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To investigate the dispersion effect of different stress waveform pulses in large diameter SHPB,a numerical simulation of stress wave pulse transmission in input bar is presented in this paper.Finite element software ANSYS was used to set up a 3-D numerical model of elastic input bar and three typical waveform pulses(rectangular waveform,triangular waveform and half-sine waveform)with the same duration time and maximum stress amplitude value were loaded to input bar.The time-stress curves of different points on input bar were traced and recorded and four specific aspects were discussed respectively.(1)For rectangular waveform,the stress non-uniformity of cross-section in bar was obvious and the stress of bar center is the largest than other parts of cross-section at the same time.For triangular waveform and half-sine waveform,stress distribution in cross-section of bar is uniform along axial direction.(2)Compared with the rectangular waveform,the results show that triangular waveform and half-sine waveform dont create obvious dispersion effect in the propagation of wave.(3)The forefront rise time(from the starting point to maximum stress amplitude value)of stress wave pulse will increase obviously with the increases of propagation distance for rectangular and triangular waveform.For half-sine waveform,the forefront rise time changes slightly along axial direction.(4)The maximum stress amplitude value of stress pulse will decrease with the increases of propagation distance for triangular waveform.While for half-sine waveform,the attenuation tendency of the maximum amplitude of stress pulse isnt obvious and maintains the original value.From the above analysis,it can be concluded that it is suitable and rational for half -sine waveform conducted in large diameter SHPB testing technique.