Academic literature on the topic 'Torsional Vibration'

One of the most important source of noise and vibrations associated with vehicles is the vibration of driveline systems. Such phenomena are subjectively associated with customer complaints. In this study the torsional vibrations of driveline systems were investigated using discretised and lumped mass models of the system. In the literature, many of the problems associated with torsional vibrations and refinement in drivelines have been tackled through relatively simple, lumped mass models combinedw ith experimentalm easurements. However, some problems remain particularly where instabilities occur or complex coupling with other vehicle vibration modes exists. The review of previous work showed that although it is important to understand the dynamic behaviour of the individual driveline components; for example, engine, clutch, gearbox, etc., the whole system must be analysed together because of all the coupling which occurs. The main source of excitation for torsional vibration of the driveline system is the engine fluctuating torque. A computer program using MATLAB subroutines was developed to obtain this fluctuation torque for different engine parameters for subsequent use in the modelling. A substructure approach, using stiffness coupling technique with combined use of residual flexibility and modal synthesis, was used to analyse free and forced vibrations of the system, as a linear system. A computer program using MATLAB subroutines was designed to facilitate application of this technique. Good agreement between results for the overall system model and substructure model was found even for a few considered modes. This substructure technique offers significant computational advantages over other methods. The effect of non-linear sources in the driveline system such as backlash, non-linear spring stifffiess, Hooke's joint and angularity of the propeller shaft on the system torsional vibrations was investigated. The effect of backlash in the driveline system was significant and, as expected, vibration levels increased as backlash increased. Hooke's joints caused an additional complex source of excitation but their significance is dictated by the details of the particular driveline design. The modelling showed that instabilities commonly referred to a shunt or shuffle could occur during clutch engagement. The stick slip frictional properties of the clutch were crucial in this behaviour and the relative importance of various design features was quantified. A mathematical model including torsional motion of the driveline system and other vehicle body motions was developed to analyse the ways in which the driveline couples with other dynamic components. Two running conditions were considered; steady state running and transient during clutch engagement. It was shown that the complete system was capable of self-excited oscillations under certain conditions during normal running as well as the instability which could occur during clutch engagement. This comprehensive model represents an important contribution of the work in this area of research in two ways. First, it clarifies understanding of the dynamic coupling between the rotational and translational components of the whole vehicle system. Second, it provides design information to tackle instability problems and to lead to reductions in overall vibration levels.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1986.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.<br>Bibliography: leaf 44.<br>by Khaja Zameeruddin Khan.<br>M.S.

Thesis (Ph. D.)--West Virginia University, 2004.<br>Title from document title page. Document formatted into pages; contains viii, 180 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 123-128).

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>Parte do processo de exploração e desenvolvimento de um campo de petróleo consiste nas operações de perfuração de poços de petróleo e gás. Particularmente para poços de águas profundas e ultra-profundas, a operação requer o controle de uma estrutura muito flexível que é sujeita a condições de contorno complexas, tais como as interações não-lineares entre broca e formação rochosa ou entre a broca e a parede de poço. Quanto a esta complexidade, o fenômeno stick-slip é um componente primordial relacionado à vibração torsional. Este pode excitar vibrações tanto axiais quanto laterais. Isso pode causar falha prematura de componentes de corda de perfuração. Assim, a redução e eliminação de oscilações do tipo stick-phase são itens muito valiosos em termos de economia financeira e de tempo de exploração. Com este propósito, este estudo tem como principal objetivo confrontar o problema de vibração torsional simulando uma estratégia de controle robusto em tempo real. A abordagem é obtida seguindo alguns passos, tais como: análise em malha aberta do sistema de perfuração considerando um atuador top drive e o sistema de coluna de perfuração; concepção de um novo controlador que utiliza diferentes velocidades angulares de referência num sistema de controle de malha fechada; controle da vibração torsional considerando a não-linearidade devida à interação de atrito na parede do poço e no fundo do poço; avaliar por meio de simulações sistemas de controle ininterruptos durante a perfuração; validação dos modelos por meio de simulações numéricas. Esta dissertação apresenta a base teórica por trás do sistema de perfuração, bem como exemplos de resultados numéricos que proporcionam uma operação de perfuração controlada estável e satisfatória.<br>Part of the process of exploration and development of an oil field consists of the drilling operations for oil and gas wells. Particularly for deep water and ultra deep water wells, the operation requires the control of a very exible structure which is subjected to complex boundary conditions such as the nonlinear interactions between drill bit and rock formation and between the drill-string and borehole wall. Concerning this complexity the stick-slip phenomenon is a major component, related to the torsional vibration and it can excite both axial and lateral vibrations. That may cause premature failure of drill-string components. So, the reduction and avoidance of stickslip oscillations are very valuable items in terms of savings and exploration time. With these intentions, this study has the main goal of confronting the torsional vibration problem using a real-time robust control strategy. The approach is obtained following some steps such as: Open-loop analysis of the drilling system considering a top-drive actuator and the drill-string system; Design of a novel controller using different angular velocity setpoints in a closed-loop system; Control of the torsional vibration considering the nonlinearity due to friction interaction in the wall and in the donwhole system; valuate a non-stop control system while drilling; Verification by numerical simulations. In this presentation the theoretical basis behind the drilling system will be given, as well examples of numerical results providing a stable and satisfactory controlled drilling operation.

