Florence Ossart

Residual stresses in punched laminations: Phenomenological analysis and influence on the magnetic behavior of electrical steels

The magnetic properties of laminated electrical steels are degraded by punching because of plasticity localized along the cutting edge, but also because of residual stresses, which may spread over the whole lamination. In this article, long-range residual stresses are analyzed via a simplified mechanical analysis. Then, their effect on the global magnetic behavior of the lamination is calculated by a magnetoelastic coupled model. It is found that the relative influence of residual stress is as important as the one of plasticity alone.

A new internal variables scalar hysteresis model respecting the wiping-out property

A new internal variable hysteresis model is proposed, in which bulging of the pinned walls and evolution of the global domain configuration are considered as distinct phenomena. Minor loops being closed for the considered FeSi lamination, the field history is memorised as in the Preisach approach, but the resulting model is simpler. Reported results show the accuracy of the model.

Magneto-elastic coupled finite element analyses

ABSTRACT The aim of this paper is to introduce a general framework to model the coupled phenomena which occur when a system of solids is subjected to thermal, magnetic and mechanical loadings. This framework constitutes the basis of the numerical methods to be developed in order to perform coupled thermo-magneto-mechanical structural analyses of electrical machines. These general concepts are illustrated by different examples.

Computation of electromagnetic losses including stress dependence of magnetic hysteresis

An internal variable magnetic hysteresis model accounting for stress dependence is implemented in a 2D finite element model, in order to investigate the effect of an elastic stress on the field and eddy current distributions in electrical steels. Hysteresis and eddy current losses in a non oriented 3%FeSi lamination are computed and discussed for various excitation field magnitudes.

Comparative Study of Real-Time HEV Energy Management Strategies

An adequate energy management strategy is the key to optimizing hybrid electric vehicle fuel efficiency. Various real-time controls have been recently developed. As each study is performed in a specific context, a comparative analysis is critically needed to point out their pros and cons. This paper proposes a comparison between three promising real-time strategies: adaptive equivalent consumption minimization strategy (A-ECMS), optimal control law (OCL), and stochastic dynamic programming (SDP). Two offline algorithms are used as benchmark: Pontryagins minimum principle and dynamic programming. Implementation and parameters setting issues are discussed for each strategy. The real-time strategies robustness is then evaluated over several types of driving cycles and a statistical analysis is conducted using random cycles generated by Markov process. Simulation results show that OCL needs improvement. A-ECMS reaches the best fuel saving performance when used with parameter sets adjusted to the driving environment, while SDP better respects the charge sustaining constraint.

An Optimal Energetic Approach for Systemic Design of Hybrid Powertrain

On-going oil stock depletion and growing environmental concerns lead automakers to develop more efficient powertrains. Today, the most promising way forward consists in research on hybrid systems. Defining the most efficient powertrain requires a systemic design. In this paper, three main levers are used: powertrain architecture, energy management and electric components design. Different powertrain architectures (series, parallel and combined) are compared: their optimal energetic performances are calculated for different INRETS driving cycles by using dynamic programming as an optimal control strategy. The most promising hybrid powertrain is the parallel one. Its behavior is more closely analyzed so as to provide technical specifications for an optimal sizing of the electric components: electric machine and battery.

Hybrid powertrain design using optimal control strategies

The urgent need of CO2 emissions saving leads automakers to develop more efficient powertrains. The present work compares different electric hybridizations to identify key guidelines to design efficient systems. The optimal energetic performances of different powertrain architectures (series, parallel and combined) are calculated by using optimal control strategies and dynamic programming. The aim is to point out the limiting factors of a given architecture and to define how electric power components should evolve to achieve a better global efficiency of the system. The battery capacity influence on CO2 saving is discussed. The distribution of electric loads is presented for different INRETS driving cycles. The influence of the electric machine efficiency on regenerative braking and internal combustion engine working points optimization is analysed. This work leads to technical specifications to choose an optimal architecture and to size the electrical components.

Setup to test biaxial stress effect on magnetomechanic coupling

Many authors provide a self-method to take into account a multiaxial stress state for magnetic coupling. By reviewing those criteria we try to point out the most general one. We also propose an original setup validated by FE calculation.

SECTION 9.16 – Elasticity Coupled with Magnetism

This chapter discusses different scalar magnetic hysteresis models that are valid for isotropic soft ferri- and ferromagnetic materials subjected to uniaxial magnetic excitations and uniaxial elastic stresses. Hereditary model that is preisach model, is described in the chapter. The Preisach model is currently recognized as a static scalar hysteresis model with well-defined properties and the more accurate prediction of minor loops. In addition, the mechanical state and in particular the stress state of the material have a great influence on its magnetic properties. Two different approaches are proposed to build a scalar Preisach-type hysteresis model that accounts for the influence of a uniaxial stress, which are explained in the chapter.