Hi,

I’m updating an old constitutive model of mine on PFC7, based on the parallel bond model (Linear Parallel Bond Model Implementation — PFC 7.0 documentation) and I noticed that the actual torque applied on a given particle seems mostly indepenent on the actual moment stored in the bond.

```
DAVect pbMomentInc = ang * pbProps_->pbAngStiff_ *(-1.0);
pbProps_->pb_M_ += pbMomentInc;
```

How is the applied torque calculated?

If I calculate it as 0.5 * shear force * contact branch, I get a result that is very close to the one provided by PFC but slightly underestimates it (<1% difference).

I see that updateResultingTorqueOnLocal takes in both the shear forces and the bending moment, but I can only trace that method up until the header for IContactMechanical.

If I want to modify the code or to obtain a non-linear bending moment, should I directly act to modify the shear force instead of the bending moment? Again, I am using a parallel bond contact model with gap > 0.

Best regards,

Marco