A new method for the separation of waves. Application to the SHPB technique for an unlimited duration of measurement

The measuring duration of an SHPB (Split Hopkinson Pressure bar) set-up is limited by the length of the bars so that there is a limitation of maximum measurable strains in material testing applications. This paper presents a new two-gauge measurement method which takes account of the correction for wave dispersion effects, which cannot be ignored for long time measurements. Using bars of equal dimensions, it allows a quasi-unlimited measuring duration which can be up to 100 times longer than the classical one. Analyses of the sensitivity of results to the imprecision of experimental data show that the method is robust and reliable. It is applied to the testing of soft materials like foam (metallic or polymeric) in the complete range of their response (nominal strains up to 80%) not only at high strain rates but also at medium strain rates (5 s−1 < e < 50 s−1), with a measuring accuracy comparable with that of the SHPB. It is also successfully used to perform large displacement tests such as crushing of metallic tubes.

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