Search Results

Computer Aided Design and Optimization are two important directions of present research activity in spur gears. A review of literature indicates that the methods available, are iterative and rather tedious. In present work the non-linear optimization problem with the minimum centre distance as an objective function has been addressed. A new design space in terms of module and pinion number of teeth has been defined. Empirical relations to obtain Feasible Optimal Centre Distance based on input torque and gear ratio for 20° pressure angle for 20 gear materials, obtained by regression analysis, have been reported. A simple nomograph has been developed which gives pinion number of teeth and standard module.

A simulation methodology for dynamic modeling of geared rotor systems such as superchargers was used for determining the housing vibration response. The approach provides an ability to make quick parametric design modifications to the model for evaluation of relative noise response with the assumption that the averaged housing vibration level correlates approximately to the noise radiating from the surface. The housing in some cases was modeled as a lumped mass representation for efficiency, and when higher accuracy of housing modes was needed, a detailed flexible Finite Element Analysis (FEA) representation was used. The interesting features of the methodology were the use of constraint equations to model the gear mesh response per unit Transmission Error (TE) input, along with summarizing the component kinetic and strain energy for each mode and the mesh compliance for fast evaluation of opportunities for noise reduction.

Gear whine is a fundamental issue associated with the design of automotive transmission gears. The evaluation of gear whine has long been a subjective rating. The goal of this paper is a comparison of the objective data and the subjective rating system. Objective analysis can not always replace the subjective evaluation completely, but it can induce a consistency that subjective rating lacks. An objective analysis method of in-vehicle gear whine order tracked data subtracted from the overall noise level over a rpm range is compared to subjective rankings to establish an objective rating. A correlation and statistical analysis of the objective data has proven effective in evaluating the noise performance of gear whine in a vehicle. There is a concern for the acoustic performance of the gears in a transmission and a consistency in the evaluation, due to the ever increasing customer awareness of noises in automobiles

Fuel injection and cylinder pressures of diesel engines have increased substantially over the past decade, as have noise levels of many engines. Test results show that these two trends are linked: gear train impact, driven by fuel system and crankshaft torsional excitation, has become a dominant noise forcing function in heavy duty diesel engines. Fuel system torsional dampers, crank gear isolators, and rear gear trains can reduce gear impact noise. Empirical equations have been developed to predict the overall noise of heavy-duty diesel engines, based only on the size and location of the gear train. These simple equations can predict engine noise levels with surprising accuracy.

Powertrain radiated noise is an important design factor that must be evaluated during the concept phase of the design process. Unfortunately, the tools currently available to evaluate radiated noise, empirically derived relationships, detailed CAE models, or experimental data, are not useful during this critical phase of the design when many of the fundamental design aspects are determined. Empirical models are too general to capture the impact of many typical design decisions, and detailed CAE models or hardware tests are not practical due to the level of design detail necessary, the cost involved, and the timing. This paper lays out a simplified approach for the prediction of powertrain radiated noise that is useful for both quantitative and qualitative evaluation of design alternatives.

The internal combustion (IC) engine is an important source of vibration in many vehicles, and understanding its dynamic response to demands from both the vehicle operator and the terrain is essential to proper engine and mount design and optimization. Development of an engineering tool for understanding this dynamic response and the resulting forces transmitted from the engine block to the supporting structure is a priority in both commercial and military engine applications. Ideally, engine dynamics and vibration would be directly simulated through effective and efficient analytical and computational models of both the internal engine component dynamics as well as engine block vibrations. The present analytical study was undertaken to produce a comprehensive and efficient rigid-body engine dynamics and vibration model which predicts engine block motion, engine mount load transmission, as well as instantaneous engine crankshaft rotational speed.

