History of Split Hopkinson (Kolsky) Bar System
The Hopkinson Pressure Bar was first suggested by Bertram Hopkinson in 1914  as a way to measure stress pulse propagation in a metal bar. Later, in 1949 H. Kolsky  refined Hopkinson's technique by using two Hopkinson bars in series, now known as the split Hopkinson bar, to measure stress and strain, incorporating advancements in the cathode ray oscilloscopes in conjunction with electrical condenser units to record the pressure wave propagation in the pressure bars as pioneered by RM Davies a year earlier in 1948 . Later modifications have allowed for tensile, compression, and torsion testing.
State of the Art of Split Hopkinson Bar System
One of the most widely used loading techniques for HSR is the split Hopkinson bar (SHB) (Hopkinson 1914) or the Kolsky bar (Kolsky 1949). Readers interested in the historical background, recent advances and extensive modifications of the SHB are referred to a recent book (Chen and Song 2011), the ASM handbook (Gray III 2000) and several recent reviews (Field et al. 2004; Gama et al. 2004; Ramesh 2008), and a review of its application to dynamic fracture toughness tests (Jiang and Vecchio 2009). The SHPB consists of a striker bar, an incident bar and a transmission bar, with a specimen sandwiched between the incident and transmission bars. When the striker bar impacts the incident bar, a compressive pulse is generated and propagates towards the specimen. Upon reaching the interface between the incident bar and the specimen, a portion of the stress pulse travels through the specimen and then transmits into the transmission bar as a compression pulse, while the remaining portion is reflected back into the incident bar as a tension pulse. Strain gauges are usually mounted at midpoints along the length of the incident and transmission bars to record the stress pulses. The principles of split Hopkinson tension bar (SHTB) and torsional split Hopkinson bar (TSHB) are similar to those of the SHPB, while the primary differences are the method of generating the tensile and torsional loading pulses, specimen geometries and the methods of attaching the specimen to the two bars. Recent major developments in SHB testing are presented by Field et al. (2004) (Table 1, P. 732). We focus on the key techniques for characterizing the dynamic response of rock materials, as summarized in Table 1.