Split-Hopkinson pressure bar

The split-Hopkinson pressure bar is an apparatus for testing the dynamic stress-strain response of materials.

History

The split-Hopkinson pressure bar was first suggested by Bertram Hopkinson in 1914 as a way to measure stress pulse propagation in a metal bar. R.M. Davies and H. Kolsky refined Hopkinson's technique by using two Hopkinson bars in series, now known as the split-Hopkinson bar, to measure stress and strain. Later modifications have allowed for tensile, compression, and torsion testing.

Compression testing

For compression testing, two symmetrical bars are situated in series, with the sample in between. The first bar is the incident bar, which is struck by a striker bar during testing. The striker bar is fired from a gas gun. The second bar is the transmitted bar, which collides with a momentum trap (typically a block of soft metal). Strain gages are mounted on both the incident and transmitted bars.

Tension testing

For tension testing the setup is essentially the same, except the gas gun fires the incident bar away from the sample. The momentum trap is also switched to the side of the incident bar.

References

*Gray, George T. "Classic Split-Hopkinson Pressure Bar Testing." Los Alamos National Laboratory.