Banca de DEFESA: Karine Fortunato Silva Barbosa

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : Karine Fortunato Silva Barbosa
DATA : 03/03/2025
HORA: 16:00
LOCAL: UNIFEI
TÍTULO:

TRIBOLOGY OF VISCOPLASTIC MAGNETO-RHEOLOGICAL FLUIDS: THE ROLE OF GREASE IN FRICTION AND WEAR IN “4-BALL” TESTS

PALAVRAS-CHAVES:

Magnetorheological fluids; Grease additives; Tribology; 4-ball test.

PÁGINAS: 172
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
ESPECIALIDADE: Materiais Conjugados Não-Metálicos
RESUMO:

This dissertation investigates the tribology of viscoplastic magnetorheological fluids, with an emphasis on the use of grease as stabilizing additives to minimize friction and wear. Magnetorheological fluids can reversibly alter their viscosity under the influence of a magnetic field, offering advantages for devices requiring motion control and damping. However, particle sedimentation presents a challenge, affecting the efficiency and stability of these fluids over time. The objective of this research was to develop formulations of magnetorheological fluids stabilized with grease and evaluate their tribological behavior in wear and friction tests using a 4-ball geometry. Six different formulations, including pure lubricants and those with additives, were analyzed to determine the best friction coefficient, wear resistance, and stability under various load and temperature conditions. Rheological and tribological tests were conducted according to DIN 51810-1/51810-2 and ASTM D-2266/D- 4172 standards, using an MCR-301 rheometer and a TE92-HS tribometer, both equipped with a magnetic field. Characterization was carried out through optical, confocal, and scanning electron microscopy analyses to evaluate surface wear and roughness. Results indicated significant variations among the tested formulations. The WG formulation showed greater strength and elasticity, with the best values for yield stress and elastic modulus. In tribological tests, the NP formulation achieved the best friction coefficient with the addition of iron powder and without a magnetic field, exhibiting higher stability with a lower standard deviation. Optical and confocal microscopy indicated reduced surface wear for the NP formulation, both pure and with iron powder under a magnetic field, despite higher roughness values in the presence of a magnetic field. Scanning electron microscopy analysis showed that the pure NP formulation and the NP with iron powder without a magnetic field exhibited the smallest wear diameters, and with iron powder and an applied field, suggesting the formation of an effective protective layer against wear. The results contribute to understanding the tribological behavior of these fluids, indicating possibilities for improvement in stability and efficiency for industrial applications that require motion control and wear resistance.

MEMBROS DA BANCA:
Presidente - 395189 - ANTONIO JOSE FARIA BOMBARD
Interna - 1560408 - MARIA ELENA LEYVA GONZALEZ
Interno - 1545324 - ROSSANO GIMENES
Externo à Instituição - TIAGO COUSSEAU