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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
2017-01-1851
Taewook Yoo, Ronald W. Gerdes, Seungkyu Lee, Daniel Stanley, Thomas Herdtle, Georg Eichhorn
Several methods for evaluating damping material performance are commonly used, such as Oberst beam test, power injection method and the long bar test. Among these test methods, the Oberst beam test method has been widely used in the automotive industry and elsewhere as a standard method, allowing for slight bar dimension differences. However, questions have arisen as to whether this Oberst test result reflect real applications. Therefore, the long bar test method has been introduced and has been used in the aerospace industry for some time. In addition to the larger size bar in the long bar test, there are a few differences between Oberst (cantilever) and long bar test (center-driven) methods. In this paper, the differences between Oberst and long bar test methods will be discussed both experimentally and numerically using Finite Element Analysis. Furthermore, guidelines for a long bar test method will be provided.
2017-06-05
Technical Paper
2017-01-1878
Kevin Verdiere, Raymond Panneton, Noureddine Atalla, Saïd Elkoun
A poroelastic characterization of open-cell porous materials using an impedance tube is proposed in this paper. Commonly, porous materials are modeled using Biot’s theory. However, this theory requires several parameters which can be difficult to obtain by different methods (direct, indirect or inverse measurements). The proposed method retrieves all the Biot’s parameters with one absorption measurement in an impedance tube for isotropic poroelastic materials following the Johnson-Champoux-Allard’s model (for the fluid phase). The sample is a cylinder bonded to the rigid termination of the tube with a diameter smaller than the tube’s one. In that case, a lateral air gap is voluntary induced to prevent lateral clamping. Using this setup, the absorption curve exhibits a characteristic elastic resonance (quarter wavelength resonance) and the repeatability is ensured by controlling boundary and mounting conditions.
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
2017-01-1882
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
2017-01-1857
Joshua R. Goossens, William Mars, Guy Smith, Paul Heil, Scott Braddock, Jeanette Pilarski
Tenneco is using fe-safe/rubber to implement fatigue analysis capabilities and workflows that offer unprecedented control over durability issues in development programs.  The implementation includes a new materials testing facility that can measure the parameters governing elastomer fatigue behavior.  Our lab measures the fatigue crack growth rate curve, crack precursor size, strain crystallization function, and cyclic stress-strain curves.  The measurement and computational capabilities are demonstrated here for a series of uniaxial, biaxial and triaxial load cases on a Front Lower Control Arm vertical ride bushing.  Abaqus was used to obtain the strain history for each load case, and fe-safe/rubber has been used to compute fatigue life and failure mode.  For each case, we present the results of fe-safe/rubber’s Critical Plane Analysis, illustrating the insights that the analysis provides in tracing the development of damage in the bushing.
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
2017-01-1880
Guojian Zhou, Xiujie Tian, Keda Zhu, Wei Huang, Richard E. Wentzel, Melvyn J. Care, Kaixuan Mao, Jiu Hui Wu
A flexible membrane-type acoustic metamaterial, is proposed, with improved sound transmission loss (STL) performance at low frequency. It is composed of a flexible, light-weight membrane material and a sheet material - Ethylene Vinyl Acetate Copolymer (EVA) with an arrangement of periodic holes. The STL was analyzed by using both computer aided engineering (CAE) calculations and experimental verifications, which depict good results in the consistency between both. An obvious sound insulation peak exists in the low frequency band, and the STL peak mechanism is the rebound-effect of the membrane surface, which is proved through finite element analysis (FEA) under single frequency excitation. Then the variation of the peak is studied by changing the structure parameters and material parameters of the metamaterial, providing a method to design sound insulation metamaterials in a specified frequency range.
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
2017-01-1885
Kunhee Lee, Sang Kwon Lee, Taejin Shin, Keun Young Kim
This paper presents a novel method predicting the variation of sound quality of interior noise depending on the change of the proprieties of absorption materials. At the first, the model predicting the interior noise corresponding to the change of the absorption material in engine room is proposed. Secondly the index to estimate the sound quality of the predicted sound is developed. Thirdly the experimental work has been conducted with eight different materials and validated the newly developed index. Finally this index is applied for the optimization of absorption material to improve the sound quality of interior noise in a passenger car.
