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SAE International Journal of Vehicle Dynamics Stability and NVH
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Acoustic Analysis of a Compact Muffler for Automotive Application

SAE International Journal of Vehicle Dynamics, Stability, and NVH

Indian Institute of Science-M. L. Munjal
Mahindra & Mahindra Ltd-Arvind Ram, Abhinav Prasad
  • Journal Article
  • 2017-01-9550
Published 2017-06-17 by SAE International in United States
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. The effect of manufacturing defects in the form of leakages and weep holes (to reduce internal corrosion) which are commonly found in automotive mufflers is investigated by modelling it as perforations. The back pressure of the muffler is predicted by…
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Diffuse Field Sound Absorption of Microperforated Panels with Special Backings

SAE International Journal of Vehicle Dynamics, Stability, and NVH

American Acoustical Products-Emanuele Bianchini
University of Kentucky-Weiyun Liu, David W. Herrin
  • Journal Article
  • 2017-01-1876
Published 2017-06-05 by SAE International in United States
Microperforated panel absorbers are best considered as the combination of the perforate and the backing cavity. They are sometimes likened to Helmholtz resonators. This analogy is true in the sense that they are most effective at the resonant frequencies of the panel-cavity combination when the particle velocity is high in the perforations. However, unlike traditional Helmholtz resonators, microperforated absorbers are broader band and the attenuation mechanism is dissipative rather than reactive. It is well known that the cavity depth governs the frequency bands of high absorption. The work presented here focuses on the development, modeling and testing of novel configurations of backing constructions and materials. These configurations are aimed at both dialing in the absorption properties at specific frequencies of interest and creating broadband sound absorbers. In this work, several backing cavity strategies are considered and evaluated. Each configuration was modeled using plane wave simulation. The numerical results were then compared to experimental results at first at the single cell level using an impedance tube test, and sequentially a multiplicity of cells were tested in…
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Effect of Component Flexibility on Axle System Dynamics

SAE International Journal of Vehicle Dynamics, Stability, and NVH

Chongqing University-Xuan Li
Northwestern Polytechnical University-Guan Qiao
  • Journal Article
  • 2017-01-1772
Published 2017-06-05 by SAE International in United States
The prediction and control of gear vibration and noise has become very important in the design of a quiet, high-quality gearbox systems. The vibratory energy of the gear pair caused by transmission error excitation is transmitted structurally through shaft-bearing-housing assembly and radiates off from exterior housing surface. Most of the previous studies ignore the contribution of components flexibility to the transmission error (TE) and system dynamic responses. In this study, a system level model of axle system with hypoid gear pair is developed, aiming at investigating the effect of the elasticity of the shafts, bearings and housing on TE as well as the contribution of flexible bearings on the dynamic responses. The load distribution results and gear transmission errors are calculated and compared between different assumptions on the boundary conditions. The modal characteristics and dynamic responses by assuming simply-support bearing and flexible bearing have also been compared. The results reveal that the system responses are sensitive to the system elasticity and shaft-bearing flexibility. The proposed approach yields a more in-depth understanding to the gear vibration…
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Model Based Approach by Combination of Test and Simulation Methodologies for NVH Investigation and Improvement of a Rear Wheel Drive Vehicle

SAE International Journal of Vehicle Dynamics, Stability, and NVH

Siemens Industry Software-Fabio Luis Marques dos Santos, Tristan Enault, Jan Deleener, Tom Van Houcke
  • Journal Article
  • 2017-01-1774
Published 2017-06-05 by SAE International in United States
The increasing pressure on fuel economy has brought car manufacturers to implement solutions that improve vehicle efficiency, such as downsized engines, cylinder deactivation and advanced torque lock-up strategies. However, these solutions have a major drawback in terms of noise and vibration comfort. Downsized engines and lock-up strategies lead to the use of the engine at lower RPMs, and the reduced number of cylinders generates higher torque irregularities. Since the torque generated by the engine is transferred through flexible elements (clutch, torsional damper, gearbox, transmission, tire), these also impact the energy that is transferred to the vehicle body and perceived by the driver. This phenomenon leads to low frequency behavior, for instance booming noise and vibration.This paper presents a combined test and CAE modelling approach (1D/3D) to reverse engineer a vehicle equipped with a CPVA (centrifugal pendulum vibration absorber). The objectives were to fully understand and predict vehicle behavior with respect to the drivetrain torsional oscillations and low frequency booming noise and vibration. For this purpose, the procedure was divided in two phases: testing and modelling.…
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Acoustically Absorbing Lightweight Thermoplastic Honeycomb Panels

