Bouncing of a projectile impacting a dense potato-starch suspension layer

Abstract

When a solid projectile is dropped onto a dense non-Brownian-particle suspension, the action of an extremely large resistance force on the projectile results in its drastic deceleration, followed by a rebound. In this study, we perform a set of simple experiments of dropping a solid-projectile impact onto a dense potato-starch suspension. From the kinematic data of the projectile motion, the restitution coefficient and timescale of the rebound are measured. By assuming linear viscoelasticity, the effective transient elasticity and viscosity can be estimated. We additionally estimate the Stokes viscosity on a longer timescale by measuring the slow sinking time of the projectile. The estimated elastic modulus and viscosity are consistent with separately measured previous results. In addition, the effect of mechanical vibration on the viscoelasticity is examined. As a result, we find that the viscoelasticity of the impacted dense suspension is not significantly affected by the mechanical vibration.

Penetration and bouncing during impact in shallow cornstarch suspensions

“…Close to publication we became aware of a similar work studying the impact of a sphere on a thin layer of cornstarch suspensions by Egawa and Katsuragi [4]. The results of that paper, where the focus lies on interpretation of the results using a Kelvin-Voigt model, appear to be in accordance with our results.…”

Impact-induced hardening in dense frictional suspensions

“…1(a), where we set the time t = 0 and height z = 0 at the moment of impact. One can observe the rebound of the impactor (u I z (t)/u * < 0) when φ ≥ 0.54 which agrees semi-quantitatively with the freefalling projectile experiment [6]. This rebound occurs due to the hardening of the suspension shortly after the impact.…”

“…After the rebound, the suspension becomes soft, and the impactor sinks with a constant speed. Note that φ for rebounds is a little higher than that in the experiment [6] since rolling friction is ignored in our simulations [23]. When the impactor bounces, one can observe a peak in F I,z shown in Fig.…”

“…Instead, they showed that the stress on the impactor increases as it approaches the bottom boundary. The importance of the boundary characterized by depth of the suspension H has been suggested by a free-falling impactor experiment [6], where rebounding motion of the impactor was observed shortly after the impact. In order to extract microscopic information of two-dimensional dry granular materials in experiments, one approach is to use photoelastic disks to visualize the force acting on each grain [7].…”

“…The latter should be treated as an impact problem in which the dependence on the impact speed and the surface effect are important. Some efforts have been made to reproduce the impact behavior through experiments [1][2][3][4][5][6]. Waitukaitis and Jaeger indicated that the added mass effect in solidification after an impact is important [1].…”