Stress uniformity process of specimens in SHPB test under different loading conditions of rectangular and half-sine input waves

Abstract

Based on the characteristics of 1D waves, the stress uniformity process in specimens under different loading conditions of rectangular and half-sine input waves was analyzed in split Hopkinson pressure bar (SHPB) test. The results show that the times of an elastic wave propagating from one end to the other in a specimen to attain stress equilibrium, is related to input waveforms and relative mechanical impedance between the specimen and the input/output bars. Hereinto, with the increae of the relative impedance, the times decreases under rectangular input waves loading, while it increases under half-sine input wave loading. The dimensionless stress value of specimen corresponding to the status of stress equilibrium increases with the increase of the relative mechanical impedance. However, the dimensionless stress value under half-sine input wave loading is significantly lower than the value under rectangular input wave loading for specimen with low mechanical impedance, and the relative differentia of the dimensionless stress values under two loading conditions decreases with the increase of the relative mechanical impedance. In general, the forced state of specimen with relatively low mechanical impedance under half-sine input wave loading is evidently superior to the state under rectangular input wave loading in SHPB test, and the advantages of forced state under half-sine input wave loading turns weak with the increase of the relative mechanical impedance.

Keywords

split Hopkinson pressure bars / stress uniformity / dimensionless stress / half-sine input wave / rectangular input wave

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