Extended Split‐Hopkinson Bar Analysis for Attenuating Materials

Abstract

The standard split‐Hopkinson bar data reduction procedure assumes uniform conditions exist over the length of the specimen allowing the average stress‐strain response to be computed. When the stress wave enters the specimen, a gradient is established along its longitudinial axis. To use the standard analysis, approximately three wave transit times within the specimen are required to produce a condition of uniform stress. For attenuating materials, the time required to achieve stress uniformity can be considerable. This results in the loss of information on the behavior of the material, as the standard analysis will not be valid during this time. Because soil is an attenuating medium, with a very low wave speed, stress uniformity is not achieved during the early portion of the experiment. Thus, in this region, the stress‐strain response cannot be resolved by the standard analysis procedure. To resolve the early time response, a modified Lagrangian analysis procedure for reducing data in plane shock wave experiments has been used. By coupling the Lagrangian analysis procedure with the standard analysis procedure, a nearly complete description of the dynamic soil stress‐strain response can be computed. To demonstrate the usefulness of this approach, experimental results on two soil types are presented.