SAE International Journal of Vehicle Dynamics, Stability, and NVH

3M Company-James M. Jonza, Thomas Herdtle, Jeffrey Kalish, Ronald Gerdes, Taewook Yoo
3M Deutschland GmbH-Georg Eichhorn
  • Journal Article
  • 2017-01-1813
Published 2017-06-05 by SAE International in United States
The aerospace industry has employed sandwich composite panels (stiff skins and lightweight cores) for over fifty years. It is a very efficient structure for rigidity per unit weight. For the automobile industry, we have developed novel thermoplastic composite panels that may be heated and shaped by compression molding or thermoforming with cycle times commensurate with automotive manufacturing line build rates. These panels are also readily recycled at the end of their service life. As vehicles become lighter to meet carbon dioxide emission targets, it becomes more challenging to maintain the same level of quietness in the vehicle interior.Panels with interconnected honeycomb cells and perforations in one skin have been developed to absorb specific noise frequencies. The absorption results from a combination and interaction of Helmholtz and quarter wave resonators. Computer modeling was used to design panels that absorb one of the problematic frequency ranges (800-1,250 Hz), caused by tires on the roadway. This was achieved in thin (7-8 mm) panels of low density (0.25-0.35 g/cc). Experimental results of acoustic absorption and transmission loss of polypropylene…
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A Study on Hypoid Gears NVH Robustness

SAE International Journal of Vehicle Dynamics, Stability, and NVH

American Axle & Manufacturing Inc.-Mohsen Kolivand, Glen Steyer, Clifford Krieger
RWTH Aachen University-Max-Ferdinand Stroh
  • Journal Article
  • 2017-01-1776
Published 2017-06-05 by SAE International in United States
Hypoid gears transmission error (TE) is a metric that is usually used to evaluate their NVH performance in component level. The test is usually done at nominal position as well as out of positions where the pinion and gear are moved along their own axis and also along offset direction to evaluate sensitivity of the measured TE to positional errors. Such practice is crucial in practical applications where the gear sets are inevitably exposed to off position conditions due to a) housing machining and building errors, b) deflections of housing, bearings, etc. under load and c) thermal expansions or contractions of housing due to ambient temperature variations. From initial design to development stage, efforts should be made to design the gear sets to be robust enough to all combinations of misalignments emanated from all three mentioned categories. This study is one such effort a) to evaluate main parameters affecting TE response of a hypoid gear set at various misalignment conditions and temperature variations under various loads as well as b) quantifying topography effects on TE…
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Effect of Friction Torque on Electromechanical Brake System Dynamics

SAE International Journal of Vehicle Dynamics, Stability, and NVH

Northwestern Polytechnical University-Guan Qiao, Geng Liu, Shangjun Ma
University of Cincinnati-Zhenghong Shi, Yawen Wang, Teik Lim
  • Journal Article
  • 2017-01-1902
Published 2017-06-05 by SAE International in United States
Actuator and roller screw mechanism are key components of electromechanical brake (EMB) system in automotive and aerospace industry. The inverted planetary roller screw mechanism (IPRSM) is particularly competitive due to its high load-carrying capacity and small assembly size. For such systems, friction characteristic and friction torque generated from rolling/sliding contacts can be an important factor that affects the dynamic performance as well as vibration behavior. This paper investigates the modeling and simulation of the EMB system in early design stage with special attention to friction torque modelling of IPRSM. Firstly, a step-by-step system model development is established, which includes the controller, servo motor, planetary gear train and roller screw mechanism to describe the dynamic behavior of the EMB system. Secondly, detailed analytical formulations are established to calculate the friction torque in the time domain for evaluating its influence on the EMB displacement dynamic response. Finally, the dynamic performance for the EMB system is simulated under various driving conditions. Simulation results show that the friction torque has a significant influence on system brake performance. Larger friction…
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Value of Optimal Wavelet Function in Gear Fault Diagnosis

