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2015-06-15
Technical Paper
2015-01-2348
Richard Kolano
This paper presents the results of a study to reduce the background noise level within a large Quiet Room built as part of the original building construction circa 1990. This room is located adjacent to other laboratory testing environments and below a mechanical mezzanine which houses an extensive array of mechanical and electrical equipment including banks of low-temperature chiller compressors, air handling units, and electrical switchgear that serves the entire building complex. This equipment was installed atop the concrete mezzanine floor deck without provisions for isolating vibration. As a result, structure borne noise from that equipment travels through the floor, radiates from the underside of the floor deck, and intrudes into the Quiet Room below. This causes the background noise level within the Quiet Room to be too high for conducting low sound level measurements and studies on vehicles brought into the Quiet Room.
2015-06-15
Technical Paper
2015-01-2171
Winston Spencer, Djamel Bouzit
Driveline plunge mechanism dynamics has a significant contribution to the driver’s perceivable transient NVH error states and to the transmission shift quality. As it accounts for the pitch or roll movements of the front powerplant and rear drive unit, the plunging joints exhibit resisting force in the fore-aft direction under various driveline torque levels. This paper tackles the difficult task of quantifying the coefficient of static friction and the coefficient of dynamic friction in a simple to use metric as it performs in the vehicle. The comparison of the dynamic friction to the static friction allows for the detection of the occurrence of stick-slip in the slip mechanism; which enables for immediate determination of the performance of the design parameters such as spline geometry, mating parts fit and finish, and lubrication. It also provides a simple format to compare a variety of designs available to the automotive design engineer.
2015-06-15
Technical Paper
2015-01-2173
Srikumar C Gopalakrishnan, Teik Lim
Modeling of elastohydrodynamic lubrication phenomena for the spiral bevel gears are performed in the present study. The damping and the friction coefficient generated from the lubricated contact area will have profound effects on the dynamics of spiral bevel gears. Thus the damping value generated from this friction model will be time varying. This makes the use of constant and empirical damping value in the dynamics of spiral bevel gears questionable. The input geometric and kinematic data required for the EHL simulations are obtained using Tooth Contact Analysis. A full numerical elastohydrodynamic lubrication simulations are carried out using asymmetric integrated control volume (AICV) algorithm to compute the contact pressures. The fast Fourier transforms are used to calculate the elastic deformations on the gear surfaces due to contact load. The computed pressures and the effective viscosity are used to calculate the time varying damping for the spiral bevel gears.
2015-06-15
Technical Paper
2015-01-2174
Yuanfeng Xia, Jian Pang, Cui Zhou, Hongcheng Li, Wenjuan Li
Study on the Bending Vibration of a Two-Piece Propeller Shaft for 4WD Driveline Yuanfeng Xia1, 2, Jian Pang1, 2,*, Cui Zhou1, 2, Hongcheng Li1, 2, Wenjuan Li1, 2 1 Changan Auto Global R&D Center, Chongqing, China, 401120 2. State Key Laboratory of Vehicle NVH and Safety Technology, Chongqing, China, 401120 * Correspondence author, e-mail address: pangjian@changan.com.cn Currently, the four wheel drive (4WD) system is widely used in Sports Utility Vehicle (SUV) due to the increasing demand of fuel efficiency and dynamic performance by customers. However, propeller shaft consisting of different universal joints and tubes on 4WD vehicle easily induces low frequency bending vibration. This paper analyzes the characteristics of driveline bending vibration of a 4WD vehicle and provides control methods to reduce the low frequency vibration caused by propeller shaft bending resonances.
2015-06-15
Technical Paper
2015-01-2176
Rajkumar Bhagate, Ajinkya Badkas, Kiran Mohan
Gear rattle is an annoying noise and vibrations phenomena of the automotive driveline, which is mainly controlled by the engine’s torque variations creating the source for torsional fluctuations. In the current work, torsional vibrations are analyzed for improving comfort of the drivetrains. A 6 DOF, 1-D multibody mathematical model for the torsional vibrations of front wheel drive automotive drivetrain is developed and utilized for the optimization of sensitive system parameters for reducing the driveline rattle. Second order differential equations of the mathematical model are solved by using MATLAB and the output response is validated with the testing data. The model is further utilized for optimizing the flywheel inertia and clutch stiffness which are considered to be most sensitive parameters for reducing the input excitations to transmission.
