CAD Forum

Hi,

I'm looking for software capable of simulating mechanical degrees of freedom. Basically, what I need is the possibility to apply constraints on selected degrees of freedom (mainly translational but rotational could be also helpful) of vertices, edges and faces. Those constraints would have to utilize global coordinate system directions but it would be great to be able to operate with local coordinate systems too. After applying constraints it should be possible to drag the model in such a way that the constraints are respected (like dragging unconstrained geometry in sketches). This is quite similar to what assembly modules of CAD software allow but I'm talking about individual parts and constraints would be different (not meant for connecting parts or fixing them completely but for fixing them in 3 different directions). This description can be quite ambiguous so let me add some examples:

1) a single vertex of a cube is constrained in all directions (translations in 3 global axes) - the cube can only rotate about that vertex when dragged
2) 3 vertices (not lying on the same straight line) are constrained in all directions - the cube can't move at all
3) a single edge is constrained in all directions - the cube can rotate about that edge
4) a single face is constrained in all directions - the cube can't move at all
5) a single face is constrained in the direction normal to it - the cube can slide in the remaining two directions
6) two orthogonal faces are constrained in directions normal to them - the cube can slide in the remaining single direction
7) three orthogonal faces are constrained in directions normal to them - the cube can't move

Those are just selected examples and there would be more options with constraints applied to rotational degrees of freedom (for example, constraining all 6 DOFs of a single edge would remove any movement).

Is there any software that could do this ?

Seems easy to do in most parametric CAD software I know of.
You could try Onshape free, it's mating system is very easy to use and it has a nice "play button" to show the free axes.

If you are looking for something outside of the CAD world, there's things like Simulink, Sim Mechanics (Matlab) and Dymola.

Thank you for the replies.

@mgibeault The problem is that CAD software operates on relative constraints between multiple parts and not directly on degrees of freedom of geometric entities belonging to individual parts. So, for example, I can't constrain a vertex in only 2 global directions. Unless I use some datum planes/axes to apply constraints, that could make sense but likely not for all cases, especially when it comes to rotational DOFs.

@SPerman It should be something CAD-based (or at least having some GUI to view and move 3D models). The ultimate goal is to make some presentations showing how different combinations of boundary conditions work in FEA.

I think you could do what you are asking for in SW. Initial setup could take a while, depending on the complexity of your model, and the number of different arrangements you want to make.

An object (part) itself has no DoF. It cannot move within itself.
An object (part) in space (assembly) is free when it doesn't have any force (constrain) applied to it.
To remove DoF from object (part), it need to connect (constrain) to something in space (assembly). Like another object (part).
Or imaginary plane, axis, point.
I'll say CAD constrain works pretty much like real world.
You are thinking out of this world.