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Technical Paper
2014-11-11
Antonio Agresta
NVH simulations for an automotive component industry represents a convenient mean to compare different solutions and make decisions on design choices based on the predictions of the component vibro-acoustic behavior. This paper presents the work carried out by the Modeling & Simulation Department of Continental Automotive Italy Spa in cooperation with LMS Italy Srl and the Department of Civil and Industrial Engineering of University of Pisa aimed at the vibro-acoustic characterization and comparison of two fuel rails assemblies (FRAs) by mean of simulations in Ansys Workbench & LMS Virtual.Lab. These simulations required a preliminary finite element (FE) modal analysis on the FRAs. To verify the reliability of the FE models, an experimental modal analysis was performed on one of the two fuel rails in free condition. The correlation between FE and test models highlighted some differences: a sensitivity study proved that the differences depend on the modeling of some brazed joints. The results of the following NVH simulations were checked by performing an acoustic impact test on the two FRAs in free condition inside an anechoic chamber.
Technical Paper
2014-11-11
James Howard Lee
As the number of off road vehicles used for recreation and work increases so does the need for these vehicles to be quiet and unobtrusive for their use to be acceptable to society. The ever increasing number has also been noticed by regulatory agencies which have developed emissions standards for off road vehicles which manufacturers are often meeting through the use of exhaust after treatment, i.e. catalytic converters. The compact size of off road vehicles and the need for high levels of utility increase the challenge of creating an effective exhaust after treatment system for these vehicles especially when a catalytic converter is included in the system. In this paper the design considerations for an off road vehicle engine exhaust after treatment system are presented and discussed. An example of implementing the design considerations is presented through an exhaust after treatment, including a catalytic converter, for a high performance, low emissions snowmobile developed for the SAE Clean Snowmobile Challenge.
Technical Paper
2014-11-11
Diego Copiello, Ze Zhou, Gregory Lielens
This paper addresses the numerical simulation of vehicle exhaust system noise using an innovative transfer matrix method (TMM) supporting high order duct modes combined with finite element method (FEM). Exhaust systems usually consist of complex volume components (mufflers, catalyzers ...) connected by simpler pipes. The noise propagation through such systems can be efficiently addressed by means of the Transfer Matrix Method (TMM). The TMM is an analytical method which allows assessing efficiently the acoustic behavior of an entire exhaust line by combining acoustic transfer matrices of each of its constitu¬ent sub-components (i.e., volume components: mufflers, catalyzers, etc.). The main assumption of this method is that within the exhaust line only the plane wave is propagating and thus the transfer matrices could be computed analytically. On the contrary, this assumption leads to a strong limitation in the maximum frequency of analysis which is the cut off frequency of the first higher order mode present in any one of the exhaust line components.
Technical Paper
2014-11-11
Sara Gronchi, Riccardo Maccherini, Raffaele Squarcini, Fabio guglielmo, Emanuela Ligarò
In the modern both small and large size engine, the acoustic emission is a very important matter increasingly studied as per specific international standards. This paper presents the study of the acoustic emission of a hydraulic rotary oil pump by means of measurement techniques and numerical approaches. This activity aims at showing a complete test-case in which both methods are used to face a noise issue and highlighting also the “weight” of the hydraulic excitation in both cases. In particular, an oil pump has been completely characterized on a test bench to verify the hydraulic performances and the noise radiation. A structural modification has been suggested with the target of altering the noise spectrum of the pump, achieving an optimization of the noise generation. From this assumption, experimental and numerical activities have started in parallel. Measurements have been carried out by means of the intensimetric method and supported also by conventional acquisitions performed with hydraulic pressure transducers, accelerometers and microphones.