2015-06-15
Technical Paper
2015-01-2177
Vikram M R, Mark Gehringer, Ramesh Patil
The powertrain and driveline systems interaction in a rear wheel drive vehicle development has gained even more attention for interior noise and vibration in emerging markets. Driveline can be the significant source for interior noise and vibration issues. Driveline concerns are across wide frequency range. These issues and frequency ranges have to be considered in the driveline integration process early in the vehicle development. Driveline integration itself is challenging to vehicle development team. Now with increased demand to have higher specific power from diesel engines makes driveline refinement more complicated, especially for rear wheel drive vehicles. Two driveline related issues were observed during evaluation in a RWD vehicle. Root cause analysis was done and it was found that first issue (lower rpm boom noise and vibration) due to higher torsional excitations, second one was (higher overall noise) due to propeller shaft bending frequency.
2015-06-15
Technical Paper
2015-01-2178
Mohamed El Morsy, Gabriela Achtenova
When localized fault occurs in a bearing, the periodic impulsive feature of the vibration signal appears in time domain, and the Corresponding bearing characteristic frequencies (BCFs) emerge in frequency domain. However, one limitation of frequency-domain analysis is its inability to handle non-stationary waveform signals, which are very common when machinery faults occur. The common technique of Fast Fourier Transforms (FFT) and Envelope Detection (ED) are always used to identify faults occurring at the BCFs. In the early stage of bearing failures, the BCFs contain very little energy and are often overwhelmed by noise and higher-level macro-structural vibrations. In order to extract the weak fault information submerged in strong background noise of the gearbox vibration signal, an effective signal processing method would be necessary to remove such corrupting noise and interference. Optimal Morlet Wavelet Filter and Envelope Detection (ED) are applied in this paper.
2015-06-15
Technical Paper
2015-01-2179
Laihang Li, Rajendra Singh
The transient vibration phenomenon in a vehicle powertrain system during the start-up (or shut-down) process is studied with focus on the properties of multi-staged clutch damper. First, a four-degree-of-freedom torsional model with multiple discontinuous nonlinearities, under flywheel motion input, is developed, and the transient event is validated with a vehicle start-up experiment. Second, the role of the nonlinear clutch damper on the transient event is investigated in time and time-frequency domains; interactions between the clutch damper and the transmission transients are estimated. Third, a semi-analytical method is applied to a simplified and validated single-degree-of-freedom powertrain system model to examine the nonlinear characteristics of clutch damper during a slowly varying non-stationary process. Finally, analytical formulas are successfully verified to approximate the nonlinear amplification level for a rapidly varying process.
2015-06-15
Technical Paper
2015-01-2180
Almahdi Saleh, Michael Krak, Jason Dreyer
This study examines clutch damper subsystem dynamics under transient excitation and validates predictions using a new laboratory experiment (subject of a companion paper). The proposed models include multi-staged stiffness and hysteresis elements as well as spline nonlinearities. Several example cases, such as two high (or low) hysteresis clutches in series with a pre-damper, are considered. First, detailed multi-degree of freedom nonlinear models are constructed, and their time domain predictions are validated by analogous measurements. Second, key damping sources that affect transient events are identified, and appropriate models or parameters are selected or justified. Finally, torque impulses are evaluated using metrics, their effects on driveline dynamics are quantified, and dynamic interactions between clutch damper and spline backlash nonlinearities are briefly discussed.
2015-06-15
Technical Paper
2015-01-2182
Yawen Wang, Junyi Yang, Xuan Li, Guohua Sun, Teik Lim
Due to the design of lightweight, high speed driveline system, the large displacement of shaft rotation and rotor dynamics must be considered to predict vibratory responses more realistically. In the current analysis, a lumped parameter model of the propeller shaft is developed with Timoshenko beam elements, which includes the effect of rotary inertia and shear deformation. The propeller shaft model is then coupled with a hypoid gear pair representation using the component mode synthesis approach. In the proposed formulation, the gyroscopic effect of both the gear and propeller shaft is considered. The simulation results show that the interaction between gear gyroscopic effect and propeller shaft bending flexibility has considerable influence on the gear dynamic mesh responses around bending resonances, whereas the torsional modes still dominate in the overall frequency spectrum.
