Theoretical estimates of the parameters of longitudinal undular bores in polymethylmethacrylate bars based on their measured initial speeds

We study the evolution of longitudinal release wave that is generated by induced tensile fracture as it propagates through solid rectangular polymethylmethacrylate (PMMA) bars different constant cross-section. High-speed multi-point photoelasticity used to register strain at three distances from site in each experiment. In all cases, oscillations develop bottom exhibit qualitative features an undular bore. The pre-strain, post-strain, rate and cross-section dimensions determine oscillations. From speed close site, we estimate well growth amplitude duration leading oscillation away using formulae derived simple analytical solution linearized Gardner equation (linearized near pre-strain level fracture). Our estimates are then compared experimental data, where good agreements these parameters found between predictions model observations. Thus, developed approach estimating key characteristics developing unsteady bore based on measured initial speeds shear waves. This does not require a prior knowledge elastic moduli for conditions experiments, which PMMA known be dependent.