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Viewing 1 to 30 of 2337
2017-06-05
Technical Paper
2017-01-1883
Arnaud Duval, Guillaume Crignon, Mickael Goret, Maxime Roux
The lightweighting research on noise treatments since years tends to prove the efficiency of the combination of good insulation with steep insulation slopes with broadband absorption, even in the context of bad passthroughs management implying strong leakages. The real issue lies more in the industrial capacity to adapt the barrier mass per unit area to the acoustic target from low to high segment or from low petrol to high diesel sources, while remaining manipulable. The hybrid stiff insulator family can realize this easily with hard felts barriers backfoamed weighting from 800 g/m² to 2000 g/m² typically with compressions below 10 mm. Above these equivalent barrier weights and traditional compressions of 7 mm for example, the high density of the felts begins to destroy the porosity and thus the absorption properties (insulation works anyway here, whenever vibration modes do not appear due to too high stiffness…).
2017-06-05
Technical Paper
2017-01-1848
Richard DeJong
From 1983 to 1995, Richard H. Lyon published several papers on Statistical Phase Analysis, showing that the average phase of the transfer functions in complex systems grows with frequency in proportion to the modal density of the system. In one dimensional systems this phase growth is the same as that of freely propagating waves. However, in two and three dimensional systems this phase growth is much larger than the corresponding freely propagating wave. Recent work has shown that these phase growth functions can be used as mode shape functions in discrete system models to obtain results consistent with Statistical Energy Analysis. This paper reviews these results and proposes naming the statistical mode shape functions in honor of Lyon.
2017-06-05
Technical Paper
2017-01-1775
Mark A. Gehringer, Robert Considine, David Schankin
This paper describes recently developed test methods and instrumentation to address the specific noise and vibration measurement challenges posed by large diameter single-piece tubular aluminum propeller shafts with high modal density. The application described in this paper is a light duty truck, although the methods described are applicable to any rotating shaft with similar dynamic properties. To provide a practical example of the newly developed methods and instrumentation, rotating and non-rotating data were acquired in-situ for several propeller shafts of varying construction, including both lined and unlined shafts. Data were also acquired with and without a torsional tuned vibration absorber attached to the driveline. The example data exhibit features that are uniquely characteristic of large diameter single-piece tubular shafts with high modal density, including the particular effect of shaft rotation on the measurements.
2017-06-05
Technical Paper
2017-01-1773
Jing Yuan
The dual phase twin synchronous drive has been developed for belt noise reduction. Two identical synchronous belts are arranged parallel side by side with one tooth staggered against other by the half pitch. The noise cancellation effect is achieved as one belt tooth engagement coincides with the other belt tooth dis-engagement. A center flange is used as a divider to prevent the belts contacting each other along the axial direction during their entrance and exit of the sprocket. An overall 20 [dBA] noise reduction has been achieved with the dual phase twin belt system compared to an equal width single belt counterpart. The vibration amplitude of the hub load is also reduced which is directly correlated to the structural borne noise. Comparing to the related dual phase helical tooth belt, also known as the eagle belt trade marked by Goodyear, the dual phase twin belt is superior in torque carrying capability; and is on par with noise mitigation.
2017-06-05
Technical Paper
2017-01-1785
Paul Bremner, Scott Clifton, Chris Todter
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 observe 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 capable of exciting glass vibration and transmitting sound.
2017-06-05
Technical Paper
2017-01-1820
Martin Sopouch, Josip Hozmec, Alessandro Cadario
This paper presents a simulation environment and methodology for noise and vibration analyses of a driven rear axle in a bus application, with particular focus on medium to high frequency range (400 Hz to 3 kHz). The workflow demonstrates structure borne noise and sound radiation analyses. The fully flexible Multi–Body Dynamics (MBD) model - serving to cover the actual mechanical excitation mechanisms and the structural domain – includes geometrical contacts of hypoid gear in the central gear and planetary gear integrated at hubs, considering non-linear meshing stiffness. Contribution of aforementioned gear stages, as well as the propeller shaft universal joint at the pinion axle, on overall axle noise levels is investigated by means of sensitivity analysis. Based on the surface velocities computed at the vibrating axle-housing structure the Wave Based Technique (WBT) is employed to solve the airborne noise problem and predict the radiated sound.
