Strain rate dependency on stress–strain relations of polypropylene



True constant strain rate tensile tests of polypropylene up to 2% initial strain were performed to investigate the strain rate dependency of the initial stress–strain gradient dσ/dε with the aid of “slack grip.” The experimental results fairly agree with even the simplest mechanical model analysis with three parameters, showing the conspicuous strain rate dependency on the initial stress–strain gradient dσ/dε. The limiting cases corresponding to zero strain rate and strain rate of infinite magnitude, both predicted by the analysis, were experimentally verified.