Experiment results were compared with computation analysis results for torsional vibration on a crankshaft system with/without a torsional viscous damper on a six-cylinder in-line type turbocharged diesel engine and a V type ten-cylinder naturally-aspirated diesel engine respectively. At first, the boundary conditions for boundary element method (BEM) model were determined to estimate the torsional stiffness of the crank-throws of the crankshafts. Then, the estimated stiffness was used to calculate the natural frequencies of the torsional vibration without the damper by dynamic stiffness matrix method. As a result, the calculated natural frequencies approximately agreed with the measured ones. Finally, the torsional vibration with the damper was analyzed by using the dynamic stiffness matrix method and complex viscous damping coefficients for the damper. The calculated torsional amplitudes and resonant engine speeds agreed with the experiment results.

Motorsports events in the US range from minor Saturday night short track dirt oval races to the huge racing complexes. Up until the late 1970-s, there were only scattered and sporadic requirements for limiting noise levels generated by racing vehicles. Recognizing the need for preparation, the Sports Car Club of America created the field staff position of National Administrator - Sound Control.

The present work was directed towards the design of a sideline microphone array specifically adapted to the visualization of automotive noise sources in the 500 Hz to 2000 Hz range. The particular design philosophy followed here involved the minimization of the array redundancy: i.e., the minimization of the number of pairs of microphones that are separated by the same distance in the same directions. The performance of sixty-four element microphone arrays designed according to this principle will be illustrated through the use of simulated motor vehicle passbys. In addition, their performance will be compared with more conventional array designs: e.g., elliptical, and spiral arrays.

The next generation of automotive engines has to meet 2004 emission limits, ideally with improved fuel economy and with noise emission which is at least 3 dBA below the current status. Using both simulation and experimental analysis these challenging requirements can only be fulfilled by clearly defining all key steps in NVH development and by applying suitable technological methods. The development procedure discussed in this paper is characterised by several aspects: two stage prediction procedure fully integrated in the design process, combustion development with a definite focus on noise, a closed loop between simulation and test bed development and consideration of noise in the calibration of engine and drivetrain management systems. Apart from meeting target noise levels, noise quality is the reference parameter which is continuously evaluated by means of the AVL Annoyance Index.

Within the PNGV program, very challenging targets in respect to vehicle fuel economy were set. These could not be met with today's gasoline engines and driveline concepts. One possible alternative approach is a hybrid vehicle with a small displacement engine that exceeds the fuel economy of conventional engines: the 1.2L DIATA (Direct-Injection-Aluminum-Throughbolt-Assembly) engine. Within the development of a CIDI engine the NVH aspects are of particular importance as the customer (i.e., driver) should not notice any negative difference to gasoline engines. Therefore, gasoline engine transparency in respect to NVH was one primary goal within the development process. This paper describes the implementation of NVH features into the engine design already in the initial concept design phases, and the consequent NVH optimization throughout the development phase.

In diesel engine trucks, the sound quality improvement as well as the noise level reduction is demanded because of their annoying exterior noise. The semantic differential method was applied to evaluate the sound quality of trucks. In order to improve the analytical accuracy, subjects who can evaluate the characteristics of sound quality were statistically selected among all the subjects. Comfortability and powerfulness were extracted as the principal components by using the data of the selected subjects. It has been clarified that the comfortability strongly relates to high frequency element ratio, high frequency level, etc. The powerfulness strongly relates to the Zwicker loudness.

Spherical beamforming was used to visualize sound radiation during a vehicle passby test. Forward and backward propagation procedures are compared in terms of computational expense. A spherical spreading correction factor is described, along with a maximum liklihood procedure for obtaining an optimal array weighting dependent on the relative distance between the microphones and the focus point. The de-Dopplerized microphone outputs are multiplied by the weighting factors and summed to yield the source strengths over a reconstruction plane “attached” to the vehicle. Results obtained using a 16 element sparse array during an actual passby are used to demonstrate the present approach.

All new European vehicles face strict drive-by noise regulations. It would help vehicle designers if they could predict drive-by noise given parameters available early in the design process. The large amount of data from previous tests suggests a new approach, using neural networks. This paper introduces neural networks and describes how to apply them to the prediction problem. The selection of suitable inputs and amount of data required is discussed. The problem can be simplified by first predicting vehicle performance. Interim results for a vehicle performance neural network are presented. Further work towards a drive-by noise neural network is proposed.

