Abstract
The influence of strain rate and temperature on the flow stress of nickel chromium molybdenum steel (SNCM 439) was studied through experiments. In the experiments, thin walled tubular specimens of short gage length were loaded at strain rates of 70-103sec-1 in shear by using a torsional split Hopkinson bar apparatus, and loaded at strain rates of 10-4-10-1sec-1 by using a combined tension-torsion loading apparatus and an Instron testing machine. The experiments were performed in shear over the temperature range -185°C to 120°C.It is shown that the strain rate sensitivity of the yield point and of the flow stress in the region of small strain at -185°C and -60°C is remarkable, and that, below about -50°C, the influence of temperature on the flow stress reveal itself remarkably. It is confirmed that the experimental results obtained on the strain rate dependency and the temperature effect on the flow stress can be described fairly well with the practical constitutive equation for an elastic/viscoplastic body proposed by one of the authors. The values of the parameters contained in the constitutive equation are also presented.
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