What is the name for the situation where Parallel paths (and fuzzy solutions) are created when unnecessary physical joints are included in the idealised model. e.g. two hinges on a door, or a forked link rod.
I have 2 equal and opposite forces acting on a floating body. Part way through the timeline, and in the absence of any excitation, the plots of the forces transition from both pushing to both pulling, and pass through zero magnitude in the process, which is nonsense. The after transition magnitude is clearly less than the before transition magnitude.
How do I convince a disbelieving auditor that the results of my analysis are nevertheless correct?
Hi John,
If you are referring to internal forces in a system (ie that result in no net force on the system), then I would consider these purely an artifact of redundancies. When dealing with rigid bodies, if you have more than one mate restraining a certain DOF on a body, the solver automatically removes the redundant one. Which one you ask, that's a good question, and there's probably some mathematical prioritization to what it selects, but it doesn't really matter. Anyway at each time step, it is re-evaluating the redundancies. In some instances, it may swap which mate it views as redundant and this would cause a change in the loads. Although typically it's all or nothing, not a sign reversal.
If you have multiple bushings (flexible joints) transferring load from one body to another, then I could potentially see this happening since they are zero length springs and load direction could change based on minor numerical error.
Let me know if this is what you're getting at or if you can provide an image or model showing the issue at hand.
Ian