Dear all,
Recently I tried to perform elastic constants MD simulations of hcp alumina using LAMMPS. Later on I tried to search the references to compare my results. I came accross with the following reference (J. H. Gieske, G. R. Barsch, Phys. Status Solidi, Vol. 29, 121 (1968)) where C14 is given as negative? Can someone explain how can stiffness be negative?
Thanks
Dear if your material at some point contain pre-strain regime. it can show negative stiffness. for example post-buckled elements which already have some stored energy. More simply, deformation is opposite to the force direction(negative stiffness). In positive stiffness case they are in same directions.
Mostly it is seen in composite when one constituent has immensely high stiffness than others.
It is also seen after transformation.
see figure . from point A to B is negative stiffness in material. Force -xaxis displacement y-axis
I just wanted to pay your attention that not only stiffness - but also masses - could be assumed to be negative in some physical models. A popular introduction to the Krein-Moser theory has been recently posted at SIAM News: https://sinews.siam.org/Details-Page/particles-with-negative-mass-and-the-krein-moser-theory
Does anyone know how to deal with negative stiffness values during numerical modelling?
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