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2017-09-17
Technical Paper
2017-01-2486
Kyung Jae Lee, Dong Won Kim, Daekyung Ko
Brake grinding noise is caused by the friction of the disc and pads. The friction generates vibration and it transmits to the body via the chassis system. We calle it structure-borne noise. To improve the noise in the vehicle development, the aspects of chassis or body's countermeasure occurs many problems, cost and time. In this reason many brake company try to make solution with brake system, like brake friction materials or disc surface. However the countermeasure of excitation system also have a lot of risk. It could occur side-effects of braking performance, and need to reverify brake noise like Creep-groan, Groan, Squeal, Judder and so on. In conclusion, It is very important making robust chassis system in initial vehicle development stage. This paper is about rear brake grind noise path analysis and countermeasure of chassis system. There are two steps to analysis. First step is impact hammer test like FRF, MODAL test.
2017-09-17
Technical Paper
2017-01-2488
Manuel Pürscher, Peter Fischer
Vehicle road tests are meaningful for investigations of creep groan noise. However, problems in reproducing experiments and partly subjective evaluations may lead to imprecise conclusions. This work proposes an experimental test and evaluation procedure which provides a precise and objective assessment of creep groan. It is based on systematic corner test rig experiments and an innovative characterization method. The exemplary setup under investigation consisted of a complete front wheel suspension and brake system including all relevant components. The wheel has been driven by the test rig’s drum against a brake torque. The main parameters within a test matrix were brake pressure and drum velocity. Both have been varied stepwise to scan the relevant operating range of the automobile corner system for potential creep groan noise. Additionally, the experiments were extended to high brake pressures, where creep groan cannot be observed under road test conditions.
2017-09-17
Technical Paper
2017-01-2487
Yasuyuki Kanehira, Yusuke Aoki, Yukio Nishizawa
Brake squeal is uncomfortable noise that occurs while braking. It is an important issue for automobile quality to prevent brake products from squealing. Brake shims are widely used to reduce squeal occurrence rate. In particular, laminated shims can effectively suppress squeal via the viscoelastic damping of an adhesive layer. However, there are cases where the damping performance at low temperature and the durability performance at high temperature deteriorate. In that regard, we thought of applying frictional damping to shims instead of relying on a temperature-sensitive adhesive layer. To study the application of frictional damping as a new damping mechanism for shims, it is necessary to clarify the characteristics thereof. In order to quantify the damping performance of shims, loss factor has been generally measured with a bending mode tester. However, the influence of friction cannot be evaluated because it is measured under pressure-free condition.
2017-09-17
Technical Paper
2017-01-2489
Christian Ball, Li Lee, Weicherng Wang
The standard method for using FEA to predict and eliminate brake squeal has been to use complex eigenvalue analysis (CEA). Energy flow analysis has been adapted for use with FEA for brake squeal as an alternate mechanism for squeal prediction. This paper demonstrates an implementation of energy flow analysis with commercially available FEA software. The approach leverages the ability of the Abaqus FEA solver to obtain a quasi-static, pre-loaded brake model, as well as Abaqus’ eigenvalue extraction algorithms to create a modal space for energy flow calculations. This modal space, as well as the pre-loaded stiffness matrix, is then utilized to calculate energy flow values between nearby system modes. Three case studies are presented that compare the results of CEA and energy flow to different systems and countermeasures adopted to reduce noise occurrence in physical testing.
2017-09-17
Technical Paper
2017-01-2484
Yoshiyuki Yamaguchi, Tsuyoshi Kondo
We considered the relation between disc brake’s in-plane mode noise and exciting energy which flows into pad surface for improving brake noise performance. The exciting energy is calculated by the pad’s displacement of disc rotating direction and pad thickness direction which is acquired by 3D scanning laser Doppler measurement system.
2017-09-17
Journal Article
2017-01-2482
Meechai Sriwiboon, Nipon Tiempan, Kritsana Kaewlob, Seong K Rhee, Donald Yuhas
Disc pad physical properties are believed to be important in controlling brake friction, wear and squeal. Thus these properties are carefully measured during and after manufacturing for quality assurance. For a given formulation, disc pad porosity is reported to affect friction, wear and squeal. This investigation was undertaken to find out how porosity changes affect pad natural frequency, dynamic modulus, hardness and compressibility for a low-copper formulation and a copper-free formulation, both without underlayer. Pad natural frequency, modulus and hardness all decrease with increasing porosity. When pad compressibility is measured by compressing several times as recommended and practiced, the pad surface hardness is found to increase while pad natural frequency and modulus remain essentially unchanged. However, there is no consistent pattern in compressibility change with increasing porosity, and thus a question arises on the validity of compressibility measurement.
