Robust Intermediate Strain Rate Experimentation Using the Serpentine Transmitted Bar

Whittington, W. R., Oppedal, A. L., Francis, D.K., & Horstemeyer, M. (2016). Robust Intermediate Strain Rate Experimentation Using the Serpentine Transmitted Bar. In S. Boussuyt, G. Schajer, A. Carpinteri (Eds.), Residual Stress, Thermomechanics & Infrared Imaging, Hybrid Techniques and Inverse Problems, Volume 9. Springer. 167--173.

The stress-strain behavior of a material at intermediate strain rates (between 5/s and 500/s) is important for characterizing dynamic deformation events. A material’s mechanical behavior can be strain rate dependent; calibrating constitutive models at actual strain rates of interest are essential for high fidelity simulations. Strain rates below 5/s are easily accomplished with conventional electro-mechanical or servo-hydraulic load frames. Strain rates above 500/s are typically performed with the split Kolsky/Hopkinson pressure bar (SHPB) and other devices depending upon the strain rate. The intermediate strain rate regime is a difficult test regime in which researchers have tried to extend the use of specially instrumented servo-hydraulic load frames or very long Hopkinson bars. We describe a novel design of a serpentine Hopkinson transmitted bar that allows for accurate and robust load acquisition in the intermediate strain rate regime. This design produces repeatable stress-strain results without the stress oscillations typical of a specially instrumented servo-hydraulic load frame and produces data for a longer test time than a conventional Kolsky/Hopkinson bar of the same length.