Original paper(Vol.46 No.11 pp.1286)

Impact tensile properties of nine per cent nickel steel

Yoshie Shinji; Albertini Carlo; Mentani Yukio

Abstract:Clarifying material dynamic behavior is of the highest priority for safety evaluation of any structure under an impact problem. Grasping the strain rate dependence of material is necessary for the evaluation of structural integrity. To derive the strain rate dependence, the impact tensile tests should be done in a way that strain rate could be maintained constant. To realize this, two kinds of testing devices have been developed in JRC (Joint Research Centre), Ispra. One is the hydro-pneumatic machine for a medium strain rate range from 0.1 to 100 s^-1 and the other is the Modified Hopkinson bar device for a high strain rate range from 100 to 5000 s^-1.
In the present study, for nine per cent nickel (9Ni) steel used for LNG (Liquefied Natural Gas) structure, the impact tensile tests were performed at strain rates up to the order of 1000 s^-1, and the experimental results obtained are compared with those of carbon steel. The current tests revealed that 9Ni steel could have 50% more safety margin of strain energy even at a strain rate in the order of 1000 s^-1 than that for carbon steel.

Key Words:dynamic material behavior, impact, tensile test, strain rate, Hopkinson bar, LNG, nine per cent nickel steel