Severity Estimation of Cracked Shaft Vibrations within Fluid Film Bearings
TL;DR: In this article, a cracked Jeffcott rotor supported on fluid film bearings was analyzed and the authors derived the equations of motion with four degrees of freedom, taking into consideration the flexibility, damping and cross coupling of the fluid film bearing.
Abstract: The equations of motion, with four degrees of freedom, taking into consideration the flexibility, damping and cross coupling of the fluid film bearings are derived for a cracked Jeffcott rotor supported on fluid film bearings. Dimensionless equations are developed for dynamic radial load, dynamic pressure developed in the fluid film bearings and coefficient of dissipation considering the journal vibrations in two harmonics; bearing fluid film stiffness and damping coefficients. These are applied to a cracked Jeffcott rotor supported on different types of bearings, i.e., cylindrical journal bearings, offset cylindrical bearings, tilting pad journal bearings and three-lobe bearings. Based on the allowable dynamic pressure developed in the fluid bearings, the severity of cracked shaft and allowable crack depths are estimated in this study. Measurement of dynamic pressure and dissipation for monitoring the crack growth is suggested. However, 2x vibration is the best indicator of cracks in the shafts. Presente...
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TL;DR: A review of the literature on cracked shaft detection and diagnostics can be found in this paper, where the authors reviewed more than 500 technical papers published in English alone in the past 30 years.
Abstract: Cracks in shafts have long been identified as factors limiting the safe and reliable operation of turbomachines. They can sometimes result in catastrophic failure of equipment (rotor bursts) and, more often, in costly process upsets, repairs and premature scrapping and replacement of equipment. Cracked shafts still pose a significant and real threat to equipment in spite of the great advances made in the areas of metallurgy, manufacturing and design. In the past two decades, much research and many resources have gone into developing various on-line and off-line diagnostic techniques to effectively detect cracks before they cause serious damage. Because of the enormous amount of ongoing research in this area (more than 500 technical papers have been published in English alone in the past 30 years), there is a real need to periodically condense and summarize the information. This paper reviews literature on cracked shaft detection and diagnostics published after 1990.
177 citations
TL;DR: In this article, the effects of various surface coatings on the tribological characteristics of the piston ring and cylinder block surface of a diesel engine were evaluated using a reciprocating wear tester.
33 citations
TL;DR: In this paper, the authors used the continuous wavelet transform (CWT) to extract sub-harmonics from the time domain signals of a rotor system coasting down through its critical speed.
23 citations
TL;DR: In this article, the continuous wavelet transform (CWT) has been applied to extract the features of transverse cracks from the time-domain signals of rotor bearing system for rotor-bearing system.
18 citations
TL;DR: In this article, the authors investigated the nonlinear dynamics of a cracked rotor system in an aircraft maneuvering with constant velocity or acceleration and found that the climbing angle of the aircraft can markedly affect the parameter range for bifurcation, for quasiperiodic response and for chaotic response as well as for system stability.
Abstract: The nonlinear dynamics of a cracked rotor system in an aircraft maneuvering with constant velocity or acceleration was investigated. The influence of the aircraft climbing angle on the cracked rotor system response is of particular interest and the results show that the climbing angle can markedly affect the parameter range for bifurcation, for quasiperiodic response and for chaotic response as well as for system stability. Aircraft acceleration is also shown to significantly affect the nonlinear behavior of the cracked rotor system, illustrating the possibility for on-line rotor crack fault diagnosis.
16 citations
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TL;DR: In this paper, a review of the field of the dynamics of cracked rotors is presented, including the modeling of the cracked part of the structure and finding different detection procedures to diagnose fracture damage.
Abstract: Propagating fatigue cracks can have detrimental effects on the reliability of rotating machinery. An early crack warning can considerably extend the durability of these very expensive machines, increasing their reliability at the same time. Vibration monitoring as a means of detecting crack initiation has been receiving much interest. A detailed study of the vibrational behavior of cracked rotating shafts, therefore, is an important problem for engineers working in the area of the dynamics of machines. This article presents a review of the field of the dynamics of cracked rotors, including the modeling of the cracked part of the structure and finding different detection procedures to diagnose fracture damage. The material should be helpful to scientists and researchers working in this area or planning to work in it in the future. Since the study of nonrotating, cracked structural elements obviously is relevant to the cracked rotor problem, the review can also be a basis for discussing the dynamics of cracked beams and columns.
387 citations
TL;DR: Apercu d'une methode de calcul des vibrations de flexion d'un arbre monte sur plusieurs paliers and presenting une fissure suivant une section as discussed by the authors.
Abstract: Apercu d'une methode de calcul des vibrations de flexion d'un arbre monte sur plusieurs paliers et presentant une fissure suivant une section. On indique comment il est possible de calculer les variations, dues a la fissure, des raideurs figurants dans les equations de mouvement. L'arbre fissure est equivalent a un arbre presque pareil mais qui presenterait un etroit troncon de section reduite. On presente une methode de calcul approche de la section reduite. Ces methodes sont utilisables sur ordinateur et leur application a des turbo-alternateurs a donne des resultats encourageants
279 citations
01 Jan 1978
142 citations
TL;DR: In this article, the stiffness and damping coefficients for ideal operating conditions were determined and their reliability ascertained by vibration measurements on high-speed rotors for four practically important journal bearing designs and the significant effects on the static load capacity of the bearing and the stability behavior of the rotor-bearing systems are illustrated and discussed.
58 citations