Technical Paper
2014-11-11
Thomas Metzinger, Christoph Raber, Christoph Wittmann
20th Small Engine Technology Conference “New development approach for wet motorcycle clutch systems” The change of the motorcycle market in the last decade ask for “solutions” for the changed requirements. The strong rising bike segment of the emerging markets characterized by one cylinder engines up to 250ccm and 25HP and a focus of low price range of the vehicle in combination with a high sales volume. These bikes normally daily used for individual transportation. On the other side you have the bike segment of the industrial countries in which the bikes used mainly for hobby purposes or as amateur bike racer. The sales volume of these segment consolidated in the last years and have several subgroups like sport bike, touring, off-road and others. All of the segments and subgroups have their individual requirements to the clutch system. Now Schaeffler combine their experience in developing and producing components for small engines and clutch systems for the automotive sector to develop the ideal clutch system for a motorbike.
Technical Paper
2014-11-11
Vishnu kumar Kuduva Shanthulal, Kannan Marudachalam, Chandramouli Padmanabhan
The diesel power train (engine and transmission) is the most significant mass contributor in a three- wheeled vehicle. High idling vibrations of a single cylinder four-stroke diesel engine causes discomfort for driver and passengers as vibrations from the engine get transmitted to the structure and the body panels through the engine mounts. The isolation of these vibrations by proper design of rubber mounts is the most effective engineering approach to improve ride quality of vehicle. In the present study, a mathematical model of the powertrain and mount system is developed; the engine and transmission are assumed to behave as a rigid body (6 degrees-of-freedom) and the compliance comes from the mounts. Both four and three mount configurations have been investigated, with the mounts being represented by three independent springs in the compression and shear modes. Since the mounts can be inclined, appropriate transformations are carried out from the local mount co-ordinate system to the global co-ordinate system.
Technical Paper
2014-11-11
Andrea Fioravanti, Giulio Lenzi, Giovanni Vichi, Giovanni Ferrara, Stefano Ricci, Leonardo Bagnoli
The intake and exhaust lines are the main elements contributing to the abatement of the acoustic emissions of an Internal Combustion Engine (ICE). Many different numerical approaches can be used to evaluate their acoustic attenuation, which is commonly expressed by the Transmission Loss. One-dimensional (1D) and three-dimensional (3D) simulations are conventionally carried out only within the acoustic domain of the muffler or the air-box. The walls of the acoustic filter are considered fully rigid and the interaction between the acoustic waves and the structure is then neglected. Moreover, the effect of the manufacturing characteristics and the attenuation of the acoustic waves due to the fluid viscothermal effects are also commonly disregarded in the numerical analysis of the filters. In addition the presence of a catalytic converter or a filter cartridge may have an influence on the numerical results. All these aspects, however, can remarkably affect the matching between simulations and experiments both at high frequencies and also at medium-low ones.
Technical Paper
2014-11-11
Kazuhiko Tanaka, Haruomi Sugita, Hibiki Saito, Masahiko Sekita
The exhaust sound of a motorcycle is one of the key appealing factors to the customers along with its styling and dynamic performances. Accordingly, various attempts have been made to realize attractiveness of exhaust sounds. Recently, there is an increasing demand to divert a common motorcycle engine to various vehicle categories. An individual engine configuration category has its own featuring exhaust sound. Despite of these circumstances, it is also required to create the best suitable sound for each vehicle category with a specific vehicle feature. Accordingly, there is a possible case in which an inline-four-cylinder engine is shared with another motorcycle model in the vehicle category with nostalgic appearances in which V-twin engine flavor is frequently featured. In this study, three essential factors were extracted from the verbal expressions that appear as adjectives, exclusively or commonly, used to illustrate the exhaust sounds in each vehicle category or engine type. We tried to develop a method applicable to various engine types to design a targeting exhaust sound, by clarifying the relationship between the position of each exhaust sound, appeared on the mapping chart for the three factors, and the feature of the waveform of the sound,.
