One-dimensional wave theory analysis of factors and characteristics influencing errors in two-wave method data processing in SHPB

A simplified calculation of the specimen’s stress-strain curve is generally conducted using the two-wave method by the split Hopkinson pressure bar (SHPB), which aligns the onset of the transmitted and reflected waves. However, this approach neglects the travel time of elastic waves within the specimen. Considering the travel time of elastic waves, this study quantitatively investigates the error characteristics and patterns of stress, strain, and strain rate in the specimen under different conditions using the theoretical two-wave method, and compares the results with those obtained using the onset-aligned two-wave method. The study reveals that the stress-time curves derived from the theoretical two-wave method are lower than the actual stress curves, whereas those obtained from the onset-aligned two-wave method are consistently higher than the actual stress curves, with the stress deviation approximating a constant value when the dimensionless time exceeds 2.0. The starting point of the stress-strain curves obtained by the theoretical two-wave method is not zero but a point on the strain axis, whereas the onset-aligned two-wave method always starts at zero. However, the slopes of the stress-strain curves obtained by both methods differ from the actual Young’s modulus of the material, and functional relationships between the slopes and the actual Young’s modulus are provided. This research offers theoretical guidance for the refined design of SHPB experiments and the accurate processing of data.