2017-09-17
Technical Paper
2017-01-2485
Tarun Teja Mallareddy, Peter Blaschke, Sarah Schneider, Daniel J. Alarcón
Brake squeal is an NVH issue experienced by brake systems and vehicle manufacturers for decades. This leads to customer dissatisfaction and the questioning of quality of the brake system. Advanced testing tools, design modification, dynamometer testing, vehicle validation etc., are performed to study, analyze and eliminate this problem. But, still it continues to exist. One of the most important reasons is the complexity of the brake pad which leads to its non-linear properties. Therefore, it is imperative to understand the behavior of the brake pad, in terms of its dynamic properties (eigenfrequencies, damping and mode shapes), under varying boundary conditions. Experimental Modal Analysis (EMA) is used to study the dynamic properties of any structure and is generally performed under free-free boundary conditions. An approach to study brake pads under pressure condition is a step towards reality, as brake pads squeal only during braking events.
2017-09-17
Technical Paper
2017-01-2529
Jae Seol Cho, JongYun Jeong, Hyoung Woo Kim, Hwa Sun Lee, Yang Woo Park, Junghwan Lim, Yoonjae Kim, Jinwoo Kim, Byung Soo Joo, Ho Jang
An index to evaluate noise propensity of the brake friction material is introduced. The noise propensity index (NPI) is composed of the mechanical properties and surface topography of the friction material after burnish, which was closely related to the stick-slip profile found at relatively low velocity. The correlation between the noise occurrence and NPI was evaluated using commercial brake linings. Test results showed that the mechanical properties such as the ratio between surface stiffness and matrix stiffness and the surface properties such as the fraction and distribution of contact plateaus determined the noise propensity of brake friction materials with a good correlation of the noise occurrence and NPI.
2017-09-17
Journal Article
2017-01-2523
Seonho Lee, Yoongil Choi, Kyuntaek Cho, Hyounsoo Park
Abstract Raceway Brinell damage is one major cause of wheel bearing (hub unit) noise during driving. Original Equipment Manufacturer (OEM) customers have asked continuously for its improvement to the wheel bearing supply base. Generally, raceway Brinelling in a wheel hub unit is a consequence of metallic yielding from high external loading in a severe environment usually involving a side impact to the wheel and tire. Thus, increasing the yielding strength of steel can lead to higher resistance to Brinell damage. Both the outer ring and hub based on Generation 3 (Gen. 3) wheel unit are typically manufactured using by AISI 1055 bearing quality steel (BQS); these components undergo controlled cooling to establish the core properties then case hardening via induction hardening (IH). This paper presents a modified grade of steel and its IH design that targets longer life and improves Brinell resistance developed by ILJIN AMRC (Advanced Materials Research Center).
2017-09-17
Technical Paper
2017-01-2528
Seongjoo Lee, JeSung Jeon, JooSeong Jeong, Byeongkyu Park, ShinWook Kim, ShinWan Kim, Seong Kwan Rhee, Wan Gyu Lee, Young sun Cho
It is widely believed or speculated that higher pad compressibility leads to reduced brake squeal and that caliper design can affect brake squeal. After encountering anecdotalcontradictory cases, this investigation was undertaken to systematically generate basic data and clarify the beliefs or speculations. In order to adjust pad compressibility, it is common to modify molding temperatures, pressures and times, which in addition to changing the compressibility, changes the coefficient of friction at the same time. In order to separate these two effects, NAO disc pads were prepared under the same molding conditions while using different thicknesses for the underlayer to achieve different compressibilities, thus changing compressibility without changing thecoefficient of friction. Test results show brake squeal increasing with increasing compressibility, contrary to the common belief.
2017-08-15
WIP Standard
J1454
This SAE Standard describes a laboratory test procedure for comparatively evaluating the durability and fatigue life qualities of a complete seat cushion by submitting the seating surface of the cushion to repetitive compressive and rotational loading with a simulated human buttocks. This document provides a uniform method of dynamically testing the durability of seat cushions on a comparative basis.