Technical Paper
2014-10-13
Harald Stoffels
The impact of the number of cylinders on two downsized gasoline engines on driving habits in the same passenger-vehicle type was investigated. This was carried out with two similar vehicles, equipped with an in-line three cylinder (i3) and an in-line four cylinder engine, both having same power, torque and transient-response behaviour. Both engine types were mated to six-speed manual transmissions with same gear-ratios and dual-mass flywheel characteristics. The study was performed by letting 21 subjects driving the same route and both vehicles consecutively. The relevant data during driving were recorded simultaneously from either vehicle integrated sensors (CAN), and secondary transducers. We found that the in-line three cylinder was operated at higher engine speeds even though it was operated at similar acceleration- and load levels like the in-line four cylinder power-train, whereat the off-set of the engine speed shows no correlation with the difference in firing frequency between both engine types.
Technical Paper
2014-10-13
Georg Johann Meingaßner, Hermann Pflaum, Karsten Stahl
Downsizing and downspeeding are currently important development approaches of the automobile industry to improve fuel efficiency and to reduce emissions. Decreased operational speeds in combination with higher combustion pressures lead to an increase of the excitation of torsional vibrations by the combustion engine. Torsional vibrations in powertrains can cause strength and NVH problems as well as lower the driving comfort and reliability of the vehicle. Simultaneously, increasing customer demands for operating smoothness and driving performance additionally exacerbate the requirements. Currently the conventional systems for reduction of torsional vibrations, e.g. dual mass flywheels, are increasingly reaching their limits. In cooperation of three institutes of the Technische Universität München (TUM) innovative concepts for an improved reduction of torsional vibrations in automotive powertrains have been developed ([1], [2], [3], [4], [5]). Several of those concepts have been realized as prototype assemblies engineered by the Gear Research Centre (FZG).
Technical Paper
2014-10-13
Zhiyong CHEN, Zhiyuan CHEN, Yang MAO, Wenku Shi, Guihui ZHANG
To research the torsional vibration damping characteristic of magneto-rheological fluid dual mass flywheel (MRF-DMF) and the control system in drive train, the multi-degree power train torsional vibration model which contains MRF-DMF and fuzzy control model are built, then the damping characteristic of MRF-DMF in several conditions are gained and compared with MRF-DMF when no control system. The result indicates: the damping characteristic of MRF-DMF effect on power train when using control is better than without control in idle, speed up, slow down, ignition and stalling, while the damping characteristic is less obvious in constant speed because the simulation condition and damping moment relatively stable.
Technical Paper
2014-10-13
Yuan Fang, Tong Zhang
Because of the vehicle market competitive and of the raise of customers’ demanding, NVH performance became an important job, especially for new energy vehicles. As the electric vehicle moving into the direction of high speed and large torque, electric vehicle vibration and noise problems highlighted gradually. In recent years, CAE has played an increasing role in the design ,development and optimization of powertrain NVH at component and system levels. The subject of this paper was the numerical and experimental evaluation of the electromagnetic and vibro-acoustic behavior of an electric powertrain. For this purpose, a coupled and fully flexible dynamics model of the electric powertrain was developed. Then electromagnetic forces including both radial and tangential force and gear mesh excitations including time-varying meshing stiffness, meshing error and meshing impact were computed, which were used to perform forced response analysis on the full FE mesh of the powertrain housing. An experimental bench was used to test the vibration acceleration and radiation noise of the electric powertrain in semi-anechoic room.
Technical Paper
2014-10-13
Anandan Sivakumar, Saishanker V, Raghvendra Gopal
Success of the vehicle in cold countries depends on performance of the vehicle under cold climatic conditions. In automobiles, structural elastomer components have strong influence on vehicle performance including NVH, ride comfort & durability. Elastomers are sensitive in nature to these climatic conditions due to its temperature dependent visco-elastic behavior. Thus, it is very important to understand structural elastomer component's performance at sub zero temperatures. In a vehicle Engine mount is used to hold engine firmly and isolate vibrations away from chassis. Vibration isolation of a mount at low temperature is generally affected by the rubber composition. Major ingredients of the rubber composition influencing the low temperature characteristics are Elastomer type, filler type, plasticizer and curing system. Rubber composition plays key role in achieving engine mount properties like static stiffness, dynamic stiffness, permanent set and durability. In this work, influence of low temperature has been successfully evaluated for engine mount application by varying elastomer type, filler type, plasticizer and curing system.
