An experimental and theoretical study of longitudinal bulk strain waves generated by fracture

From a dipole lattice model, we derive a Boussinesq-type equation that governs the propagation of a longitudinal strain wave in a uniform pre-strained bar with constant cross section. We then describe an experiment based on high-speed, single-point photoelasticity to measure strain waves in a Polymethylmethacrylate (PMMA) bar generated when it breaks whilst undergoing a tensile test. The experimental results are finally compared to the model predictions, showing a good correspondence in terms of wave propagation, strain rate at the leading edge and amplitude and frequency of the following ripple.