On the stress overshoot in cluster crystals under shear

Abstract

Using non-equilibrium molecular dynamics simulations we study the yielding behaviour of a model cluster crystal formed by ultrasoft particles under shear. We investigate the evolution of stress as a function of strain for different shear rates, $\dot{\gamma }$, and temperatures. The stress-strain relation displays a pronounced maximum at the yielding point; the height of this maximum, ${\sigma }_{\text{p}}$, increases via a power law with an increasing shear range and tends to saturate to a finite value if the limit shear rate goes to zero (at least within the considered temperature range). Interestingly, this behaviour can be captured by the Herschel-Bulkley type model which, for a given temperature, allows us to predict a static yield stress ${\sigma }_{\text{p}}^0$ (in the shear rate tending to zero limit), a characteristic timescale ${\tau }_{\text{c}}$, and the exponent $\alpha$ of the above-mentioned power-law decay of the ${\sigma }_{\text{p}}$ at high shear rates. Furthermore, for different temperatures, the ${\sigma }_{\text{p}}$ can be scaled as functions of $\dot{\gamma }$ onto a single master curve when scaled by corresponding ${\tau }_{\text{c}}$ and ${\sigma }_{\text{p}}^0$. Moreover, for a given shear rate, ${\sigma }_{\text{p}}$ displays a logarithmic dependence on temperature. Again, the ${\sigma }_{\text{p}}-T$ curves for different shear rates can be scaled on a single logarithmic master curve when scaled by a corresponding fitting parameters.

arXiv comment9 pages, 4 figures, 1 table

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Cited by in corpus (2)

• On the yielding of a defect-rich model crystal under shear: insights from molecular dynamics simulations
• Elasticity in crystals with high density of local defects : insights from ultra-soft colloids