Hi,
I have a question to the combination of Hertz contact model and rolling model. Consider a particle with high overlap rotating in elastic region -> that results in a stiffer k_n and k_t -> results in a stiffer k_r in rolling behaviour. Now the overlap is reduced and the particles roll back -> kn kt is lower, also kr is lower -> results in a larger back rotation because of the lower k_r now. Attached is a sketch of this rolling case. So do I have to use hook if I want to use the epsd rolling model?
kind regards
Joshua
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JoshuaP | Wed, 11/25/2015 - 11:44
Introduction of a shape parameter and a constant kr
Hey,
there is a new paper of M. Jiang 'A nvel three-dimensional contact model for granulates incorporating rolling and twisting resistance'
Since the determination of Kr in the paper of J. Ai is based on the paper of Jiang, I found out that on page 152 chapter 2.5 Model implementation and parameters of Jiangs paper, he introduced a constant Ks (tangential contact stiffness) which is independet of the used hertz model and is used for determination of Kr (rolling stiffness). So he uses a Kr independent of his normal contact model. The change of Kr dependent on the overlap (combining hertz and epsd in LIGGGHTS) can yield to wrong behaviour in my oppinion (see picture above).
Also Jiang introduced a shape parameter \beta which is easy to implement. With the use of the shape parameter he obtains different shearing behaviour. So this parameter can be used to fit the shearing behaviour in a shear test.
Regards
Joshua