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Viewing 181 to 210 of 8653
Technical Paper
2014-04-01
Atul Devidas Pol, Praveen Naganoor
Abstract Achieving targeted global modes (torsion, vertical bending and lateral bending) is one of the main enablers in meeting desired NVH performance characteristics of a new vehicle program. The torsion mode of next generation Land Rover - Freelander was lagging behind its target while the development cycle was quite progressed beyond underbody freeze. There was a challenge to recover more than 8 Hz in BIW torsion mode. A combination of Nastran Sol 200 (design sensitivity and optimization) and iterative process was adopted to demonstrate how the mode could be recovered with optimum mass penalty to the program. The paper states the existing modal status when this work was taken up. Next it elucidates design sensitivity/optimization module outcome which identifies sensitive areas to improve torsion mode. Then it describes how feasible design solutions were developed while iterating using Nastran Sol 103 modal analysis, based on the outcome of above sensitivity/optimization analyses, to converge to the specified target.
Technical Paper
2014-04-01
Xiaozhen Sheng, Shouhui Huang, Sheng Tian, Xia Cao, Youlin Huang
Abstract Subject to excitations from pressure pulsations in boost air, the rubber pipe connecting the turbo compressor outlet and the intercooler of an engine vibrates structurally and radiates noise. If the pipe is improperly selected, the resulted vibration may be strong enough to radiate noise which is sufficient to damage the sound quality of the vehicle. This paper presents an initial analysis on this issue. First, formulae are derived for predicting vibration and sound radiation of the pipe for a given pressure pulsation, resulting in sound transmission index for the pipe to quantify its sound insulation behavior. Then effects on the sound transmission index are investigated for pipe parameters such as pipe wall thickness, Young's modulus and density of pipe material.
Technical Paper
2014-04-01
Hyungtae Kim, Sehwun Oh, Ki-Chang Kim, Ju Young Lee, Jungseok Cheong, Junmoo Her
Abstract It is common knowledge that body structure is an important factor of road noise performance. Thus, a high stiffness of body system is required, and determining their optimized stiffness and structure is necessary. Therefore, a method for improving body stiffness and validating the relationship between stiffness and road noise through CAE and experimental trials was tested. Furthermore, a guideline for optimizing body structure for road noise performance was suggested.
Technical Paper
2014-04-01
Ravi Kiran Cheni, Chetan Prakash Jain, Revathy Muthiah, Srikanth Gomatam
Abstract Automotive OEMs quest for vehicle body light weighting, increase in Fuel efficiency along with significant cut in the emissions pose significant challenges. Apart from the effect on vehicle handling, the reduction of vehicle weight also results in additional general requirements for acoustic measures as it is an important aspect that contributes to the comfort and the sound quality image of the vehicle, thus posing a unique challenge to body designers and NVH experts. Due to these conflicting objectives, accurate identification along with knowledge of the transfer paths of vibrations and noise in the vehicle is needed to facilitate measures for booming noise dampening and vehicle structure vibration amplitude. This paper focuses on the application of a unique design and development of vehicle body structure anti-vibration dynamic damper (DD), unique in its aspect in controlling booming noise generated at a specific RPM range. Design methodology follows the concept of Mass-damper system on vehicle body or engine structure where panel with multi-degree of freedom vibrating at medium level frequency is transferred to damper which is vibrating at same resonant frequency in 180° opposite phase.
Technical Paper
2014-04-01
Changxin Wang, Deguang Fang, Fuxiang Guo
Abstract To find out the main excitation sources of a bus floor's vibration, modal analysis and spectral analysis were respectively performed in the paper. First we tested the vibration modal of the bus's floor under the full-load condition, and the first ten natural frequencies and vibration modes were obtained for the source identification of the bus floor's vibration. Second the vibration characteristic of the bus floor was measured in an on-road experiment. The acceleration sensors were arranged on the bus's floor and the possible excitation sources of the bus, which includes engine mounting system, driveline system, exhaust system, and wheels. Then the on-road experiment was carefully conducted on a highway under the four kinds of test condition: in-situ acceleration, uniform velocity (90km/h, 100km/h, 110km/h, 120km/h), uniform acceleration with top gear, and stall sliding condition with neutral gear. After that, by performing order tracking analysis and spectral analysis, the 1st order rotation frequency of the driveline and the 2nd order frequency of engine were identified to be the main cause of bus floor's vibration.
