The use of the direct impact Hopkinson pressure bar technique to describe thermally activated and viscous regimes of metallic materials
The influence of strain rate over domains involving the thermal activation and the viscous drag behaviour of the dislocations is discussed. While it is recognized that the Koslky–Hopkinson technique or split Hopkinson pressure bar technique can generate data up to the upper strain-rate limit of the thermal-activated regime, it is necessary to use a direct impact Hopkinson pressure bar technique to access the viscous regime. Data generated with this technique are presented for a series of metals, including steel, nickel, copper and tungsten alloys. The motivation to generate such data is provided through three industrial applications.
A CONSTITUTIVE MODEL FOR STRAIN RATES FROM 10-4 TO 106 s-1
Developpement d'un modele constitutif pour l'analyse des materiaux a taux de deformation unitaire eleve. Analyse de la validite de ce modele pour des essais d'impact a des taux de deformation de 10 −4 s −1 sur du tantale. Simulation a une plaque soumise a une force de charge de 230 GPa. Calcul de la relation entre la force-limite et le taux de deformation et entre la force-limite et la temperature pour un taux de deformation de 10 −4 s −1
Simulation and control of hybrid renewable energy system connected to the grid
This paper presents a control and simulation of hybrid renewable energy system connected to the grid. The studied system includes a photovoltaic panel, synchronous permanent magnet generator based wind turbine, and a battery for storage energy. The PV array and wind systems are connected to the common DC bus by a boost converter. The battery is connected by a bi-directional DC/DC converter, and then integrated into the AC utility grid via a common DC/AC inverter. In order to extract the maximum energy, a simulation study has been carried out according to the meteorological conditions (wind speed and variable solar irradiance) while maintaining power quality at a satisfactory level. In order to capture the maximum power, a MPPT algorithm is applied for both wind turbine and photovoltaic panel. The modeling and simulation of the whole system has been performed under Matlab/Simulink environment. The obtained results show that the current and the voltage of grid side are sinusoidal and alternative forms, and the power injected to the grid is around the power produced by the hybrid system.