Increased accuracy of SHPB test apparatus to better evaluate naval steels

Abstract

The use of high strength steel alloys for shipbuilding applications has increased in recent years in an effort to decrease costsassociated with the manufacture (i.e. material and welding costs) and operation (i.e. fuel economy) of naval vessels. The use ofthinner hull plate has implications for many design criteria, including high strain rate (impact and shock loading) performance.Increasingly, numerical modeling is being used to simulate high strain rate loading events on naval vessels, such as collisions and weapons attacks, with a goal of assessing operational limits. Accurate and reliable high strain rate material data must be used to ensure the accuracy of the numerical models. Confidence in measured data can only be achieved if the potential sources of errorin the measurement system have been eliminated, minimized or characterized. The mechanical behavior of three naval alloys, MIL S-16216K (HY-80), ASTM A517 grade F and CSA G40-21 350WT cat 5 were quantified under high strain rate (103s-1) compression using a Split Hopkinson Pressure Bar (SHPB) apparatus. A systematic error analysis was conducted on the SHPB apparatus to identify potential sources of error in the test set-up, data acquisition and data processing. The identified sources of error were then eliminated, minimized or compensated for, in order to improve the accuracy of the testing apparatus. SHPB compression data are compared to quasi-static tensile behavior. Metallography was conducted before and after high strain rate testing in order to investigate the deformation mechanisms that occurred in the alloys during the high strain rate loading events.