Banca de QUALIFICAÇÃO: Igor Dal Osto Pereira

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : Igor Dal Osto Pereira
DATE: 27/10/2022
TIME: 14:30
LOCAL: VORTEX
TITLE:

Rheology of magnetorheological and anisotropic suspensions in steady and unsteady shear flows.

KEY WORDS:

Magnetorheological suspension, magnetoviscous effect, shear-thinning effect, viscoelastic moduli, stress relaxation function, residual stress, anisotropy

PAGES: 100
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUMMARY:

In this work, is characterized under the experimental point of view the rheological behavior of two magnetorheological suspensions. These complex fluids have the same base fluid, which is mineral oil, and differ in relation to the type of ferromagnetic particles used in their composition. The solute in one of the suspensions is magnetite powder, with an average particle size of 8nm. The second type of suspension is formed by dispersing carbonyl iron powder (5nm) in the base fluid. It is important to note that, although the particles are nanometric, they form non-Brownian micrometric structures (agglomerates or anisotropic chains) when in suspension, thus giving rise to magnetorheological suspensions Three experimental methodologies are implemented in this study. The first one refers to tests under permanent shear in the presence of a magnetic field, through which the behavior of the apparent viscosity and shear stress of the magnetorheological suspensions is examined as a function of the magnetic field strength, the shear rate and the particle volume fraction of the complex fluid. This allows the verification of the adherence of the rheological behavior of such fluids to generalized Newtonian fluid models. The second methodology concerns experimental tests with transient-type flows, that is, in the step-strain regime in the presence of a magnetic field. From this experimental analysis it is obtained, for the different magnetorheological suspensions, their stress relaxation functions dependent on the magnetic field intensity and, based on them, it is calculated their relaxation times. It is also verified that the shear stress does not relax to zero in magnetorheological suspensions when in the presence of a magnetic field, but to a residual stress, which is evaluated as a function of the field strength. The third methodology refers to tests with oscillatory shear in the presence of magnetic field, in linear viscoelasticity regime, in which the viscoelastic modulus of magnetorheological suspensions are obtained as a function of frequency and magnetic field intensity for a condition of small deformations. Additionally, the shear elastic modulus of the magnetorheological suspensions are calculated in the low frequency limit and presented in terms of the magnetic field intensity. The new stages of the thesis will also be presented and discussed as well as the schedule of activities.

BANKING MEMBERS:
Externo ao Programa - 3087995 - ANDRE VON BORRIES LOPES
Interno - 1170729 - FRANCISCO RICARDO DA CUNHA
Externo à Instituição - PAULO CESAR DE MORAIS
Interno - 2730343 - RAFAEL GABLER GONTIJO