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Viewing 1 to 30 of 6265
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
2017-01-1877
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
2017-01-1852
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
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.
2017-05-15 ...
  • May 15-16, 2017 (8:30 a.m. - 4:30 p.m.) - Troy, Michigan
Training / Education Classroom Seminars
Today's necessity for quickly delivering products to market limits product development time and leaves less room for error and 're-dos.' With so many plastic materials available, it is crucial that those involved in product design understand resin properties and how they affect part design and manufacturability. To help you make the best plastic choices the first time, this seminar provides an overview of polymer chemistry, explains the methods for testing properties of plastics and presents a method of systematic selection that will optimize your plastics material selection process.
2017-05-10
Event
2017-04-24
WIP Standard
AMSR25988A
This specification covers oil-and-fuel-resistant fluorosilicone elastomer rubber sheets, strips, molded parts, and extruded shapes for aeronautical and aerospace applications.
2017-04-21
WIP Standard
AS153J
Add integral silicone cuff max length and OD to flared parts standards
2017-04-21
WIP Standard
AS154H
Add integral silicone cuff max length and OD to flared parts standards
2017-04-21
WIP Standard
AS155H
Add integral silicone cuff max length and OD to flared parts standards
CURRENT
2017-04-20
Standard
AS614D
This SAE Aerospace Standard (AS) defines the requirements for a heavy-duty polytetrafluoroethylene (PTFE) lined, metallic reinforced, hose assembly suitable for use in high temperature, high pressure, 4000 psi, aircraft and missile hydraulic fluid systems.
CURRENT
2017-04-18
Standard
MA620SUP1A
This supplement forms a part of Aerosapce Standard MA620, Hose Assemblies, Convoluted Polytetrafluorethylene Metallic Reinforced, High Temperature, Medium Pressure, Aircraft, Metric and shall be used to identify hose assembly standards citing this procurement specification.
2017-04-13
WIP Standard
AMS3793/3C
This specification covers three classes of para-aramid tape and webbing of a single width and with varying weights.
2017-04-13
WIP Standard
AMS3793C
This specification and its supplementary detail specifications cover para aramid in the form of tape and webbing. These products have been used typically in construction of parachutes and their accessories, but usage is not limited to such applications.
CURRENT
2017-04-12
Standard
AS154G
Add integral silicone cuff max length and OD to flared parts standards
CURRENT
2017-04-12
Standard
AS155G
Add integral silicone cuff max length and OD to flared parts standards
Viewing 1 to 30 of 6265

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