Modification of SHPB set-up based on wave separation technique and dynamic Saint-Venant's principle

Split Hopkinson Pressure Bar (SHPB) has become a frequently used technique for measuring uniaxial compressive stress-strain relationship of various engineering materials under high strain rate. By using the strain measurements on incident and transmit bars, the average stress, strain and strain rate histories within the specimen can be evaluated by given formulas based on one-dimensional wave propagation theory. However, the one-dimensional wave propagation assumption in pressure bars cannot been assured when large diameter or viscoelastic bars are used for testing brittle or cellular materials. One of the important error sources comes from the long time shift distance between the gauge position and the bar/specimen interface. This paper presents a modification of SHPB set-up based on wave separation technique and dynamic Saint-Venant's principle, which can greatly cut off the time shift distance and the pressure bar length. The proposed method is validated using numerical test based on FE simulations.