2015-06-15
Technical Paper
2015-01-2183
Thomas Wellmann, Kiran Govindswamy, Jeff Orzechowski, Sudharsan Srinivasan
Integration of automatic engine start/stop systems in “conventional” drivetrains with 12V starters is a relatively cost effective measure to reduce fuel consumption. Therefore, automatic engine start/stop systems are becoming more prevalent and increasing market share of such systems is predicted. A quick, reliable and consistent engine start behavior is essential for customer ac-ceptance of these systems. The launch of the vehicle should not be compromised by the start/stop system, which implies that the engine start time and transmission readiness for transmitting torque should occur within the time the customer releases the brake pedal and de-presses the accelerator pedal. Comfort and NVH aspects will continue to play an important role for customer acceptance of these systems. Hence, the engine stop and re-start behavior should be imperceptible to the driver from both a tactile and acoustic standpoint.
2015-06-15
Technical Paper
2015-01-2185
Simon Eicke, Steffen Zemke, Ahmed Trabelsi, Matthias Dagen, Tobias Ortmaier
The trend toward lightweight construction and the reduction of mechanical absorbers in the powertrain coupled with higher engine torques strengthen the problem of noticeable vibrations of the vehicle in different driving situations. In contrast, customers of passenger cars make ever increasing demands on the ride comfort. It follows that the investigation of these effects plays a major role to develop strategies for improvements. One important issue of these problems is power hop, which is an undesired oscillation during acceleration with high torque requirements by the driver. This vertical oscillatory motion of a wheel stimulates vehicle vibrations, which are harmful to the powertrain and reduce the comfort of the passengers. In this paper the results of driving tests on various road surfaces are presented. Subject of the investigation are different types of cars with longitudinal and transversal mounted engines as well as with front and rear wheel drive.
2015-06-15
Technical Paper
2015-01-2187
Mark A. Gehringer, Keith Thompson
This paper describes the development of a semi-automated end-of-line driveline system balance tester for an automotive assembly plant. The overall objective was to provide final quality assurance for acceptable driveline noise and vibration refinement in a luxury performance vehicle. The problem to be solved was how to measure the driveline system unbalance within assembly plant constraints including cycle time, operator capability, and integration with a pre-existing vehicle roll test machine. Several challenging aspects of the tester design and development are presented and solutions to these challenges are addressed. Major design aspects addressed included non-contacting vibration sensing, data acquisition/processing system and vehicle position feedback . Development challenges addressed included interaction of engine and driveline vibration orders, flexible driveline coupling effects, tachometer positional reference error and vehicle-to-vehicle variation of influence coefficients
2015-06-15
Technical Paper
2015-01-2184
Syeda Mahmud, Shahjada Pahlovy
Fuel efficiency can be improved by reducing the energy loss of power train and it’s components. Some estimates shows that about 14%–30% of the energy from the fuel gets used to move a car down the road and 5-6% energy is lost due to drive train. Therefore, a potential improvement of power train components can lower the fuel consumption significantly. Due to the engagement and disengagement process of transmission clutches, a frictional heat is generated which leads to some damage to clutches. Therefore, it is necessary to cool down the disks to increase the service life of clutch. An automatic transmission fluid (ATF) is delivered in between the friction disks and separator plate to cool them. Since the friction plates and separator plates are always in relative motion to each other, a shear force is generated on the fluid in the gap between the disks. This shear force generates a drag torque which is considered as a loss.
