Cooling crack propagation

When polymer melts are accelerated during the manufacturing processes such as injection molding and afterwards cooled down quickly, the stretched molecular chains cannot relax, which leads to orientations in the direction of melt flow. These oriented polymer chains act differently toward ESC influences as compared to nonoriented molecules. Orientation perpendicular to the crack propagation direction may result in a higher ESCR, as will be shown in the following discussion. 

Computer codes developed at PNC, CANIS-J for calculation of fracture mechanics parameters, and CANIS-G for simplified crack propagation tests of a cylinder with circumferential and axial flaws and with a cylinder with an axial temperature gradient conduted by the Air-cooling Thermal Transient Test Facility(ATTF) are continued. 

The first figures represent early data on a- processed STA plate, whereas the remaining figures are for P-processed material. The crack propagation rates of the latter are similar to that of P-an-nealed ELI Ti-6A1-4V. It is readily apparent that the rapid cooling rates, which refine the trans-... 

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