Análise da influência de trincas transversais no comportamento estático e dinâmico de eixos flexíveis

Abstract

The structural health monitoring of rotating machines has been an important tool in the industry, providing safe operating conditions for these equipments. A commonly used technique for this purpose is based on the construction of mathematical models that allow the analyses of the system. This approach has gained even more prominence due to the ability to detect small changes in physical parameters, such as stiffness reduction as caused by the existance of cracks in shafts. Since the occurrence of cracks may cause failures in rotating machines and, consequently, unnecessary expenses, this work proposes to evaluate the static and dynamic behavior of a disc-shaft-bearing system in order to verify the influence of an open crack with different severities. Two finite element models were developed in MatLab® (1D) and Ansys® (3D model) environments and the obtained responses were compared with experimental results. A crack was inserted into the 1D model from the additional flexibility calculated through the the linear fracture mechanics theory. In this conctext, the concepts of deformation energy release rate, stress intensification factor, and Castigliano's theorem were used. Regarding the 3D model, the crack was simulated by means of a saw cut included in the cross section of the shaft. The length of the finite element with a crack was modified to approximate the results of the 1D model and experimental ones.