Specimen size and shape effect in split Hopkinson pressure bar testing

The results from an experimental and computational study on the effects of specimen size and shape on split Hopkinson pressure bar (SHPB) testing are presented. The effects of the L/D ratio (length L divided by diameter D) along with specimen shape (cylindrical versus square prismatic) were investigated. Even though specimens having a circular cylindrical cross-section are traditionally used in SHPB testing, a square cross-section specimen has advantages associated with in situ imaging of the specimen side surfaces during stress wave propagation. The results presented here show a strong correlation in specimen response between the two types of specimens. Different ranges of L/D ratios are recommended for obtaining stiffness and strength data at near constant strain rates.