2017-06-05
Technical Paper
2017-01-1886
Siwen Zhang, Jian Pang, Jun Zhang, Zhuangzhuang Ma, Xiaoxuan Zhang, Congguang Liu, Lihui Deng
In this paper, the subjective evaluation method for the air-borne sound insulation performance of vehicle body in reverberation room is developed and investigated. To improve the credibility of the traditional subjective evaluation methods for the air-borne sound insulation, the test vehicles are placed in the reverberation room and exposed in the homogeneous reverberation sound field. The stationary vehicle's interior noise is recorded by using a digital artificial head. The noise testing method in reverberation room demonstrates more credible than the traditional methods based on the standard deviation analysis of vehicle external fields. With paired comparison scoring method, the recorded interior noises of six different vehicles are replayed and evaluated subjectively by 22 appraisers in the sound quality room. Kendall's correlation coefficient and circular error rates are introduced to check the consistency and correctness of the appraisers' evaluation scores.
2017-06-05
Technical Paper
2017-01-1852
Satyajeet P. Deshpande, Pranab Saha, Kerry Cone
Most of NVH related issues start from the vibration of structures where often the vibrations at resonance radiates the energy in terms of sound. This phenomenon is more pragmatic at low frequencies. This paper discusses a case study where different viscoelastic materials were evaluated on a bench study and then carried on to system level evaluation. A steel panel with a glazing system was used to study both airborne and structureborne noise radiation. System level studies were carried out using experimental modal analysis to shift and tune the mode shapes of the structure using visco-elastic materials with appropriate damping properties to increase the sound transmission loss. The paper discusses the findings of the study where the mode shapes of the panel were shifted and resulted in an increase in sound transmission loss and eventually resulted in reduced sound level in the cabin interior.
2017-06-05
Technical Paper
2017-01-1884
Ruimeng Wu, David W. Herrin
Sound absorbing materials are commonly compressed when installed in passenger compartments or underhood applications altering the sound absorption performance of the material. However, most prior work has focused on uncompressed materials and only a few models based on poroelastic properties are available for compressed materials. Empirical models based on flow resistivity are commonly used to characterize the complex wavenumber and characteristic impedance of uncompressed sound absorbing materials from which the sound absorption can be determined. In this work, the sound absorption is measured for both uncompressed and compressed samples of fiber and foam, and the flow resistivity is curve fit using an appropriate empirical model. Following this, the flow resistivity of the material is determined as a function of the compression ratio. The procedure outlined in the paper is a simple approach for characterizing compressed materials that only.
2017-06-05
Journal Article
2017-01-1765
Albert Allen, Noah Schiller, Jerry Rouse
Corrugated-core sandwich structures with integrated acoustic resonator arrays have been of recent interest for launch vehicle noise control applications. Previous tests and analyses have demonstrated the ability of this concept to increase sound absorption and reduce sound transmission at low frequencies. However, commercial aircraft manufacturers often require fibrous or foam blanket treatments for broadband noise control and thermal insulation. Consequently, it is of interest to further explore the noise control benefit and trade-offs of structurally integrated resonators when combined with various degrees of blanket noise treatment in an aircraft-representative cylindrical fuselage system. In this study, numerical models were developed to predict the effect of broadband and multi-tone structurally integrated resonator arrays on the interior noise level of cylindrical vibroacoustic systems.
2017-06-05
Technical Paper
2017-01-1812
Steven Sorenson, Gordon Ebbitt, Scott Smith, Todd Remtema
In an effort to reduce mass, future automotive bodies will feature lower gage steel or lighter weight materials such as aluminum. An unfortunate side effect of lighter weight bodies is a reduction in acoustic transmission loss (TL). For barrier based systems, as the total system mass (including the sheet metal, decoupler, and barrier) goes down the transmission loss is reduced. If the reduced surface density from the sheet metal is added to the barrier, however, performance can be restored (though, of course, this eliminates the mass savings). In fact, if all of the saved mass from the sheet metal is added to the barrier, the TL performance may be improved over the original system. This is because the optimum performance for a barrier based system is achieved when the sheet metal and the barrier have equal surface densities. That is not the case for standard steel constructions where the surface density of the sheet metal is higher than the barrier.
2017-06-05
Journal Article
2017-01-1813
James M. Jonza, Thomas Herdtle, Jeffrey Kalish, Ronald Gerdes, Taewook Yoo, Georg Eichhorn
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. 3M has developed novel thermoplastic composite panels that may be heated and shaped by compression molding or thermoforming with cycle time commensurate with automotive manufacturing lines 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 of Helmholtz resonators and quarter wave destruction interference effects.
