Propagation of Rarefaction Pulses in Discrete Materials with Strain-Softening Behavior

TL;DR

This paper explores the propagation of rarefaction pulses in discrete, strain-softening materials, providing exact solutions for specific nonlinear force-displacement relationships and analyzing wave behavior through theoretical and numerical methods.

Contribution

It presents an exact long-wave approximation solution for rarefaction waves in nonlinear discrete systems with strain-softening behavior, supported by numerical validation.

Findings

Exact solution for n=1/2 case matches numerical results.

Stationary rarefaction waves can be generated by impact.

Wave dynamics depend on the power-law exponent n.

Abstract

Discrete materials composed of masses connected by strongly nonlinear links with anomalous behavior (reduction of elastic modulus with strain) have very interesting wave dynamics. Such links may be composed of materials exhibiting repeatable softening behavior under loading and unloading. These discrete materials will not support strongly nonlinear compression pulses due to nonlinear dispersion but may support stationary rarefaction pulses or rarefaction shock-like waves. Here we investigate rarefaction waves in nonlinear periodic systems with a general power-law relationship between force and displacement $F \propto \delta^{n}$, where $0 < n < 1$. An exact solution of the long-wave approximation is found for the special case of $n = 1/2$, which agrees well with numerical results for the discrete chain. Theoretical and numerical analysis of stationary solutions are discussed for different values of $n$ in the interval $0 < n < 1$. The leading solitary rarefaction wave followed by a dispersive tail was generated by impact in numerical calculations.