SAE International Journal of Vehicle Dynamics, Stability, and NVH

CTU-Gabriela Achtenova
Helwan University-Mohamed El morsy
  • Journal Article
  • 2017-01-1771
Published 2017-06-05 by SAE International in United States
Gear fault diagnosis is important in the vibration monitoring of any rotating machine. When a localized fault occurs in gears, the vibration signals always display non-stationary behavior. In early stage of gear failure, the gear mesh frequency (GMF) contains very little energy and is often overwhelmed by noise and higher-level macro-structural vibrations. An effective signal processing method would be necessary to remove such corrupting noise and interference. This paper presents the value of optimal wavelet function for early detection of faulty gear. The Envelope Detection (ED) and the Energy Operator are used for gear fault diagnosis as common techniques with and without the proposed optimal wavelet to verify the effectiveness of the optimal wavelet function. Kurtosis values are determined for the previous techniques as an indicator parameter for the ability of early gear fault detection. The comparative study is applied to real vibration signals. First, to eliminate the frequency associated with interferential vibrations, the vibration signal is filtered with a band-pass filter determined by a Morlet wavelet whose parameters are optimized based on maximum Kurtosis.…
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An Efficient Input Mobility Mapping Computational Method

SAE International Journal of Vehicle Dynamics, Stability, and NVH

PSA Groupe-Laurent Gagliardini
  • Journal Article
  • 2017-01-1806
Published 2017-06-05 by SAE International in United States
The input mobility is a crucial structural parameter regarding vibro-acoustic design of industrial objects. Whatever the frequency range, the vibrational power input into a structure -and consequently the average structural-acoustic response- is governed by the input mobility. When packaging structure-borne noise sources, the knowledge of the input mobility at the source connection points is mandatory for noise control. The input mobility is classically computed at the required points as a specific Frequency Response Function (FRF). During an industrial design process, the choice of connection points requires an a priori knowledge of the input mobility at every possible location of the studied structure-borne source, i.e. a mapping of the input mobility. The classical FRF computation at every Degree Of Freedom (DOF) of the considered structure would lead to consider millions of load cases which is beyond current computational limits.This paper presents how to efficiently compute the full map of band-averaged input mobility over a Finite Elements mesh. The proposed method is based upon a modal decomposition of the structural response and analytical frequency integration; consequently, it…
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FWD Halfshaft Angle Optimization Using 12 Degree of Freedom Analytical Model

SAE International Journal of Vehicle Dynamics, Stability, and NVH

General Motors-Wallace Hill, Dennis Kinchen, Mark A. Gehringer
  • Journal Article
  • 2017-01-1770
Published 2017-06-05 by SAE International in United States
This paper describes the development of an analytical method to assess and optimize halfshaft joint angles to avoid excessive 3rd halfshaft order vibrations during wide-open-throttle (WOT) and light drive-away events. The objective was to develop a test-correlated analytical model to assess and optimize driveline working angles during the virtual design phase of a vehicle program when packaging tradeoffs are decided. A twelve degree-of-freedom (12DOF) system model was constructed that comprehends halfshaft dynamic angle change, axle torque, powertrain (P/T) mount rate progression and axial forces generated by tripot type constant velocity (CV) joints. Note: “tripot” and “tripod” are alternate nomenclatures for the same type of joint. Simple lumped parameter models have historically been used for P/T mount optimization; however, this paper describes a method for using a lumped parameter model to also optimize driveline working angles. The 12DOF model results enable evidence-based decisions during the virtual vehicle phase for driveline working angles, powertrain mount rate and locations relative to P/T center of gravity. Several challenges were encountered and addressed during the 12DOF model development and correlation…
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