THE EFFECT OF BLOCK BRAKING ON THE RESIDUAL-STRESS STATE OF A SOLID RAILWAY WHEEL

A finite element, numerical model of a solid railway wheel was perfect ed permitting the simulation of a block braking operation. The analyse s performed backed by experimental tests, permitted the degree of vari ation in the residual stress state (induced by differential quenching heat treatment and successive tempering) caused by particularly heavy braking to be evaluated. The results highlight the influence of the ma in braking parameters (force and time) and the thermal history previou sly suffered by the wheel. Finally, the thermal fatigue strength of th e component, although in an approximate way, was checked on the basis of the calculated stress state and through the introduction of the dat a of a real and particularly significant route into the model. This de monstrated the broad safety margin with which the wheel operates and a lso brought to light the dangerous nature of particularly severe braki ng which can drastically modify the residual stresses induced by the h eat treatment, moving them towards tensile stresses.