Softening and residual loss modulus induced by loop trajectories of dissipative jammed grains under oscillatory shear.

From a theoretical study of the mechanical response of jammed materials comprising frictionless and overdamped particles under oscillatory shear, we found that the material becomes soft, and the loss modulus remains finite even in the quasi-static limit at an intermediate strain amplitude without any irreversible plastic deformation.The trajectories of the particles in this region exhibit hysteresis loops. The loop trajectories were characterized quantitatively through Fourier analysis, and we succeeded in theoretically connecting the origins of the softening of the material and residual loss modulus with the responsible Fourier components.