The objective of this study is to present a dynamic model of a backhoe-loader including cab dynamics in order to simulate the vibration levels transmitted to the operator. For this purpose, analytical solutions of the cab and the machine are developed by deriving the equations of motion of the system and the state space forms of the solution are implemented in the commercially available simulation software, MATLAB/Simulink. In addition to the analytical solution, a model is developed using the physical modeling toolboxes of MATLAB/SimMechanics. Cab model developed in SimMechanics is extended to simulate whole machine dynamics by inserting machine body and tire parameters. Vibration data is acquired from the machine for experimental validation of the models. Analytical and SimMechanics solution are evaluated by comparing the seat acceleration results for the same inputs. Furthermore, simulation results obtained from the models and the measurement results are found to be in agreement in both time and frequency domain.

The methods of analysis used to determine ultimate bearing capacity of piles are applied to a field case in Turkey. During the pile driving works of the Atat&uuml / rk Culture Center in Samsun, Delmag D22-13 and Delmag D-15 diesel pile driving hammers have been used. The ultimate bearing capacity and skin friction values calculated using static formulas have been given as input to the wave equation pile analysis program FADWAVE written by J.E.Bowles. The analytical method used in this program was based on the wave propagation in solids originated in 1962 by E.A.L.Smith. The results obtained from the program are compared with each other.

Orientador: Robson Pederiva / Dissertação (mestrado) -Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T18:23:14Z (GMT). No. of bitstreams: 1 Sanches_FabioDalmazzo_M.pdf: 633170 bytes, checksum: a1620e7b33649f4441407be8d0f78500 (MD5) Previous issue date: 2008 / Resumo: Este trabalho apresenta uma metodologia de identificação dos parâmetros de rigidez e amortecimento dos mancais de rolamento de um sistema mecânico rotativo. O método proposto é baseado na equação matricial de Ljapunov e na representação do sistema na forma de espaço de estados. Através da definição de correlações, inserida na equação matricial, monta-se um estimador que relaciona os parâmetros físicos do sistema com as matrizes de correlações das variáveis medidas no domínio do tempo, não sendo necessário o conhecimento da excitação. O objetivo do trabalho é fazer um estudo teórico da aplicação dessa metodologia de identificação em sistemas reais. São feitas simulações considerando-se um sistema rotativo de vinte graus de liberdade excitado aleatoriamente, caso estático, e por desbalanceamento em diversas freqüências de rotação e de características de mancal. Os resultados numéricos demonstram que o método proposto é robusto e viável, podendo ser aplicado na identificação de uma máquina real / Abstract: This work presents an identification methodology of stiffness and damping parameters of rolling bearings in a rotor-bearing system. The proposed method is based on Ljapunov matrix equation and state space representation. Through the definition of correlations used in matrix equation, it is possible to generate an algorithm that relates system physical parameters to the correlation matrixes of the measured variables in time domain without the knowledge of the external input forces. The purpose of this work is to make a theoretical study of the viability of this methodology used in real systems. Simulations were performed considering a rotating system with twenty degrees of freedom excited by random forces, system at rest, and by unbalance forces considering several rotation frequencies and bearing characteristics. The numerical results show the proposed method is feasible and it can be used to identify real machines / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Orientador: Paulo Roberto Gabriel Kurka / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-11T06:28:28Z (GMT). No. of bitstreams: 1 Guilherme_KarendeLolo_D.pdf: 2419963 bytes, checksum: 554ac4d31b46ae66bd610d91ebaa931a (MD5) Previous issue date: 2008 / Resumo: Este trabalho tem como objetivo propor um modelo de dinâmica flexível dos componentes de um compressor alternativo monocilíndrico de refrigeração. Tal modelo representa um aperfeiçoamento da modelagem dinâmica utilizada, que supõe mancais rotativos fixos ou pinados. A modelagem dinâmica flexível do compressor é útil na analise dos esforços de natureza elástica e dissipativa que ocorrem nos mancais de sustentação do conjunto. Esses resultados podem também ser utilizados numa correta medição da energia dissipada pelos mancais. O modelo dinâmico utiliza um mecanismo biela-manivela, pistão e eixo, sujeitos ao carregamento da pressão que o fluido refrigerante exerce sobre o pistão no interior do cilindro. A modelagem incorpora efeitos giroscópicos e utiliza mancais flexíveis nos acoplamentos dos componentes, o que proporciona maior mobilidade ao modelo. O Método de Newton Euler é utilizado na analise das forças e momentos atuantes no sistema para a obtenção das equações diferenciais que representam o seu movimento. As equações dinâmicas, por sua vez, são resolvidas numericamente através do método de Runge-Kutta. Observou-se que a modelagem da oscilaãoo dos componentes rotativos no conjunto eixo-biela-manivela é capaz de produzir esforços diferenciados nos mancais do compressor quando comparado aos esforços de mancal presentes num modelo pinado / Abstract: The work consists in fiding a flexible dynamics model of a single cylinder, reciprocating refrigeration gas compressor. The model represents an improval to the current dynamic model of compressors, that use fixed or pinned rotation journal bearings. An efficient dynamic model of the compressor is useful in the analysis of elastic and dissipative loads that occur in the system¿s internal bearings. The results produced by the model can also be employed in the correct measurement of the energy dissipated at the bearings. The dynamic model consists of a rotor, cranckshaft, connecting rod and piston, all subject to the load from compression of the refrigerant fluid. The model incorporates gyroscopic effects and utilizes flexible bearing couplings, which yield greater mobilty to the moving mechanisms. The Newton-Euler method is used in the analysis of acting forces and torques, establishing the necessary differential equations that describe the movement of the system. A numerical solution of the dynamic equations is obtained through use of the Runge-Kutta method. Application of the model shows that oscillations of the rotating internal components of the compressor yield increased loads to the bearings, as compared to a pinned rotation model / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

