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

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(Xi, t), and the inversely deduced strain waves, ε(Xi, 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 Xi 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