2017-06-05
Technical Paper
2017-01-1808
Francis Nardella
In a previous report, it was shown that power transmission through the camshaft reduced the first mode natural frequency of the powertrain and translated its convergence with dominant engine excitatory harmonics to a lower engine speed resulting in a marked reduction in torsional vibration for geared 6 cylinder compression ignition engines for aviation. This report describes a sweep though 2 and 4 stroke engines with differing numbers of cylinders configured as standard gear reduction (SGRE) and with power transmission through the camshaft (CDSE). Four and 6 cylinder engines were modeled as opposed boxer engines and 8, 10 and 12 cylinder engines were modeled as 180-degree V-engines. Mass-elastic models of the different engine power train configurations were modeled using the torsional vibration module in Shaft Designer obtained from SKF (Svenska Kullagerfabriken). Crankshaft, camshaft, gearing, pistons, piston pins and connecting rods with bolts were modeled in Solidworks.
2017-06-05
Technical Paper
2017-01-1856
Junji Yoshida, Koki Tanaka, Rie Nakamoto, Ken Fukasawa
Operational transfer path analysis (TPA) is one of TPA methods recently developed. This method calculates contributions of reference points (e.g., engine mount) to the response point (e.g., vehicle interior noise/vibration) using only the operational data. Through this operational TPA (OTPA), effective noise/vibration reduction can be achieved. On the other hand, many accurate vibraton modes can be obtained recently by the progress of CAE technique. However, it is not eacy to find out which calculated vibration modes of the structure (e.g., vehicle flame) affect the response point (e.g., steering) largely. In this study, we then combined the OTPA technique with CAE to obtain high contributing mode. As the test structure, a rear flame of a small constraction machine model was employed. Firstly, the vibration modes were obtained by CAE (eigenmode analysis) and 25 modes were obtaiend under 250 Hz. Subsequently, operational vibration of the structure was measured.
2017-06-05
Technical Paper
2017-01-1804
Chulwoo Jung, Hyeon Seok Kim, Hyuckjin Oh, Kwang Hyeon Hwang, Hun Park
An efficient method to determine bush stiffness of passenger cars for satisfying requirement of noise and vibration is developed. In general, a passenger vehicle includes various types of bush to connect systems and control forces (loads) transferred between systems which affect characteristics of noise and vibration of the vehicle. Noise and vibration of a vehicle are mainly caused by forces from power train (engine and transmission) and road excitation. While a vehicle is in operation, road excitation is applied to the vehicle through bushes. If a bush transfers less force to the body structure, levels of noise and vibration will be decreased. In other words, it is necessary to well determine characteristics of bushes when developing passenger vehicles. Bush stiffness is one of key factors to affect the performance of noise and vibration of the vehicle.
2017-06-05
Technical Paper
2017-01-1859
Filip Franek, Jungu Kang, Jeon Uk, Sunguk Choi
Abstract: Structure-born vibrations are often required to be localized in a complex structure, but in such dispersive medium, the vibration wave propagates with speed dependent on frequency. This property of solid materials causes an adverse effect for localization of vibrational events. The cause behind such phenomena is the propagating wave envelope that changes its phase delay and amplitude in time and space as it travels in dispersive medium. This problem was previously approached by filtering a signal to focus on frequencies of the wave propagating with similar speed, what improved accuracy of cross-correlation results. However, application of this technique has not been researched for localization of vibrational sources by a localization technique. In this work we take advantage of filtering prior to cross-correlation calculation while using multiple sensors to indicate approximate location of vibration sources.
