ASTM E23 details the requirements for impact testing of Charpy specimens. Additionally, the application we were asked to perform required NIST (National Institute of Standards and Technology) certified results.
Since our test required impact energy of 100 Ft-Lbs, we chose the SI-1K3 Pendulum Impact Tester equipped for Charpy applications up to 300 Ft-Lbs. This machine has specific foundation requirements to ensure accurate test results, which can be found in the pre-installation manual. Special tongs (W-3550) are required for handling and placing the Charpy specimen into the machine anvil for both room and low temperature applications. NIST certification requires that the verification specimens must be broken on the machine. There are three verification specimen sets for consideration and the ASTM standard requires that at least two sets be broken, which must include the high-energy series:
- Set five Low Energy Series (approximately 10 - 15 Ft-Lbs) break at -40° C
- Set five High Energy Series (approximately 65 - 100 Ft-Lbs) break at -40° C
- Set five Super High Energy Series (approximately 130 - 180 Ft-Lbs) break at room temperature
We chose to break the High Energy and Super High Energy Series to certify our machine breaks for approximately 100 Ft-Lbs. Since NIST requires that the specimens be cooled to -40° C and then tested at that temperature, it is necessary to have a cooling bath for high series energy breaks. When we complete the testing, we will send NIST our documentation that includes the impact energies of each specimen along with the broken specimens for certification review. We can expect either certification (pass) or a failure report that includes suggestions for modifications to meet the next NIST certification attempt.
We recommend reviewing the standard to fully understand the test set up, procedures, and result requirements.