This Thesis is about the application of Statistical Energy Analysis (SEA) to the study of noise and vibration in motor vehicles. Methods for predicting the transmission of structural waves between body panels in motor cars are given. A complex joint technique based on the wave dynamic stiffness approach is discussed in detail. This technique can account for the complexities of the joint structures found in motor vehicles. Transmission of vibration energy between panels connected by a curved section of panel has been investigated using the complex joint modelling technique. Wave Intensity Analysis(WIA) and SEA were used to calculate the coupled panel vibration levels based on transmission coefficients calculated using the complex joint techniques. Energy Level Differences (ELDs) were measured for comparison with predicted results using laboratory models. SEA failed to accurately predict the ELDs except at low frequencies. However WIA was able to predicted the ELDs with reasonable accuracy using an existing expression for transmission at a panel corner joint. Two SEA models of a small passenger car have also been constructed. One assumes simpler joint configurations when calculating transmission coefficients and the other uses the complex joint technique. Panel ELDs were measured using a small passenger car. The SEA model using the complex joint method gives better agreement with measured ELDs than did the model using the simpler joints. saloon Sound Pressure Level (SPL) as a result of engine noise was measured. Both SEA models of the vehicle gave good agreement between measured and predicted Saloon SPL. A noise problem associated with exhaust misalignment is also investigated.

Thesis (M.S.)--Rochester Institute of Technology, 1984. / Typescript. Includes bibliographical references (leaves 75-78).

Results are presented of an experimental and analytical study of the longitudinal vibrational response of a modified Agena-B vehicle. The empty, unpressurized vehicle was excited with sinusoidal loads and the response was measured through a frequency range including the first two classical longitudinal. modes of the structure. Non-axisymmetric shell response (shell vibration modes) was noted extensively during the experimental tests. Comparison of the analytical and results indicates that a one-dimensional analytical model gave good results in comparison with experimental results. / Master of Science

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.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008. / Suspension seats are commonly used for earth moving machinery to isolate vehicle operators from vibrations transmitted to the vehicle body. To provide the required stiffness and damping for these seats, air-springs are typically used in conjunction with dampers. However, to eliminate the need for additional dampers, air-springs can be used in conjunction with auxiliary air volumes to provide both spring stiffness and damping. The damping is introduced through the flow restriction connecting the two air volumes. In this study, simplified models of an air-spring were derived followed by a model including the addition of an auxiliary volume. Subsequent to simulations, tests were performed on an experimental apparatus to validate the models. The air-spring models were shown to predict the behaviour of the experimental apparatus. The air-spring and auxiliary volume model followed the trend predicted by literature but showed approximately 27 % lower transmissibility amplitude and 21 % lower system natural frequency than obtained by tests when using large flow restriction diameters. This inaccuracy was assumed to be introduced by the simplified mass transfer equations defining the flow restriction between air-spring and auxiliary volume. The models however showed correlation when the auxiliary volume size was decreased by two thirds of the volume actually used for the experiment. This design of a prototype air-spring and auxiliary volume is presented for a suspension seat used in articulated or rigid frame dump trucks. The goal of this study was to design a suspension seat for this application and to obtain a SEAT value below 1,1. The design was optimised by varying auxiliary volume size, flow diameter and load. A SEAT value of less than 0,9 was achieved.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2007. / Noise, Vibrations and Harshness (NVH) characteristics are becoming ever more significant in today’s vehicle manufacturing industry. Similar to good vibration and harshness characteristics, the perception of a vehicle’s quality is enhanced by a well sounding vehicle interior. This study’s main aim was to develop objective equations to directly optimise interior sound quality of light commercial vehicles ( ½ ton LCVs) on the South African market. The effects the noise of the engine, the wind and road/tyre interaction during steady-state conditions have on the interior sound quality of eleven comparable vehicles was investigated with the aid of a binaural head. Steady-state condition in this content refers to the fact that vehicles were tested at constant speeds, no acceleration involved. A strong emphasis was laid on the influence road noise has on the interior sound quality of LCVs. Other objectives for the thesis were, to provide a method to benchmark the interior SQ of LCVs and to develop target values for objective metrics for these vehicles. Establishing a comprehensive literature survey formed another objective of this study. It seeks to provide a summary of the modern SQ analysis procedure and the findings of a number of studies. The survey also presents an opportunity to compare this thesis’s results with previous studies. A last objective was to develop a list of possible hardware modifications that would improve the vehicle interior sound quality, influenced by different noise sources. A strong correlation between vehicle and engine speed and Zwicker loudness as well as Aure sharpness was found, for all test conditions. The road surface roughness was observed to also have a strong influence on the objective metrics of vehicle interior SQ. Loudness was found to be around 25% higher and sharpness around 5.6% lower in vehicles driving on rough tar roads than on smooth roads. Good correlations between a newly developed metric (the SPF), an equation in Zwicker loudness and Aure sharpness, and subjective ratings was obtained for a number of test conditions. Four objective equations, as well as target values for loudness and sharpness have been developed to objectively optimise the sound quality of LCVs. Benchmarking interior sound quality utilising the developed equations, will ensure continuous improvements in the SQ sector for future LCVs.

