A COHESIVE ZONE MODEL FOR THE INVESTIGATION OF THE BREATHING MECHANISM OF TRANSVERSAL CRACKS IN ROTORS

A COHESIVE ZONE MODEL FOR THE INVESTIGATION OF THE BREATHING MECHANISM OF TRANSVERSAL CRACKS IN ROTORS

Liong, R. T.; Proppe, C.

Full Article:

The presence of a crack reduces the mean stiffness of the rotor system and introduces a stiffness variation during the revolution of the shaft. How the variable part of the rotor stiffness varies between a minimum (for a closed crack) and a maximum (for an open crack), depends on the so-called breathing mechanism. The breathing mechanism is known when the open and closed parts of the cracked area are known for all angular positions of the rotor. Here, finite element (FE) and multi-body simulation (MBS) is introduced. It is based on a representation of the fracture process zone by a cohesive zone model (CZM). First, the cracked elastic shaft with various relative crack depths is modelled by FE. As a second step, the FE model of the shaft is transferred into an MBS model in order to analyze the dynamic loads, due to the crack, and the inertia force acting during rotation at different rotating speeds. Finally, the vibration responses in the centroid of the shaft obtained from the MBS have been exported into the FE model in order to observe the breathing mechanism. This proposed technique provides a useful tool for the analysis of rotor systems containing cracks, reveals the shape of the open crack part during rotation and helps investigating the dynamic behaviour of cracked shafts.

The presence of a crack reduces the mean stiffness of the rotor system and introduces a stiffness variation during the revolution of the shaft. How the variable part of the rotor stiffness varies between a minimum (for a closed crack) and a maximum (for an open crack), depends on the so-called breathing mechanism. The breathing mechanism is known when the open and closed parts of the cracked area are known for all angular positions of the rotor. Here, finite element (FE) and multi-body simulation (MBS) is introduced. It is based on a representation of the fracture process zone by a cohesive zone model (CZM). First, the cracked elastic shaft with various relative crack depths is modelled by FE. As a second step, the FE model of the shaft is transferred into an MBS model in order to analyze the dynamic loads, due to the crack, and the inertia force acting during rotation at different rotating speeds. Finally, the vibration responses in the centroid of the shaft obtained from the MBS have been exported into the FE model in order to observe the breathing mechanism. This proposed technique provides a useful tool for the analysis of rotor systems containing cracks, reveals the shape of the open crack part during rotation and helps investigating the dynamic behaviour of cracked shafts.

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DOI: 10.5151/meceng-wccm2012-18800

Referências bibliográficas

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Como citar:

Liong, R. T.; Proppe, C.; "A COHESIVE ZONE MODEL FOR THE INVESTIGATION OF THE BREATHING MECHANISM OF TRANSVERSAL CRACKS IN ROTORS", p-2288-2301. In: In Proceedings of the 10th World Congress on Computational Mechanics [= Blucher Mechanical Engineering Proceedings, v. 1, n. 1]. São Paulo: Blucher, 2014.
ISSN 23580828, DOI 10.5151/meceng-wccm2012-18800