クレイズ発生と成長の統計的研究

Abstract

In spite of many works on the initiation and growth of crazes, few studies on plastic deformation caused by crazing inherent in high polymer solids have been performed. In this paper, as the first step to describe plastic deformation in high polymer quantitatively, the craze density, i.e., the number of crazes per unit surface area, and the craze growth rate were investigated, and their statistical nature were examined.The experiments were performed under the action of a crazing agent, kerosene, at room temperature (20±1°C) with a constant load type testing machine on the specimens of polycarbonate and polyvinylchloride. The dependences of craze initiation and growth on applied stress and testing time were determined by photographs taken through an optical microscope without stopping the test.The main results were: (1) the variation of craze density with time can be described successfully by a simple rate theory, (2) the distribution of the craze growth rate, which has essentially a statistical nature, is approximated by a normal distribution function and (3) the dispersion of craze length at a certain time can be explained by a statistical theory which takes into account both the distribution function of growth rate and the density variation of crazes with time.