User-defined Requests with Bushing Markers don't work when Frequency Bushings are used

Question

Hello, colleagues.

I began to work with frequency bushings from A/Car Ride, as it's the simplest way to go away from velocity-dependent damping for NVH/Durability purposes.

The case: I want to analyse time-domain loading conditions of suspension parts in places where they are connected by bushings. For this purpose I create "type and marker" requests, where I and J markers are I and J bushing markers and the R marker is attached to one of connected parts and orientated as I need.

This works fine with ordinary bushings, but when frequency bushings are used, requests results are completely empty. Meanwhile, default bushing requests, generated automatically, have no issue with loading representation.

The screenshot attached shows the result of loading on a bushing of ordinary and frequency types (the MBS model is the same, only bushing type was replaced).

Thank you in advance for helping to clarify this issue.

UPD: occasionally (thanks to multi-thread run) noticed that frequency bushing is a GFORCE element, but ordinary bushing is a FIELD element. Maybe this is the reason of the issue (despite of having bushing markers names the same after switching between bushing types): I and J markers of FIELD element turn into I and RM markers of GFORCE element.

Attached Files (1)

Jesper Slattengren · Accepted Answer

Yes, so you have to use the I and Floating-J markers from the GFORCE to get the force.

The reason that a GFORCE is that it is a pain to write a FIESUB for complex elements like a FD bushing. With the FIESUB, you also have to provide all the partial derivatives. This is easy for a regular linear or non-linear bushing but not for a frequency dependent element.

THE GFOSUB on the other hand is very straight-forward and Adams will calculate the derivatives through perturbation just like almost all other elements.