J. Phys. IV France 10 (2000) Pr9-433-Pr9-438
Effect of strain rate change during uniaxial dynamic tensile tests on instability strainH. Kobayashi1, M. Dairnaruya1, T. Nojima2 and T. Kajino1
1 Department of Mechanical Systems Engineering, Muroran Institute of Technology, Mizumoto, Muroran 050-8585, Japan
2 Division of Aeronautics and Astronautics, Kyoto University, Sakyou-ku, Kyoto 606-8501, Japan
In order to investigate the effect of strain rate change during dynamic tests on the stress-strain curves, an analytical study using the maximum load condition and a simple constitutive equation, [MATH], was carried out. Three kinds of typical loading pulse, i.e. a usual constant incident pulse, an acceleration pulse and a deceleration pulse, were chosen. When the incident pulse is assumed to be [MATH], these pulses correspond, respectively, to the cases with β=0,β>0 and β<0. From the analysis, an instability strain or a strain at maximum load point, ε*, was derived to be [MATH]. It was found that the instability strain increases with the increase of acceleration parameter, β, of loading pulses. To check this analytical result, a series of dynamic tensile tests for 0.45%C steel using SHPB apparatus was performed with the three types of loading pulse. A tapered striker tube was used for acceleration and deceleration dynamic tests. The experimental result agreed well with that predicted by the analysis.
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