The heat build-up and stress heterogeneity effects on PE

Lili Wan (1) , Cristian Ovalle (1) , Lucien Laiarinandrasana (1)

1 CDM - Centre des Matériaux

The heat build-up induced by the conversion of plastic work into dissipative heat [1] is a common and, eventually, dangerous phenomenon on polymers subjected to static or cyclic loading. The temperature rise, linked to the strain rate and the local stress state, promotes the microstructural alteration and mechanical properties degradation. Therefore, without consideration of the temperature rise, the components lifetime may be over-estimated by the available prediction models. In order to study the coupled heat build-up mechanisms and stress heterogeneity effects on PolyEthylene (PE), uniaxial tensile and fatigue tests were carried out on both flat and axisymmetric tensile samples with two notch radii, i.e. different initial stress triaxiality ratios. During loading, the sample surface temperature was recorded using a high-accuracy infrared camera. Image processing was applied to measure the sample geometry evolution, e.g. the notch opening increase. Besides, based on Bridgman theory, the analytical stress fields were computed. A significant dependence of the temperature field with the notch root radius was observed. Under the same loading condition, samples with smaller notch root radius showed more brittle failure. The elastic compliance, the maximum net stress and failure characteristics were all influenced by the stress triaxiality ratio and crosshead speed. For instance, the higher the crosshead speed, the higher the maximum net stress. A good correlation was obtained between the heat build-up temperature evolution and the region of the re-necking as well as that of the initiation of final failure; moreover, a significant heat build-up was observed during the crack propagation [2]. Further work will investigate the heat build-up and stress heterogeneity effects on fiber-reinforced thermoplastics. The development and numerical implementation of a fully-coupled thermomechanical model, accounting for the heat build-up, will be an encouraging challenge. [1] G.I. Taylor and H. Quinney. Proc. R. Soc. Lond. A, 143:307–326, (1934). [2] D.Rittle. Mechanics of Materials, 32:131–147, (2000).

Domaines: Mécanique des matériaux [physics.class-ph]; Matériaux et structures en mécanique [physics.class-ph]

Lili Wan, Cristian Ovalle, Lucien Laiarinandrasana. The heat build-up and stress heterogeneity effects on PE. ACEX2021 - 14th International Conference on Advanced Computational Engineering and Experimenting, Jul 2021, Malta, Malta. ⟨hal-03510841⟩