Orientador: Hans Ingo Weber / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-24T05:43:03Z (GMT). No. of bitstreams: 1 Mattos_MarcioCoelhode_D.pdf: 10130294 bytes, checksum: 5b9cef82256f8fd05f78a1341b08ac10 (MD5) Previous issue date: 1998 / Resumo: Apresentamos neste trabalho uma investigação sobre as mudanças na dinâmica de sistemas com vibroimpacto. Particularmente estamos interessados no estudo da migração das freqüências características destes sistemas. Podemos considerar que um dado sistema com vibroimpacto tende a um sistema com impacto degenerado quando a folga deste sistema tende a zero ou a um valor maior que a amplitude de vibração do sistema na coordenada de impacto. Podemos também denominar estes sistemas como sistemas lineares associados ao sistema com impacto, se o impacto' for a única não linearidade presente no sistema. Mostramos que existe uma relação intrínseca entre a resposta do sistema com impacto e os sistemas lineares associados, ou sistemas degenerados. Para investigar esta relação, analisamos a resposta de sistemas com dois e três graus de liberdade com impacto em uma de suas coordenadas. Além disto, investigamos experimentalmente a resposta de uma viga engastada-livre excitada randomicamente e com impactos em sua extremidade livre. Observamos boa correlação entre os resultados numéricos e, experimentais. Propomos uma função para a migração da primeira freqüência característica da resposta de sistemas com vibroimpacto. O caminho da migração depende da distribuição da energia total fornecida ao sistema entre os diversos modos de vibração dos sistemas lineares associados / Abstract: This works presents an investigation on the changes in the dynamics of vibroimpact systems as their clearance is varied. Particularly we are interested in the migration of the characteristic frequencies of impact systems. We can consider that a given vibroimpact system reaches to a degenerated impact system when the clearance reaches to zero or to a value which is greater than the amplitude of the response of the system at the impact coordinate. We also can call these systems as associated linear systems of a given impact system, if the impact is the only nonlinearity which takes place. We show that there is an intrinsic relation between impact systems and their associated linear systems, or degenerated systems. To investigate this relation we consider the free response of 2-DOF and 3-DOF impact systems with impact in one of their coordinates. On the other hand, we have performed an experimental investigation in a randomly excited cantilever beam with impacts on its free end. We have found good agreement between numerical and experimental results. We have proposed a function for the migration of the first characteristic frequency of impact systems. The migration way depends on distribution of the total energy supplied to system among the vibration modes of the associated linear systems / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering / It has been said that experimental modal analysis (EMA) "grew to prominence because the engineering community was incapable of properly analyzing the dynamics of commercially significant structures" [24]. The advent of powerful theoretical methods, such as the Finite Element Method (FEM) has not, however, resulted in the demise of EMA. In fact both FEM and EMA have undergone rapid growth and the merging of the two into an effective design and diagnostic tool has had a major impact on the engineering community's approach to dynamics related problems. In this study, the term dual has no mathematical connotations and is used to describe the complementary use of the techniques of EMA and FEM. The mining industry, worldwide, has experienced dynamics related problems in the operation of conveyances in vertical shafts. A study undertaken in South Africa investigated the behaviour of shaft steelwork and skips, resulting in a set of design guidelines for future shaft steelwork designs. This work only investigated the dynamic behaviour of skips. In this project, the ABAQUS and MODEL SOLUTION FEM codes were used to construct models of a. mine cage. An impact modal test was carried ant on the cage, using a GenRad 2515 CAT system, An impact hammer, suitable for exciting large structures, and a strain gauge force transducer were designed and built for the purpose of the test. The natural frequencies and mode shapes obtained from both FEM and EMA are compared by means of the modal assurance criterion (MAC). The test data is used to tune the model to produce accurate results. The model Could then be used (with minimal further test work) for predicting the response of the structure to dynamic loading or the effects of structural modifications. / Andrew Chakane 2020

