A numerical analysis of the dynamic behaviour of sheet steel perforated by a conical projectile under ballistic conditions

Backup bearing is a key safety component of the rotating machinery with the active magnetic bearings (AMBs). Owing to many unexpected reasons, the AMB rotor running at the full speed may drop onto the backup bearings. Sometimes, the full clearance whirling motion is induced, which is harmful to the machine. Therefore, it is quite important to know the transient behaviour of the AMB rotor and the backup bearing. Till date, a lot of works have been performed on the AMB rotor drop and various mathematical models were established. However, most of them took into account only the interaction between the rotor journal and the backup bearing but neglected the interaction between the shaft and the stator component. As we know, for a real AMB machinery, there should be seal components, and the clearance of the seal component is very small to avoid the leakage. If an AMB failure occurs, the interaction between the shaft and the seal component is likely to happen. Thus, it is more reasonable to include this factor into the AMB rotor drop model. The problem is addressed in this work. The previous model is extended to include the shaft-stator contact. The numerical analysis based on two sets of AMB rotor data shows that the dynamic behaviour of the AMB changes greatly, if the shaft-stator contact is considered. There is no longer an optimum support damping to prevent the harmful full clearance whirling motion, and at this time, a well-balanced AMB rotor is preferred.

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Local and global stability of a piecewise linear oscillator

Philosophical Transactions of the Royal Society of London Series A Physical and Engineering Sciences ◽

10.1098/rsta.1992.0019 ◽

1992 ◽

Vol 338 (1651) ◽

pp. 533-546 ◽

Cited By ~ 36

Keyword(s):

Mathematical Model ◽

Numerical Analysis ◽

Nonlinear Oscillator ◽

Dynamic Behaviour ◽

Piecewise Linear ◽

Global Bifurcation ◽

Simple Mathematical Model ◽

Periodic Excitation ◽

Restoring Force ◽

Modern Methods

Machines and mechanisms with moving parts, subjected to periodic excitation, often show unexpected dynamic behaviour, and impacts due to their connection clearances may occur. The most simple mathematical model is a one degree-of-freedom nonlinear oscillator governed by a piecewise linear symmetric function to describe the restoring force. The system’s response, which can be quite rich and complicated, is described in detail. Modern methods for a combined analytical and numerical analysis are used to study local and global bifurcation conditions, coexisting solutions and their associated domains of attraction.

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Macroprobe Mode for the Study of Segregation in Steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100134909 ◽

1990 ◽

Vol 48 (2) ◽

pp. 260-261

Author(s):

Auclair Gilles ◽

Benoit Danièle

Keyword(s):

Mechanical Properties ◽

Spatial Distribution ◽

High Performance ◽

Volume Fraction ◽

Sheet Steel ◽

Acquisition Time ◽

Chemical Information ◽

X Ray ◽

Accurate Quantitative Analysis ◽

Optical Micrographs

During these last 10 years, high performance correction procedures have been developed for classical EPMA, and it is nowadays possible to obtain accurate quantitative analysis even for soft X-ray radiations. It is also possible to perform EPMA by adapting this accurate quantitative procedures to unusual applications such as the measurement of the segregation on wide areas in as-cast and sheet steel products.The main objection for analysis of segregation in steel by means of a line-scan mode is that it requires a very heavy sampling plan to make sure that the most significant points are analyzed. Moreover only local chemical information is obtained whereas mechanical properties are also dependant on the volume fraction and the spatial distribution of highly segregated zones. For these reasons we have chosen to systematically acquire X-ray calibrated mappings which give pictures similar to optical micrographs. Although mapping requires lengthy acquisition time there is a corresponding increase in the information given by image anlysis.

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