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The current ability of the Virtual Aerodynamic/ Aeroacoustic Wind Tunnel to predict interior vehicle sound pressure levels is demonstrated using an automobile model which has variable windshield angles. This prediction method uses time-averaged flow solutions from a lattice gas CFD code coupled with wave number-frequency spectra for the various flow regimes to calculate the side window vibration from which the sound pressure level spectrum at the driver's ear is determined. These predictions are compared to experimental wind tunnel data. The results demonstrate the ability of this methodology to correctly predict wind noise spectral trends as well as the overall loudness at the driver's ear. A more sophisticated simulation method employing the same lattice gas code is investigated for prediction of the time-accurate flow field necessary to compute the actual side glass pressure spectra.

Sound propagation in a typical automotive air handling system was studied using the finite element and boundary element methods. The focus was on sound propagation characters and critical resonant frequencies of the system. A given sound source was applied as the excitation to the system. Frequency response analyses were performed, emphasizing the low and mid frequency ranges. The predicted critical frequencies, associated modal configurations, and corresponding sound pressure level fields were investigated. Both the finite element and boundary element methods were applied, and results by the two methods were compared and discussed.

A sound simulation technique has recently been developed that allows the NVH engineer to subjectively and objectively predict the passenger compartment noise levels due to radiated transmission gear noise. By using the simulation technique, a noise evaluation can be performed in the early stages of vehicle development, allowing NVH analysts and design engineers to address potential noise concerns well before production of the vehicle is scheduled to begin.

A building-block method, often used for simulating automotive systems, is described in this paper for simulating a driveline system. In the method, a driveline supplier's design responsible components are modeled with explicit FE models. Model accuracy is verified by testing and correlating the components in a free-free condition. Non-design responsible components are modeled using lumped parameters and/or modal models. These components and the validated design responsible components are integrated into a system model and connected using simple lumped parameter connections. Correlation at the system level is performed by making adjustments to the connection parameters and to the parameters of the non-design responsible components. The resulting system model has been used to accurately predict operating responses in a driveline system.

This paper describes a bench test evaluation method for vibratory forces caused by a propeller shaft. Most of the vibratory forces are usually generated at the joints of a propeller shaft. They are classified as vibratory forces of axial, radial and moment directions. Axial force can be easily evaluated by measuring the load washer outputs. On the contrary, radial and moment forces can not be analyzed enough clearly even though the outputs are measured, because the load washer for both forces is the same and the outputs depend on the sum of these forces. In this paper, an algorithm for the evaluation method is described. In this method the outputs, as a sum of the forces, are by computation translated separately into kinds of forces which are generated at each joint. The translated results are calculated using an inverse matrix of influence coefficients between the forces and the outputs. Using this method, the evaluation is effective for analyzing the mechanism of the forces.

We have developed a vibration damping technique for the Oil Pan to reduce radiation noise. This technique makes use of oil viscosity. To increase vibration damping of oil pan, we use oil viscosity by forming a thin oil film between the oil pan bottom and an added inner plate. This paper presents the results of vibration tests that were conducted to study the oil damping mechanism and results of applying to a small high-speed diesel engine.

An anti-backlash camshaft gear has been developed for the Cummins B Series 4-cylinder diesel engines. This gear reduces the gear train impact to result in lower engine noise levels and improved engine sound quality. The greatest benefit is at the low idle condition, where an engine noise reduction of about 2 dB(A) has been observed. Noise reductions throughout the engine speed and load range are also significant. The first application of this noise reduction gear is for a light duty pickup truck.

Due to improving levels of vehicle refinement and the growing importance of vehicle sound quality, transmission whine is an issue of increasing interest to vehicle manufacturers. This paper describes the development of a set of novel tools for the prediction of gear whine from spur and helical external gear systems. Transmission whine is primarily generated by transmission error, which is a deviation of meshing gears from a perfectly conjugate (smooth) motion due to manufacturing tolerances, tooth corrections and elastic deflection due to transmitted torque. The transmission error excites the geared shaft and bearing system leading to dynamic forces at the bearings, which in turn excite the transmission casing causing it to radiate noise.

