Signal Gain Mechanism for a Hollow Transmission Pressure bar with an end cap

摘要

Errors in a split Hopkinson pressure bar test with a hollow transmission bar were found by analyzing the transmitted strain signal gain mechanism. To generate these errors, a hollow transmission bar with an end cap was employed and the value of the gained transmitted strain wave and specimen strain were derived. The hollow Hopkinson pressure bar technique is a material dynamic properties testing technology used to increase the amplitude of the transmitted signal by reducing the transmission bar cross-sectional area. However, since both the process of stress wave propagation and the transmitted strain signal gain mechanism in a hollow transmission bar are unclear, hollow transmission bars were used to compensate such discrepancies. In this paper, stress wave theory was used to analyze these phenomena. It was found that the transmitted wave at the variable cross section occurs many times in a hollow transmission bar and also the time lags of the transmitted waves distort the gained transmitted wave. The values of specimen strain and the transmitted wave were analyzed when a hollow transmission bar was employed. To verify the theoretical analysis, two groups of simulations of the transmitted signal gain processes with LS-DYNA have been undertaken, the results of which are in excellent agreement with the analysis results.