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Traditionally, the development of automotive drivelines incorporating hypoid or spiral bevel gearing using Computer Aided Engineering (CAE) methods have included the analysis of gear contact patterns independent of the influence of the flexible members of the driveline such as the housing and shafting. The gear tooth form development typically occurs using various non-linear gear contact solutions available on the market, but the final refinement of the gear itself usually must wait until the actual hardware can be fabricated and tested in the driveline system. This behavior may result in several costly and time consuming iterations of testing, modifying, and re-testing a gearset, since the up-front CAE tools did not account for the flexibility of the driveline system, nor factors such as bearing pre-load effects, thermal growth, driveline torque levels, dynamic modes of the shafting, and many other important factors.

Development of modern powertrains used in car and truck applications is more competitive than ever before. Powertrains and components previously considered to be advanced technology, such as hybrids and dual-clutch transmission technology, are now commonplace, being designed and manufactured in all worldwide markets. In order to stay competitive, powertrain OEMs must simultaneously optimize attributes such as performance, cost, weight, durability, fuel economy and NVH while producing new, desirable designs with reduced product development timelines. Oftentimes, the ideal solution for optimization of gear whine will result in an unexpected deterioration of durability, and vice versa. An advanced software tool was previously developed for the design of transmissions and transaxles, including analysis of the vibration, efficiency and durability performance under specified speeds and loads.

Vehicle cabin gear whine levels have long been known to contribute to driver annoyance and perceptions of poor quality in passenger cars and trucks, as well as contributing to operator fatigue in helicopters and heavy machinery. For material handling vehicles, radiated gear whine not only influences annoyance and fatigue of operators, but also creates unwanted noise in the operational environment such as warehouses and plants. Upfront management of gear whine levels using predictive software tools is therefore critical for satisfactory design of gearboxes used in such applications. One challenge, however, is selecting the proper boundary conditions for modeling a gearbox acting as a load-bearing structural member used in the material handling vehicles.

In order to effectively evaluate automatic transmission gear noise and vibration performance using a hemi-anechoic test facility, it is essential to understand the coupling mechanism between the transmission internals and the dynamometers and associated shafting. Once this coupling mechanism is well understood, each major frequency response of the resulting torsional vibration operating data can be properly categorized according to the source: transmission-internal, facility, or driveshaft. This knowledge helps noise and vibration engineers properly manage vibration peaks in transmission operating data by ensuring that the issue of concern is not inadvertently influenced by the facility system. Analytical simulations and tests were performed on a transmission operated in a hemi-anechoic facility to evaluate gear vibration using various driveshafts, followed by a program of vehicle testing.

Effectively managing transmission noise, vibration and harshness (NVH) has become increasingly important for maximizing customer satisfaction and fostering the perception of quality in contemporary cars and trucks. As overall vehicle and engine masking levels have dramatically decreased in recent times, low level tonal noises generated by transmission internals have gained significance and therefore have a greater effect on the NVH performance of vehicles. Recognizing the importance of this trend, Ford Motor Company recently designed and built a state-of-the-art research and development facility to be used for reducing noise and vibration generated by automatic and manual vehicle transmissions. The significant design features and validation results of this facility are described in this paper.

A sound simulation technique has recently been developed that allows the NVH engineer to subjectively and objectively predict the passenger compartment noise levels due to radiated transmission gear noise. By using the simulation technique, a noise evaluation can be performed in the early stages of vehicle development, allowing NVH analysts and design engineers to address potential noise concerns well before production of the vehicle is scheduled to begin.

In rear wheel drive vehicles, passenger perceived tonal noise is often generated by high frequency rotational vibrations of the transmission output shaft. This rotational vibration is excited by the transmission and couples with the dynamic and inertial properties of the driveline and suspension to generate forces through the suspension attachment locations. This paper demonstrates an approach which uses experimental techniques to measure the rotational dynamics of the output shaft and noise path analysis procedures to predict the vehicle system interaction and resulting vehicle noise contribution from this path. An evaluation of three rotational data acquisition techniques, a measurement technique used to characterize a vehicle's torsional acoustic sensitivity, and an application of mobility coupling to the torsional noise path is presented.

Emergency Diesel Generators are used in the nuclear industry for stationary stand-by power in order to safely shut down a reactor unit in the event of loss of off site power. Therefore, a high diesel engine reliability and availability must be maintained. Engine turbochargers often experience operating failures resulting in extended down time and costly repairs. Improved turbocharger vibration testing using time synchronous averaging is one method for evaluating the operating condition of a turbocharger. Typical vibration collection methods result in the turbocharger vibration being masked by the high background noise associated with the reciprocating nature of the engine. Time synchronous averaging reduces the background noise and allows accurate measurement of the 1x RPM component and harmonics of the turbocharger. Trends of the turbocharger vibration may then be established for diagnostic purposes, giving the analyst another tool for improving engine reliability and availability.