Study on dynamic mechanical properties of high nitrogen steels

Reliable dynamic mechanical properties of high nitrogen steels are necessary for the design and assessment of armor structures subject to impact and blast. A series of experiments, based on Hopkinson bar techniques, were conducted and described in this study. The dynamic compression, tensile and shear properties of high nitrogen steel had been tested, and the stress-strain curves under high strain rates were obtained. The results have been showed as follows: High nitrogen steel has a remarkable strain rate strengthening effect. Compared to the static curves, the constitutive curves of dynamic tension and compression move upper. The dynamic compressive yield strength of high nitrogen steel increases first and then decreases with the increase of strain rate, and the yield strength varies in the range of 1465-1549 MPa within the range of 1147-2042 s−1 strain rate; The tensile strength of high nitrogen steel increases with the increase of strain rate. When the strain rate is greater than 1341 s−1, the tensile strength will not increase and the curve tends to be gentle. The pure shear yield strength of the high nitrogen steel is above 800 MPa.