抄録
It is a well known fact that cold worked thermoplastics have a tendency to change their shapes at elevated temperatures. In the case of material fabricated in the molten state, a similar deforming behaviour is found that discs sliced from the extruded round bar deform into a cone shape and also calendered sheets shrink in the longitudinal direction without any application of external force. The deformation which is called as recovery - induced thermal deformation here and is a recovery of strain memorized in thermoplastics at the time of material processing, increases with the increase of temperature and with the time duration at the subsequent reheating. Two new forming process based upon this phenomena are proposed in this paper. The above deformed cone is bulged into a complicated shaped cup with the assistance of a low comperessed air blow. A sheet is bent to various shapes with the aid of line heating. Dimensional stability of the formed parts produced by these processes is confirmed to be acceptable.
