A fully coupled damage model with stress triaxiality and Lode dependence

International audienceAbstract In the present work, an advanced CDM model considering stress triaxiality and Lode angle effect is proposed. The framework of thermodynamics of irreversible processes with state variables is used to build the constitutive equations accounting for strong and full coupling between all the dissipative phenomena. The proposed model is implemented into Finite Element (FE) code ABAQUS/Explicit via a user material subroutine (VUMAT). A detailed parametric study with various values of the new material parameters is conducted in order to show the predictive capability of the proposed model. Applications to sheet metal forming simulation have been performed to validate the damage prediction capability of the proposed model, and the numerical simulation results are analysed and discussed

Impact of dietary restriction on peroxidative effects of nickel chloride in wistar rats

International audienceThe purpose of this study, carried out in Wistar rats, was to evaluate the protective effect of dietary restriction (performed by intermittent fasting) against oxidative stress induced by a low concentration of nickel chloride in kidney, liver, uterus, and ovary. Lipid peroxidation (TBARS), catalase activity, and the levels of vitamins E and A in the blood were investigated in rats feed for 1 month either daily (N) or 1 day over two (intermittent fasting, IF) and then injected (NNi, IFNi) or not with nickel chloride (30 moles/kg body weight/day) for 10 days. Ni induced a significant increase of TBARS in organs of N rats. Intermittent fasting alone or associated to nickel treatment did not result in TBARS change in IF and IFNi rats. Catalase activity levels were found to be similar in N and IF rats. In Ni-treated rats a transient increase of catalase activity appeared at day 1 in the kidney and days 1 and 3 in the liver. Then, catalase activity was found to be inhibited until day 10. In the uterus and ovary, catalase activity was always found to be inhibited. In IFNi rats, no significant increase of catalase activity was observed as compared to IF rats. Vitamin E was inhibited from the 1st to the 10th day in Ni rats, whereas no significant changes were noted in IFNi rats. A moderate decrease of vitamin A was only found at days 1 and 3 in Ni rats. In conclusion, intermittent fasting is able to protect from oxidative stress induced by low concentration of Ni, but catalase and Vitamins E and A do not seem to be involved