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تسجيل مستخدم جديدStart-up shear of spherocylinder packings: effect of friction
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Claus Heussinger
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We study the response to shear deformations of packings of long spherocylindrical particles that interact via frictional forces with friction coefficient $mu$. The packings are produced and deformed with the help of molecular dynamics simulations combined with minimization techniques performed on a GPU. We calculate the linear shear modulus $g_infty$, which is orders of magnitude larger than the modulus $g_0$ in the corresponding frictionless system. The motion of the particles responsible for these large frictional forces is governed by and increases with the length $ell$ of the spherocylinders. One consequence of this motion is that the shear modulus $g_infty$ approaches a finite value in the limit $elltoinfty$, even though the density of the packings vanishes, $rhoproptoell^{-2}$. By way of contrast, the frictionless modulus decreases to zero, $g_0simell^{-2}$, in accordance with the behavior of density. Increasing the strain beyond a value $gamma_csim mu$, the packing undergoes a shear-thinning transition from the large frictional to the smaller frictionless modulus when contacts saturate at the Coulomb inequality and start to slide. In this regime, sliding friction contributes a yield stress $sigma_y=g_inftygamma_c$ and the stress behaves as $sigma=sigma_y+g_0gamma$. The interplay between static and sliding friction gives rise to hysteresis in oscillatory shear simulations.
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