In the case of Split Hopkinson Pressure Bar (SHPB) testing, violent impacts are common. Oftentimes a material experiences deformation and loading and failure in a total in 50 micro-seconds (0.000050 seconds). This sudden exceeding of a materials strength is a result of an impact generated through an impact of a striker bar traveling at up to 150 ft/sec (over 100mph). The striker suddenly stopped by impacting an incident bar, sends a stress pulse through the incident bar to the material sample being tested. A part of the energy is transmitted through the sample to the transmission bar and some is reflected off of the sample. Strain gages mounted on the system capture this dynamic event and through data processing (often in a program like SURE-Pulse), the user can determine the material’s behavior at a given strain rate. The need for evaluating properties at increased strain rates increases the severity of these bar/sample collisions.
These impacts that take various sample materials past their strength limits eventually wear on the system’s high strength maraging steel bars. Insuring that bars ends are flat and free of damage is critical to obtain consistent, high integrity material property data. Newly manufactured bars are ground to precise flatness, but if hard materials are tested at extreme rates (strain rates up to 104), damage can occur. Until now, this issue has been mitigated by ‘impedance matched’ bar end inserts and sending bars in for regrinding once damaged. Another option is now available…
Introducing SURE-Grind – SURE-Grind repairs the damage a SHPB system incurs during rigorous testing. It seamlessly mounts to the SURE-Flat base and bars and striker ends can be quickly reground to a flat, mirror like finish.
Contact us today to purchase our latest SURE-Test module.