Experimental evidence of solitary wave interaction in Hertzian chains

TL;DR

This study experimentally investigates how solitary waves in Hertzian chains interact, revealing phase shifts and secondary wave formation, with experimental results showing larger amplitudes than simulations due to rolling friction effects.

Contribution

First experimental demonstration of solitary wave interactions in Hertzian chains, highlighting phase shifts and secondary wave generation, and identifying friction effects as a key factor.

Findings

Solitary waves cross with a phase shift during collision.

Secondary solitary waves emerge post-collision, with amplitudes proportional to incident waves.

Experimental amplitudes are larger than numerical predictions, likely due to rolling friction.

Abstract

We study experimentally the interaction between two solitary waves that approach one to another in a linear chain of spheres interacting via the Hertz potential. When these counter propagating waves collide, they cross each other and a phase shift respect to the noninteracting waves is introduced, as a result of the nonlinear interaction potential. This observation is well reproduced by our numerical simulations and it is shown to be independent of viscoelastic dissipation at the beads contact. In addition, when the collision of equal amplitude and synchronized counter propagating waves takes place, we observe that two secondary solitary waves emerge from the interacting region. The amplitude of secondary solitary waves is proportional to the amplitude of incident waves. However, secondary solitary waves are stronger when the collision occurs at the middle contact in chains with even number of beads. Although numerical simulations correctly predict the existence of these waves, experiments show that their respective amplitude are significantly larger than predicted. We attribute this discrepancy to the rolling friction at the beads contacts during solitary wave propagation.