Yield and transient effects during the plastic deformation of solid polymers

摘要: Tensile tests were performed on seven commercial polymers at 22° C and constant true strain rates of 10−4 to 10−1 sec−1. The imposed the minimum section each sample with aid a diametral transducer, an exponential function generator closed-loop hydraulic testing machine. investigated were: high low density polyethylene, polytetrafluoroethylene, polypropylene. polyvinylchloride polyamide 6 66. True yield drops observed in rigid glassy polymers, whereas yielding was more gradual semi-crystalline or plasticized polymers. Strain rate change also performed, during which one order magnitude increases decreases specimens. “Normal” transients small strains samples containing rubbery phase, while “inverse” nature phase. With increase initiated, “normal” changed character “inverse”. Transient straining interrupted permit period stress relaxation holding unloaded condition prior resumption straining. A quantitative model is proposed, based dynamics plastic waves accounts for transition from transient behaviour increasing strain, explains opposite effects specimen unloading restraining transients.