Modeling the Mechanical Response of a Dual-Phase Steel Based on Individual-Phase Tensile Properties

In this work, the engineering stress–strain tensile curve and the force-deflection bending curve of two Dual-Phase (DP) steels are modeled, combining the mechanical data of fully ferritic and fully martensitic steels. The data is coupled by a modified law of mixture, which includes a partition parameter q that takes into account the strength and strain distributions in both martensite and ferrite phases. The resulting constitutive model is solved in the context of the finite element method assuming a modified mixture rule in which a new parameter q′ is defined in order to extend the capabilities of the model to deal with triaxial stresses and strains and thus achieve a good agreement between experimental results and numerical predictions. The model results show that the martensite only deforms elastically, while the ferrite deforms both elastically and plastically. Furthermore, the partition factor q′ is found to strongly depend on the ferritic strain level. Finally, it is possible to conclude that the maximum strength of the studied DP steels is moderately influenced by the maximum strength of martensite.

Distribution of generated friction heat at wheel-rail contact during wheel slipping acceleration

This paper presents an innovative method for determining the distribution of the friction generated heat from the contact of a locomotive wheel and rail, as well as the heat partition factor, during wheel slipping of an accelerating locomotive. The new method combines the finite element analysis simulation and experimental determination of the temperature distribution in a downsized model of a wheel and rail. As a result of a virtual experiment by the finite element analysis, an empirical dependence between the temperature distribution and the heat partition factor was established. The determination of the dependence enabled finding of the exact value of the heat partition factor by the optimization procedure based on matching temperatures obtained by the virtual and real experiment.