Technical Paper
2014-04-01
Hangsheng Hou
Abstract The purpose of this work is to analytically investigate automotive exhaust system noise generation and propagation phenomena. The turbulent exhaust gas flow interacts with the exhaust system structure, and as a result of this interaction, the structure vibrates and radiates noise. In the meantime, pressure wave becomes acoustic wave at its outlet. This study focuses on an exhaust system and carrying out transient fluid-structure analysis by using an explicit finite element solver that is capable of solving the Navier Stokes equations for turbulent, compressible viscous fluids as well as the field equations for solid structures in a fully coupled fashion. The time domain signals obtained from the transient analysis are post-processed to yield frequency domain data, sound pressure levels, noise source pattern as well as the selected acoustic field contour snapshots. The work involves evaluating different design proposals and comparing their corresponding sound pressure levels and acoustic fields.
Technical Paper
2014-04-01
Vijay Antony John Britto, Kalyankumar Sidram Hatti, Sai Sankaranarayana, Sivasankaran Sadasivam, Ekambaram Loganathan
Abstract Commercial vehicle NVH attributes primarily focus on interior noise for driver's comfort and exterior noise for environmental legislation. Major sources for both the interior and exterior noise are power train unit, exhaust and air intake system. This paper focuses on development of Air Intake System (AIS) for better interior and exterior NVH performance for medium and heavy commercial vehicles. For air intake system, structural radiations from its panels and nozzle noise are significant contributors on overall vehicle NVH. Noise generation mechanism in air intake system occurs due to opening and closing of the valves and inlet air column oscillation by sharp pressure pulse from cylinder. Based on benchmarking, vehicle level targets have been arrived, and then cascaded to system and sub-system level targets. For air intake system, targets for nozzle noise at wide open throttle condition have been set for exterior NVH performance. These targets are further cascaded down to transmission loss (TL), snorkel breathing mode, isolation & dynamic stiffness attributed for improvement in interior/exterior noise and sound quality.
Technical Paper
2014-04-01
Todd Tousignant, Kiran Govindswamy
Abstract Increased customer expectation for NVH refinement creates a significant challenge for the integration of Diesel powertrains into passenger vehicles that might have been initially developed for gasoline engine applications. A significant factor in the refinement of Diesel powertrain sound quality is calibration optimization for NVH, which is often constrained by performance, emissions and fuel economy requirements. Vehicle level enablers add cost and weight to the vehicle and are generally bounded by vehicle architecture, particularly when dealing with a carry-over vehicle platform, as is often the case for many vehicle programs. These constraints are compounded by the need to make program critical sound package content decisions well before the availability of prototype vehicles with the right powertrain. In this paper, a case study on NVH development for integration of a light duty Diesel powertrain is presented. A process, based on a time-domain transfer path methodology was applied to provide focused engineering development of powertrain and vehicle level NVH enablers.
Technical Paper
2014-04-01
Swapnil S. Kulkarni, Muragendra Magdum, Ravi B.
Abstract Automotive shock absorber shims are subjected to deformation while generating the pressure differential across the rebound and compression chambers. Considering the contact, large deflection, and material this shim stack deformation will be nonlinear throughout the working velocity of shock absorbers. The deformation of shim stack mainly depends on number and geometry of deflection disk, number and geometry of ports, and clamping disk geometry on which shims are rested. During the rebound and compression stroke of the shock absorber, the oil flows through the piston and base valve ports. High pressure oil developed during mid and high velocity of shock absorber results in deflection of shim stack in piston and base valve assembly. This deflection leads to oil leakage through the shim stack which results in change in damping force by the shock absorber. The fluid pressure from the flow passage (well) acting over surface area of shim differs while causing an elastic bending of the shims.