Brake squeal, which is a noise, occurs in the range of frequencies 1 to 16 kHz is an important task for research to develop the vehicle passenger comfort. This phenomena has been studied many years theoretically and experimentally to gain better performance of brake and eliminating the squeal problem. The work presented here is focusing on the effect of the brake pad manufacturing on the generation of brake squeal. A simple proposed three-degree of freedom model has been used in the study to simulate the brake components (pad, caliper, and disc). The brake squeal and frequency response of brake pad has been measured at different working conditions (pressure, sliding speed, and brake pad type). A comparison between the theoretical and experimental work has been made and a good agreement was found between the theoretical prediction of the brake assembly natural frequency and the experimental measurement.

In this study, multi-planar Nearfield Acoustical Holography (NAH) is used to investigate noise radiated from the front, side and rear areas of single tires on a two-wheel trailer. Contributions to the radiated noise from the leading edge, trailing edge, and sidewall of the tire are identified. Two tires - an experimental monopitch tire and a production passenger car tire - are evaluated on a smooth asphalt pavement at 58 km/hr. From the measured complex pressure, acoustic intensity is reconstructed on three planes surrounding the tire using modified NAH procedures. Additionally, sound power levels are presented in tabulated and spectra forms. Tire noise generating mechanisms are inferred based on the results.

This paper discusses the methods of reducing weight of sound package through a new approach in sound absorption and insulation. In contrast to conventional sound package theory, a light porous material with high absorption (Ultra Light material) is used to replace a conventional porous/barrier sandwich material (classic), which results in an equivalent or better noise reduction in-vehicle with significant weight reduction. A Noise Reduction (NR) test was conducted with a box equipped with both the Ultra Light material and classic material. A SEA model of the same setup was also analyzed. Results from both the test and the analysis show that it is possible to achieve weight reduction by replacing conventional porous/barrier sandwich materials with light porous materials with high absorption.

During the development of a Statistical Energy Analysis (SEA) model, the most important step leading toward higher quality and confidence is the model validation process. In this paper, three different ideal source environments are employed to validate a SEA model of a minivan; diffuse field in a reverberation room, free field in an hemi-anechoic room and single-point excitation by a shaker. The tests were intended to emphasize the air-and structure-borne paths of the model separately. During the reverberation room test, capability of the model to track the design changes was checked by perturbing the configuration of the vehicle in successive steps. Finally, the performance of the validated SEA model is demonstrated by using an operational load case.

An approximate analysis method for brake squeal is presented. Using MSC/NASTRAN a geometric nonlinear solution is run using a friction stiffness matrix to model the contact between the pad and rotor. The friction coefficient can be pressure dependent. Next, linearized complex modes are found where the interface is set in a slip condition. Since the entire interface is set sliding, it produces the maximum friction work possible during the vibration. It is a conservative measure for stability evaluation. An averaged friction coefficient is measured and used during squeal. Dynamically unstable modes are found during squeal. They are due to friction coupling of neighboring modes. When these modes are decoupled, they are stabilized and squeal is eliminated. Good correlation with experimental results is shown. It will be shown that the complex modes baseline solution is insensitive to the type of variations in pressure and velocity that occur in a test schedule.

Environmental concerns as well as regulatory requirements are driving the development of alternative vehicle propulsion systems. Electric vehicles (EV's) are attractive because they emit no pollutants. In this paper, we examine the sound quality characteristics of wind and powertrain noise in electric vehicles. Sound quality is an important attribute of EV's, because the expectation is that they will be very quiet due to the absence of an internal combustion engine. As we show in this paper, the absence of engine noise is both a blessing and a curse for sound quality. For wind noise, the results show that electric and gasoline vehicles have equivalent wind noise loudness levels at all speeds. However, at lower speeds (50-60 mph), the EV is judged to have more wind noise even though the level was the same as the gasoline vehicle! The difference is that, in the EV, there is no engine noise to mask the wind noise.