抄録
Fatigue fracture behavior of the smooth specimens of polycarbonate was investigated in the range of low cyclic stress. In such fatigue tests, specimens fail during the process of crack initiation and propagation like metal. An experimental program was set up to examine the process of initiation and growth of a surface crack. This was accomplished by careful observations by using the transmitted light photographs of a surface crack on the smooth specimen of polycarbonate during the rotating bending fatigue test at the speed of 2Hz at room temperature. It was shown that the initiation of the surface crack appeared from a very small inclusion near the surface of specimen at 10-30% of the fatigue life. The experiment showed that the surface crack propagation was hindered by the shear bands formed at the both ends of a crack. The final length of surface crack was discussed in terms of a combination of the stress amplitude and the stress intensity factor at the end of crack. From these results, it became evident that the characteristic behavior of the crack initiation and growth in the smooth specimen of polycarbonate was affected significantly by the mechanical properties and yield behavior of the material.