2015-06-15
Technical Paper
2015-01-2190
Manchi Venkateswara Rao
Mount development and optimization plays a significant role in vehicle NVH refinement as they significantly influence overall driving experience. Dynamic stiffness is a key parameter that directly affects the mount performance. Conventional dynamic stiffness evaluation techniques are cumbersome and time consuming. The dynamic stiffness of mount depends on the load, frequency of application and the displacement. The above parameters would be far different in the test conditions under which the mounts are normally tested when compared to operating conditions. Hence there is need to find the dynamic stiffness of mounts in actual vehicle operating conditions. In this paper, the dynamic stiffness of elastomeric mounts is estimated by using a modified matrix inversion technique popularly termed as operational path analysis with exogenous inputs (OPAX).
2015-06-15
Technical Paper
2015-01-2193
Masami Matsubara, Daiki Tajiri, Makoto Horiuchi, Shozo Kawamura
Generally as change of vibration characteristics of a tire, natural frequency of a load and rolling tire is lower than that of an unrolling tire. This phenomena is considered to be due to the change of tire stiffness. Early studies described the reason why the change was caused by property of rubber material. One of the evaluation tire stiffness is sidewall stiffness. This stiffness, which have an influence on tire vibration characteristics, is also important design parameter for carry the vehicle body. Tire sidewall is parts of resisting the tension due to inflation pressure. Hence, it is considered that tire sidewall stiffness is decided by tension of inflation pressure and structural dynamic characteristics including property of rubber material. It is necessary to reveal the dynamic characteristic of tire sidewall stiffness. This study describes tire sidewall stiffness as difference of inflation pressure.
2015-06-15
Technical Paper
2015-01-2192
Manchi Venkateswara Rao, Jos Frank, Prasath Raghavendran
Meeting various customer(s) requirements with the given automotive product portfolio within the stipulated time period is a challenge. Design of product configuration matrix is an intelligent task and it requires information about vehicle performance for different configurations which helps in deciding the level of new development. Most often the situation arises, particularly in the field of NVH, to strike the right balance between engine power and structural parameters of the body. The sensitivity of engine power on the overall NVH behavior is the key information necessary to take major business decisions. In this paper, the effect of change in torsional fluctuation of the engine on the NVH behavior of the rear wheel drive vehicle is experimentally studied. The torsional fluctuation of the driveline are given as input with the help of electric motor to the existing test vehicle at its differential end and the current NVH levels are measured.
2015-06-15
Technical Paper
2015-01-2198
Masami Matsubara, Nobutaka Tsujiuchi, Takayuki Koizumi, Akihito Ito, Kensuke Bito
Tires of passenger cars greatly influence the performance of NVH (Noise, Vibration and harshness). Especially, it is important to reveal the tire vibration characteristics because there is a strong correlativity between the tire vibration and the interior noise of passenger cars as against road noise, one of the NVH performance. Early studies on the tire vibration characteristics for road noise focused on tire vibration of radial direction, circumferential mode is known, because this mode is dominant in vertical spindle force. However, recent studies of NVH prediction with development, including tires as car substructure, found that not only the circumferential mode, but also the lateral bending mode affect interior noise. Tire vibration mode making noise and vibration problem differs depending on axle vibration direction, and it is demand a comprehensive approach for this problem. This paper presents a new approach for evaluation of natural frequency of tire.
2015-06-15
Technical Paper
2015-01-2274
Paul R. Donavan, Bruce Rymer
Rumble strips are used commonly through the United States to alert drivers that they have wandered out of the lane of travel and need to take corrective action. In general, there are two conflicting requirements for rumble strips: producing sufficient warning for vehicle operators and minimizing the exterior noise that can create community annoyance. A measurement program was completed to assess driver input versus exterior noise generation for four vehicles designs and two approaches to rumble strip design. The vehicles included a small compact car, an immediate size car, a full sport utility vehicle, and a medium duty dump truck. The rumble strips included one of conventional design providing shorter wavelength input to the tire and one designed to provide longer wavelength, more harmonic input to the tire.
2015-06-15
Technical Paper
2015-01-2303
Katherine Tao, Alan Parrett, David Nielubowicz
The headliner system in a vehicle is an important element in vehicle noise control. In order to predict the performance of the headliner, it is necessary to develop an understanding of the substrate performance, the effect of air gaps, and the contribution from any acoustic pads in the system. Current Statistical Energy Analysis (SEA) models for predicting absorption performance of acoustic absorbers are based on material Biot properties. However, the resources for material Biot property testing are limited and cost is high. In this paper, modeling parameters for the headliner substrate are identified from a set of standard absorption measurements on substrates, using curve fitting and optimization techniques. The parameters are then used together with thickness/design information in a SEA model to predict the vehicle headliner system absorption performance.