Technical Paper
2014-04-01
John Morello
Abstract As automotive and commercial vehicle OEM's continue their quest to reduce cost, product selection, quality, and reliability must be maintained. On-engine and wheel located connection systems create the greatest challenges due to the extreme levels of vibration. In the past, devices were fewer, and there where less direct connects in high vibration locations (Engine/ wheel sensors, electronic controllers, fuel injectors). Instead, small wire harnesses (“pigtails”) were commonly used. These pigtails can dampen the effect of the environment which includes mild to severe vibration by keeping the environmental effect away from the electrical connection contact point. Electrically connecting directly to the device creates new challenges in the connection system with the increased threat of fretting corrosion. Suppliers supporting OEM's are attempting to meet these direct connect requirements with lubrication, precious metal plating, and high contact force contacts. Some are more effective than others, and all have their drawbacks.
Technical Paper
2014-04-01
Prasad Rao Yerraguntla, Shashi Kulkarni, Deepak Asthana
Abstract Automotive Audio Signaling system is very vital and is controlled by local regulatory requirements. In India, usage of horn is very frequent due to highly congested traffic conditions, and is in the order of 10 to 12 times per kilometer. This results in the deterioration of the “contact”, which enables the functioning of the device. Hence the device requires premature replacement or frequent tuning, which are time consuming and results an increase in warranty costs and cost of service as well. Thus, to overcome this problem a unique and novel approach is proposed in this paper which enhances the life of the automobile horn, by implementing an additional pair of Contacts on circuit breakers, providing a parallel path for the power supply. This effort ensures that the life of the horn is increased by 5 times than the existing design. In addition, this approach completely eliminates the problems of premature failure or frequent tuning, yet without any change in the physical dimensions of the device, thus ensuring that no additional engineering efforts are required for its implementation.
Technical Paper
2014-04-01
Michael Delbaere, Didier Frachon, Gerald Masson
Abstract Many synchronous electric motors require a very accurate position sensor compatible with a sinusoidal control. The purpose of such a control is to enable an efficient and smooth operation enhancing the comfort by limiting vibrations. In some cases related to mechanical constraints, we have to deal with through-shaft design. One can quote for examples power drives for Electric or Hybrid Electric Vehicles as well as for Electric Power Steering motor. More generally, these sensors need to keep a simple and robust design and a restricted number of parts as they are submitted to high vibration levels, a wide temperature range and speeds of several krpm. In order to meet such requirements, MMT has developed a magnetic sensor principle offering a competitive alternative to the conventional inductive resolver type sensors. The basics of this solution is a through shaft angular position sensor using one or two Hall-effect probes. These Hall IC measure the angle of the magnetic field generated by a ring or a disc magnet.
Technical Paper
2014-04-01
Sameer U. Kolte, David Neihguk, Abhinav Prasad, Samir Rawte, Aditya Gondhalekar
Abstract A typical powertrain mount design process starts with performing the system calculations to determine optimum mount parameters, viz. position, orientation and stiffness values to meet the desired NVH targets. Therefore, a 6 degrees of freedom lumped parameter system of powertrain and mounts is modelled in Matlab®. The approach is to decouple the torque roll axis mode from the remaining five rigid body modes so that the response to the torque pulses is predominantly ‘oscillations about Torque Roll Axis’. This is achieved by optimizing the above mount parameters within specified constraints so that ‘Rotation about the torque roll axis’ is one of the natural modes of vibration. The tool developed here uses ‘Particle Swarm Optimization(PSO) algorithm’ because of its ease of implementation and better convergence to the solution. The algorithm is programmed in TK solver®. Further, for the given torque input, the harmonic response of the powertrain mounted on optimized mounts, is evaluated for comparison with NVH targets.
Technical Paper
2014-04-01
George Nerubenko
Abstract The results of dynamical study of new patented Torsional Vibration Damper for an engine crankshaft are presented. Design and structure of Torsional Vibration Damper is based on author's US Patent 7,438,165 having the control system with instantaneous frequencies tuner for all frequencies in running engine. Basically the tuner should be designed in three optional manners: having mechanical structure, electromechanical structure with control system and micro-channels filled by electrolyte solution. The focus of the study is on Torsional Vibration Damper equipped with micro-channels filled by electrolyte solution. Mathematical model based on the system of ordinary differential equations describing the rotation and vibration of mechanical components combined to Navier-Stokes equations reflecting the fluid flow and Poisson - Boltzmann equations applicable for electrolyte solution flow in micro-channels has been used for the analysis of the dynamic behavior of engine crankshaft system having proposed Torsional Vibration Damper.