2017-07-27
Magazine
The Rapid Rise of Beryllium-Aluminum Alloys in Aerospace Aeroacoustic Simulation Delivers Breakthroughs in Aircraft Noise Reduction Using System Simulation to Manage Increasing Thermal Loads on Aircraft Fuel Systems Ensuring the Compliance of Avionics Software with DO-178C Microwave Photonic Notch Filter Helps Ensure Critical Mission Success Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer New testing technique requires less material, gives more accurate results. Combustion Characteristics of Hydrocarbon Droplets Induced by Photoignition of Aluminum Nanoparticles Test methodology allows analysis of combustion dynamics for subscale rocket injectors under super critical conditions. Vapor Pressure Data and Analysis for Selected Organophosphorous Compounds: DIBMP, DCMP, IMMP, IMPA, EMPA, and MPFA Determining the thermophysical properties of chemical warfare agent simulants can help evaluate the performance of defensive equipment.
CURRENT
2017-07-24
Standard
J2625_201707
This procedure is applicable to squeal type noise occurrences for passenger car and light truck type vehicles that are used under conventional operating conditions. For the purposes of this test procedure, squeal is defined as occurring between 900 and 18 000 Hz.
2017-07-10
Technical Paper
2017-28-1922
S Nataraja Moorthy, Manchi Rao, Prasath Raghavendran, Sakthi Babu
Abstract NVH is becoming one of the major factor for customer selection of vehicle along with parameters like fuel economy and drivability. One of the major NVH challenges is to have a vehicle with aggressive drivability and at the same time with acceptable noise and vibration levels. This paper focuses on the compact utility vehicle where the howling noise is occurring at higher rpm of the engine. The vehicle is powered by three cylinder turbocharged diesel engine. The noise levels were higher above 2500 rpm due to the presence of structural resonance. Operational deflection shapes (ODS) and Transfer path analysis (TPA) analysis was done on entire vehicle and powertrain to find out the major reason for howling noise at higher engine rpm. It is observed that the major contribution for noise at higher rpm is due to modal coupling between powertrain, half shaft and vehicle sub frame.
2017-07-10
Technical Paper
2017-28-1926
Jos Frank, Sohin Doshi, Manchi Rao, Prasath Raghavendran
Abstract In today’s automotive scenario, noise vibration and harshness (NVH) has become a synonym for quality perception. This paper evaluates the problem of vibration and noise experienced in M2 category 40 seat bus and suggests the counter measures. Severe vibration is experienced on the bus floor, predominantly towards rear part of the bus. Vibration along with acoustic boom occurs prominently in 4th gear wide open throttle operating condition between 1300-1600 rpm of the engine. This paper focuses on reducing NVH levels by working on the transfer path with little modifications on power-train. Preliminary torsional measurements conducted on powertrain indicated high torsional excitation in the driveline during the problematic rpm zone. Further, Operational Deflection Shape (ODS) analysis revealed that the transfer path to the cabin is rear differential unit and suspension links. The dominant frequencies were identified along the transfer path and suitable modifications were done.
2017-07-10
Technical Paper
2017-28-1925
Asif Basha Shaik Mohammad, Ravindran Vijayakumar, Nageshwar Rao Panduranga
Abstract The automotive market has seen a steady increase in customer demands for quiet and more comfortable tractors. High noise at Operator Ear Level (OEL) of tractor is the major cause of fatigue to the operator. With growing competition, and upcoming legislative requirement there is ominous need for the agricultural tractor manufacturers to control noise levels. The objective of this study is noise reduction on agricultural tractor by stiffening sheet metal components. The design and analysis plays a major role for determining the root cause for the problem. Once the problem and its root cause were well defined, the solution for addressing the problem would be made clear. The engine excitation frequency and Sheet metal Components such as fender and platform natural frequency were coming closer and are leading to resonance.
2017-07-10
Technical Paper
2017-28-1936
Prasad Padavala, Judsonrajkumar Thaveedu, G Senthilkumar, Jaganmohan Rao Medisetti
Abstract Exterior noise reduction of a vehicle has become important nowadays in order to meet the stringent pass by noise regulations. First step in this process is the identification of dominant noise sources. There are several noise sources which can contribute to the pass by noise like gearbox, turbocharger, oil sump, exhaust muffler, air intake etc. The dominant noise sources can be identified with the near field noise, component vibration measurements combined with experimental modal analysis. This paper discusses about the noise source identification and exterior noise reduction of a shortest wheel base intermediate commercial vehicle, which is having a 4-cylinder inline diesel engine.
