A Split Hopkinson Pressure Bar (SHPB) is used to test the high strain rate material properties of materials. The Hopkinson bar is used to impose a dynamic load on a material specimen akin to loads the material will experience in service. A lot of components experience dynamic loads while in service i.e. the load and loading rate changes with time. These components range from suspension systems on bikes and cars to armor plating used to protect our War fighters. It’s paramount that we understand how the material properties change as a function of the service loads. REL uses the Hopkinson bar for testing the dynamic material properties of developed, especially metal matrix composites.
A gas gun is charged with nitrogen to create the impact incident. A striker bar of various lengths will produce different loading durations i.e. short striker bars impart short time duration loads. The impact of the striker bar triggers data collection from the strain gages located on the incident and transmission bars. From the data collected by the strain gauges, Stress, Strain, and Strain Rate can be calculated.
REL builds Split Hopkinson pressure bars for research institutions. The diameter of the bar is the size of the SHPB. REL also builds non-metallic SHPB. These bars are typically employed on lower strength samples like polymer foams and bio-tissue. There are a wide range of options available for the SHPB.
These options include:
1. Size (0.25” to 3”)
2. Bar Construction material (Steel or Polymer)
3. Frame construction (Steel or Polymer)
4. Data Collection System
5. Momentum Trapping
Reference information from Dr. G. Subhash, University of Florida
ASM Dynamic Indentation Testing paper
ASM Ceramic Testing paper