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2015-09-29
Technical Paper
2015-01-2871
Mounika Katragadda, Kalyan Deepak Kolla, Venkata Suresh Yaparala
Abstract In the automotive industry many components face fatigue failure due to prolonged vibrations. This is commonly known as Vibration Induced Fatigue (VIF). There are two approaches to evaluate this; time & frequency domain. A straight forward and widely used method is the rainflow counting technique in the time domain. This counting algorithm is readily available and, apart from the time history, it needs only one variable input (the number of stress ranges). In case of high cycle fatigue, longer time histories are required for a statistically representative fatigue estimate, which makes the time domain approach consume large amounts of time and resources. This shifts our interest towards frequency domain methods. In the frequency domain, Dirlik's method is proven to be robust and gives closer results to the time domain.
2015-09-29
Technical Paper
2015-01-2856
Hongbin Wang, Ojas Patil, QingHui Yuan, Aaron Hertzel Jagoda
EXTENDED ABSTRACT Fuel economy of both highway and off-highway vehicles is a major driver for new technology development. One of the technologies to meet this driver is a digital valve based hydraulic system. Digital Hydraulics technology employs high speed on/off valves to achieve the same functionality with no throttling loss. Furthermore, by forming various architecture by using digital valves, it provides the system level capability and flexibility for energy saving and productivity improvement. There are many challenges in fully realizing the full efficiency benefits of the system in an actual application. These challenges include packaging, durability, a change in the operator's perception of the vehicle as well as hydraulic system performances during operation. One significant issue is the noise, vibration and harshness (NVH) of the system. Due to the nature of the digital valve operation, there are severe transient dynamics in the fluid system.
2015-09-29
Technical Paper
2015-01-2781
Rohit Saha, Yonghong Liu, Mahesh Madurai Kumar, Bill Kendrick, Long-Kung Hwang, Liyun Lucas, Dinh Ngo
Abstract This paper demonstrates the use of a system level model that includes torsional models of a Cummins diesel engine and an Allison transmission to study and improve system NVH behavior. The study is a case where the two suppliers of key powertrain components, Cummins Inc. and Allison Transmission Inc., have collaborated to solve an observed NVH problem for a vehicle customer. A common commercial tool, Siemens' AMESim, was used to develop the drivetrain torsional system model. This paper describes a method of modelling and calibration of baseline engine and transmission models to identify the source of vibration. Natural frequencies, modal shapes, and forced response were calculated for each vehicle drive gear ratio to study the torsional vibration. Several parametric studies such as damping, inertia, and stiffness were carried out to understand their impact on torsional vibration of the system.
2015-09-27
Technical Paper
2015-01-2684
Seongjoo Lee, ShinWook Kim, ShinWan Kim, Seong Rhee
Rear disc brake squeal test results confirm the disc wear - brake squeal correlation reported earlier on front disc brakes. A significant amount of Fe transferred from the disc to the NAO pad surface is detected and the distribution of the transferred Fe is very non-uniform on the pad surface. The pad surface formulation reaches that of Low-Steel Lomets. Disc pads from a noisier brake retain more transferred particles than from a less noisy brake. The pad surface retains more transferred Fe after noise test procedures than after performance test procedures. The transferred Fe particles are either barely visible or invisible. During brake noise test procedures, discs wear in weight as much as disc pads. No correlation is found between average in-stop Mu, maximum in-stop Mu or in-stop delta Mu and brake squeal.
2015-09-27
Technical Paper
2015-01-2686
Enrique Wegmann, Achim Dohle
Abstract The NVH behavior of brake systems remains a core problem for the brake industry. Many efforts have been made to achieve a better system understanding, but the prediction of noise occurrence based on measurable parameters remains unsatisfactory. By considering the brake pad as one key component within the brake system, until today different measurement methods describing its material properties have been developed. This work analyses the correlation of all important “state of the art” friction material/pad parameter measurement methods to the NVH behavior of a specific brake system on a statistical basis. The answer to the question “does the NVH parameter for friction materials exist” ? will be derived from these correlation results.