Technical Paper
2014-10-13
Zhi-yong CHEN, Ning SUN, Wenku Shi
In order to improving structure and performance of magneto-rheological dual mass flywheel (MRF-DMF), some parameters effects on dynamic characteristics are acquired by parameters analysis. The dynamic stiffness and loss angle in different current and different frequency are gained through dynamic characteristic test. The fluid-structure interaction finite element model of MRF-DMF is built and the accuracy is verified by comparison between test and simulation. Based on the model , the parameters analysis is done and the law of MRF viscosity、 arc spring stiffness, working clearance, rotor radius and axial width effect on dynamic characteristics are gained, it will prove some guidance for the structure and performance improvement.
Technical Paper
2014-10-13
Daniela Siano, Fabio Bozza, Luigi Teodosio, Vincenzo De Bellis
This paper reports 1D and 3D CFD analyses aiming to improve the gas-dynamic noise emission of a downsized turbocharged VVA engine through the re-design of the intake air-box device, consisting in the introduction of external or internal resonators. Nowadays, modern SI ICEs show more and more complex architectures that, while improving the brake specific fuel consumption (BSFC), may be responsible for the increased noise radiation at the engine intake mouth. In particular VVA systems allow for the actuation of advanced valve strategies that provide a reduction in the BSFC at part load operations thanks to the intake line de-throttling. In these conditions, due to a less effective attenuation of the pressure waves that travel along the intake system, VVA engines produce higher gas-dynamic noise levels. The worsening of the engine gas-dynamic performance can be compensated with a partial re-design of the air-box device, without significantly penalizing the engine power output. In order to find new design configurations of the air-box device capable of improving the noise levels, different numerical models can be successfully employed.
Technical Paper
2014-10-13
Jouji Kimura, Katsuhiro Hoshina, Kousuke Kawase, Koji Matsui, Atsushi Yamamoto
This paper describes the characteristics and mechanism of crankshaft impact noise that radiates from the cylinder body at full load medium engine speeds, based on the mechanism for axial vibration of crankshaft coupled with torsional vibration of crankshaft. Crankshaft Impact noise (hereinafter referred to as ‘impact noise’) is heard as an intermittent noise from the front of the 6-cylinder in-line engine at the full load engine speeds from 1000rpm to 1500rpm, predominant at 1200rpm, and the impact noise frequency ranges from 1.5 kHz to 3.5 kHz. The following steps were taken to prove that impact noise is caused by an axial vibration of crankshaft coupled with a torsional vibration of crankshaft. Firstly, impact noise was heard from the engine front, and thus the noise at a distance of one meter from the engine front, the vibrations on the cylinder body at No.1 crank-journal center and the crank angle were measured at a full load speed of 1200 rpm. In the measurement, the large vibrations (hereinafter referred to as ‘impact vibration’) were detected three times per two rotations of crankshaft at about 50° after the firing top dead centers (50° ATDC) of No.1, No.3 and No.2 cylinders, and impact noise was detected at a crank angle of about 50°ATDC of No.1 cylinder and at this angle, the impact vibration was the largest.
Technical Paper
2014-09-30
Masahiro Akei, Takayuki Koizumi, Nobutaka Tsujiuchi, Takayuki Yamauchi
This paper describes the prediction of vibration and transfer path analysis (TPA) using the multi body dynamics (MBD) model of engine and measured frequency response functions (FRF). In agriculture machines, a demand for comfortable work environment is increasing. Reduction of noise and vibration at an operator position is one of these demands. In order to improve the vibration at evaluation position that is operator position, it is important that we take measures against the most contributed transfer path from vibration source to evaluation position. TPA has been used to grasp each contribution of vibration transfer paths. In the TPA, input force from vibration source to passive part should be identified accurately. In the traditional TPA, determination of force is done by mount stiffness method and matrix inversion method. In these traditional methods, the determination of force is done using only experimental result. Therefore, it is difficult to predict beforehand effects of improvement for structure and isolation system.