2017-07-10
Technical Paper
2017-28-1944
Asif Basha Shaik Mohammad, Ravindran Vijayakumar, Nageshwara Rao Panduranga
Abstract The vibration and acoustic behaviour of the internal combustion engine is a highly complex one, consisting of many components that are subject to loads that vary greatly in magnitude and which operate at a wide range of speeds. The interaction of these components and the excitation of resonant modes of vibration is a major problem for the powertrain engineer when optimising the noise and vibration characteristics of the engine. This paper summarises a study that has been undertaken to assess and optimise the dynamic behaviour of a current production diesel engine with the objective of reducing radiated noise from the engine. The dynamic behaviour of the diesel engine has been assessed using simulation tools. The dynamic analysis will predict the forces and displacements at each of the nodes of the model by forced response analysis. Predicted results and experimentally measured values were found to be in close agreement.
2017-07-10
Technical Paper
2017-28-1952
Utkarsh Sharma, Simson T. Wilson, Santosh Lalasure, K. Rajakumar
Abstract Today’s automotive industry in the process of better fuel efficiency and aiming less carbon foot print is trying to incorporate energy saving and hybrid technologies in their products. One of the trends which has been followed by Original Equipment Manufacturers (OEMs) is the usage of Electric Power Steering (EPS) system. This has been an effective option to target fuel saving as compared to hydraulically assisted power steering system. EPS has been already tested successfully, not only on system level but also on vehicle level for endurance and performance by OEMs as per their norms and standards. Over the decade, NVH (noise, vibration & harshness) have become one of the touch points for customer perception about vehicle quality. This leads us to a commonly perceived problem in EPS or manual type steering system i.e. rattle noise.
CURRENT
2017-07-06
Standard
AIR6297
This document describes a method to calculate noise level adjustments at locations behind an airplane (described by an angular offset or directivity) at the start of takeoff roll (SOTR). This method is derived from empirical data from jet aircraft (circa 2004), most of which are configured with wing-mounted engines with high by-pass ratios (Lau, et al., 2012). Methods are also described which apply to modern turboprop aricraft.
2017-06-17
Journal Article
2017-01-9550
David Neihguk, M. L. Munjal, Arvind Ram, Abhinav Prasad
Abstract A production muffler of a 2.2 liter compression ignition engine is analyzed using plane wave (Transfer Matrix) method. The objective is to show the usefulness of plane wave models to analyze the acoustic performance (Transmission Loss, TL) of a compact hybrid muffler (made up of reactive and dissipative elements). The muffler consists of three chambers, two of which are acoustically short in the axial direction. The chambers are separated by an impervious baffle on the upstream side and a perforated plate on the downstream side. The first chamber is a Concentric Tube Resonator (CTR). The second chamber consists of an extended inlet and a flow reversal 180-degree curved outlet duct. The acoustic cavity in the third chamber is coupled with the second chamber through the acoustic impedances of the end plate and the perforated plate.
2017-06-05
Technical Paper
2017-01-1787
Jan Biermann, Adrien Mann, Barbara Neuhierl, Min-Suk Kim
Abstract Over the past decades, interior noise from wind noise or engine noise have been significantly reduced by leveraging improvements of both the overall vehicle design and of sound package. Consequently, noise sources originating from HVAC systems (Heat Ventilation and Air Conditioning), fans or exhaust systems are becoming more relevant for perceived quality and passenger comfort. This study focuses on HVAC systems and discusses a Flow-Induced Noise Detection Contributions (FIND Contributions) numerical method enabling the identification of the flow-induced noise sources inside and around HVAC systems. This methodology is based on the post-processing of unsteady flow results obtained using Lattice Boltzmann based Method (LBM) Computational Fluid Dynamics (CFD) simulations combined with LBM-simulated Acoustic Transfer Functions (ATF) between the position of the sources inside the system and the passenger’s ears.
2017-06-05
Technical Paper
2017-01-1785
Paul Bremner, Scott Clifton, Chris Todter
Abstract Measurements of interior wind noise sound pressure level have shown that dBA and Loudness are not adequate metrics of wind noise sound quality due to non-stationary characteristics such as temporal modulation and impulse. A surface microphone array with high spatio-temporal resolution has been used to measure and analyze the corresponding non-stationary characteristics of the exterior aero-acoustic loading. Wavenumber filtering is used to observe the unsteady character of the low wavenumber aero-acoustic loading components most likely to be exciting glass vibration and transmitting sound.
2017-06-05
Technical Paper
2017-01-1784
Guillaume Baudet
Abstract Wind noise in automobile is becoming more and more important as customer requirements increase. On the other hand great progress has been made on engine and road noises. Thus, for many vehicles, wind noise is the major acoustic source during road and motorway driving. As for other noises, automobile manufacturers must be able for a new car project to specify, calculate and measure each step of the acoustic cascading: Source Transfers, both solid and air borne In the case of automotive wind noise, the excitation source is the dynamic pressure on the vehicle’s panels. This part of the cascading is the one influenced by the exterior design. Even if many others components (panels, seals, cabin trims) have a big influence, the exterior design is a major issue for the wind noise. The wind noise level in the cabin can sometimes change significantly with only a small modification of the exterior design.
