TY - CHAP A1 - Volkova, Viktorija A1 - Kazakevitch, M. I. T1 - Application of Qualitative Methods to Research of Polyharmonic Oscillations N2 - The development of the qualitative methods of investigation of dynamic systems, suggested by the authors, is the effective means for identification of dynamic systems. The results of the extensive investigations of the behaviour of linear dynamic systems and symmetrical system with double well potential under polyharmonic excitation are given in the paper. Phase space of dynamic systems is multi-dimensional. Each point of this space is characterized by not less than four co-ordinates. In particular: displacement, velocity, acceleration and time. Real space has three dimensions. It is more convenient for the analysis. We consider the phase space as limited to three dimensions, namely displacement, velocity and acceleration. Another choice of parameters of phase planes is also possible [1, 2]. Phase trajectory on a plane is of the greatest interest. It is known that accelerations of points are more sensitive to deviations of oscillations from harmonic ones. It is connected with the fact that power criteria on it are interpreted most evidently. Besides, dependence is back symmetric relative to axis of the diagram of elastic characteristic. Only the phase trajectories allow establishing a type and a level of non-linearity of a system. The results of the extensive investigations of the dynamic systems behaviour under polyharmonic excitation are given in the paper. The use of the given phase trajectories enables us to determine with a high degree of reliability the following peculiarities: - presence or absence of non-linear character of behaviour of a dynamic system; - type of non-linearity; - type of dynamic process (oscillations of the basic tone, combinative oscillations, chaotic oscillations.). Unlike existing asymptotic and stochastic methods of identification of dynamic systems, the use of the suggested technique is not connected with the use of a significant amount of computing procedures, and also it has a number of advantages at the investigation of complicated oscillations. KW - Dynamik KW - Schwingung KW - Polyharmonische Funktion Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-3684 ER - TY - THES A1 - Lüdtke, Cornelius T1 - Systemidentifikation von Bauteilen mittels optischer Messmethoden N2 - Im Rahmen der Forschung an Bauteil- und Fügestellendämpfung wurden die Schwingungen der Bauteile bisher mit 1D-Laser-Vibrometern gemessen. Nun steht ein 3D-Laser-Scanner zur Verfügung. Diese Arbeit beschäftigt sich mit der Frage, ob mit dem 3D-Laser-Scanner bessere und weitere relevante Daten bei der Schwingungsmessung gewonnen werden können. KW - Schwingung KW - Schall KW - Dauerhaftigkeit KW - Eigenform KW - Vibrometer KW - Laser Scanner Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20150706-24293 ER - TY - CHAP A1 - Grigrieva, Polina A1 - Lymarenko, Yulia T1 - Mathematical modeling of nonlinear effects for vibrodiagnostics of fatigue cracks N2 - The vibration control of complicated mechanical structures is impossible without proper mathematical models that allow to have a true apprehension of events occurring in structural member before the starting of the experiment and correct the diagnostic experiment in case of need. An approach that implies using of a discrete model reflecting all required features of a prototype system and permitting of an effective analytical and numerical investigation is proposed in the work. At first a discrete model of a bladed disk with flaw is considered. Taking into account the symmetry of the structure by utilization of mathematical tools of group presentation theory the number of degrees of freedom of the system is diminished. Small damage of the disk is regarded as perturbation of structure symmetry. The distinction of vibration characteristics such as natural frequencies and mode shapes of damaged and undamaged systems is determined theoretically with the help of perturbation theory and can be used as an effective diagnostic criterion of a small-scale damage of the structure. In the second part of the work a non-linear two-mass model of an acoustic emission in a damaged structure is proposed. On basis of the numerical integration of the nonlinear differential equations and expansion of the derived solution into a Fourier series free and forced vibrations of the model are investigated. It is shown that proposed model reflects all characteristic properties of vibrations of damaged structures: reduction of natural frequency, sub- and super-resonances, acoustic effects. KW - Nichtlineare Mechanik KW - Schwingung KW - Modellierung Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2917 ER - TY - JOUR A1 - Galffy, Mozes A1 - Wellmann Jelic, Andres A1 - Hartmann, Dietrich T1 - Lifetime-oriented modelling of vortex-induced across-wind vibrations on bridge tie rods N2 - The influence of vortex-induces vibrations on vertical tie rods has been proved as a determinant load factor in the lifetime-oriented dimensioning of arched steel bridges. Particularly, the