In this paper, efficient approximate solutions are developed for microscale diffusion inside porous electrodes. Approximate solutions developed for the microscale diffusion are then coupled with governing equations for the macroscale to predict the electrochemical behavior of a lithium-ion cell sandwich. Approximate solutions developed facilitate the numerical simulation of batteries by reducing the number of differential algebraic equations resulting from the discretization of governing equations.

Recent interest in lithium-ion batteries for electric and hybrid vehicles, satellite, defense, and military applications has increased the demand on the computational efficiency of lithium-ion battery models. This paper presents an effective approach to simulate physics based lithium-ion battery models in real-time ͑milliseconds͒ for simulation and control in hybrid environments. The battery model used for the simulation is derived from the first principles as an isothermal pseudo two-dimensional model with incorporation of concentrated solution theory, porous electrode theory, and due consideration for the variations in electronic/ionic conductivities and diffusivities using the Bruggmann coefficient.

A numeric symbolic solution technique is introduced for the simulation of ac impedance response of electrochemical devices. The proposed method is numerical in the spatial coordinates and yields a closed form symbolic solution in the system parameters. The system of algebraic equations obtained by the spatial discretization is written in matrix form and solved symbolically. Although this method is capable of simulating ac impedance data for systems with multiple coupled partial differential equations, the method and its advantages over classical methods are illustrated using diffusion in a planar electrode.

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Aluminium alloy AA 2219 is used in aerospace applications because of its good weldability, stress corrosion resistance, and mechanical properties over a wide temperature range of + 250 to - 250 ° C. The elastic-plastic fracture toughness JIc has been measured on 7.4 mm thickness autogenous alternating current tungsten inert gas welded plates of 2219-T87 alloy in the as welded condition, using a single specimen technique. The present paper elucidates the variation of JIc across the weld joint. The toughness was evaluated at three different locations across the weld, namely, in the weld, fusion boundary, and heat affected zones, and compared with parent metal toughness. It was found that the fracture toughness across the weld was higher than the parent metal toughness. The fusion boundary had the lowest toughness among the three zones across the weld joint. The variation of toughness among the different zones is explained with reference to fractographic observations.