Curve Interpolation

fliesenf

Hello,

I tried to include dynamic bearing stiffness in a MBD system. The curves were determined by the producer and should be correctly. In the transient analysis I got the following warning:

I think that means, that the curve is not defined in the necessary region. But these high X values (displacement in mm) should never be reached in reality, because the displacement of a bearing is much smaller (factor 100-1000).

When my comprehension is right (the X values in the screenshot were needed), my static system have to be wrong. Am I right with this assumption or is there another mistake?

Thank you!

Praful

Hello fliesenf

your understanding is right. the model may not have been set up correctly.

1) how are you modeling the "dynamic stiffness" ? Note that when a stiffness for a spring or bushing is not a constant value, it is represented as a Force. So the curve that you are creating should be a Force v/s displacement curve (and not Stiffness v/s displacement).

2) what is the reference for the displacement ? Generally, a displacement function between 2 markers is used. Does the displacement function used matches with the reference that was used to generate the data ?

3) Check the interpolation that you are obtaining (Akima or Cubic) . Does that look good ?

4) check for any other abnormalities in the model. Such as a high mass/inertia value etc. ?

5) It looks like there are several springdampers or bushings which you are representing with a non-linear curve. Just keep one of them active while setting others to a constant stiffness value (Linear in the Springdamper or bushing properties) to figure out what is causing this behavior.

 

Good luck !

Regards

Praful