Undular bores generated by fracture

Undular bores, or dispersive shock waves, are non-stationary waves propagating as oscillatory transitions between two basic states, in which the oscillatory structure gradually expands and grows in amplitude with distance travelled. In this work we report an important new mechanism of generation of nonlinear dispersive shock waves in solids. We demonstrate for the first time, using high-speed pointwise photoelasticity, the generation of undular bores in solid (polymethylmethacrylate) pre-strained bars by natural and induced tensile fracture. For the distances relevant to our experiments, the viscoelastic extended Korteweg-de Vries (veKdV) equation is shown to provide very good agreement with the key observed experimental features for suitable choice of material parameters, while some local features at the front of the bore are also captured reasonably well by the linearisation near the nonzero pre-strain level. The experimental and theoretical approaches presented open new avenues and analytical tools for the study and applications of dispersive shock waves in solids.