chain and sprocket model with idlers contact problem

KeyuWang_UWO

Hello,

I am running a chain and sprocket model with idlers. But the time step becomes smaller as it runs and the animation falls apart.

I set the joints as revolute joint with one compliant, and contacts are 'links&cutters to middle idler', 'links&cutters to bottom idler', 'links to sprocket'.

I tried to debug, it seems that if I involve 'links&cutters to bottom idler' contact, problem occurs.

Anybody has any idea what is wrong？

Thanks,

Keyu

DWT-MV-20251009model-finalversion_Archive.zip

Orestis_YB

Hello @KeyuWang_UWO,

I have noticed the instabilities that you are mentioning. Here are some tips when you are using a model with contacts as mentioned in

Best Practices for Running 3D Contact Models in MotionSolve

1. Mesh quality is important. Here you are using parasolid graphics so the mesh is created every time you are running the model. You can define the mesh coarseness either by the entity editor for each contact or for all contacts simultaneously from Global Simulation Settings→ Analysis Settings→ General. There you could also increase number of CPUs that are being used to make contact detection algorithm a little bit faster.

2. Contact parameters. If the penetration is large it is suggested to increase contact stiffness. In this particular case where there is significant instability in the model I would suggest to increase damping and reduce penetration depth as well as adding friction in the contact.

3. Solver Settings. When using contacts consider reducing maximum step size to 1e-3s or lower and also use a maximum order of 2.

If you try the above you'll get a proper behavior.

I have also modified Motion entity using an expression with a STEP() function to increase the speed gradually from 0 to pi in 0.5s.

I would also suggest to maybe import the geometry using HyperMesh (File→ Import→ Geometry or FEM using HyperMesh). This method will create a body, CG point and graphic for each component. This time though the graphics will already be in H3D so you will save valuable time every time you simulate.

Hope this helps!

Best regards,
Orestes