Premium
The effect of strain rate on the stress–strain curve of oriented polymers. II. The influence of heat developed during extension
Author(s) -
Hall I. H.
Publication year - 1968
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1968.070120412
Subject(s) - isothermal process , strain rate , materials science , strain (injury) , thermodynamics , viscose , adiabatic process , stress (linguistics) , deformation (meteorology) , polymer , composite material , mechanics , physics , medicine , linguistics , philosophy
The temperature changes which take place in a yarn during extension are considered. From thermodynamical considerations and the heat‐transfer coefficient it is shown that extension of the yarns studied will take place isothermally at strain rates below 0.04 sec. −1 and adiabatically at rates above 4 sec. −1 It is not possible to make an accurate estimate of the magnitude of the temperature rise during adiabatic extension, because of the lack of information on internal energy changes during irreversible extension, but by assuming these to be zero it is estimated that the temperature is likely to rise by 20–30°C. at strains above 10%. Results from a study of the effect of strain rate on the stress‐strain curves of five different yarns show in all these materials a range of strain rate in which the stress that produces a given strain increases less rapidly with strain rate than elsewhere. For viscose and poly(ethylene terephthalate) this effect occurs in the expected range of strain rate, and its magnitude is of the correct order for it to be attributed to the temperature rise resulting from the transition from isothermal to adiabatic extension. For the other materials the transition does not seem likely to provide a complete explanation of this effect. There is no evidence that the transition significantly affects the breaking properties.