A Split Hopkinson Pressure Bar (SHPB) is used for high strain rate material testing to understand material performance under dynamic conditions.
A Split Hopkinson Pressure Bar (SHPB), also known as a Kolsky Bar, 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 that which the material will experience in dynamic situations like vehicle crashes or other high-energy events.
How Does a Split Hopkinson Pressure Bar System Work?
A Split Hopkinson Pressure Bar / Kolsky Bar system will contain a precision accelerator, an incident bar, a transmission bar, and a stopping mechanism that are aligned and mounted on a flat base.
The accelerator is charged with pressurized gas to accelerate a striker bar at a measured velocity to create an impact incident. Striker bars of various lengths are used to produce a range of loading durations i.e., short striker bars impart short time duration loads. The impact of the striker bar on the incident bar sends a stress pulse traveling down the incident bar (at the speed of sound) that is detected by a strain gauge mounted on the bar.
The pulse (a longitudinal wave) continues through the incident bar to the material sample to be tested. The test specimen is typically mounted between the incident and transmission bars. Due to impedance mismatches, part of the wave is reflected back into the incident bar (measured by strain gage) and part of the wave is transmitted into the transmission bar (measured by strain gage). The wave traveling through the system triggers data collection from the strain gages located on both the incident and transmission bars. Stress, strain, and strain rate are then calculated from the data collected by the strain gauges. This measured strain can be verified through the use of a high-speed camera often used in high strain rate testing. A Split Hopkinson Pressure Bar (SHPB) / Kolsky Bar 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 that which the material will experience in dynamic situations like vehicle crashes or other high-energy events.
Understanding Material Performance
From occupant protection components of a vehicle, ballistic and blast-resistant armor, to high-impact sports and volcanic eruptions, scientists need to understand the performance of a material under dynamic conditions. The Split Hopkinson Pressure Bar / Kolsky Bar is the ideal tool because it provides a controlled impulse of energy.
REL designs and builds custom Split Hopkinson Pressure Bars / Kolsky Bars for a variety of companies and research institutions. We offer multiple SHPB configurations to accommodate various types of testing including:
Learn more about our high strain rate testing systems.