2015-09-27
Technical Paper
2015-01-2688
Hayuru Inoue, Kumi Hashimoto, Yoichi Kumemura
Abstract It is well known that improving NV performance and weight saving are reciprocity. Brake squeal free is one of the top priority issues during development of brake system. To date, complex eigenvalue analysis has been utilized for prediction of brake squeal. It solves the structural instability problems by modal coupling which is the phenomenon that natural frequencies of normal modes are quite consistent. The positive real parts of complex eigenvalues are identified as instable vibration which causes brake squeal. On the other hand, the needs for light-weight brake system are higher than before due to recent trends of economizing fuel consumption and high driving performance. In order to obtain coexistence of brake squeal free with weight saving, shape optimization technique has been proposed for complex eigenvalue analysis.
2015-09-27
Technical Paper
2015-01-2687
Aditya Kant Choudhary, Yogesh Mense, Saurabh Singh, Mahesh Shridhare
Abstract Brake noise is one of the common complaints and an irritant not just for the vehicle occupants but equally for the passers-by. Brake noise is actually vibration that is occurring at a frequency that is audible to the human ear. This occurrence of brake noise like brake squeal (>1 kHz) and groan (<1 kHz) is often very intense and can lead to vehicle complaints. During a brake noise event, vehicle basic structure and suspension system components are excited due to brake system vibration and result in a resonance that is perceived in the form of a noise. Proposed work discusses an experimental study that is carried out on a vehicle for addressing concern regarding disc brake squeal and groan noise. Based on the preliminary inputs, vehicle level study was carried out in order to simulate the problem and objectively capture its severity.
2015-09-27
Technical Paper
2015-01-2689
Katsuhiro Uchiyama, Yuji Shishido
Abstract Brake groan analysis and improvement is progressing based on experimental measurements. An advanced brake assembly FEA model was built which considers torsional stiffness of suspension for analyzing creep groan. Creep groan is a representative groan noise of brake system from stick-slip phenomenon standpoint. This year we will present our study for advantageous direction for reduction of creep groan which will focus on friction material µ vs. Velocity (µ-V) property, friction material physical properties and relative velocity between brake pads and rotor by advanced brake assembly FEA model.
2015-09-27
Technical Paper
2015-01-2702
Chihoon Jo, Jaeseung Cheon, Jongsung Kim, Yongsik Kwon
Abstract EMB (Electro-Mechanical Brake) which converts electrical motor power to brake clamping force at each wheel is a system that has been investigated and developed by various automotive part suppliers through the years. In particular, as the number of electrically powered vehicles, such as hybrid electric vehicles, electric vehicles and fuel cell electric vehicles, has expanded, the EMB has received increased interest due to its fast response that is much suited for effective cooperative control with regenerative braking. However, issues such as cost competitiveness, reliability and regulations need to be solved for commercialization [1-2]. A new concept, the hybrid Electro-Mechanical Brake (hEMB) is characterized by a dual piston structure linked by hydraulics inside of the caliper. It is possible to reduce the required motor power and increase the level of emergency back-up braking through the amplification effect of the dual piston mechanism [3].
2015-09-27
Technical Paper
2015-01-2690
Joo Sang Park
Abstract There are three kinds of noise mechanisms which are stick-slip, self-excited vibration and unstable dynamic behavior. This study is of a pad unstable behavior caused by pad spring contact stiffness and weak forces and improving a lower squeal noise due to self-excited vibration in brake system. This paper discusses a theoretical approach, numerical and experimental test to understand the squeal mechanism for unstable pad behavior and the analysis and measurement of mode coupling between brake components to decrease noise propensity. Three different approach are considered to understand noise mechanism. Fundamental approach is more important than experimental modal analysis, CEA (Complex Eigen value Analysis) because the minimal vibration analysis is principle approach which has been proved by many researchers. CEA and modal test is useful to study the relationship between lower squeal noise and self-excited vibration for more details.
