An efficient Signal processing technique for split Hopkinson pressure bar test

Split Hopkinson pressure bar (SHPB) is an important apparatus used for characterizing the mechanical behavior of materials at high strain rates in the range of 102 - 104 s-1. An SHPB apparatus consists of a gas gun, a striker bar, an incident bar, a transmission bar and a measurement system. The specimen is compressed between the incident and transmitted bars. The strain gages measure the incident, reflected and transmitted strain pulses. These strains are then processed to obtain strain and stress in the specimen. Because of the dynamic nature of this test, developing an efficient signal processing algorithm is of great importance. In this work, such a program for processing of strain signals is developed. First, the useful part of each signal is cut off. Since the wave speed in the bars depends on frequency, the wave shape disperses by propagation through the bars. Therefore, the signals are then shifted to minimize the dispersion effects. Synchronizing of the signals is implemented and the stress and strain data are finally computed. Moreover, the efficiency of dispersion correction and signal synchronization algorithms on stressstrain curves of different materials is shown through several examples.