Effects of stress triaxiality ratio on the heat build-up of polyamide 11 under loading

Abstract

Adiabatic heat build-up in polymers attributed to the conversion of plastic work into dissipative heat is a well known phenomenon. The temperature in the vicinity of a crack tip due to heat build-up may be exceptionally high so that it can locally reach the glass transition temperature Tg, even though the ambient testing temperature is lower than Tg. A significant alteration of the local material response and damage mechanisms is then induced. By simultaneous measurement of temperature during experimental tests under quasi-static loading and for a wide range of stress triaxiality ratios, a Gurson-Tvergaard-Needleman based thermo-mechanical constitutive model, integrating temperature-dependent coefficients, has been developed. Predictive capabilities of the proposed thermo-mechanical model to simulate the isothermal behaviour of PolyAmide 11 (PA11) have led to adiabatic simulations, to account for the heat build-up highlighted experimentally, of ductile crack extension. The model parameters were identified using experimental data obtained from PA11 samples with a given stress triaxiality ratio. Predicted evolutions given by the proposed constitutive model for other stress triaxiality ratios and geometries are found to be in good agreement with experimental data.