Technical Paper
2014-09-30
John Stuart, Stefano Cassara, Brendan Chan, Nicholas Augustyniak
This paper will deal with a phenomenon commonly observed in commercial highway vehicles with solid-beam front axles. The phenomenon is typically self-excited and manifests itself as a sustained oscillation about the kingpin in two forms, shimmy and wobble. Wobble is defined as a rotational oscillation about the kingpin while shimmy is wobble accompanied by axle tramp and hop motions. To fully understand the causes of the phenomenon and to develop a corrective action plan, a cross functional team was formed which employed multiple tools and strategies. A tractor that exhibited the phenomenon was selected for physical evaluation and was subsequently baseline tested by measuring the frequency and amplitude of the oscillation at various vehicle speeds. An ADAMS model was developed to simulate the tractor and reproduce the vehicle behavior. A DOE was developed to quantify the impact of a large number of variables and combinations of variables for both physical testing and simulation. Assorted variables were found to have primary, secondary and tertiary impact on the phenomenon.
Technical Paper
2014-09-30
Vladimir V. Vantsevich, Jeremy P. Gray, Dennis Murphy
Through inverse dynamics-based modeling and computer simulations for a 6x6 unmanned ground vehicle in stochastic terrain conditions, this paper analytically presents a coupled impact of different driveline system configurations and a suspension design on vehicle dynamics, including vehicle mobility and energy efficiency. A new approach in this research work involves an estimation of each axle contribution to the level of potential mobility loss/increase and/or energy consumption increase/reduction. As it is shown, the drive axles of the vehicle interfere with the vehicle’s dynamics through the distribution of the wheel’s normal reactions and wheel torques. The interference causes the dynamics of the independent systems to become operationally coupled/fused, and thus diminishes the vehicle’s mobility and energy efficiency. The analysis is achieved by the use on new mobility indices and energy efficiency indices which are functionally coupled/fused. Four possible scenarios are considered to trade between mobility and energy efficiency improvements by re-distributing power between the drive axles in severe/extreme terrain conditions, including poor mu-conditions, and high longitudinal and lateral slopes.
Technical Paper
2014-09-30
Masahiro Akei, Takayuki Koizumi, Nobutaka Tsujiuchi, Takayuki Yamauchi
 In recent years, the demand for low noise operating agricultural machines is increasing. The engine installed on machines is one of a major sound source. The air-borne noise radiated from the vibration of the engine surface affects the sound quality of the surrounding and at the operator’s point.  For the reduction of noise radiated from the engine, the engine enclosure and the sound absorbing material into the engine room are adopted.  However, the installation of the sound absorbing material leads to the increase in product cost. The structural improvement of the engine room also causes the increase in development period of the product. In order to reduce the noise level effectively at evaluation points, it is necessary to grasp the characteristics of sound source, and predict the improvement effect in advance.  In this study, the sound source model of a diesel engine that is installed on the agricultural machine is identified by inverse-numerical acoustic analysis (INA). INA is a method to identify the surface vibration of sound source from the sound pressure around sound source.
Technical Paper
2014-09-30
John Anderson
This paper describes the development and testing of a Dynamic Vibration Absorber to reduce frame beaming vibration in a highway tractor. Frame beaming is as old as the ladder frame. It occurs when the first vertical bending mode of the frame is excited by road or wheel-end inputs. This is frequently a smooth-road problem that occurs at highway speeds (50 to 60 MPH) when the tire rotational frequency coincides with the frame beaming frequency. Rear drive tire run-out is especially good at exciting the frame. It is primarily a driver comfort problem. Up until now, few options were available to resolve this problem. The paper will review the phenomenon, design factors affecting a vehicle's sensitivity, and the principles of Dynamic Vibration Absorbers (AKA Tuned Mass Dampers). Finally, the paper will describe simulation and testing that led to the development of an effective vibration absorber as a field fix.
