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A comprehensive procedure to estimate the probability of extreme vibration levels due to mistuning / Y.-J. Chan in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 11 (Novembre 2010) . - 08 p. Titre : A comprehensive procedure to estimate the probability of extreme vibration levels due to mistuning Type de document : texte imprimé Auteurs : Y.-J. Chan, Auteur ; D. J. Ewins, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Blades  Conjugate  gradient  methods  Curve  fitting  Gas  turbines  Monte  Carlo  methods  Vibration  measurement Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A new procedure is developed to find the probabilities of extremely high amplification factors in mistuned bladed disk vibration levels, typical of events which occur rarely. While a rough estimate can be made by curve-fitting the distribution function generated in a Monte Carlo simulation, the procedure presented here can determine a much more accurate upper bound and the probabilities of amplification factors near to that bound. The procedure comprises an optimization analysis based on the conjugate gradient method and a stochastic simulation using the importance sampling method. Two examples are provided to illustrate the efficiency of the procedure, which can be 2 or 3 orders of magnitude more efficient than Monte Carlo simulations. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] A comprehensive procedure to estimate the probability of extreme vibration levels due to mistuning [texte imprimé] / Y.-J. Chan, Auteur ; D. J. Ewins, Auteur . - 2011 . - 08 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 11 (Novembre 2010) . - 08 p. Mots-clés : Blades  Conjugate  gradient  methods  Curve  fitting  Gas  turbines  Monte  Carlo  methods  Vibration  measurement Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A new procedure is developed to find the probabilities of extremely high amplification factors in mistuned bladed disk vibration levels, typical of events which occur rarely. While a rough estimate can be made by curve-fitting the distribution function generated in a Monte Carlo simulation, the procedure presented here can determine a much more accurate upper bound and the probabilities of amplification factors near to that bound. The procedure comprises an optimization analysis based on the conjugate gradient method and a stochastic simulation using the importance sampling method. Two examples are provided to illustrate the efficiency of the procedure, which can be 2 or 3 orders of magnitude more efficient than Monte Carlo simulations. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]

Effects of contact interface parameters on vibration of turbine bladed disks with underplatform dampers / C. W. Schwingshackl in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 08 p. Titre : Effects of contact interface parameters on vibration of turbine bladed disks with underplatform dampers Type de document : texte imprimé Auteurs : C. W. Schwingshackl, Auteur ; E. P. Petrov, Auteur ; D. J. Ewins, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Blades  Damping  Discs  (structures)  Fatigue  Friction  Mechanical  contact  Shock  absorbers  Torsion  Turbines  Vibrations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The design of high cycle fatigue resistant bladed disks requires the ability to predict the expected damping of the structure in order to evaluate the dynamic behavior and ensure structural integrity. Highly sophisticated software codes are available today for this nonlinear analysis, but their correct use requires a good understanding of the correct model generation and the input parameters involved to ensure a reliable prediction of the blade behavior. The aim of the work described in this paper is to determine the suitability of current modeling approaches and to enhance the quality of the nonlinear modeling of turbine blades with underplatform dampers. This includes an investigation of a choice of the required input parameters, an evaluation of their best use in nonlinear friction analysis, and an assessment of the sensitivity of the response to variations in these parameters. Part of the problem is that the input parameters come with varying degrees of uncertainty because some are experimentally determined, others are derived from analysis, and a final set are often based on estimates from previous experience. In this investigation the model of a commercial turbine bladed disk with an underplatform damper is studied, and its first flap, first torsion, and first edgewise modes are considered for 6 EO and 36 EO excitation. The influence of different contact interface meshes on the results is investigated, together with several distributions of the static normal contact loads, to enhance the model setup and, hence, increase accuracy in the response predictions of the blade with an underplatform damper. A parametric analysis is carried out on the friction contact parameters and the correct setup of the nonlinear contact model to determine their influence on the dynamic response and to define the required accuracy of the input parameters. