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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 293-294 (Sept. 2005), p. 475-482 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Model based fault identification techniques can be used to diagnose local faults in rotating machinery; the equivalent loads that represent fault forces can be used to identify the fault location. But in some cases the equivalent loads smeared over many nodes, and make it hard to identify accurate fault location and transient fault force. In this paper, the fault location is identified using least squares fitting approach by the system’s vibration shape when the fault signal is periodic or quasi-periodic. And after the fault location is ascertained, the transient fault forces can be identified by transient residual vibration using simple matrix multiplications and additions. Numerical simulations and experiment on rotor to stator rub are used to test the method, which proved the efficiency of the method
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 293-294 (Sept. 2005), p. 355-364 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A quantitative identification procedure for local rubbing fault in rotor systems based on a hybrid model is proposed. The hybrid model combines finite element model of rotor and rigid discs, online identified oil film stiffness and elastic supports. The identification algorithm of oil film parameters is stated in detail. The hybrid model based diagnosis process for local rubbing fault is described with assumption of periodic rubbing forces. With the help of modal expansion technique, the estimated rubbing forces at each node along rotor are checked for the rubbing position. The estimated rubbing forces at ascertained position are then used in fault severity assessing quantitatively next. These approaches have been tested successfully on a test rig with single rotor double discs
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 304-305 (Feb. 2006), p. 141-145 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The nonlinear chatter in grinding machine system is discussed analytically in the paper. In higher speed grinding process, the self-excited chatter vibration is mostly induced by the change of grinding speed and grinding wheel shape. Here the grinding machine tool is viewed as a nonlinear multi-D.O.F. autonomous system, in which hysteretic factors of contact surfaces are also introduced. Firstly, the DOFs of the above system are reduced efficiently without changing its dynamic properties by utilizing the center manifold theorem and averaging method. Then, a low dimensional system and corresponding averaging equations are obtained. The stability and bifurcation of chatter system are discussed on the base of deduced averaging equations. It is proved that chatter occurs as a Hopf bifurcation emerging from the steady state at the origin of system. The theoretical analyses on the multi-DOF chattering system will lead to further understanding of the nonlinear mechanisms of higher speed grinding processes
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 2463-2466 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Rotating machinery, such as steam turbo, compressor, and aeroengine etc., are widely usedin many industrial fields. Among the important rotor faults, the fatigue crack fault, which can lead tocatastrophic failure and cause injuries and severe damage to machinery if undetected in its earlystages, is most difficult to detect efficiently with traditional methods. In the paper, based on the truthof the change of the mode shapes of the cracked structure, a new method by combining accurate finiteelement model of rotor with multi-crack in shaft and artificial neural network (ANN) is proposed toidentify the location and depth of cracks in rotating machinery. First, based on fracture mechanics andthe energy principle of Paris, the accurate FE model of the rotor system considering several localizedon-edge non-propagating open cracks with different depth, is built to produce the specific modeshapes. Then a set of different mode shapes of a rotor system with localized cracks in several differentpositions and depths, which will be treated as the input of the designed ANN model, can be obtainedby repeating the above step. At last, with several selected crack cases, the errors between the resultsobtained by using the trained ANN model and FEM ones are compared and illustrated. Meanwhile,the influences of crack in the different position on the identification success are analyzed. The methodis validated on the test-rig and proved to have good effectiveness in identification process
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 754-757 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents mainly the nonlinear dynamics of the mechanical system withsectional frictions and combination friction coefficients. It is clear that the nonlinear dynamiccharacteristics of mechanical systems with sectional frictions are quite different from those ofclassical machinery, and have more precise and valuable in many practical projects. Theexpressions of various nonlinear forces are given firstly and the approximation solutions of thesystem are found with asymptotic method in nonlinear theory, and the combination frictioncoefficients and damping coefficients of the materials are obtained. Then some nonlinear dynamiccharacteristics of the system with sectional frictions are also discussed. The results are veryimportant for designers of these machines
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 359-360 (Nov. 2007), p. 494-498 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In grinding process, chatter vibrations known as self-excited vibrations, becomeincreasingly problematic and must be avoided. Firstly, experimental measurements of chattervibrations in a numerical control (NC) grinding machine tool are introduced for the case of a specialalloy workpiece being carried on. Then, frequency spectra of chatter vibrations are analyzed. Thewavelet package transform technique is used to describe original chatter signals in the term of scaledenergy of frequency bands. At last, fractal dimensions of the reconstructed signals in consecutivefrequency bands of chatter vibrations are calculated. These results are helpful for understanding of thenonlinearity of chatter vibrations
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 762-765 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Vibratory pile driver-extractor is broadly applied in civil constructions, but the frictionvibration theory and dynamic characteristics of friction vibration are not studied well. In this paper,the vibration friction characteristics and dynamics of pile driving process are studied based onnonlinear dynamics and friction theory. A dynamic model of system is established firstly, and thennonlinear dynamic principle and working process are studied in details. The simulation results canprovide useful guidance for both vibration friction research in engineering and design in thedevelopment of such machines
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 758-761 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper mainly focus on vibration friction and discuss the dynamic characteristics ofthe friction under the vibration working condition. It is rather valuable to study such a special kindof friction vibration in engineering. Many practical projects have already proved that under thevibration working condition, the friction force between workpieces can be reduced obviously. Wearand damage of the machine parts can be obviously decreaed.The work efficiency can be improvedgreatly. The Characteristic of friction under the vibration working condition is described in thepaper firstly. Two fundamental experiments illustrate the basic features of vibration friction. Withthe nonlinear dynamics and tribology of vibration friction, some key machinery is introduced in thepaper briefly. The study of vibration tribology is attracting more and more interest of investigators
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 1688-1691 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The corrosion surface of hot-dip galvanized steel is regarded to be fractal and containsabundant self-similar information. In most cases, the corrosions of surface are not uniform asconsidered. For such an uneven eroded surface, regional fractals are introduced here in order toimprove the analysis accuracy for local corrosions. Basing on the singular value decomposition ofsurface image, fractal dimensions of the energy norm along with the energy scale are analyzed.Combining energy norm of singular values and wavelet transform, the corrosion surfaces aredescribed in different scales and decomposed levels
    Type of Medium: Electronic Resource
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