Vibrations of Rotationally Periodic Structures
Vibrations of Rotationally Periodic Structures

Author: Andres M. Rodriguez

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

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Blisk components are an integral part of jet engines and power generation systems. Composed of a single monolithic structure, integral blisks combine the blade-and-disk portion of primary components such as the fan, compressor stage, or turbine stage. This design modification increases the aerodynamic performance while decreasing the cost and eliminating time of assembly. However, these benefits come with the loss of blade-disk connection interfaces, which greatly reduces the structure’s damping and its ability to attenuate unwanted structural vibrations. Blisk dynamics are impacted by mistuning, which is a disruption of the periodic symmetry of otherwise identical bladed sections. This disruption degrades the overall performance of components. This dissertation advances theoretical and experimental studies into mistuning, both in terms of characterization and vibration localization. A theoretical analysis of wave propagation in periodic structures shows that vibration localization arises from two separate generating mechanisms: an isolated defect or random variations throughout the structure. Through two novel metrics--the band flatness factor and the localization amplification criterion--we establish a unique approach to identifying localized modes on cyclic structures. We present a novel framework that distinguishes between the response of the tuned and mistuned system. A characteristic single-degree-of-freedom response of the tuned system to engine-order forcing forms the basis of our mistuning characterization framework. The actual mistuning (or tuned system) characterization is performed through computations of a modified modal assurance criterion, termed here the modal mistuning criterion. The modal mistuning criterion uses frequency response function data obtained from engine order-forcing profiles and tuned system modes derived from a model to compute the modal contribution to a mistuned response. Finally, this mistuning characterization metric is validated through experimental tests on multiple academic blisk components.

Vibration of Nearly Periodic Structures and Mistuned Bladed Rotors
Vibration of Nearly Periodic Structures and Mistuned Bladed Rotors

Author: Alok Sinha

Publisher: Cambridge University Press

Published: 2017-06-16

Total Pages: 201

ISBN-13: 1108101348

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This is the first comprehensive volume on nearly periodic structures and mistuned blade vibration. Alok Sinha presents fundamental concepts and state-of-the-art techniques in the analysis of free and forced response of a nearly periodic structure, weaving together his own work (covering thirty-five years of research in this field) with works by other researchers. He also discusses similarities between tools used in bladed rotor analysis and condensed matter physics. Specific subjects covered include the reasons behind mode localization, the reasons behind amplitude amplification of steady-state response, state-of-the-art computational techniques for mistuned bladed rotors including multistage rotors, identification of mistuning from measured response, vibration localization in linear atomic chains, and analysis of two-dimensional periodic structures.

Vibration of Periodic Structures
Vibration of Periodic Structures

Author: Gautam SenGupta

Publisher: Elsevier

Published: 2023-10-27

Total Pages: 268

ISBN-13: 0323990231

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Vibration of Periodic Structures introduces the fundamentals of periodic structure theory by considering the simplest model – wave propagation in an infinitely long periodic spring-mass system. It then shows how the knowledge of the stop and pass bands can be utilized to find the natural frequency distribution in a finite periodic structure. The basic concepts are further extended to wave propagation in infinitely long periodically supported beams and plates; distribution of natural frequencies of a similar structure of finite length; vibration of skin-stringer structures; and structuralacoustic properties of a section of an aircraft fuselage, based on a combination of the finite element method and the periodic structure theory, in a highly cost-effective manner.This book is a valuable resource of information for practicing engineers in various industries, e.g., civil, mechanical, or aerospace engineering, dealing with vibration of structures with periodic properties, including prediction of supersonic flutter characteristics of aerospace structures. It will also prove to be a beneficial reference for researchers involved with wave propagation in metamaterials and phononic devices."Readers who have wanted a clear and connected account of vibration of periodic structures will find this treatment accessible and stimulating and will want to add this volume to their personal or institutional library. – Prof. Earl Dowell, Duke University, Durham, NC, USA - Shows how the periodic structure theory can be combined with the finite element method to model a section of an airplane fuselage to study its structural-acoustic characteristics - Features developing methods for predicting the dynamics of periodic structures in a cost-effective manner - Guides the reader to predict and reduce response of periodically stiffened structures to random excitations

Computer Aided Analysis and Design of Machine Elements
Computer Aided Analysis and Design of Machine Elements

Author: Rao V. Dukkipati

Publisher: New Age International

Published: 2006

Total Pages: 486

ISBN-13: 9788122412567

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Beginning with the formulation of specific design problems, this book goes on explains theories of failure. It considers factors involved in optimization of design, followed by a detailed description of static, transient and dynamic analysis.