Gear whine can be reduced through a combination of gear parameter selection and manufacturing process design directed at reducing the effective transmission error. The process of gear selection and profile modification design is greatly facilitated through the use of simulation tools to evaluate the details of the tooth contact analysis through the roll angle, including the effect of gear tooth, gear blank and shaft deflections under load. The simulation of transmission error for a range of gear designs under consideration was shown to provide a 3-5 dB range in transmission error. Use of these tools enables the designer to achieve these lower noise limits. An equally important concern is the dynamic mesh stiffness and transmissibility of force from the mesh to the bearings. Design parameters which affect these issues will determine the sensitivity of a transmission to a given level of transmission error.

In the NVH design optimization of automotive structures, the spectral properties of dynamic forces transmitted from rotating machinery to its housing is of primary interest. This paper describes the application of an indirect dynamic force estimation technique, more commonly known as transfer path analysis, to an operational transfer case. Through the implementation of an inverse transfer matrix technique, dynamic forces transmitted to a transfer case housing are estimated at a discrete number of locations. This paper describes the experimental and analytical methodology employed for dynamic force estimation as well as statistical techniques for solution optimization. Good correlation is shown to exist between frequencies of known physical phenomena and estimated dynamic forces for a total of nine (9) operational variations of transfer case speed and torque.

The purpose of this paper is to explain a methodology for diagnosing noise and vibration of internal components of the automatic transaxle and particularly for park disengagement clunk. The method for determining contributing lash is three-fold. First the lash values are physically measured. Secondly, in-vehicle test data is taken using accelerometers, microphones, and stress gages. The data is taken at a baseline condition and then when various lash interfaces are set at zero. Thirdly, component impact testing can be done to identify noise contributing parts. For the condition of park disengagement clunk this method helps to diagnose the source of the noise. When a vehicle is parked on an incline and the transaxle put in park, there is an energy transfer of the weight of the vehicle through the transmission and onto the suspension of the vehicle. When the transmission is pulled out of park, the released energy results in a loud clunk. The clunk has a high and low frequency content.

This paper discusses how the multi-body dynamics approach combined with flexible body effects is being applied to predict the bearing loads, the vibrations of crankshaft, the orbit plots of individual journal, and the performance of bearing (such as minimum film thickness and maximum film pressure) due to structural flexibility. The oil film effects in the journal bearing are implemented using both impedance method and hydrodynamic fluid film with finite element method. An application example of a V6 engine was given in this paper to show this sophisticated simulation model and to predict the dynamic response of the flexible system and loads in the journal bearings.

The effect of suspension system parameters on NVH performance is presented using the results of a design of experiments analysis of a quarter-car model with elastomeric elements. The elastomeric elements are modeled using Maxwell elements with stiffness increasing with frequency. Fourteen design parameters are considered. The force spectrum acting on the sprung mass is partitioned into frequency bands. The amplitude in each frequency band as well as location and amplitudes of resonance peaks in the force spectrum are used as response variables. Major factors that effect each response variable are quantified using sensitivity coefficients. Constrained optimization studies were run to identify the minimum and maximum responses that can be expected. Suspension and bushing designers can use this work to estimate the behavior of design alternatives early in the design process.

A combined finite element method (FEM), multibody system simulation (MSS), and hydrodynamic (HD) bearing simulation technique can be applied to solve for engine crankshaft and cylinder block dynamics. The cylinder block and crankshaft are implemented in the MSS program as flexible FEM structures. The main bearing oil film reaction is described in the MSS program by a pre-calculated reaction force database. The results are displacements and deformations of the crank train parts and the main bearing reaction forces. Verification of the tool was carried out by comparison of main bearing cap accelerations to measured data.