2015-09-27
Journal Article
2015-01-2682
Masaaki Nishiwaki, Ryutaro Misumi
Abstract It is well known that disc brake squeal is often caused by high friction coefficient pad materials. Disc brake squeal is caused by dynamic unstable system under small disturbance of friction force variation. Today, disc brake squeal comes to be simulated by FEA, but it is very difficult to put so many dynamic unstable solutions into stable solutions. Therefore it is very important to make it clear the influence of friction force variation. This paper describes a study on trigger of disc brake squeal generation. First, the development of experimental set-up for disc brake squeal basic research and experimental results are described. Second, the equation of motion in disc brake squeal is derived and the vibration induced by small disturbance are analyzed. Furthermore, kinetic energy increase per 1 cycle in minute vibration are calculated, which represents the influence of friction and wear between disc and pad with caliper.
2015-09-27
Journal Article
2015-01-2691
Ju Young Kim, Jeongkyu Kim, Young Min Kim, Wontae Jeong, Hojoon Cho
Abstract In the brake system, unevenly distributed disc-pad contact pressure not only leads to a falling-off in braking feeling due to uneven wear of brake pads, but also a main cause of system instability which leads to squeal noise. For this reason there have been several attempts to measure contact pressure distribution. However, only static pressure distribution has been measured in order to estimate the actual pressure distribution. In this study a new test method is designed to quantitatively measure dynamic contact pressure distribution between disc and pad in vehicle testing. The characteristics of dynamic contact pressure distribution are analyzed for various driving conditions and pad shape. Based on those results, CAE model was updated and found to be better in detecting propensity of brake squeal.
2015-09-27
Journal Article
2015-01-2678
Diego Adolfo Santamaria Razo, Johan Decrock, Ann Opsommer, Maarten Fabré, Fernao Persoon
Abstract Friction performance is the result of the interaction between rotor and friction material surfaces. Kinetic energy has to be transformed into heat, plastic deformations, chemical reactions and wear debris. The later generates the formation of the so-called third body layer and its initiation, growth and degradation will generate the actual friction coefficient and vibrations behavior. Some raw materials seem to promote third body layer formation more than others. The composition of plateaus usually contains iron oxide, copper, carbon, silicon and calcium. Since copper free materials are under development, the importance of understanding the third body layer formation has become bigger. Promaxon® D is widely used in NAO non steel formulations. It is a calcium silicate with a special morphology that influences friction material at two levels: the macro -bulk- scale and the micro -surface- scale. Bulk effect is related to the volume and porosity degree of the friction material.
2015-09-27
Technical Paper
2015-01-2683
Sarah Chen, Steve Hoxie
Abstract Developing a quiet brake system has been a constant task for OEMs as well as their brake suppliers. As a major component in the brake system, the rotor plays a significant role in brake noise performance. Owning to the cost and damping property advantages, gray iron is still the most widely used material for brake rotor application. When pads/rotor coupling is examined to address noise issues, however, most efforts have been on pads and insulators. Rotor specifications are rather general and the component is typically accepted based on grades defined by mechanical property minimum (mostly in G3000 SAE J431). Nevertheless, we have found that gray iron within a grade can have wide microstructure variations, and the deviation (especially on the rotor friction surface) can critically affect the noise propensity in addition to friction output performance and wear characteristics. In this work, the impact of brake disc material on brake noise and output performance is investigated.
