Towards split Hopkinson pressure bar standardization — Interlaboratory comparison of experimental variability across routine practice

This is the authors' abstract. We don't add key points for this paper.

The Split Hopkinson Pressure Bar (SHPB) technique is one of the most widely used methods for characterizing metallic materials under high strain-rate compression. The present study examines interlaboratory variability in SHPB measurements obtained in three independent laboratories operating their routine experimental configurations. For clarity, the participating laboratories are referred to throughout the paper as PUT (Poznan University of Technology), MUT (Military University of Technology), and IFTR (Institute of Fundamental Technological Research of the Polish Academy of Sciences). The comparison was intentionally designed to reflect standard day-to-day laboratory practice rather than a fully unified one-factor-at-a-time protocol. All specimens were manufactured by Electrical Discharge Machining from the same material batches, whereas the specimen dimensions and SHPB setups remained laboratory-specific. Three structural steels, namely S235JR+N, S460NL+N, and S690QL, were investigated over a range of strain rates. The results show that noticeable differences in the measured stress–strain response arise even when the material origin and fabrication route are controlled. The most pronounced discrepancies occur in the initial part of plastic flow, before dynamic force equilibrium is fully established, where the measured response may be influenced by interacting effects associated with specimen geometry, interfacial friction, waveform quality, pulse shaping, calibration strategy, and setup-specific wave-propagation characteristics. Numerical simulations were used as a supporting tool to interpret the influence of specimen geometry and friction on the measured response. The study therefore does not propose a universal SHPB standard; instead, it identifies practical sources of interlaboratory scatter and formulates recommendations for more transparent and harmonized reporting and testing practice.