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Thanks. Everything is as expected then, always good to hear. For motion engines, I prefer not to use them as we can simply assign velocity directly. Soon, you will not have to modify anything in Newton, since this behaviour of non-dynamic bodies is currently being implemented. Test scripts without Newton is not a good thing IMHO, you are putting yourself in a special case wich will never happen in routine simulations. It can hide existing problems or create problems that would not exist with Newton.I partially agree. I guess it depends on the task. I found quite useful the use of motion engines to test contact laws.
Partially is good enough. ;)
I would have a question about the ratcheting. I have run the same test also for HM and of course I do not get the same good result as in the case of the linear formulation. The reason is that in HM the tangential stiffness depends on the normal force (or say on the overlapping alike), and this is different from the initial one once I come back with the rotation (say at the last step). Hence shear force is not equal to zero although granular ratcheting is avoided. Do you think this is expected? I have not really investigated too much the granular ratcheting in the literature. Is this phenomenon perhaps addressing only the linear elastic case?I don't know your model enough to give a precise answer. Based on what you write, it seems you could proove irreversible behaviour in cycles even the analytical way? Variable stiffness makes me wonder if it is not something linked to the well known issue in hypoelastic models, see e.g.
http://linkinghub.elsevier.com/retrieve/pii/S0749641903001347. Quoting :"it is demonstrated that all hypothetical materials with non-potential finite elastic or hypo-elastic constitutive relations can create an energy from nothing, i.e. work as perpetual motion machines. This gives a ‘physical’ proof of necessity of potential conditions in general finite elasticity and hypo-elasticity and their extensions to finite viscoelasticity."
Cheers. Bruno
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