Technical Paper
2014-09-30
Yiting Kang, Subhash Rakheja, Wenming Zhang
Different types of axle suspension systems have evolved for large size mining trucks to achieve improved attenuation of terrain-induced whole-body vibration (WBV) transmitted to the operator and to attain higher operating speeds. The hydro-pneumatic struts are increasingly being used together with different linkage configurations, which could yield widely different kinematic and dynamic properties and thereby the ride and handling performance of the vehicle. This paper presents comprehensive analyses of the different independent front suspension linkages that have been implemented in various off-road vehicles, namely a composite linkage Macpherson strut type suspension (CLT), a candle type suspension (CT), a longitudinal arm type suspension (LAT), and a double wishbone type suspension (DWT). The relative performance analyses are evaluated on the basis of handling dynamics of a 190 tons mining truck. The kinematic variations in camber, caster, inclination angle, toe-in and horizontal wheel center displacements of different linkage suspensions are synthesized via wheel bounce excitations in the MapleSim platform.
Technical Paper
2014-09-30
Anatoliy Dubrovskiy PhD, Sergei Aliukov, Yuriy Rozhdestvenskiy PhD, Olesya Dubrovskaya, Sergei Dubrovskiy
At present, we have developed a fundamentally new design of adaptive suspension systems of vehicles. Their technical characteristics and functional abilities are far better than the existing designs of suspensions. We have developed the following main suspension components of vehicles: a lockable adaptive shock absorber with an ultra-wide range (hyper range) of control performance, implementing "lockout" mode by means of blocking adaptive shock absorber, and an elastic element (spring, torsion, and so on) with progressive non-linear characteristic and automatic optimization of localization of work areas. Our design has no analogues in the practice of modern transport engineering. Our patents confirm the novelty and efficiency of our major design decisions. Advantages of our developments in the vehicle suspensions are the following: Firstly, it should be noted that when the vehicle is in a wide range of speeds in a so-called "comfort zone", we were able, by applying the non-linear elastic element, to reduce significantly the stiffness of the elastic suspension elements in compare with the regular structures - at least in two times!
Technical Paper
2014-09-30
Xianjian Jin, Guo-Dong Yin, Youyu Lin
Knowledge of vehicle dynamics variables is very important for vehicle control systems that aim to improve handling characteristics and passenger safety. However for both technical and economical reasons some fundamental data (e.g., Lateral tire-road forces and vehicle sideslip angle) are not measurable in a standard car. This paper proposes a novel Interacting Multiple Model Filter-Based method to estimate lateral tire-road forces by utilizing real-time measurements. The method uses measurements (yaw rate, roll rate, accelerations, steering angle and wheel speed) only from sensors which have already been integrated in modern cars. The estimation method of lateral tire-road forces is based on an interacting multiple model (IMM) filter that integrates in-vehicle sensors of in-wheel-motor-driven electric vehicles to adapt multiple vehicle-road system models to variable driving conditions. Considering extended roll dynamics and load transfer, a four-wheel nonlinear vehicle dynamics model (NVDM) is built.
Technical Paper
2014-09-30
Venkatesan C, Mohan Rao
Durability of components plays a major role in the total cost of ownership of a commercial vehicle. The powertrain mount is one such component which is constantly at work in a vehicle and its rubber characteristics play a major role in the NVH and Life of the component. This paper presents the enhanced durability benefits obtained by changing the polymer composition, manufacturing methods and design optimization of a powertrain mount. The methodology involved characterization of the existing mount, arriving a new compound formulation, making of prototypes, experimental validation for durability and repeatability in the laboratory combined with rigorous on field vehicle trials. NVH measurements were also carried out on the improved mounts. The above exhaustive exercise resulted in the development of a comprehensively far better mount than an existing mount with improved durability without compromise on NVH properties. The cost benefit in terms of the total vehicle life was enhanced to a large extent.