Technical Paper
2014-04-01
Manchi Venkateswara Rao, Jos Frank, Mohit Kohli
Abstract Brake groan noise is resolved without any major change in the design of brake system and vehicle sub-system components in the development phase of a utility vehicle. The groan noise is observed during the end of the stopping of the vehicle under moderate braking. The concerned NVH issue is perceived as unacceptable noise in the passenger compartment. Groan induced vibration is subjectively felt on steering and seat frame. A typical process is established to successfully reproduce the groan which helped in precisely evaluating the effect of modifications proposed. The temperature range of the disc which has the highest probability to produce the groan noise is found out experimentally. The transfer path analysis is carried out to find the path contributions from suspension. Acoustic transfer functions from considered paths are measured with the suspension removed from vehicle. Effects of addition of mass on various locations of suspension and stiffness change of suspension bushings are studied.
Technical Paper
2014-04-01
Eric Frank, Peter Jacobsen
Abstract As the demand for Sound Quality improvements in vehicles continues to grow, robust analysis methods must be established to clearly represent end-user perception. For vehicle sounds which are tonal by nature, such as transmission or axle whine, the common practice of many vehicle manufacturers and suppliers is to subjectively rate the performance of a given part for acceptance on a scale of one to ten. The polar opposite of this is to measure data and use the peak of the fundamental or harmonic orders as an objective assessment. Both of these quantifications are problematic in that the former is purely subjective and the latter does not account for the presence of masking noise which has a profound impact on a driver's assessment of such noises. This paper presents the methodology and results of a study in which tonal noises in the presence of various level of masking noise were presented to a group of jurors in a controlled environment. Their subjective ratings were collected and correlated to noise and vibration metrics.
Technical Paper
2014-04-01
Gang Tang, Jinning Li, Chao Ding, Yunqing Zhang
Abstract This paper describes a simplified model to identify sprung mass using golden section method, the model treats the unsprung mass vertical acceleration as input and the sprung mass vertical acceleration as output, which can avoid the nonlinear influence of trye. Unsprung mass can be also calculated by axle load and the identified sprung mass. This study carries out road test on the vehicle ride comfort and takes a scheme that the group of 20 km/h is used to identify sprung mass and the group of 80 km/h is used to verify the identification result. The similarity of the results from the simulation and experiments performed are, for the sprung mass, 98.59%. A conclusion can be drawn that the simple method to measure the sprung mass in the suspension systems in used vehicles, such as the vehicle shown here, is useful, simple and has sufficient precision.
Technical Paper
2014-04-01
HakSon Han, ChulMin Park, JeongHoi Heo, Sang Kyu Kang
Abstract In order to achieve the proper automobile interior sound, the tailpipe noise of the exhaust system must be considered as a main contributor. This paper describes a study of the achievement of dynamic sound quality through exhaust system design. Firstly, we determined the vehicle's interior sound quality and established a target sound using a subjective assessment of 10 benchmark vehicles. The exhaust noise target is determined by means of transfer path analysis focusing on the noise source and how it's impacted by the muffler design. The exhaust system is commonly modeled as a combination of source strength and impedance. We obtained the source character by the wave decomposition method using two microphones and six loads ultimately leading to an optimized design of the inner muffler structure. Based on this study, we achieved dynamic interior sound and improved exhaust system performance.
Technical Paper
2014-04-01
Xiaobing Liu, Paul Nahra, Anna Strehlau
Abstract Engine stop/start systems are one technology being developed to meet ever tightening fuel economy regulations. Several production vehicles in the market have adopted stop/start systems with 12 volt batteries and enhanced starters. During engine autostart events (restart after autostop), the engine/vehicle vibration may be objectionable to customers. In this paper, the impact of extended range retarded intake cam phasing on first cycle combustion and vehicle vibration during engine autostart is provided. The engine intake cam phasers of a production vehicle were modified so the effective compression during autostart could be set as low as 3.5. Achieving these autostart conditions while maintaining typical cam timing positions under cold start conditions is achievable with an innovative dual park phaser. NVH measurements and engine speed traces indicate that this approach reduced vibration during engine autostart by a measurable amount. Subjective driver feedback was also positive.
