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The increased adoption of downsized engines along with higher electrical demand is generating a challenge to the Front-End Accessory Drive (FEAD) system functioning and validation. One alternative to speed up the validation of potential design solutions is the in-vehicle experimental tests approach. Nevertheless, experimental data collection during in-vehicle FEAD evaluation imposes some challenges due to, for instance, packaging space constraints and sample rate required to capture the dynamic events during vehicle operation, among others. In order to overcome this limitation, the objective of this research is focused in the development of a customized test rig that emulates FEAD layout of an actual automobile in a simulated operating condition.

Increasingly research has been conducted lately towards reduction of both fuel consumption and gases emission in automotive vehicles propelled by Internal Combustion Engines. Among many initiatives, downsizing of those engines has been broadly adopted, arising side effects as increased vibration levels along Front-End Accessory Drive (FEAD) system. The present study focuses on the potential improvement of transmission efficiency and of vibration levels along FEAD by considering different layouts for the system. Multiple combinations of alternator pulley technologies and tensioner types are evaluated either during in-vehicle tests or in customized test rig that emulates vehicle FEAD in operating conditions. Specific transducers spred over the vehicle and at test rig assure the relevant data are captured for every layout arrangement investigated.

Vehicle alternator pulleys with one-way-clutch and vibration attenuation mechanisms have recently been adopted in modern vehicles in order to reduce or mitigate undesirable side effects of torsional vibrations generated by Internal Combustion Engines (ICE) during its normal operation. It is noticeable how excessive vibration can be particularly detrimental to the components of the Front-End Accessory Drive (FEAD) system. Increase of inertia forces due to the use of larger alternators along with the increase in torsional vibration amplitudes of downsized engines added up with lower idling speeds to reduce emissions have set a challenge for proper FEAD functioning and validation. In order to validate potential design solutions, in-vehicle experimental tests are an important approach. How to define an adequate test plan, execute test cycles and post-process bulk experimental data to assure proper assessment of alternator pulley alternatives is a key factor of success.

Vehicle consumers are becoming more and more insightful and watchful, design alone is not anymore the main factor of differentiation. Generally, they evaluate and compare different models searching for the best cost benefit package, wherein acoustical comfort is an important requirement in the decision. The OEM’s, on the other hand, unceasingly search to identify these requirements so that they`re taken into account in the process of conception of new models. They consider countless information, ranging from the perception of the consumers and information from satisfaction research up to comparative analysis data between competing models (benchmarking), thus defining what’s called targets of the project. In order to realize benchmarking analysis in the NVH field, dozens of operational and laboratory tests are realized, generating hundreds of gigabytes of objective or quantitative data and subjective or qualitative data.

Currently, the simulation models in acoustics and vibrations are built considering only the main structures of the vehicle, as its basic structure (Body-in-white, BIW), doors, dashboard, and so on. To take into account the contribution of components with less influence (such as carpets, seats, sound insulation, and so on) in the behavior of the overall response of the model, the average characteristics of these materials are inserted evenly distributed in these models. However, to obtain models with better correlation levels is necessary to consider local characteristics of the application of these components. In this work was developed and numerically validated, the model that describes the standardized test of “Oberst Beam” (ASTM E 756-98) to obtain the damping of the blankets used for damping of the panel vibration. With these characteristics, in future work, is expected to be possible, also with a good correlation, consider the effect of these materials on whole vehicle.

Currently the numerical simulations of the vibro-acoustic behavior of vehicles are built considering only major structures, such as its basic structure (body in white), doors, dashboard etc. To take into account the contribution of other components (such as trims, seats, sound insulation etc.) to the overall response of the model, the average characteristics of these materials are inserted globally in this model. However, for more correlated models is necessary to consider local characteristics of these components. This work presents the numerical procedure for simulating the effect of the structural damping of viscoelastic coatings and the acoustic absorption of the trims such that its effects can be considered in the model of the full vehicle. The operating forces applied to the model were estimated from the laboratory and road tests using the SPC/TPA technique.