2015-09-27
Journal Article
2015-01-2673
Toshikazu Okamura
Abstract Brake judder is one of the most serious problems in automotive-brake systems, and brake discs play a significant role in judder. There are two types of brake judder: cold and hot. Hot judder is caused by the thermo-mechanical deformation of a disc rotor due to high-speed braking. There are several causes and shapes of the deformation, e.g., coning and circumferential waviness. Circumferential waviness of brake discs is typically found as a butterfly shape in a 2nd rotational-order and corrugation (or hot-spotting) around a 10th order, which are caused by thermo-mechanical buckling. The author focused on the effects of material and dimensional homogeneity on the transient and permanent wave-like deformation of ventilated discs in low rotational-orders during repetitive high-speed braking. The tested discs were in two groups that had the same design and gray-cast-iron class but were cast in two foundries by using horizontal- and vertical-molding machines, respectively.
2015-09-22
Technical Paper
2015-36-0106
L. F. Cóser, A. Oliveira, B. N. Hualpa, J. R. F. Arruda, D. A. Siviero
Abstract Poroelastic materials are commonly used in passive noise control due to their low cost and relative efficient acoustic absorption characteristics in the middle to high frequency range. They are constituted by a rigid and a fluid phase responsible for the dissipation mechanisms attenuating the propagation of acoustic waves inside the material. The understanding of these phenomena and their translation into parameters existing in the mathematical formulations for poroelastic materials are of paramount importance in the design of optimized structures for choosing the proper materials for each application. This work presents studies on the validation of a melamine foam characteristics using the equivalent fluid model from Johnson-Champoux-Allard (JCA) and a rigid structure.
2015-09-22
Technical Paper
2015-36-0107
L. F. Cóser, A. Oliveira, J. R. F.Arruda
Abstract Simple and complex sound sources can be constructed using loudspeakers assembled on the surfaces of platonic solids such as the cube and the dodecahedron, whose implicit mathematical properties enable their application in acoustic radiation studies. By using special phase combinations of the electric signals applied to each loudspeaker, complex sound fields can be produced with their distinct spatial patterns. In many applications (such as aeroacoustics of cars and airplanes) monopoles, dipoles and quadrupoles are sufficient in the investigation of acoustic phenomena. Their experimental validation is usually performed using a circular microphone array to measure the sound pressure field around the test object. This approach can be very complicated and poses many challenges in terms of test setup, execution and post-processing. Therefore, there is a need for new experimental methods to characterize acoustic sources.
2015-09-22
Technical Paper
2015-36-0245
Guilherme Silva, Reinaldo Santos
Abstract Modern customer and legislation requirements have led to a high demand for energy efficient low pollutant engines. Such efficiency is commonly achieved through the deployment of turbochargers, in both Diesel and Otto engines. This strategy, replacing high displacement engines, is a tendency commonly designated as downsizing. This allows higher power outputs, increased energy efficiency and lower emissions allied with lower weight on the vehicle’s power pack. Those turbocharger units consists basically of a compressor connected by a solid shaft to a turbine, which is propelled by the exhaust gases in order to compress (boost) the intake charge air to the engine, increasing pressure in the system. The turbocharger system is commonly a source for synchronous/sub-synchronous noises, as well as compressor or turbine related NVH issues, which must be mitigated in order to fulfill customers’ expectations.
2015-09-22
Technical Paper
2015-36-0284
Eduardo Hiroaki Nishi, Marlon Casagrande Rodrigues, Antonio Humberto Dutra Cardoso
Abstract Since January 2015, Brazil put into effect the PROCONVE/MAR-I (Programa de Controle da Poluição do Ar por Veículos Automotores para Máquinas Agrícolas e Rodoviárias), which drives the country to the same stringent emissions standards used by the American (EPA Tier III) and European (Euro Stage IIIA) markets. As a result, new pollutants and noise emissions levels were established and although very important for the society health, this issue (noise) has been left behind in this kind of vehicle. Therefore, an extremely challenging target has to be pursued, regarding the current political and economical situation and also the resources availability to achieve those targets. The present work investigates the influence of the noise generated during the combustion process in MAR-I engines by modeling the calibration parameters, which allows to identify the contribution of the combustion in the global engine noise and possibly reducing it and hence the product reckoned costs.