Technical Paper
2014-04-01
Manivasagam Shanmugam, Raghavendra Kharatmal, Shirish Satpute
Abstract This paper describes the rapid design and development of thin walled powertrain components which act as external cover for engine subsystem assemblies. Computer Aided Engineering plays a major role in reducing the overall product development lead time. An approach by using ‘Simulation Driven Design and Development’ helps the developers to bring the necessary confidence about the components' required functionality during the design stage itself. During the design stage, typical inputs available for the development of these components are the broad dimensions obtained from the packaging considerations. The designer is required to develop the concepts targeting least noise radiation from component surfaces due to various excitations. Based on cost considerations, the designer can even opt for plastic materials instead of steel. The current paper considers two major noise radiation members namely valve cover and timing gear cover for rapid product development. A conventional modal analysis followed by harmonic response studies provides the basis for the iterations towards designing these members.
Technical Paper
2014-04-01
Kwang-Ho Oh, Won Hee Han, Jun-Ho Jang, Yong-Choo Tho, Hak Hyun Kim
Abstract Light weighting is a critical objective in the automotive industry to improve fuel efficiency. But when redesigning parts for light weight, by changing from metal to plastic, the resulting design gives NVH issues due to differences in part mass and material stiffness. Many parts were not converted from metal to plastic because of NVH issues that could not be solved. Many engine parts such as cylinder head cover, air intake manifold, oil pan and etc. previously made of metal have since long been replaced with plastic. But timing chain cover has not been replaced because of the aforementioned issue. Sealing performance due to the dynamic characteristics of the application is another challenging factor. In this paper, the key aspects of the plastic timing chain cover as well as its advantage are presented.
Technical Paper
2014-04-01
Julie Blumreiter, Chris Edwards
Abstract There is significant motivation to extend the operating range of naturally aspirated HCCI combustion to high load (8-12 bar IMEP) to attain a combustion strategy with the efficiency benefits of HCCI but without the lost power density of a lean or highly diluted charge. Currently, the high-load limit of HCCI combustion is imposed by a phenomenon commonly known as ringing. Ringing results when the kinetically-driven autoignited combustion process proceeds in such a way as to form strong pressure waves which reverberate in the engine. Inhomogeneities and gradients in mixture reactivity lead certain regions to react ahead of others, and as a result, coupling can occur between a pressure wave and the reaction front. This paper seeks first to sort several related but distinct issues that impose the high load limit: ringing, engine damage, peak in-cylinder pressure, peak rate of pressure rise, and engine noise. The fundamental gasdynamics underlying the upper load limit for premixed, autoignited engines are explored and elucidated with a quasi-1D reacting compressible flow model.
Technical Paper
2014-04-01
Se Jin Park, Seung Nam Min, Murali Subramaniyam, Heeran Lee, Dong Gyun Kim, Cheol Pyo Hong
Abstract Vibration is both a source of discomfort and a possible risk to human health. There have been numerous studies and knowledge exists regarding the vibrational behavior of vehicle seats on adult human occupants. Children are more and more becoming regular passengers in the vehicle. However, very little knowledge available regarding the vibrational behavior of child safety seats for children. Therefore, the objective of this study was to measure the vibrations in three different baby car seats and to compare these to the vibrations at the interface between the driver and the automobile seat. The test was performed on the National road at the average speed of 70 km/h and acceleration levels were recorded for about 350 Sec (5.83 min). One male driver considered as an adult occupant and a dummy having a mass of 9 kg was representing one year old baby. Four accelerometers were used to measure the vibration. All measured accelerations were relative to the vertical direction. Vibration Analysis Toolset (VATS) was used for time domain analysis.
Technical Paper
2014-04-01
Prasad Kumbhar, Ning Li, Peijun Xu, James Yang
In vehicle driving environment, the driver is subjected to the vibrations in horizontal, vertical, and fore-aft directions. The human body is very much sensitive to whole body vibration and this vibration transmission to the body depends upon various factors including road irregularities, vehicle suspension, vehicle dynamics, tires, seat design and the human body's properties. The seat design plays a vital role in the vibration isolation as it is directly in contact with human body. Vibration isolation properties of a seat depend upon its dynamic parameters which include spring stiffness and damping of seat suspension and cushion. In this paper, an optimization-based method is used to determine the optimal seat dynamic parameters for seat suspension, and cushion based on minimizing occupant's body fatigue (occupant body absorbed power). A 14-degree of freedom (DOF) multibody biodynamic human model in 2D is selected from literature to assess three types of seat arrangements. The human model has total mass of 71.32 kg with 5 body segments.