welded connection plates between the suspenders and the arches often exhibit cracks induced primarily rods. In this context, the synchronization of the vortex-shedding to the rod motion in a critical wind velocity range, the so-called lock-in effect, is of essential interest. KW - Finite-Elemente-Methode KW - Physikalisches Verfahren KW - Brückenbau KW - Schwingung Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-2536 ER - TY - CHAP A1 - Abramian, A. K. A1 - Litvin, S.S. T1 - AUTOPARAMETRIC STABILIZER OF OSCILLATION AMPLITUDE N2 - A method of automatic maintenance of vibration amplitude of a number of mechanisms at given level, when exiting force amplitude is varied greatly is given. For this purpose a pendulum is attached to a mechanism through a viscoelastic hinge. Load of a pendulum can move along an arm and it is viscoelastic connected to it. KW - Schwingung KW - Amplitude KW - Stabilisierung KW - Automatisiertes System KW - Viskoelastisches Gelenk Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-5674 ER - TY - THES A1 - Abeltshauser, Rainer T1 - Identification and separation of physical effects of coupled systems by using defined model abstractions N2 - The thesis investigates at the computer aided simulation process for operational vibration analysis of complex coupled systems. As part of the internal methods project “Absolute Values” of the BMW Group, the thesis deals with the analysis of the structural dynamic interactions and excitation interactions. The overarching aim of the methods project is to predict the operational vibrations of engines. Simulations are usually used to analyze technical aspects (e. g. operational vibrations, strength, ...) of single components in the industrial development. The boundary conditions of submodels are mostly based on experiences. So the interactions with neighboring components and systems are neglected. To get physically more realistic results but still efficient simulations, this work wants to support the engineer during the preprocessing phase by useful criteria. At first suitable abstraction levels based on the existing literature are defined to identify structural dynamic interactions and excitation interactions of coupled systems. So it is possible to separate different effects of the coupled subsystems. On this basis, criteria are derived to assess the influence of interactions between the considered systems. These criteria can be used during the preprocessing phase and help the engineer to build up efficient models with respect to the interactions with neighboring systems. The method was developed by using several models with different complexity levels. Furthermore, the method is proved for the application in the industrial environment by using the example of a current combustion engine. T2 - Identifikation und Separation physikalischer Effekte von gekoppelten Systemen mittels definierter Modellabstraktionen T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2017,1 KW - Strukturdynamik KW - Wechselwirkung KW - Schwingung KW - Berechnung KW - Numerische Berechnung KW - Modellbildung KW - Schwingungsanalyse KW - Simulationsprozess Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-28600 ER - TY - JOUR A1 - Abdelnour, Mena A1 - Zabel, Volkmar T1 - Modal identification of structures with a dynamic behaviour characterised by global and local modes at close frequencies JF - Acta Mechanica N2 - Identification of modal parameters of a space frame structure is a complex assignment due to a large number of degrees of freedom, close natural frequencies, and different vibrating mechanisms. Research has been carried out on the modal identification of rather simple truss structures. So far, less attention has been given to complex three-dimensional truss structures. This work develops a vibration-based methodology for determining modal information of three-dimensional space truss structures. The method uses a relatively complex space truss structure for its verification. Numerical modelling of the system gives modal information about the expected vibration behaviour. The identification process involves closely spaced modes that are characterised by local and global vibration mechanisms. To distinguish between local and global vibrations of the system, modal strain energies are used as an indicator. The experimental validation, which incorporated a modal analysis employing the stochastic subspace identification method, has confirmed that considering relatively high model orders is required to identify specific mode shapes. Especially in the case of the determination of local deformation modes of space truss members, higher model orders have to be taken into account than in the modal identification of most other types of structures. KW - Fachwerkbau KW - Holzkonstruktion KW - Schwingung KW - three-dimensional truss structures KW - vibration-based methodology KW - numerical modelling Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20230525-63822 UR - https://link.springer.com/article/10.1007/s00707-023-03598-z VL - 2023 SP - 1 EP - 21 PB - Springer CY - Wien ER -