2017-06-05
Technical Paper
2017-01-1892
Yosuke Tanabe, Masanori Watanabe, Takafumi Hara, Katsuhiro Hoshino, Akira Inoue, Masaru Yamasaki
Predicting vibration of motor gearbox assembly driven by a PWM inverter in an early development stage is demanding, because the assembly is one of the dominant noise sources of electric vehicle (EV). In this paper, we propose a simulation model that can predict the transient vibration excited by gear meshing, reaction force from mount and electromagnetic forces including carrier frequency component of inverter up to 10 kHz. By employing the techniques of structural model reduction and state space modeling, the proposed model enables to predict the vibration of assembly in operating condition to simulate with a system level EV simulator. A verification test was conducted to compare the simulation result with running test result of EV. Although the absolute value of simulation is 10 dB different from test at most, we conclude that the model can well predict the trend of the dominant order vibration caused by the electromagnetic force of motor including the carrier frequency of inverter.
2017-06-05
Technical Paper
2017-01-1780
Yong Xu
Research Objective: For MT vehicles, gearbox rattle is a common NVH problem which influences the comfort level of vehicle. In order to prevent rattle in the design phase of vehicle, this work aimed to study the excitation mechanism and influence factors of gearbox rattle, and then to propose effective measures. Methodology: First, the root cause of gearbox rattle problem was studied with the aid of classical dynamical theories. And then the simulation model of vehicle powertrain system was built via Matlab-Simulink. Then some critical parameters of the model and some experiential optimum proposals were selected to perform a sensitivity analysis on the torsional vibration, which is the root cause of rattle. Referring the simulation results, the dual-mass flywheel was selected as the most effective solution to gearbox rattle. Results: The simulation results indicated the critical parameters for optimization to prevent gearbox rattle problem in the design phase of the vehicle.
2017-06-05
Technical Paper
2017-01-1768
Yong Xu
Purpose: For rear-wheel-drive (or all-wheel-drive) vehicles, the vibration and noise that caused by driveshaft often become the main factors that influence the comfort level of vehicle. In order to control and improve the NVH problems related to driveshaft, this work aimed to study the excitation mechanism and transfer path of driveshaft vibration, and then to propose effective measures. The purpose of this work was to propose an effective way to improve the NVH performance by controlling the additional excitation force of U-joints in the early phase of project. Methodology: First, the rotation order characteristics of driveshaft were studied with the aid of classical dynamics. Then a rigid-elastic coupling model of vehicle powertrain was modelled with the theory of multi-body dynamics. By inputting the actual vehicle parameters into the model, the acceleration operation of vehicle could be simulated.
2017-06-05
Technical Paper
2017-01-1803
John Van Baren
The accumulated damage that a product experiences in the field due to the variety of vibration stresses placed upon it will eventually cause failures in the product. The failure modes resulting from these dynamic stresses can be replicated in the laboratory and correlated to end use environment to validate target reliability requirements. This presentation addresses three fundamental questions about developing accelerated random vibration stress tests. Question#1: What random profile is needed (and for how much time) to accurately simulate the end use environment over the life-cycle of my product? Question #2: My product operates in many different vibration environments, how can I confidently combine them into one accelerated test?Question #3: How can I use the FDS to accelerate my test?
2017-06-05
Technical Paper
2017-01-1891
Todd Freeman, Kelby Weilnau
Similar to the automotive industry, the expectations from customers for the noise and vibration performance of personal vehicles such as golf carts, ATV’s, and side-by-side vehicles has continued to evolve. Not only do customers expect these types of vehicles to be more refined and to have acoustic signatures that match the overall performance capabilities of the vehicle, but marketing efforts continue to focus on product differentiators which can include the acoustic and vibration performance. Due to this increased demand for acoustic and vibration performance, additional NVH efforts are often required to meet these expectations. This paper provides a sample of some of the efforts that have occurred to further refine and develop the noise and vibration signature for golf carts.
