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2015 | Buch

Vibrations and Stability of Complex Beam Systems

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This book reports on solved problems concerning vibrations and stability of complex beam systems. The complexity of a system is considered from two points of view: the complexity originating from the nature of the structure, in the case of two or more elastically connected beams; and the complexity derived from the dynamic behavior of the system, in the case of a damaged single beam, resulting from the harm done to its simple structure. Furthermore, the book describes the analytical derivation of equations of two or more elastically connected beams, using four different theories (Euler, Rayleigh, Timoshenko and Reddy-Bickford). It also reports on a new, improved p-version of the finite element method for geometrically nonlinear vibrations. The new method provides more accurate approximations of solutions, while also allowing us to analyze geometrically nonlinear vibrations. The book describes the appearance of longitudinal vibrations of damaged clamped-clamped beams as a result of discontinuity (damage). It describes the cases of stability in detail, employing all four theories, and provides the readers with practical examples of stochastic stability. Overall, the book succeeds in collecting in one place theoretical analyses, mathematical modeling and validation approaches based on various methods, thus providing the readers with a comprehensive toolkit for performing vibration analysis on complex beam systems.

Inhaltsverzeichnis

Frontmatter
Introductory Remarks
Abstract
A great number of mechanical systems are complex structures composed of two or more basic mechanical systems whose dynamic behavior is conditioned by their interaction. The systems connected by an elastic layer constitute one group of such mechanical structures which are commonly encountered in mechanical, construction and aeronautical industry. Mechanical systems formed by elastic connection of their members, due to the nature of the dynamic interaction conditioned by elastic connections are characterized by complex vibration and a higher number of natural frequencies. Since the number of natural frequencies depends on the number of basic elements joint together, such mechanical systems are exposed to an increased likelihood of creating resonance conditions which can cause breakage and damage. With the view to putting theoretical research into engineering practice, a great number of linear dynamic models describing the motion of a system were created. Such models are important as they give the initial approximation of the solution and a general insight into a dynamic behavior of the system at slight motion. If technical practice requires further investigation of system behavior, these dynamic models provide solid ground for the continuation of research with non-linearity effects.
Vladimir Stojanović, Predrag Kozić
Free Vibrations and Stability of an Elastically Connected Double-Beam System
Abstract
Free oscillations and static stability of two elastically connected beams are considered in Chapter 2. At various examples it is shown analytically obtained results and impacts of some mechanical parameters of the system on the natural frequencies and amplitudes. Verification of obtained results is shown by comparison with results of the existed classical models. New scientific contribution in this chapter is formulation of the new double-beam model described with new derived equations of motion with rotational inertia effects and with inertia of rotation with transverse shear (Rayleigh’s model, Timoshenko’s model, Reddy - Bickford’s model). It is formulized the static stability condition of the two elastically connected beams of different types with analytical expressions for the various values of critical forces. Numerical experiments confirmed the validity of the analytical results obtained by comparing the results of the models existing in the literature. From chapter 2 it can be concluded that the effects of rotational inertia and transverse shear must be taken into account in the model of thick beams because errors that occur by ignoring them are increasing with the increasing the mode of vibration.
Vladimir Stojanović, Predrag Kozić
Effects of Axial Compression Forces, Rotary Inertia and Shear on Forced Vibrations of the System of Two Elastically Connected Beams
Abstract
This chapter covers the solution for forced vibrations of two elastically connected beams of Rayleigh’s, Timoshenko’s and Reddy-Bickford’s type under the influence of axial forces. Scientific contribution is presented through the analytical solutions in forms of three cases of forced vibrations - Harmonic arbitrarily continuous excitation, the continuous uniform harmonic excitation and harmonic concentrated excitation. Analytical solutions were obtained by using the modal analysis method. Based on the results derived in this chapter, it can be made a conclusion that the differences in the approximations of the solutions depending of the used model gave a good solutions just in cases of Timoshenko’s and Reddy-Bickford’s theory for thick beams in higher modes also in forced vibrations regime and must be taken into account.
Vladimir Stojanović, Predrag Kozić
Static and Stochastic Stability of an Elastically Connected Beam System on an Elastic Foundation
Abstract
Chapter 4 considers the static and stochastic stability of the elastically connected three beams on an elastic foundation. It is derived a new set of partial differential equations for static analysis of deflections and critical buckling force of the complex mechanical system and it is presented comparison study of the static stability between mechanical systems with one, two and three beams on an elastic foundation. It is analytically determined critical buckling force for each system individually. It is concluded that the system is the most stable in the case of the one beam on elastic foundation.
Vladimir Stojanović, Predrag Kozić
The Effects of Rotary Inertia and Transverse Shear on the Vibration and Stability of the Elastically Connected Timoshenko Beam-System on Elastic Foundation
Abstract
Chapter 5 analyzed free vibration of the multiple elastically connected beams of Timoshenko’s type on an elastic foundation under the influence of axial forces. Analytical solutions for the natural frequencies and the critical buckling forces are determined by the trigonometric method and verified numerically. It is shown that the fundamental natural frequency in the first mode of the multiple beam system tends to the value of the natural frequency of the system with one beam resting on an elastic foundation with the tendency of increasing the number of connected beams with the same stiffness of the layers between.
Vladimir Stojanović, Predrag Kozić
The Effects of Rotary Inertia and Transverse Shear on Vibrations and Stability of the System of Elastically Connected Reddy-Bickford Beams on Elastic Foundation
Abstract
Chapters 6 analyzed free vibration of the multiple elastically connected beam system of Reddy-Bickford’s type on an elastic foundation under the influence of axial forces with the comparison of the frequency and stability theoretical research for all four types of the beam’s theory. Analytical solutions for the natural frequencies and the critical buckling forces are determined by the trigonometric method and verified numerically as in case in the previous chapter. In the case of the Reddy-Bickford’s model, it is shown that the natural frequency provides the best solution approximation.
Vladimir Stojanović, Predrag Kozić
Geometrically Non-linear Vibrations of Timoshenko Damaged Beams Using the New p-Version of Finite Element Method
Abstract
Chapter 7 presents geometrically nonlinear forced vibrations of damaged Timoshenko beams. In the study it is developed new p-version of finite element method for damaged beams. The advantage of the new method is compared with the traditional p-version of finite element method and provides better approximations of solutions with a small number of degrees of freedom used in numerical analysis.
Vladimir Stojanović, Predrag Kozić
Conclusion
Abstract
The problems of beam vibration present a basic mechanical system encountered in mechanical engineering, civil engineering, aeronautical and transportation industry. Determining solutions of greater accuracy becomes increasingly significant in the reality of technical practice in cases the analysis of the motion of complex systems as deformable bodies with indefinite degree of vibration freedom is required. The existence of more precise approximations of solutions for certain elements allows the elimination a cumulative error effect in finding the solutions for complex dynamic systems.
Vladimir Stojanović, Predrag Kozić
Backmatter
Metadaten
Titel
Vibrations and Stability of Complex Beam Systems
verfasst von
Vladimir Stojanović
Predrag Kozić
Copyright-Jahr
2015
Electronic ISBN
978-3-319-13767-4
Print ISBN
978-3-319-13766-7
DOI
https://doi.org/10.1007/978-3-319-13767-4

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