2015-06-15
Technical Paper
2015-01-2319
Uije Kim, Matthew Maunder, Phil Grant, Duncan Mawdsley
A new pass-by noise test method has been introduced, in which engine speeds and loads are reduced (compared to the old test method) to better reflect real world driving behaviour. New noise limits come into effect on 1 July 2016, and tighten by up to 4dB by 2026. The new test method is recognised internationally, and it is anticipated that the limits will also be adopted in most territories around the world. To achieve these tough new pass-by noise requirements, vehicle manufacturers need to address several important aspects of their products. Vehicle performance is critical to the test method, and is controlled by engine torque, speed of response to accelerator pedal input, transmission type, overall gear ratios, tyre rolling radius, and resistance due to friction and aerodynamic drag. Noise sources (exhaust, intake, powertrain, driveline, tyres) and vehicle noise insulation are critical to the noise level radiated to the far-field.
2015-06-15
Technical Paper
2015-01-2320
Andreas Schuhmacher
Indoor vehicle pass-by noise applications deal with measuring the exterior noise from a vehicle fixed on a chassis dynamometer in a large hemi-anechoic room. During a standardised acceleration test, the noise is measured with an array of microphones placed in the far-field, and the overall noise level versus vehicle position can be simulated. In addition, the indoor facility allows controlled and repeatable measurements independent of weather. The indoor testing can be extended with pass-by contribution analysis for engineering purposes providing information about the pass-by noise contribution from major noise sources during the test. This work presents a novel application of blind source separation to vehicle measurements from an indoor pass-by measurement campaign for estimating pass-by noise contribution from tyres and engine during different operating conditions.
2015-06-15
Technical Paper
2015-01-2204
Michael Funderburg
The ability of various plasticizers to impact the vibration damping properties of polyvinyl chloride (PVC) plastisols was investigated. A material must have good viscoelastic properties in order for it to be an effective vibration damper. However, it is evident that not all viscoelastic materials are good vibration dampers. Consider flexible (plasticized) PVC, for example. PVC formulations demonstrating the same glass transition temperature may have widely different damping capabilities. This presentation will show that the type of plasticizer substantially impacts the damping ability of the final PVC composite. Initially, flexible PVC formulations with varied plasticizers were screened via dynamic mechanical thermal analysis (DMTA) to determine which ones would likely have good damping properties. Formulations which exhibited promising results with DMTA were then tested via an Oberst bar damping test (SAE J1637).
2015-06-15
Technical Paper
2015-01-2280
Bernd Philippen, Roland Sottek
Transfer Path Analysis and Synthesis is a widely-used troubleshooting and engineering method in the development process of a car. An engine TPA model should include the engine mounts because they are important elements of the structure-borne paths from the engine to the driver’s ears. This allows identifying if the structure, the sound radiation or the mount is a weak point of the transmission. A mount can be characterized, e. g., by a mount attenuation function, a four-pole model, or a simple parametric mount model. If the mount characteristics are known, the influence of a different mount on the structure-borne sound can be virtually predicted without a real modification. The mount characteristics could be determined on special test rigs but the transferability to the real situation is often questionable because the same boundary conditions on the test rig and in the car are difficult to guarantee.
2015-06-15
Technical Paper
2015-01-2334
David Bogema, Gary Newton, Mark Stickler, Chris Hocking, Frank Syred
Realistically experiencing the sound and vibration data through actually listening to and feeling the data in a full-vehicle NVH simulator remarkably aids the understanding of the NVH phenomena and speeds up the decision-making process. In the case of idle vibration, the sound and vibration of the idle condition are perceived simultaneously, and both need to be accurately reproduced simultaneously in a simulated environment in order to be properly evaluated and understood. In this work, a case is examined in which a perceived idle quality of a vehicle is addressed. In this case, two very similar vehicles, with the same powertrain but somewhat different body structures, are compared. One has a lower subjective idle quality rating than the other, despite the vehicles being so similar.