2017-06-05
Technical Paper
2017-01-1870
Saeed Siavoshani, Prasad Balkrishna Vesikar, Daniel Pentis, Rajani Ippili
The objective of this paper is to develop a robust methodology to study the internal combustion (IC) engine block vibrations and to quantify the contribution of combustion pressure loads and inertial loads (mechanical loads) to the engine block vibrations. This study is not extended to the sound pressure generated by the engine and contribution analysis for that response. In an IC engine, the combustion and mechanical/inertial loads are the main sources of engine block vibrations. They both contain not only strong harmonic content due to their repetitive nature but also transient broadband impact loads. Therefore, it is difficult to identify/separate the contribution of combustion and inertial loads in the vibration response due to their correlated frequency excitations. One of the tools utilized in the industry to separate the combustion and mechanical noise is the Wiener filter.
2017-06-05
Technical Paper
2017-01-1766
Dirk von Werne, Stefano Orlando, Anneleen Van Gils, Thierry Olbrechts, Ivan Bosmans
Methodology to secure cabin noise and vibration targets is presented. Early in the design process, typically in the Joint Definition Phase, Targets are cascaded from system to component level to comply to the overall cabin noise target in various load cases. During the Detailed Design Phase, 3D simulation models are build up to further secure and refine the vibro-acoustic performance of the cabin noise related subsystems. Noise sources are estimated for the target setting based on analytical and empirical expressions from literature. This includes various types of engine noise – fan, jet, and propeller noise – as well as turbulent boundary layer noise. For other noise sources, ECS and various auxiliaries, targets are set such as to ensure the overall cabin noise level. To synthesize the cabin noise, these noise sources are combined with estimates of the noise transfer through panels and the cavity effect of the cabin. This part is again based on analytical and empirical formulations.
2017-06-05
Technical Paper
2017-01-1881
Charles Moritz, Satyajeet Deshpande
As part of the update process to SAE J1637, Laboratory Measurement of the Composite Vibration Damping Properties of Materials on a Supporting Steel Bar, the Acoustical Materials Committee commissioned a round robin study to determine the current lab to lab variation, and to better understand best practices for composite loss factor measurements. Guidance within the current standard from a previous round robin study indicates a coefficient of variation of 35% for laboratory to laboratory measurements. It was hoped that current instrumentation and test practices would yield lower variability. Over the course of 2 years, 10 laboratories tested 4 bars, three with damping materials and one bare bar. These bars were tested at 20°C, -5°C, 10°C, 25°C and 40°C and 55°C. The damping materials were intentionally selected to provide low damping, moderate, and high damping as difficulties in determining the composite loss increase with increasing damping.
2017-06-05
Technical Paper
2017-01-1879
Pranab Saha
Traditionally, the damping performance of a visco-elastic material is measured using Oberst bar damping test, where a steel bar is excited using a non-contacting transducer. However, in an effort to lightweight the vehicles, serious effort is put in to change the body panels from steel to aluminum and composite panels in many cases. These panels cannot be excited using a non contacting transducer, although in some cases a very thin steel panel (shim) is glued to the vibrating bar to introduce ferrous properties to the bar so it can be excited. In the off highway vehicles, although the panels are made of steel, they are very thick and are difficult to excite using the Oberst bar test method. This paper discusses a measurement methodology based on mechanical impedance measurements and has the potential to be a viable/alternate test method to the Oberst bar testing. In the impedance method, the test bar is mounted to a shaker at the center (Center Point method).
2017-06-05
Technical Paper
2017-01-1836
Fangfang Wang, Peter Johnson, Hugh Davies, Bronson Du
Introduction Whole-body vibration (WBV) is associated with several adverse health and safety outcomes including low-back pain and driver fatigue. Recently introduced active suspension truck seats have been shown to reduce WBV exposures up to 50% relative to industry standard air-suspension seats, but drivers do not universally prefer these active suspension seats and their higher costs concern some companies. The objective of this study was to evaluate the efficacy of three commercially-available air-suspension truck seats for reducing truck drivers’ exposures to WBV. Methods Seventeen truck drivers operating over a standardized route were recruited for this study and three commercially available air suspension seats were evaluated. The predominant, z-axis average weighted vibration (Aw) and Vibration Dose Values (VDV) were calculated and normalized to represent eight hours of truck operation.