This dissertation is concerned with the problem of slewing large flexible structures in space and simultaneously suppressing any vibrations. The equations of motion for a three-dimensional spacecraft undergoing large rigid-body maneuvers are derived. The elastic motions are assumed to remain in the linear range. A method of substructure synthesis is presented which spatially discretizes the equations of motion. A perturbation approach is used to solve the equations of motion. The zero-order equations describing the rigid-body maneuver are independent of the first-order vibration problem which includes small rigid-body motions. The vibration problem is described by linear nonself-adjoint equations with time-dependent coefficients. Minimum-time, single-axis rotational maneuvers are considered. The axis of rotation is not necessarily a principal axis. The optimal maneuver force distribution is proportional to the corresponding rigid-body modes with the mass acting as the control gain. The premaneuver eigenvectors are used as admissible vectors to reduce the degrees of freedom describing the vibration of the spacecraft during the maneuver. Natural control and uniform damping control are used to suppress the vibrations during the maneuver. Actuator dynamics cause a degradation of control performance. The inclusion of the actuator dynamics in the control formulation partially offsets this effect. The performance of these control techniques is adversely affected by actuator saturation but they remain effective. Numerical results are presented for a spacecraft in orbit and in an earth-based laboratory. / Ph. D.

All vehicles have changing payloads that affect their dynamic response. Compared to passenger vehicles, heavy machinery have larger and more greatly varying payload masses, higher centers of mass, and encounter larger disturbances. These factors lead to significant increases in the amount of vibration experienced by heavy machinery operators. This fact, when coupled with the large amount of exposure time that a typical heavy machinery operator incurs, leads to much greater vibration dosage values for the heavy machinery operator. In addition, the heavy machinery operator faces equal or greater opportunity for accident. The chance of accident, along with the increased vibration dosage, leads to an operating condition with significant safety risks, both short and long term. It has been shown that payloads affect both the stability and vibration isolation properties of a vehicle. Large payloads reduce vehicle stability while increasing the amount of vibration transmitted to the operator. A method to compensate for these loading affects would prove to be a useful technique to increase the safety of the vehicle, both in terms of accident avoidance and long term health effects of vibration. This thesis provides such payload compensation techniques. Improved vehicle dynamics were accomplished with the use of both active and semi-active suspension control. The active systems used are optimal control based, and provided the greatest improvements in vehicle performance. An optimal controller designed around a nominal payload, however, proved insufficient for operation over the entire payload range due to too large peak actuator forces at low payloads. A multiple model approach was used to remedy this problem. Semi-active systems based on a Linear Quadratic Regulator with output feedback and damping selection via static deflection were developed. The semi-active systems would require far less power than the active systems, with the need for knowledge of fewer systems states. It was shown that despite these lower demands, the semi-active systems closely approach the performance of the fully active systems.