Collection
2014-04-01
This technical paper collection covers intake/exhaust/powertrain and chassis noise and vibration.
Collection
2014-04-01
This technical paper collection sets out to reflect the recent advances on the research, development and practices of Powertrain NVH treatment. The coverage includes: engine, engine subsystem and components noise and vibration; powertrain systems noise measurement and instrumentation; powertrain systems noise analysis.
Technical Paper
2014-04-01
Marco Mammetti, Marina Roche Arroyos
Abstract Over recent years IDIADA has developed several prototype electric vehicles as well as testing a number of electric powertrain configurations. Generally the electric motor output shaft delivers the torque to the transmission under a considerable level of high-frequency load variation and with noticeable torque irregularities that must be smoothed out in order to fulfill general NVH targets. This paper deals with the development phase of a prototype vehicle in which a specific testing activity was carried out to improve the overall NVH behavior of the powertrain. For this purpose, the mechanism of energy transference from the current to the motor and from the motor to the downstream driveline components was deeply characterized. The activity was aimed at smoothing the abrupt change in torque delivery and limiting the transfer of torque irregularities from the motor to the transmission. The torque control software calibration and the driveline elements were developed in order to reduce the noise and vibration critical frequency ranges.
Technical Paper
2014-04-01
Mohit Kohli, S Nataraja Moorthy, Manchi Venkateswara Rao, Prasath Raghavendran
Abstract The present quiet and comfortable automobiles are the result of years of research carried out by NVH engineers across the world. Extensive studies helped engineers to attenuate the noise generated by major sources such as engine, transmission, driveline and road excitations to a considerable extent, which made other noise sources such as intake, exhaust and tire perceivable inside. Many active and passive methods are available to reduce the effect of said noise sources, but enough care needs to be taken at the design level itself to eliminate the effect of cavity resonances. Experimental investigation of cavity resonances of real systems is necessary besides the FEA model based calculations. Acoustic cavity resonance of vehicle sub systems show their presence in the interior noise through structure borne and air borne excitations. Cavity resonances for some systems e.g. intake can only be suppressed through resonators. The exact location and nature of acoustic cavity resonance needs to be found as accurately as possible to bring out the best from a resonator.
Technical Paper
2014-04-01
Manchi Venkateswara Rao, Jos Frank, Prasath Raghavendran
Abstract Accurate quantification of structure borne noise is a challenging task for NVH engineers. The structural excitation sources of vibration and noise such as powertrain and suspension are connected to the passenger compartment by means of elastomer mounts and spring elements. The indirect force estimation methods such as complex dynamic stiffness method and matrix inversion method are being used to overcome the limitations of direct measurement. In many practical applications, the data pertaining to load dependent dynamic stiffness of the connections especially related to mounts is not available throughout the frequency range of interest which limits the application of complex dynamic stiffness method. The matrix inversion method mainly suffers from the drawback that it needs operational data not contaminated by the effect of other forces which are not considered for calculation. In this paper, a new method is proposed in which the structure borne noise associated with powertrain is quantified easily and reliably.
Technical Paper
2014-04-01
Marcus Becher, Stefan Becker
Abstract This paper focuses on the applicability of numerical prediction of sound radiation caused by an axial vehicle cooling fan. To investigate the applicability of numerical methods, a hybrid approach is chosen where first a CFD simulation is performed and the sound radiation is calculated in a second step. For the acoustic simulation an integral method described by Ffowcs-Williams-Hawkings is used to predict the sound propagation in the far-field. The simulation results are validated with experiments. The corresponding setup in experiments and simulation represents an overall system which includes the cooler, the cooling fan and a combustion engine dummy. To optimize the economical applicability in terms of simulation setup and run time, different approaches are investigated. This includes the simulation of only one blade using a periodic boundary condition as compared to the whole fan geometry. In the CFD simulation an SAS-turbulence-model is applied. The results show that this is a very useful approach considering the challenges in prediction of numerical sound.
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