2017-06-05
Technical Paper
2017-01-1805
Krzysztof Prażnowski, Jaroslaw Mamala
The vibrations of the sprung mass of a passenger car, traveling on a road surface, are random and are its main source but not the only one. The resulting force ratio is further confounded by other factors occurring at the interface of the pneumatic tire with the road surface, such as non-uniformity of tires, errors shape and imbalances. The resulting the additional inertia force acts on the previously brought kinematic force acting on the car body. Occurring at the time of the sprung mass vibrations of the car body can be treated as a potential source of diagnostic information, but their direct identification is difficult. Moreover, all basic identification is complicated by force derived from random interference unevenness in the road. Then the ratio defined as SNR accepts negative values. Due to the lack of description in the literature conclusive research to identify the unbalance the whole pneumatic wheel real conditions, conducted its own experimental research.
2017-06-05
Technical Paper
2017-01-1882
Pravin P. Hujare, Anil D. Sahasrabudhe
The reduction of vibration and noise is a major requirement for performance of any vibratory system. Due to legislative pressures in terms of external pass by noise limit of vehicles and customer requirements for better noise and ride comfort in vehicle, NVH attribute has become an important parameter. Major sources for vehicle pass-by noise consist of powertrain, tire and wind. Damping treatment is important to reduce vibration and noise radiation. The passive constrained layer dampening (CLD) treatment can be used to reduce structure-borne noise of vibrating structure using viscoelastic damping material. The performance of the passive constrained layer damping (CLD) treatment can further be enhanced by new segmentation technique. The concept of segmented CLD is based on edge effect. The efficiency of segmenting a constrained layer damping treatment relies on the fact that a high shear region is created in the viscoelastic layer.
2017-06-05
Technical Paper
2017-01-1877
Justin Gimbal, Joy Gallagher, John Reffner
Damping materials are applied to the vehicle body during production to provide passenger comfort by reducing noise and structural vibration through energy dissipation. Noise, Vibration, and Harshness (NVH) Engineers identify critical areas of the vehicle body for material placement. Damping materials, which include liquid applied dampers, are typically put directly on the structure; covering large areas. These film forming materials can be spray applied using automation and, after baking, result in a cured viscoelastic damping layer on the target substrate. Typical liquid applied dampers contain an aqueous dispersion of film forming polymer which functions to bind inorganic materials together in the coating and provide a composite structure that dissipates energy. Representative damping coatings were prepared from dispersions of polymers with varying viscoelastic properties and chemical compositions.
2017-06-05
Technical Paper
2017-01-1778
Enrico Galvagno, Antonio Tota, Mauro Velardocchia, Alessandro Vigliani
This paper explores the potentiality of reducing noise and vibration of a vehicle transmission thanks to powertrain control integration with active braking system. The torsional backlashes between transmission rotating components (gears, synchronizers, splines, CV joints), in the presence of external disturbances, coming from the driver, e.g. during tip-in / tip-out maneuvers, or from the road, e.g. crossing a speed bump or driving on a rough road, may lead to NVH issues known as clonk. In this study, first of all the positive effect of a brake torque application at the driving wheels during such maneuvers on transmission NVH performance is shown. After that, a powertrain/brake integrated control strategy is proposed. The braking system is activated in advance with respect to the perturbation and it is deactivated immediately after to minimize the energy loss.
2017-06-05
Technical Paper
2017-01-1823
Dennis J. Kinchen
Powertrain mounting systems design and development involves creating and optimizing a solution using specific mount rates and multiple operating conditions. These mount rates become the recommended “nominal” rates in the specifications. As is typical of natural materials, the properties have variation resulting in a tolerance around the nominal specification which leads to differences in noise and vibration performance. A system that is robust to this variation is desired. The design and development process requires evaluation of these mounts to ensure that the noise and vibration performance is consistently met. During the hardware development of the powertrain mounting system a library of mounts that include the range of production variation is studied however this is time consuming. In this paper, a methodology is described to reduce the hardware evaluation time and provide a recommended optimal solution that is robust in the presence of production mount property variation.