Orientador: Milton Dias Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-17T17:39:07Z (GMT). No. of bitstreams: 1 Simionatto_ViniciusGabrielSegala_M.pdf: 5623305 bytes, checksum: 1fa9e5b17f2a168dfa754ee947f53417 (MD5) Previous issue date: 2011 / Resumo: O desenvolvimento de novas tecnologias na área automotiva e as restrições cada vez mais apertadas com relação a emissões culminaram em veículos cada vez mais leves, silenciosos e potentes. Por este motivo, os trens de potência atuais são cada vez mais susceptíveis a fenômenos de NVH. Além disso, pelo fato de os motores atuais emitirem menor nível de ruído, alguns destes fenômenos tornam-se mais perceptíveis. Neste contexto se encaixa o trabalho atual. Sabe-se que muitos problemas desta área são solucionados realizando alterações no disco de embreagem, e por isto, neste trabalho estuda-se a influência dos parâmetros de seu pré amortecedor nos fenômenos de shuffle e clunk. São feitas análises do trem de potência linearizado, por este ser um procedimento muito comum na área de desenvolvimento deste sistema. Após isso, analisa-se o mesmo sistema, através de simulações numéricas, porém considerando não linearidades no disco de embreagem e nos engrenamentos, onde foi considerado o impact damping. Identifica-se os pares engrenados que mais contribuem para o surgimento do fenômeno de clunk, e a influência dos parâmetros do pré-amortecedor sobre ambos os fenômenos / Abstract: The development of new technologies on automotive engineering and the toughening emissions laws led to the design of lighter, more silent and more powerful vehicles. For this reason, today's powertrains are more prone to NVH phenomena. Furthermore, the noticeability of those phenomena is increased since newer engines produce lower noise levels. This is the subject in which this work fits into. It is known that many of the NVH phenomena can be attenuated by performing changes on the parameters of the clutch disc, and because of it, the influence of the parameters of the clutch damper on shuffle and clonk is studied in this work. For being a widely used procedure on the development of drivelines, a inear analysis is performed on a linearized model of a powertrain. After that, using umerical integration methods, further analyses are performed on a nonlinear model of the driveline, considering that the clutch disc and the gear meshes are nonlinearities. The latter's energy loss is modeled used impact damping. The geared pairs that contribute most for the clunk phenomenon are identified, and finally the influence of the parameters of the clutch damper on both phenomena are stated / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Orientador: Milton Dias Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-17T18:54:27Z (GMT). No. of bitstreams: 1 Miyasato_HugoHeidy_M.pdf: 3357683 bytes, checksum: 9fcd8bd237500580084498c606879165 (MD5) Previous issue date: 2011 / Resumo: Fenômenos de ruído, vibração e sua severidade (NVH) são uma grande preocupação da indústria automotiva desde o século 20. A fim de atingir uma vantagem competitiva, as montadoras têm se focado na melhora do desempenho de NVH dos seus produtos para lidar com um cenário de mercado global competitivo. No intuito de verificar o comportamento do sistema durante o processo de desenvolvimento, métodos computacionais são aplicados para encontrar melhores abordagens e na previsão de problemas, economizando tempo e orçamento da empresa gastos na construção de protótipos e testes. Nesse trabalho, gear rattle, um ruído induzido por impacto cuja causa são as engrenagens sem carga da transmissão, será modelado e simulado. É diagnosticado com maior intensidade em veículos com motores diesel em marcha lenta e excitado especificamente quando uma faixa de frequências que causa grande amplitude de vibração nos elementos internos da caixa de câmbio é alcançada. Modelos lineares do trem de potência em ponto morto ou em tração serão estudados, compreendendo as suas características básicas, tais como frequências naturais e modos associados que podem ser representativos do fenômeno. Esse sistema possui elementos com fortes não-linearidades, tais como a rigidez estratificada com histerese da embreagem e a folga entre os dentes dos engrenamentos. Uma caracterização mais realista será incluída no modelo com uma rigidez variante no tempo para o engrenamento helicoidal, utilizado em todas transmissões manuais, com uma componente dissipativa adequada aos impactos. Para verificar condições de operação que podem somente ser avaliadas segundo formulação não-linear, simulações serão realizadas para verificar a eficácia de orientações de solução e propostas de modificação encontradas na literatura / Abstract: Noise, Vibration and Harshness (NVH) phenomena are a great concern of the automotive industry since the twentieth century. In order to achieve a commercial advantage, manufacturers have focused on improving the NVH performance of their products to cope with a competitive global market scenario. To verify the behavior of the system during the design process, computational methods are applied to find a better approach and foresee problems, saving company budget and time spent in prototypes and tests. In this work, gear rattle, a impact-induced noise caused by the unloaded gear teeth inside the gearbox, will be modeled and simulated. It is diagnosed with a higher intensity in diesel vehicle engines at idle speed and in a more specific way excited when a range of frequency that causes large amplitude of vibration in the internal elements of the gearbox is reached. Linear models of the powertrain operating in idle and traction will be studied, in order to understand its basic characteristics, such as natural frequencies and associated vibration modes that could be representative to this phenomena. This system has elements with strong nonlinearities such as the stratified stiffness with hysteresis of the clutch and the backlash between the gear teeth. A more realistic feature will be included in the model with a time variable stiffness for the helical gear mesh, used in all manual transmissions, with a suitable dissipative component for the impacts. To verify operational conditions which can only be evaluated with nonlinear formulation, simulations will be made to verify the effectiveness of solution guidelines and modification procedures found in literature / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica