Efeito do espessante e da viscosidade de graxas na resistência ao desgaste em ensaio disco-contra-disco

One of the ways to control the friction between rail and wheel is the use of greases on the rail.Therefore, when the train passes by curves stretches, the contact between the wheel and the gauge corner is lubricated.The use of greases presents a lot of benefits to the railroad system, once it can increase the life cycle of wheels and rails and reduce the fuel consumption, the friction coefficient, and the component wear.However, there is a knowledge gap regarding the relationship between grease formulation and its performance.Therefore, this paper proposes to relate the effect of grease viscosity and thickener (lithium and calcium) with the ability to reduce wear.For that purpose, tests were carried out on the twin disc tribometer with four different greases.For that purpose, tests were carried out on the twin disc tribometer with two different greases.The results pointed out that grease increases the surface roughness of the rail disc, as a result of grease entering the pre-existing crack, which causes a hydraulic pressure inside the crack responsible for increasing the speed of propagation.However, the use of greases was beneficial, since it reduced the mass loss and the friction coefficient when compared to dry tests.In addition, it was observed that the grease with lower viscosity (50 cSt) presented a better performance in wear when compared to the grease with higher viscosity (500 cSt), since the Ca50 and Li50 showed lower mass loss, lower crack size, and lower hardened layer lenght.This is because the higher viscosity grease exerts a greater hydraulic effect inside the crack.It was also concluded that, when comparing greases of the same viscosity, lithium thickened greases presented a better performance to reduce wear, for both viscosities tested, as they presented a lower mass loss in relation to the tests carried out with the calcium grease.Therefore, for the tested conditions, of boundary and mixed lubrication regimes, the performance of the grease in wear is controlled by the thickener

Grease · Tribometer · Adhesion, Friction, and Surface Interactions · Gear and Bearing Dynamics Analysis · Railway Engineering and Dynamics

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  Open Access•Caroline A Schneider, Wayne S Rasband et al.•Nature Methods•2012

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