2017-06-05
Technical Paper
2017-01-1854
John T. Anton, Jason Ley, Ikpreet S. Grover, David Stotera
Liquid-applied sound deadener (LASD) is a light-weight, targeted vibration damping treatment traditionally used in the automotive market for body-in-white (BIW) panels. Water-based LASDs may cure over a wide range of conditions from room temperature to over 200°C. However, curing conditions commonly affect change in the damping characteristics. A thorough understanding of the relationship between curing conditions and subsequent damping performances will inform the material selection process and may allow pre-manufacturing designs to be adjusted with limited impact during validation. This paper aims to strengthen the quantitative understanding of the role LASD curing conditions have on damping performance by observing the effects of variations in thickness and cure temperature as measured by the Oberst method.
2017-06-05
Technical Paper
2017-01-1807
Richard DeJong, Gordon Ebbitt
The SEA model of wind noise requires the quantification of both the acoustic as well as the turbulent flow contributions to the exterior pressure. The acoustic pressure is difficult to measure because it is usually much lower in amplitude than the turbulent pressure. However, the coupling of the acoustic pressure to the surface vibration is usually much stronger than the turbulent pressure, especially in the acoustic coincidence frequency range. The coupling is determined by the spatial matching between the pressure and the vibration which can be described by the wavenumber spectra. This paper uses measured vibration modes of a vehicle window to determine the coupling to both acoustic and turbulent pressure fields and compares these to the results from an SEA model. The interior acoustic intensity radiating from the window during road tests is also used to validate the results.
2017-06-05
Technical Paper
2017-01-1761
Daniel Fernandez Comesana, Graciano Carrillo Pousa, Emiel Tijs
The automotive industry is currently increasing noise and vibration requirements of vehicle components. A detailed vibro-acoustic assessment of every supplied element is commonly enforced by most vehicle manufacturers. Traditional End-of-line (EOL) solutions often encounter difficulties adapting from controlled environments to industrial production lines due the presence of high levels of noise and vibrations generated by the surrounding machinery. In contrast, particle velocity measurements performed near a rigid radiating surface are less affected by background noise and they can potentially be used to address noise problems even in such conditions. The vector nature of particle velocity, an intrinsic dependency upon surface displacement and sensor directivity are the main advantages over conventional solutions. As a result, quantitative measurements describing the vibro-acoustic behaviour of a device can be performed at the final stage of the manufacturing process.
2017-06-05
Technical Paper
2017-01-1829
Guillaume Loussert
The new fuel efficiency and emission standards have forced OEMs to put emphasis on different strategies such as engine downsizing, cylinder deactivation... Unfortunately these new technologies may lead to increased powertrain vibrations generated by the engine and transmitted to the chassis and the car cabin, such that their reduction or elimination has become a key topic for the automotive industry. The use of active engine mounts, acting directly on the fluid of an hydromount, or active vibration dampers, acting as an inertial mass-spring system, are very effective solutions, particularly when using electromagnetic based actuators. Nevertheless, all electromagnetic actuators technologies are not equals and the choice of such actuators must be considered carefully by taking into account the full performances and the overall cost of the solutions. This paper presents an electromagnetic actuator technology, that can be considered as the best tradeoff between performances and cost.
2017-06-05
Technical Paper
2017-01-1840
Thierry Bourdon, Rainer Weber, Johann Massinger
Nowadays, the automotive industry is increasingly facing of reducing vibration & noise in the vehicle. More particularly on the engine area, the development of fuel components based on high pressure pumps, rails, any pipes and injectors are a subject of a particular NVH attention. The use of modern digital techniques such as 3D finite element vibroacoustic, leads to use virtual prototyping as complementary to traditional real hardware prototypes development. Among interest, number of iterative loops to reach a best design brings an important value to new product development with an optimized cost. Basically the core part of virtual prototyping is about 3D finite element models for each component. It is quite challenging to establish these models, as they must mimic the entire physical phenomenon of real structure borne hardwares sound in the whole audible frequency range.
Viewing 1 to 30 of 2337

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