2015-09-22
Technical Paper
2015-36-0325
Wagner Rossi de Sá, Henrique Leandro Silveira, Robson Pederiva
Abstract This work develops the kinematic and dynamic analysis of a diesel engine mounted on cushions, obtaining the nonlinear equations of motion and its integration has the vibration responses of the engine. With the system response values, are simulated different position settings and characteristics of the cushions for the qualitative and quantitative evaluation of the dynamic changes occurring in the system.
2015-09-22
Technical Paper
2015-36-0336
Fabio G. Ferraz, Roberto K. Morinaga, José T. Tardeli
Abstract Exhaust system noise has significant impact on vehicle exterior and interior noise. In a vehicle development, during early design verification phase, the exhaust tailpipe orifice noise performance is measured and validated at the proving ground tracks using design intent prototype parts developed and delivered by supplier, following previously technical specifications agreements and specific package constrains and targets. At late design verification phase, new measurements are performed in production intent prototype parts, and the results achieved are compared with initial measurements made for design intent prototype parts - with conflicting results in some situations.
2015-09-22
Technical Paper
2015-36-0448
Patrícia Helena de Oliveira Teixeira, Ronnie Rodrigo Rego, Anderson Vicente Borille, Jonny Salzgeber
Abstract This work is developed under the context of determining a suitable power-recirculation gear test design. Its operation parameters are determined by the usual speed values to what the Brazilian automotive transmission systems are submitted. The operating parameters generate forces that act as a frequency source, inducing mechanical vibrations to the structure. The level of the vibrations must be supervised so it does not reach values which correspond to the structure natural frequency. In such cases, resonance zones and noise at the measurement devices occur, causing wrong measurement data and, even further, structural failures. This paper analyzes the application of a method to investigate operational conditions and, eventually, redesign the rig’s main elements, to escape from resonance and noise zones. The modal analysis appears as a suitable tool for this purpose, giving as an output the description of structure natural vibration response.
2015-09-22
Technical Paper
2015-36-0532
Pedro Grego, Robson Pederiva
Abstract This work studies the dynamical behavior of a belt-tensioner pulley, constructed with a nonlinear spring and submitted to dry-friction on the contact of the pin with an articulated arm. Friction models are addressed, and the Duffing's equation is used to model the spring's nonlinear behavior. A mathematical model of the belt-tensioner is presented, and the influences of friction and pre-load moment are numerically investigated. The Stick-Slip behavior of the system is also studied. It is seem that the varying normal load, the friction asymmetry and the pre-load moment can change the Stick-Slip behavior. Finally, a method is presented to map the dynamical behavior of the belt-tensioner
2015-09-22
Technical Paper
2015-36-0560
Juan J. García, Alexandre Català, Xavier Montané
Abstract The rapid growth of Electric Vehicles (EV’s) and Hybrid Electric Vehicles (HEV’s) has increased the concern that the relative silence of these type of vehicles will result in an increased risk to pedestrian safety. A practical solution to this problem is to add artificial sounds to EV's to aid their detection by pedestrians and other vulnerable road users. Acoustic warning systems for EV’s should increase pedestrian safety and simultaneously produce a small impact on environmental noise levels. This paper shows the main advantage of using a directive acoustic source implemented as a beamforming loudspeaker array in an EV to increase pedestrian safety and control the effect on noise pollution. An example of such a system has been implemented in a Nissan Leaf vehicle and its performance in realistic situations has been assessed.