Torsional vibration is an oscillatory angular twisting motion in the rotating members of a system. It can be deemed quite dangerous in that it cannot be detected as easily as other forms of vibration, and hence, subsequent failures that it leads to are often abrupt and may cause direct breakage of the shafts of the drive train. The need for sufficient analysis during the design stage of a rotating machine is, thus, well justified in order to avoid expensive modifications during later stages of the manufacturing process. In 1998, a project was initiated by the Turbomachinery Research Consortium (TRC) at Texas A&M University, College Station, TX, to develop a suite of computer codes to model torsional vibration of large drive trains. The author had the privilege of developing some modules in Visual Basic for Applications (VBA-Excel) for this suite of torsional vibration analysis codes, now collectively called XLTRC-Torsion. This treatise parleys the theory behind torsional vibration analysis using both the Transfer Matrix approach and the Finite Element approach, and in particular, validates the results generated by XLTRC-Torsion based on those approaches using experimental data available from tests on a 66,000 HP Air Compressor.

The area of powertrain dynamics has received considerable attention over a number of years. The recent introduction of more stringent emission requirements together with economic pressure has led to a particular focus on increasing powertrain efficiency. This has seen the incorporation of on-board, real-time measurements to predict system behaviour and engine condition. In this domain, accurate models for all powertrain components are important. One strategy to improve accuracy is to evaluate the assumptions made when deriving each model and then to address the simplifications that may introduce large errors. To this end, the aim of the work presented in this dissertation was to investigate the consequences of some of the more common assumptions and simplifications made in low frequency torsional powertrain models, and to propose improved models where appropriate. In particular, the effects of piston-tocylinder friction, crank/gudgeon pin offset, and the torsional behaviour of tyres were studied. Frequency and time domain models were used to investigate system behaviour and model predictions were compared with measurements on a small single cylinder engine. All time domain engine and powertrain models also include a variable inertia function for each reciprocating mechanism. It was found that piston-to-cylinder friction can increase the apparent inertia variation of a single reciprocating engine mechanism. This has implications for the nonlinear behaviour of engines and the drivetrains they are connected to. The effect of crank/gudgeon pin offset also modified the nonlinear behaviour of the mechanism. Though, for typical (small) gudgeon offset values these effects are small. However, for large offset values, achievable practically with crank offset, the modification to the nonlinear behaviour should not be ignored. The low frequency torsional damping properties of a small pneumatic tyre were found to be more accurately represented as hysteretic rather than viscous. Time domain modelling was then used to extend the results to a multi-cylinder engine powertrain and was achieved using the Time Domain Receptance (TDR) method. Various powertrain component TDRs were developed using Laplacians. Powertrain simulations showed that piston-to-cylinder friction can provide additional excitation to the system.

Dynamic behavior of flexural-torsional coupled vibration of rotating beams using the Rayleigh-Ritz method with orthogonal polynomials as basis functions is studied. The present work starts from a review of the development and analysis of four basic types of beam theories: the Euler-Bernoulli, Rayleigh, Shear and Timoshenko and goes over to a study of flexural-torsional coupled vibration analysis using basic beam theories. In obtaining natural frequencies, orthogonal polynomials used in the Rayleigh-Ritz method are studied as an efficient way of getting results. The study is also performed for both non-rotating and rotating beams. Orthogonal polynomials and functions studied in the present work are : Legendre, Chebyshev, integrated Legendre, modified Duncan polynomials, the eigenfunctions of a pinned-free uniform beam, and the special trigonometric functions used in conjunction with Hermite cubics. Studied cases are non-rotating and rotating Timoshenko beams, bending-torsion coupled beam with free-free boundary conditions, a cantilever beam, and a rotating cantilever beam. The obtained natural frequencies and mode shapes are compared to those available in various references and results for coupled flexural-torsional vibrations are compared to both previously available references and with those obtained using NASTRAN finite element package.<br>Master of Science