2003 Volume 52 Issue 3 Pages 288-293
Despite of much research on the effects of factors such as temperature and strain rate on yield stress in amorphous glassy polymers, the yield phenomenon, including stress drop starting just after yielding, has not been understood qualitatively. Furthermore, the importance of this constitutive law can improve the processes of forming and injection molding. In order to investigate yielding and formation process of shear bands followed by slip lines in amorphous glassy polymers, simple shear tests were executed under constant speed and creep at room temperature using quenched and annealed specimens of polycarbonate and polyvinyl chloride. The deformation process was observed through a polarizing microscope during the test. It is shown that for as-received and annealed materials, yielding occurs after the initiation of slip lines, and the formation and extension of shear bands, while for quenched materials, yielding begins at the formation of shear bands without slip lines. These results may be able to predict whether there are two types of the plastic deformation in amorphous glassy polymers.