2015-09-22
Technical Paper
2015-36-0277
Yuri Fernandes dos Santos, Márcio da Silva Moura, André Luiz Martelli, Osmar Franco, Enrico Zucchi, Renata Gonçalves, Edgar Rabi
Abstract Acoustics, in a broad sense, is an essential product attribute in the automotive industry, therefore, it is relevant to study and compare theoretical and numerical predictions to experimental acoustic measurements, key elements of many acoustic development processes. The numerical methods used in the industry for acoustic predictions are widely used for exhaust system optimization. However, the numerical and theoretical predictions very often differ from experimental results, due to modeling simplifications, temperature variations (which have high influence on speed of sound), manufacturing variations in prototype parts among others. This article aims to demonstrate the relevant steps for acoustics development applied in automotive exhaust systems and present a comparative study between experimental tests and computer simulations results for each process. The exhaust system chosen for this development was intended for a popular car 4-cylinder 1.0-liter engine.
2015-09-22
Technical Paper
2015-36-0333
Carlo Vezzá, Eider Moraes, Fernando Ooki
Abstract The acoustic comfort inside the vehicle justifies important attention during its development phase, because customers desire a quiet interior to have a more relaxing environment, easier to have conversations and to listen to the radio. Generally, acoustic insulators are distributed on vehicle body to minimize the portion of noise that enters the vehicle and, in the interior, absorber components are used to reduce the cabin noise reverberation. Internal noise absorption is mainly performed by headliners, carpets and seats. In order to contribute to the sound absorption inside the vehicle made through the seats and to propose a foam and fabric configuration that demonstrates the best acoustic performance, this work aims to compare combinations of three different foam densities with eight different fabrics using the Kundt´s tube.
2015-09-21
Article
Principal Engineer considers acoustic holography as the next step in the further development of its new noise measurement system.
2015-09-15
Technical Paper
2015-01-2477
Alessandro Gardi, Roberto Sabatini
Abstract This paper presents the conceptual design of a new low-cost measurement system for the determination of pollutant concentrations associated with aircraft operations. The proposed system employs Light Detection and Ranging (LIDAR) and passive electro-optics equipment installed in two non-collocated components. The source component consists of a tuneable small-size and low-cost/weight LIDAR emitter, which can be installed either on airborne or ground-based autonomous vehicles, or in fixed surface installations. The sensor component includes a target surface calibrated for reflectance and passive electro-optics equipment calibrated for radiance, both installed on an adjustable support. The proposed bistatic system determines the column-averaged molecular and aerosol pollutant concentrations along the LIDAR beam by measuring the cumulative absorption and scattering phenomena along the optical slant range.
2015-09-15
Technical Paper
2015-01-2605
Jamnie Yazmín Achem Calahorra, Hilda E. Esparza Ponce, Patricia Zambrano Robledo, Facundo Almeraya Calderón, Citlalli Gaona Tiburcio
Abstract Thin films deposited by magnetron sputtering are review in terms of their potential and present uses in the aircraft industry. The aircraft alloys substrates were Ti-6Al-4V and Incoloy 800HT, using a target of yttrium stabilized zirconia (YSZ) with nominal composition of 8% Y2O3 (wt%) and the remainder of ZrO2. The chemical composition of the films was determined by X-ray energy dispersion (EDS). The electrochemical noise behavior show that the coatings decreased propagation of pitting, leading to a state of passivation or uniform corrosion, and also possess superior corrosion resistance over the individually substrates.
2015-09-15
Technical Paper
2015-01-2620
Philip Van Baren
Abstract Random vibration control systems produce a PSD plot by averaging FFTs. Modern controllers can set the degrees of freedom (DOF), which is a measure of the amount of averaging to use to estimate the PSD. The PSD is a way to present a random signal-which by nature “bounces” about the mean, at times making high excursions from the mean-in a format that makes it easy to determine the validity of a test. This process takes time as many frames of data are collected in order to generate the PSD estimate and a test can appear to be out of tolerance until the controller has enough data to estimate the PSD with a sufficient level of confidence. Something is awry with a PSD estimate that achieves total in-tolerance immediately after the test begins or immediately after a change in level, and this can hide dangerous over or under test conditions within specific frequency bands, and should be avoided.
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