Technical Paper
2014-09-30
Iman Hazrati Ashtiani, Mehrnoosh Abedi
Road trains have been applied as one of the efficient ways for transportation of goods in different countries like United States, Canada, Brazil and Australia. These long vehicles have a wide variety in length or towing systems like fifth wheel or dolly draw-bar and based on specific measured and regulation could be authorized to move in specific roads. In order to avoid hazard and danger in case of accidents of these vehicles, safety performance of a specific type of these vehicles, called B-train, is investigated in this paper. A Multi-Body Dynamics (MBD) model of a B-train, which consists of a prime mover and two trailers coupled by fifth wheels, are simulated in first phase of study. The developed dynamic model is capable of simulating required tests as well as SAE lane change and constant radius turn for roll and yaw stability analysis and safety evaluation. As far as transportation of fuel or other hazardous liquid are a common usage of B-train vehicles, the effects of liquid fill level variation are also considered in this research.
Technical Paper
2014-09-30
Rahul Ramola, G Senthilkumar, P kannan, Muralidharan Chennakrishnan
The demand for comfort level in commercial vehicles is steadily increasing. Hence, fine-tuned performance parameters and attributes are required to fulfill the expectations from these vehicles. Refinement of noise and vibration without affecting performances of sub-systems and components has become extremely challenging. This paper presents an approach to identify and reduce the whistling noise that was perceived in the passenger compartment when the vehicle was accelerated above 50 Kmph. Whistling noise is a characteristic of aerodynamic behavior of a component and is produced in the higher RPM and frequency range. Thus Engine Cooling fan, turbocharger, intake unit, exhaust,Alternators and Compressors were suspected. Interior noise measurements revealed that the whistling noise is of specific order. Using NVH techniques like Order tracking and Near field measurements, HVAC alternator was identified as the source of whistling noise. Narrow down approach using noise analysis confirmed the alternator cooling fan as problematic noise radiating component.
Technical Paper
2014-09-28
Prashant Mahale, Aziz Bohari, Raajha M P
Brake noise is an emerging concern in Indian Auto-industry; with brake squeal being the most evident form of brake NVH. Squeal noise generation attributes to many parameters including kinematics of braking parts during pressure application, structural dynamic behavior which in turn depends on coupling at resonant frequencies of different parts of brake assembly, material of brake parts, operating clearances in the mating parts etc. The genesis of brake squeal lies in the generation of unstable frictional forces during braking event. These frictional forces induce uncontrolled amplification of brake parts vibration, which in turn tend to produce perceivable sound or noise. The magnitude this vibration induced squeal depends on co-efficient of friction, braking pressure, speed and temperature of friction material. It is known from typical squeal evaluations on dynamometer that at different temperatures of friction, the ability/ occurrence, of squeal is different, typically in the range of 50oC to 200oC.
Technical Paper
2014-09-28
Taeho Jung, Jeongkyu Kim
This paper deals with grind noise in vehicles which is a low frequency vibration problem at 100~1kHz that appears in low brake pressures and extremely low speed where there is a transition from static to dynamic condition. Recently, the customer complaints have increased for grind and creep groan noise more than squeal noise. Low frequency brake noise is a combined effect of brake and suspension systems working with each other. The noise transmission path is also important. Experimental results are confirmed through ODS, Modal, TPA and 3D acoustic camera for noise transmission path. Finally, reduction methods of grind noise are presented.
Technical Paper
2014-09-28
Jung Hoon Woo, Jeongkyu Kim, kwang Yun kim, Daekyung Ko
Creep groan noise occurs in a stopped vehicle by the simultaneous application of torque to the wheel and the gradual release of brake pressure in-vehicle. It is the low frequency noise and giving the driver a very uncomfortable feeling. It is caused by the stick-sleep effect at the lining and disc interface. Recently, the field claim of low frequency creep groan has increased. And there is a lot of efforts to creep groan noise by means of modification of lining material. On this paper, Transfer path of creep goan noise was analyzed through ODS and TPA. Additionally the correlation between Source (Brake torque variation, Brake vibration) and Creep Groan Sound level wasdiscussed. Finally countermeasure to Creep Groan noise was suggested.
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