G.H Majzoobi - Professor
K Rahmani - PhD Student
S Lahmi - MSc, Department of Mechanical Engineering, Bu-Ali Sina University,Hamedan ,Iran

Split Hopkinson bar (SHB) is a well-known device for mechanical characterization of materials under dynamic loading. The device can be compressive, tensile, torsional or shear. The effect of dimensions of SHB in particular the length to diameter ratio, L/d, of the bars has been the subject of numerous investigations over the past several decades. However, little work has so far been performed on the forgoing ratio in torsional Hopkinson bar (TSHB). In this work, the length to diameter ratio of the input or output bar, L/d, is studied by numerical simulation and theory through Lagrange diagram of the TSHB. It is found that for L/d>80, the incident, reflected and transmitted wave lengths obtained fromsimulations and Lagrange diagram are the same. This value of L/d is quite consistent with that usually recommended for compressive and tensile versions of SHB. The numerical model of TSHB is validated by Lagrange diagram and experiment.

Torsional Hopkinson bar, Lagrange diagram, Length to diameter ratio, simulation