Anomalous Behavior of the Coefficient of Normal Restitution in Oblique Impact

The coefficient of normal restitution in an oblique impact is theoretically studied. Using a two-dimensional lattice model for an elastic disk and an elastic wall, we demonstrate that the coefficient of normal restitution can exceed unity and has a peak against the incident angle in our simulation. We also explain this behavior based upon a phenomenological theory.

Figure 1

The elastic disk and wall consisted of random lattice.

Figure 2

Numerical and theoretical results of the relation between ${\Psi }_1$ and $e$.

Figure 3

The schematic figure of a hard disk sliding on a soft wall. $x$ coordinates of both ends of the contact area $AB$ are $x=x_a$ and $x=x_b$.

Figure 4

Numerical and theoretical results of the relation between ${\Psi }_1$ and $\mu$.