A new approach of estimating the modal parameters of operating piston engines is presented. The developed approach represents a combination of concepts from currently existing analyses such as the natural excitation technique (NExT), conditioned input analysis (CIA), and conditioned source analysis (CSA), and is hence termed “conditioned NExT analysis (CNA)”. NExT analysis can be employed to estimate modal parameters of structures in their naturally excited states. However, the existence of strong combustion induced periodic forcing makes the application of NExT analysis to operating engines difficult, if not impossible. CIA and CSA, built on concepts of partial and virtual coherence respectively, can effectively condition operating engine vibration data so as to remove any periodic energy associated with the process of combustion.

Power train noise reaches the interior through structureborne paths and through airborne transmission of engine casing noise. To determine transfer functions from vibration to interior noise a shaker was attached at the engine attachment points, with the engine removed. A simple engine noise simulator, with loudspeaker cones on its faces, was placed in the engine compartment to measure airborne transfer functions to interior noise. Empirical noise estimates, based on the incoherent sum of contributions for individual source terms times the appropriate transfer function, compared remarkably well with measured levels obtained from dynomometer tests. Airborne transmission dominates above 1.5kHz. At lower frequencies engine casing radiation and vibration contributions are comparable.

Modal Analysis is a well established technique which defines the inherent dynamic properties of the structure. At the same time the experimental harmonic analysis by shaker method is also a very important tool in solving some of the engine induced vibration problems in the automotive structure. Computer simulation technique using finite element methodology has been very effective tool in simulating the problem. However the right combination of these techniques has been a tricky situation. The paper describes the methodology of using right combination of these techniques to reduce the motorcycle chassis vibration which are induced by engine and drive-line excitation in minimum time. The method involves the Finite Element Modelling with shell elements, experimental harmonic analysis with frequency sweep upto 600 Hz, validation of the FE model, animation techniques and find out correct modification to fine tune the structure to eliminate the engine induced vibrations in the frame.

Finite element analysis is a computerized method widely used in industry to model and solve engineering problems relating to complex systems. Perhaps the most common use of finite element analysis is in the field of solid mechanics where it is used to analyze structural problems. To achieve the correct results the component and all mating interfaces must be modeled properly. Previously this was done by performing the analysis, manufacturing a prototype based on this design, and then physically determine the natural frequencies of the prototype attached to the interface structure. Once the actual natural frequencies are determined, the boundary conditions and other modifications of the finite element model are adjusted using a trial and error method until an acceptable correlation with the measured frequencies is achieved.

Several vibration-isolating equipments with metal spring, air spring, rubber spring, a shock absorber and a viscoelastic damper are developed by aiming at the optimum adjustments. The purpose of this paper is to study the new spring-mass system using non-linearity of magneto-spring and instability of float control. The dynamic spring constant and the damping coefficient of magneto-spring are dependent of a motion of amplitude. They are a much better characteristic for the suspension system compared with the current mechanical pairs composed of metal or air spring and a shock absorber. The vibration-isolating structure that combines the non-linear magneto-spring and the linear metal spring has the same effectiveness as a dynamic vibration reducer. For that reason, the suspension system using magneto-spring can reduce the vibration energy with a small stroke.

Brake judder is a forced vibration occurring in different types of vehicles. The frequency of the vibration can be as high as 500 Hz, but usually remains below 100 Hz and often as low as 10-20 Hz. The driver experiences judder as vibrations in the steering wheel, brake pedal and floor. For high frequency brake judder, the structural vibrations are accompanied by a sound. In the present paper the vibration amplitude (in terms of angular deflection, velocity or acceleration) of the caliper has been used as a quantitative measure of the vibration level. Brake Torque Variation (BTV) is the primary excitation for the vibrations. The mechanical effects generating BTV are linked not only to manufacturing tolerances but also to tribological issues. Uneven disc wear as well as Thermo-Elastic Instabilities (TEI) can lead to judder. Especially the effect of the wheel suspension on the transfer of the vibrations to the driver has to be considered.