Vibration Suppression of a Rotationally Periodic Structure Using an Adaptive/PPF Control Law
Vibration Suppression of a Rotationally Periodic Structure Using an Adaptive/PPF Control Law

Author: Mark J. Keller

Publisher:

Published: 2001-03-01

Total Pages: 187

ISBN-13: 9781423530565

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For a compressor disk, effective vibration suppression requires broadband control, and the elimination of inter-blade coupling forces. Previous researchers achieved this using an active/passive piezoelectric shunt network. Unfortunately, optimal tuning of the shunt requires prior knowledge of the coupling strength, which is not well defined. This thesis uses an adaptive parameter estimator to eliminate the inter-blade coupling forces. In addition, the passive shunt is replaced with an analogous positive position feedback method. The resulting control law was used on a simulated four and eight bladed system. While substantial reductions in system response were achieved for the Adaptive/PPF control technique, the parameter estimates did not always converge to the correct solution. Similar reductions in the response were achieved using PPF control by itself.

Exact Analysis Of Structures With Periodicity Using U-transformation
Exact Analysis Of Structures With Periodicity Using U-transformation

Author: Hon Chuen Chan

Publisher: World Scientific

Published: 1999-01-08

Total Pages: 348

ISBN-13: 9814495530

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This book introduces an analytical method, the U-transformation method, for the exact analysis of structures with the periodic property. The physical meaning of U-transformation is fully explained and the application of this technique to derive exact analytical solutions for a wide variety of structures with the periodic property is thoroughly illustrated. The book also provides useful exact and explicit formulas for many practical engineering problems. Many of these solutions are new results that have just appeared in international journals. The practical engineering structures considered in the book include continuous beams, stiffened plates, trusses, grillages, double layer grids and so on.

Introduction to Finite Element Vibration Analysis
Introduction to Finite Element Vibration Analysis

Author: Maurice Petyt

Publisher: Cambridge University Press

Published: 2010-08-23

Total Pages:

ISBN-13: 1139490060

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This is an introduction to the mathematical basis of finite element analysis as applied to vibrating systems. Finite element analysis is a technique that is very important in modeling the response of structures to dynamic loads. Although this book assumes no previous knowledge of finite element methods, those who do have knowledge will still find the book to be useful. It can be utilised by aeronautical, civil, mechanical, and structural engineers as well as naval architects. This second edition includes information on the many developments that have taken place over the last twenty years. Existing chapters have been expanded where necessary, and three new chapters have been included that discuss the vibration of shells and multi-layered elements and provide an introduction to the hierarchical finite element method.

Vibration Mechanics
Vibration Mechanics

Author: Haiyan Hu

Publisher: Springer Nature

Published: 2022-02-08

Total Pages: 504

ISBN-13: 9811654573

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This book is a novel tutorial for research-oriented study of vibration mechanics. The book begins with twelve open problems from six case studies of vibration mechanics in order to guide readers in studying the entire book. Then, the book surveys both theories and methods of linear vibrations in an elementary course from a new perspective of aesthetics of science so as to assist readers to upgrade their way of learning. The successive chapters offer a theoretical frame of linear vibrations and waves, covering the models of vibration systems, the vibration analysis of discrete systems, the natural vibrations of one-dimensional structures, the natural vibrations of symmetric structures, and the waves and vibrations of one-dimensional structures. The chapters help readers solve the twelve open problems step by step during the research-oriented study. The book tries to arouse the interest of graduate students and professionals, who have learnt an elementary course of vibration mechanics of two credits, to conduct the research-oriented study and achieve a helical upgrade understanding to vibration mechanics.