The effect of an insulated rail joint (IR J) on the contact stress variation near wheel±rail contact zones was simulated by employing three-dimensional ®nite element models. Three linear elastic IR J materials, i.e. epoxy-®breglass, polytetra¯uoroethylene (PTF E) and N ylon-66, were investigated. Contact elements were used to simu late the interaction between the wheel and rail contact points. N umerical results showed that the presence of IR J might signi®cantly affect the wheel±rail contact stress distrib utions. R esults also indicated that the traditional H ertzian contact theory is no longer available to predict the contact stress distribution around the rail joints.
The effect of neodymium substitution on the lanthanum site in La 0.7−x Nd x Pb 0.3 MnO 3 perovskite polycrystalline has been systematically studied. The substitution of neodymium for lanthanum causes structure change from rhombohedral to orthorhombic. Ferromagnetism is suppressed as neodymium content increases. The magnetic order changes from a ferromagnetic long-range order with x = 0.0 to a spin-glass nature with x = 0.7. Besides, the ferromagnetic-paramagnetic transition temperature values are lower for the neodymium phases than for the lanthanum ones. Therefore, the introduction of neodymium degrades symmetry of the structure, diminishes the spin-coupling exchange interaction, and results in changes of magnetic properties. This fact is in good agreement with increasing the B value in Bloch's T 3/2 law and decreasing the spin-wave stiffness parameter D in quadratic dispersion relation.
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