2017-06-05
Technical Paper
2017-01-1814
Todd Tousignant, Kiran Govindswamy, Vikram Bhatia, Shivani Polasani, W Keith Fisher
The automotive industry continues to develop new powertrain and vehicle technologies aimed at reducing overall vehicle level fuel consumption. Specifically, vehicle light weighting is expected to play a key role in helping OEM’s meet fleet CO2 reduction targets for 2025 and beyond. Corning’s Gorilla® Glass Hybrid laminate solution offers more than 30% weight reduction compared to conventional automotive laminate. Additionally, Gorilla Glass Hybrid laminates provide improved toughness, better optics, and enables better vehicle dynamics by lowering the vehicle center of gravity. Although thin glazing offers multiple advantages, glazing weight reduction leads to an increase in transmission of sound through the laminates for certain frequencies. This paper documents a study that uses a systematic test-based approach to understand the sensitivity of interior vehicle noise behavior to changes in acoustic attenuation driven by installation of lightweight glass.
2017-06-05
Technical Paper
2017-01-1815
Pranab Saha, Satyajeet P. Deshpande
This paper discusses the importance of dissipative sound package system in the automotive industry and how it works. Although this is not a new technique at this stage, it is challenging to meet the subsystem target levels that were originally developed for parts based on barrier decoupler concept. This paper reviews the typical construction of a dissipative system and then emphasizes the importance of different layers of materials that are used in the construction, including what they can do and cannot do. The paper also discusses the importance of proper manufacturing of the part.
2017-06-05
Journal Article
2017-01-1816
Mahsa Asgarisabet, Andrew Barnard
Carbon Nanotube (CNT) thin film transducers produce sound with the thermoacoustic effect. Alternating current passes through the low heat capacity CNT thin film changing the surface temperature rapidly. CNT thin film does not vibrate, instead it heats and cools the air adjacent to the film, creating sound pressure waves. These transducers are inexpensive, transparent, stretchable, flexible, magnet-free and lightweight. Because of their novelty, developing a model and better understanding the performance of CNT transducers is useful in technology development in applications that require ultra-lightweight sub-systems. The automotive industry is a prime example of where these transducers can be enabling technology for innovative new component design. Developing a multi-physics (Electrical-Thermal-Acoustical) FEA model, for planar CNT transducers is studied in this paper.
2017-06-05
Technical Paper
2017-01-1817
Steven M. Gasworth, Vasudev Nilajkar, Matteo Terragni
Polycarbonate (PC) glazing as a one-for-one glass replacement offers a 50% weight reduction, but exhibits several dB lower sound transmission loss (STL) in the low frequency range where tire and engine noise are dominant. In the high frequency range where wind noise is dominant, PC glazing offers an STL at least comparable to its glass counterpart, and an STL exceeding glass when this frequency range encompasses the glass coincidence frequency. However, a key value proposition of PC glazing is the opportunity for feature integration afforded by the injection molding process generally used for forming such glazing. Two component (2K) molding fuses a second shot of plastic material behind, and along the perimeter of, the transparent PC first shot. This second shot can incorporate features and implement functions that require additional components attached or peripheral to a glass version.
2017-04-29
WIP Standard
GA-F17AA
This is a general agreement applicable to Committee F specifications for materials which are deemed to be sensitive to strain rate during tensile testing.
CURRENT
2017-04-27
Standard
AS1895/7E
SCOPE IS UNAVAILABLE.
2017-04-26
WIP Standard
AMS1640D
This specification covers a corrosion-removing compound in the form of a liquid concentrate.
2017-04-26
WIP Standard
AMS4905F
This specification covers one type of titanium alloy plate in the beta-annealed condition.
2017-04-26
WIP Standard
AMS4907L
This specification covers a titanium alloy in the form of sheet, strip, and plate. These products have been used typically for parts requiring a combination of weldability, ductility, and good notch-toughness down to –423 °F (–253 °C), but usage is not limited to such applications. Certain processing procedures and service conditions may cause these products to become subject to stress corrosion cracking; ARP982 recommends practices to minimize such conditions.
2017-04-26
WIP Standard
AMS4916L
This specification covers a titanium alloy in the form of sheet, strip, and plate.
2017-04-26
WIP Standard
AMS4922D
This specification covers a titanium alloy in the form of seamless tubing.
2017-04-26
WIP Standard
AMS4935L
This specification covers a titanium alloy in the form of extruded bars and shapes, flash welded rings, and stock for flash welded rings. These products have been used typically for parts that do not require heat treatment but require high mechanical properties in the annealed condition and for which processing above the beta transus is permissible, but usage is not limited to such applications. This alloy exhibits high strength-to-weight ratios up to 750 °F (399 °C).
2017-04-26
WIP Standard
AMS4938B
This specification establishes requirements for titanium forgings of any shape or form from which finished parts are to be made. (See 8.3, 8.5.4, and 8.7). These forgings are used typically in the manufacture of high-performance parts when control of short-transverse tensile, fracture toughness, tensile creep, or tensile rupture is required, but usage is not limited to such applications.
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