Figure 6. Progressive damage in a plastic comparing the nonlinear to the linear response (courtesy of Peter Nagy). In the experiment, a plastic rod, fixed at one end and free at the other, was shaken at its fixed end in shear until failure (indicated by the x-axis, or number of shear cycles). The linear and nonlinear behavior was monitored at each step, and the normalized response of each is plotted on the y-axis. We see that the linear responses (in this case wave dissipation in blue and wavespeed in red) are relatively insensitive to induced damage until just before the sample fails. The nonlinear response is affected early on in the damage process, and becomes enormous very quickly.