How to output force of a User Subroutine Bushing (difined by GFOSUB)?

Garand

Hello everyone,

I difined a Bushing with user subroutine GFOSUB in Python, the input is Bushing velocity and displacement and returns six-point force, like:

def GFOSUB(id, time, par, npar, dflag, iflag):
…
return [FX, FY, FZ, MX, MY, MZ]

The simulation performed correctly, but the output of Bushing force is zero. As shown in Figs below. Bushings in Fig. 1 are all general Bushings, the force in the middle is an external force

In Fig.2, GFOSUB Bushing on the left and general Bushing on the right. The GFOSUB Bushing force has vanishes, but force of another Bushing seems similar, means there is no error in the model setup.

The problem is I need the GFOSUB Bushing force for debugging, so how can I get it to output correctly?

Sincere gratitude，

Garand

Praful

Hello Garand - I think I found the problem. This could be a bug in MotionView where it is not writing the correct marker id for j_marker_id in the <Post_Request statement. (I am presuming you are using xml)

There are couple of workarounds you can use to get around this problem.

1. Use a Force entity instead of Bushing with the same GFOSUB. and define an output on the Force. (Actually, when Bushing is made anything but Linear, it goes as a Force to the solver.)
2. if you are very particular about using the Bushing entity, you may define the output <Post_Request statement in a Template

Hope this helps.

Praful