Análise do comportamento dinâmico de um disco de palhetas flexíveis na presença de uma trinca transversal modelada pela abordagem FLEX

Abstract

Detecting incipient cracks in rotating systems using classical techniques can be a very onerous task. On the other hand, as the dynamic behavior of a system manifests changes in its mechanical properties, mathematical models can be used to simulate the presence of cracks in these structures, allowing a precise understanding of the effects induced by this non-linearity and consequently helping diagnostic procedures and identification of this type of failure. In this sense, this dissertation aims to analyze the dynamic behavior of a flexible-blade disk in the presence of incipient transverse cracks through the numerical-computational implementation of models developed in previous researches. To this end, it is considered as object of study a system composed of a rigid rotor with a flexible foundation and four flexible blades connected to a rigid mass at the free end, having a transverse crack in one of the blades and with movement restricted to the plane. In the modeling of rotating beams, the finite element method applied to the Euler-Bernoulli beam theory and the second-order linearized strain vector are considered. For the crack, the presence in one of the blades, for different depths and positions, is simulated using the FLEX model. The equations of motion are developed applying the Lagrange method and solved using the Newmark time integration technique associated with the Newton-Raphson iterative process. The dynamic responses are evaluated and compared to the healthy system in the time, modal and frequency domains, and with stability maps, which are constructed considering Floquet's theory. The results demonstrate that the modeling of transverse cracks using the FLEX approach is appropriate to represent the dynamics of cracked rotating systems.