Numerical simulation of wave propagation and dispersion in sensing block and Hopkinson bar test

Abstract

The mixed system composed by a Sensing block system and a Hopkinson bar is a new method to investigate mechanical properties of materials under high strain rates. In practice, however, wave dispersion distorts pulse shape and may limit the accuracy of results. Using finite element simulation, it is shown in this work that a half sinusoidal pulse decreases wave dispersion. Moreover, it is also demonstrated that the higher the rise time the lower the wave dispersion. It is known that a half sinusoidal pulse with a great rise time may be obtained by inserting a deformable disk (pad) between the incident bar and the sensing block. This fact is verified in this work using an appropriate constitutive suitable for the rise time. Optimum characteristics are found for the sensing block, the most suitable material and dimensions. The use of deformable pad is also important when brittle materials are tested; this is because the increase in pulse rise time allows a gradual stress application.