2015-06-15
Technical Paper
2015-01-2339
Márcio Calçada, Alan Parrett
Sound absorption materials can be key elements for mass-efficient vehicle noise control. They are utilized at multiple locations in the interior and one of the most important areas is the roof. At this location, the acoustic treatment typically comprises a headliner and an air gap up to body sheet metal. The performance requirement for such a vehicle subsystem is normally a sound absorption curve. Based on headliner geometry and construction, the sound absorption curve shape can be adjusted to increase absorption in certain frequency ranges. In this paper an overall absorption metric is developed to relate design parameters to an absorption curve shape which results in improved in-vehicle performance. This metric is based on sound absorption coefficient and articulation index. Johnson-Champoux-Allard equivalent fluid model and diffuse field equations are used. The results are validated using impedance tube measurements.
2015-06-15
Technical Paper
2015-01-2341
Marc Ingelmann, Holger Bickelmann
BASF supplies the automotive industry with parts made of the Micro-cellular Polyurethane Elastomer - Cellasto®, a material with unique characteristics in NVH applications. For over 50 years our automotive customers are relying on our materials, with the Jounce Bumper being our best known applications. Top mounts and coil-spring-isolators are also a key offering to the industry. A lot of functions in automotive and non-automotive products are using Cellasto® as damping element, such as armrests, seats, torque-dampers, handheld machines etc. The dynamic performance of Cellasto , combined with the ability to work in limited packages, makes it the ideal choice. The amplitude selective damping fits to the automotive requirements: small amplitudes are generating a low damping of the material; high amplitudes are increasing the damping.
2015-06-15
Technical Paper
2015-01-2300
Robert Fiedler, Chadwyck Musser, Petr Cuchý
This paper addresses the NVH design of a light rail vehicle whose maximum allowable interior SPL levels at certain speeds are regulated and may vary between countries, states, and cities. The objective of this study was to predict sound pressure levels (SPL) at several interior locations across a wide range of frequencies and estimate if the current design configuration will meet the noise level limits. Statistical Energy Analysis (SEA) was used to predict interior SPL and to understand and rank the various noise contribution paths and give a better understanding of the physics of transmission and what types of design changes are most effective to reduce the overall interior SPL to meet targets. A typical light rail vehicle is composed of a frame-like structure covered by lightweight panels and with interior panels that are increasingly made from composites, sandwich, laminated, or honeycomb materials or extruded panels.
2015-06-15
Technical Paper
2015-01-2225
Peng Yu, Tong Zhang, Jing Li, Shiyang Chen, Rong Guo
Faced on transient vibration of EV, considering the characteristics of the electric drive system, active and passive integrated transient vibration control method of power train mounting system was proposed. First, models of power train system and mounting system were established, modal characteristics were grasped by simulation and experiment; a feed-forward controller was constructed from the active control perspective, mounting system transient vibration and power train torsion vibration were reduced; based on this, further optimization of mounting system was conducted from a passive control perspective. Results show that the active and passive integrated control method can effectively reduce the dynamic reaction force of mounting points, improve the vibration conditions of power train and body as well.
2015-06-15
Technical Paper
2015-01-2359
Craig Reynolds, Jason Blough, Carl Anderson, Mark Johnson, Jean Schweitzer
Sound power is commonly estimated using either a reverberant chamber or an anechoic environment as described by the ISO 3741:2012 and ISO 3744:2012 standards respectively. Both methods require the volume of the noise source to be less than 1% of the chamber volume leading to a requirement of relatively large test chambers. Torque converter cavitation noise testing in an enclosed metallic test fixture violates both standards due to volume and/or space requirements. This paper describes a new method developed to accurately determine torque converter sound power through characterization of the test environment. Two types of reference noise sources were created to represent torque converter geometries and noise output. A tweeter was used to output broadband high frequency noise typical of cavitation noise. The first source consisted of the torque converter cover and tweeter only. The second used the cover and pump with a tweeter in place of the turbine, stator, and clutch.
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