| 초록 |
Residual stresses are developed during injection molding process and these cause a warpage and invoke a birefringence in a molded article. Birefringence and residual stress have been observed in injection molded PC, PS, and PMMA specimens according to injection molding conditions. Computer simulation has been performed and compared with experimental observation of birefringence. Locations near gate showed higher residual stress than locations far from gate. Long cooling time, high melt temperature, and long packing time reduced residual stress. Residual stress in opaque products can be measured by chemical cracking test. Cracks developed according to the level of residual stress. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded by injection molding. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. |
