Title: Mechanical response of granular matter exposed to impact

Author (Invited): Lou Kondic, NJIT

Abstract:

In the first part of the talk, we will discuss generic features of a response of a dense granular material exposed to an impact of an intruder. We will start by describing effective models describing this response, and proceed by comparison of these models with our discrete element simulations. These simulations will concentrate on particular on the role of friction and order on determining the system's response and the intruder's dynamics. The attached figure, where snapshots of tangential forces between the granular particles are shown, gives an example of this response. In the considered systems these tangential forces are to a large degree responsible for slowing down the motion of an intruder [1]. In the second part of the talk, we will discuss recent experimental and computational results concentrating on the response of a granular system on the much faster time scales. High speed imaging of an impoct on photoelastic particles have uncovered strong acoustic-type of behavior during impact, including large force fluctuations at very short time scales [2]. We will discuss properties of these fluctuations, how they influence the dynamics, and in particular the role of stochasticity in determining mechanical response of the considered systems. [1] L. Kondic, X. Fang, W. Losert, C.S. O'Hern, R.P. Behringer, Phys. Rev. E, vol. 85, 011305 (2012) [2] A. Clark, L. Kondic, and R.P. Behringer, Phys. Rev. Lett., vol. 109, 238302 (2012)