Banca de QUALIFICAÇÃO: LENIN LEE HUAMAN VALDIVIA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : LENIN LEE HUAMAN VALDIVIA
DATA : 27/05/2022
HORA: 08:00
LOCAL: CAMPUS DE SANTO ANDRE, REMOTAMENTE
TÍTULO:

STABILITY AND DYNAMIC BEHAVIOR OF A VISCOELASTIC PIPE DISCHARGING INTERNAL FLUID

PÁGINAS: 100
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Mecânica
SUBÁREA: Mecânica dos Sólidos
ESPECIALIDADE: Dinâmica dos Corpos Rígidos, Elásticos e Plásticos
RESUMO:

This master’s work addressed the stability and behavior of a viscoelastic pipe arranged vertically, fixed at the top and free at the lower end, discharging internal fluid. The system is not conservative because the fluid in motion is an infinite source of energy supply. The pipe is seen as a slender structure, subject to small deflections and rotations so that the Euler-Bernoulli beam theory is adopted. Longitudinal deformation of the pipe is not considered. The pipe material behaves according to the Kelvin-Voigt viscoelastic model.  The study of the effects of viscoelastic dissipation leads to the paradox of loss of stability due to energy dissipation, a subject of special scientific interest. The internal fluid is stable, incompressible, and uniform at constant velocity. The partial differential equation of movement of the system is obtained by the Newtonian approach when analyzing the dynamic equilibrium of elements of tube and fluid, which is dimensionless by introducing the dimensionless parameters of mass, discharge velocity, viscoelastic and gravity. The equation of motion is discretized using the Galerkin method, where the deflection of the tube is approximated by the sum of the products of two functions, spatial and temporal. The spatial functions are the modes shape in free vibration of the cantilever pipe, while the temporal functions are harmonics that define the amplitude of the oscillation. To study the stability of the system, the velocity of the fluid is gradually increased and at each point velocity the characteristic equation of the system is solved, obtaining the natural frequencies. The set of natural frequencies that are complex quantities is presented in the Argand diagram where it is possible to directly identify the critical velocity from which the system becomes unstable via ordinary Hopf bifurcation, it is also possible to predict the flutter and the type of movement developed by the pipe, purely harmonic, aperiodic decay, periodic oscillatory motion with positive or negative damping. The effects of the dimensionless parameters of mass, viscoelasticity, and gravity on the values of the critical velocities of the internal fluid are also studied. In the second phase of research development, for the defense of the master's thesis, the dynamic response in the time domain of a particular system will be addressed when applying a periodic excitation force.

 

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1761050 - JUAN PABLO JULCA AVILA
Membro Titular - Examinador(a) Externo à Instituição - RENATO MAIA MATARAZZO ORSINO - IMT
Membro Titular - Examinador(a) Externo à Instituição - GUILHERME ROSA FRANZINI - USP
Membro Suplente - Examinador(a) Interno ao Programa - 1604134 - CICERO RIBEIRO DE LIMA