I have a question about proper bushing definition in Adams (especially in Car). Probably this issue have already solved many times, but it is still essential for modelling.
The question is: what is the right way to define active and reactive bodies in bushing? Some say that one should use the mechanism (say, vehicle suspension) topology and follow through it from part that give an excitation (a wheel, for example) to parts which react on this excitation. Also, there is an idea to consider I/J parts for bushing as inner/outer rings.
There is an issue when it comes to bushings with different radial stiffness. When you model such a bushing with different I/J parts order, you receive different results of bushing reaction. This difference may lead to different behaviour of related elements. I suppose it's related with bushing formulation described in the KB8013987 tech article.
For instance, there is a toelink, which has a bushing with different radial stiffnesses and a spherical joint. In this case different I/J parts order lead to different rotation of toelink around its axis and to different values of spherical joint working angle.
The point to note in the main question is - "If we have a bush having unsymmetrical bush (radial) stiffness, then how do we decide I-J parts". The point arises because of slight change in the results when we interchange I-J parts.
However, if we interchange I-J parts for a bush having symmetrical (radial) stiffness, the results remain the same.
Kindly check if there is any change in results if you interchange "I-J" parts for Spring, Damper and Bump-stopper.
As @Jesper Slattengren notes in his first response -"it does not really matter. You just find a convention that you like"