Studies on high strain-rate behavior of materials by using a new method combining HPB technique with Lagrangian analysis

Abstract
A new method by combining the Lagrangian analysis with the Hopkinson pressure bar technique (LA-HPB) is developed to experimentally investigate the rate-dependent response of polymers, taking Nylon as an example. In such technique, the Hopkinson input bar plays not only a role of transferring impact loading to the specimen, but also provides a stress-particle velocity combining gauge at the bar-specimen interface. Thus the indispensable requirement of simultaneously measuring the stress boundary condition is satisfied if the stress wave profiles are to be correctly determined from a set of particle velocity profiles measured. It is shown that both the inversely deduced stress waves, σ(X_i, t), and the inversely deduced strain waves, ε(X_i, t), reasonably reflect the distinct characters of visco-elastic waves propagating in polymer specimens. In the present example, four dynamic stress-strain curves at different X_i can be experimentally determined in one test, simultaneously providing four satisfactory stress-strain curves in the strain rate order of 10² s⁻¹ for the tested Nylon.