I need a general joint body-ground where I put as reference the body to be fixed and mobile the body to be moved...am I right?

[peteroznewman]

An image would help to understand what you want.

If the splits are connected to the teeth, and the teeth are in a skull or mandible bone, and there is some joint between those bones, what is the lateral arms between the splits for?  Isn't that overconstraining the problem?  Or are the lateral arms flexible?  If so, they should be modeled and not represented as Joints.

[m.caragiuli]

Hi,

yes, the splints are bonded to the teeth and the teeth have been fixed in all the dof. But now it is like the two components (upper and lower)are separated from each other. Look at the image.

a force should be applied at the lower splint, but of course it should be transmitted also to the upper one. Currently, they are not connected, but actually there should be two lateral arms which join the lateral screw of the lower splint to the lateral screw of the upper splint. These arms allow the mandible to be advanced since they are telescopic.

[peteroznewman]

A telescopic arm is modeled using two bodies. Use a Translation Joint between the two bodies to allow them to telescope.

What freedom of movement do the screws that fasten the arms allow each arm to have? Is it Fixed or a Revolute or a Spherical joint freedom?

Note that two telescoping arms with a spherical joint at each end is the same as no constraint.

[m.caragiuli]

Hi Peter,

the screws are fixed to the splints, I've applied the force to be transmitted dircetly onto the screws. So without modelling the arms it is sufficient to use a translation joint between the two splints? Note that the upper bodies aren't allowed to move.

Many thanks!