2017-06-05
Technical Paper
2017-01-1790
Vinayak H. Patil, Ravi Kumar Sara, T. R. Milind, Rodney C. Glover
Abstract Vehicle noise emission requirements are becoming more stringent each passing year. Pass-by noise requirement for passenger vehicles is now 74 dB (A) in some parts of the world. The common focus areas for noise treatment in the vehicle are primarily on three sub-systems i.e., engine compartment, exhaust systems and power train systems. Down- sizing and down- speeding of engines, without compromising on power output, has meant use of boosting technologies that have produced challenges in order to design low-noise intake systems which minimize losses and also meet today’s vehicle emission regulations. In a boosted system, there are a variety of potential noise sources in the intake system. Thus an understanding of the noise source strength in each component of the intake system is needed. One such boosting system consists of Turbo-Super configuration with various components, including an air box, supercharger, an outlet manifold, and an intercooler.
2017-06-05
Technical Paper
2017-01-1795
Ahmad Abosrea, Tamer Elnady
Abstract Flow-generated noise has recently received a lot of attention within the process of designing exhaust and intake systems. Flow-generated noise can limit the amount of sound reduction a muffler can introduce inside ducts. This is more important in the modern system design where mufflers are compact and the flow speeds become higher in different sections inside the muffler. In this paper, three measurement techniques are used to measure the flow-generated noise from a duct element. The first is based on calculating the sound power levels inside a reverberation room according to ISO 3741. The radiated noise is measured from the muffler body as a source of noise, then from the tail pipe as an active one-port source. The second is based on sound power measurements inside the ducts using the active two-port theory. The third is measuring the sound pressure radiation inside an anechoic room.
2017-06-05
Technical Paper
2017-01-1799
Nagasuresh Inavolu, Jaganmohan Rao Medisetti, S. Nanda Kumar, J Lingeshkumar, Akshay Loya, Mvgprasad MV
Abstract Engine noise reduction is one of the highest priorities in vehicle development from the viewpoint of meeting stringent noise regulations. Engine noise reduction involves identification of noise sources and suppression of noise by changing the response of sources to input excitations. Noise can originate from several mechanical sources in engine. The present work focuses on systematic study of the behavior or response of engine structure and its ancillaries to engine excitation and thereby assess their contribution to overall engine noise. The approach includes engine noise and vibration measurement and component ranking using engine noise and vibration measurement in a non-anechoic environment, structural analysis of engine including experimental modal testing of engine and its components, etc. Correlation of the above obtained results is performed to identify the noise sources. Later, ranking of critical components was performed based on results of cladding exercise.
2017-06-05
Technical Paper
2017-01-1792
Magnus Knutsson, Erik Kjellson, Rodney Glover, Hans Boden
Abstract Increased demands for reduction of fuel consumption and CO2 emissions are driven by the global warming. To meet these challenges with respect to the passenger car segment the strategy of utilizing IC-engine downsizing has shown to be effective. In order to additionally meet requirements for high power and torque output supercharging is required. This can be realized using e.g. turbo-chargers, roots blowers or a combination of several such devices for the highest specific power segment. Both turbo-chargers and roots blowers can be strong sources of sound depending on the operating conditions and extensive NVH abatements such as resonators and encapsulation might be required to achieve superior vehicle NVH. For an efficient resonator tuning process in-duct acoustic source data is required. No published studies exists that describe how the gas exchange process for roots blowers can be described by acoustic sources in the frequency domain.
2017-06-05
Technical Paper
2017-01-1802
Dong chul Lee, Insoo Jung, Jaemin Jin, Stephan Brandl, Mehdi Mehrgou
Abstract In the automotive industry, various simulation-based analysis methods have been suggested and applied to reduce the time and cost required to develop the engine structure to improve the NVH performance of powertrain. This simulation is helpful to set the engine design concept in the initial phase of the powertrain development schedules. However, when using the conventional simulation method with a uniformed force, the simulation results sometimes show different results than the test results. Therefore, in this paper, we propose a method for predicting the radiated noise level of a diesel engine using actual combustion excitation force. Based on the analytical radiated noise development target, we identify the major components of the engine that are beyond this development target by in the frequency range. The components of the problem found in this way are reflected in the engine design of the early development stage to shorten the development time.
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