Abstract
In order to investigate yielding in amorphous polymers, shear and tensile tests have been performed in the conventional ranges of strain rate and temperature using amorphous samples. In the serial study, when the experiments on the effect of strain rate on yield stress have been executed at room temperature using amorphous polyethylene terephthalate (PET) samples, the yield mode was discovered to change drastically at a critical strain rate. In this paper, this yield mode transition was investigated at shearing. It was shown that 1.there were two different yield modes, (a) yielding governed mainly by localized shear bands (; LSB mode) and (b) yielding by diffuse slip lines (; DSL mode) and 2.while the LSB mode appeared in the case where the strain rate was high and the temperature was low, the DSL one occurred where the strain rate was low and the temperature was high.
