Investigation on partition of plastic work converted to heat during plastic deformation for reactor steels based on inverse experimental-computational method

This paper aims at studying the ratio of plastic work converted to heat, β (Taylor and Quinney, 1934) in pressure vessel steels used in VVER-440 energetic reactors by an inverse-experimental and computational analysis. The experiments were performed with different strain rates on a thermal-mechanical testing machine from DSI (model GLEEBLE-3800). Because of the magnitude of strain rate during the experiments it cannot be modelled as an adiabatic process, also the heat transfer during the tests has to be taken into account. Analytical model was carried out to account for the conduction, convection and radiation heat losses that occur during the tests. A thermodynamically based thermo-elasto-plastic model is used to describe both the stress-strain behavior and temperature evolution in these steels under monotonic uniaxial loading. The governing equation system of thermo-elasto-plasticity was implemented in MATLAB software. It is found that β is always smaller for compression than that of tension. The results for 15Ch2MFA (bainitic structure with fine grains) show a rather strong dependence on strain rate, whereas 08Ch18N10T (austenitic structure with coarse grains) is practically independent. The results obtained by the investigation correspond to the literature.