Modal parameter identification of a structure is done through modal testing and modal analysis using various system identification methods. These methods employ linear input-output relationships to extract the modes of a structure. There are cases where laboratory testing of a structure is not possible or information about the structure under operating conditions is seeked. A set of techniques called Operational Modal Analysis have been developed for modal parameter identification in operating conditions of a structure. These techniques use only response measurements to extract the modes. The aim of this study is to investigate the applicability and use of three selected time-domain methods adapted to operational modal analysis. The algorithms are programmed in Matlab&copy / environment, and various cases are evaluated using computer simulations for each method. Two of the selected methods are evaluated on a laboratory scale test setup.

Mathematical models that are built in order to simulate the behavior of structures, most often, tend to respond differently than the actual structures in their initial state. In order to use the mathematical models and their computational outputs instead of testing the real structure under every possible case, it is mandatory to have a mathematical model that reflects the characteristics of the actual structure in the best possible way. In this thesis, the so called model updating techniques used for updating the mathematical models in order to make them respond in the way the actual structures do are investigated. Case studies using computationally generated test data are performed using the direct and indirect modal updating techniques with the software developed for each method investigated. After investigating the direct and indirect modal updating techniques, two of them, one using frequency response functions and the other using modal sensitivities, are determined to be the most suitable ones for aircraft structures. A generic software is developed for the technique using modal sensitivities. A modal test is carried out on a scaled aircraft model. The test data is used for updating of the finite element model of the scaled aircraft using the modal sensitivities and the usability of the method is thus evaluated. The finite element model of a real aircraft using the modal test data is also updated using the modal sensitivities. A new error localization technique and a model updating routine are also proposed in this thesis. This modal updating routine is used with several case studies using computationally generated test data and it is concluded that it is capable of updating the mathematical models even with incomplete measured data.

Oil feed grooves are implemented in reciprocating compressor piston applications to assure a constant supply of lubricating oil on bearing surfaces and decrease friction loss. In a hermetically sealed compressor, due to small clearances encountered, oil supply becomes critical in order not to operate in boundary lubrication regime. Due to the small size of the piston and small piston &ndash / cylinder clearance, a partial lubrication regime is present. In the current study, a model that solves Reynolds&rsquo / equation for piston-cylinder lubrication and the average Reynolds&rsquo / equation that considers the effect of roughness on partially lubricated bearing for a compressor piston with oil feed grooves is developed. A parametric study is carried out to investigate the effects of piston design parameters and then arrive at an improved piston performance by using alternative designs for oil feed groove and the other design parameters.

Flutter analyses and tests are the major items in flight certification efforts required when a new air vehicle is developed or when a new external store is developed for an existing aircraft. The flight envelope of a new aircraft as well as the influence of aircraft modifications on an existing flight envelope can be safely determined only by flutter tests. In such tests, the aircraft is instrumented by accelerometers and exciters. Vibrations of the aircraft at specific dynamic pressures are measured and transmitted to a ground station via telemetry systems during flutter tests. These vibration data are analyzed online by using a flutter test software with various methods implemented in order to predict the safety margin with respect to flutter. Tests are performed at incrementally increasing dynamic pressures and safety regions of the flight envelope are determined step by step. Since flutter is a very destructive instability, tests are performed without getting too close to the flutter speed and estimations are performed by extrapolation. In this study, pretest analyses and flutter prediction methods that can be used in various flight conditions are investigated. Existing methods are improved and their applications are demonstrated with experiments. A novel method to predict limit cycle oscillations that are encountered in some modern fighter aircraft is developed. The prediction method developed in this study can effectively be used in cases where the nonlinearities in aircraft dynamics and air flow reduce the applicability of the classical prediction methods. Some further methods to reduce the adverse effects of these nonlinearities on the predictions are also developed.