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...] [article] Effects of contact interface parameters on vibration of turbine bladed disks with underplatform dampers [texte imprimé] / C. W. Schwingshackl, Auteur ; E. P. Petrov, Auteur ; D. J. Ewins, Auteur . - 2012 . - 08 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 08 p. Mots-clés : Blades  Damping  Discs  (structures)  Fatigue  Friction  Mechanical  contact  Shock  absorbers  Torsion  Turbines  Vibrations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The design of high cycle fatigue resistant bladed disks requires the ability to predict the expected damping of the structure in order to evaluate the dynamic behavior and ensure structural integrity. Highly sophisticated software codes are available today for this nonlinear analysis, but their correct use requires a good understanding of the correct model generation and the input parameters involved to ensure a reliable prediction of the blade behavior. The aim of the work described in this paper is to determine the suitability of current modeling approaches and to enhance the quality of the nonlinear modeling of turbine blades with underplatform dampers. This includes an investigation of a choice of the required input parameters, an evaluation of their best use in nonlinear friction analysis, and an assessment of the sensitivity of the response to variations in these parameters. Part of the problem is that the input parameters come with varying degrees of uncertainty because some are experimentally determined, others are derived from analysis, and a final set are often based on estimates from previous experience. In this investigation the model of a commercial turbine bladed disk with an underplatform damper is studied, and its first flap, first torsion, and first edgewise modes are considered for 6 EO and 36 EO excitation. The influence of different contact interface meshes on the results is investigated, together with several distributions of the static normal contact loads, to enhance the model setup and, hence, increase accuracy in the response predictions of the blade with an underplatform damper. A parametric analysis is carried out on the friction contact parameters and the correct setup of the nonlinear contact model to determine their influence on the dynamic response and to define the required accuracy of the input parameters. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...]

The amplification of vibration response levels of mistuned bladed disks / Y.-J. Chan in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 10 (Octobre 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 10 (Octobre 2011) . - 08 p. Titre : The amplification of vibration response levels of mistuned bladed disks : its consequences and Its distribution in specific situations Type de document : texte imprimé Auteurs : Y.-J. Chan, Auteur ; D. J. Ewins, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Amplification  Blades  Damping  Discs  (structures)  Fatigue  Vibrations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : It is known that small differences between nominally identical turbomachine blades, known as mistuning, can lead to significant variation in their vibration response levels. A commonly used term in mistuning studies called the “amplification factor” is clearly defined in this paper, and the high sensitivity of high-cycle-fatigue-related fatigue life to the level of vibration response levels is presented. Computer simulations are run to study the distribution of the amplification factor in three situations, namely, (i) bladed disks with damping mistuning, (ii) EO excitation of bladed disk modes in the veering region, and (iii) apparently tuned bladed disks. In addition to running simulations, the upper bound of the adjusted amplification factor in damping-mistuned bladed disks is derived theoretically. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013300 [...] [article] The amplification of vibration response levels of mistuned bladed disks : its consequences and Its distribution in specific situations [texte imprimé] / Y.-J. Chan, Auteur ; D. J. Ewins, Auteur . - 2011 . - 08 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 10 (Octobre 2011) . - 08 p. Mots-clés : Amplification  Blades  Damping  Discs  (structures)  Fatigue  Vibrations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : It is known that small differences between nominally identical turbomachine blades, known as mistuning, can lead to significant variation in their vibration response levels. A commonly used term in mistuning studies called the “amplification factor” is clearly defined in this paper, and the high sensitivity of high-cycle-fatigue-related fatigue life to the level of vibration response levels is presented. Computer simulations are run to study the distribution of the amplification factor in three situations, namely, (i) bladed disks with damping mistuning, (ii) EO excitation of bladed disk modes in the veering region, and (iii) apparently tuned bladed disks. In addition to running simulations, the upper bound of the adjusted amplification factor in damping-mistuned bladed disks is derived theoretically. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013300 [...]