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Abbas, Ahmad
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New Half Shaft Bench Test Methodology for NVH Characterization

FCA US LLC-Wei Yuan, Ahmad Abbas, Francisco Antonio Sturla
Siemens PLM Software-Saeed Siavoshani, Prasad Balkrishna Vesikar
Published 2019-06-05 by SAE International in United States
The main purpose of this paper is to develop a reliable bench test to understand the vibratory behavior of the half shafts under applied torque comparable to an idle condition. In some cases, the half shaft path is a major factor influencing the idle vibration in the vehicle. At idle condition vehicle vibrations are caused by engine excitation and then they pass through different paths to the body structure. Half shaft manufacturers generally characterize shaft joints for their frictional behavior and typically there is no data for vibration characteristics of the half shaft under idle conditions. However, for predictive risk management, the vibratory behavior of the half shaft needs to be identified. This can be achieved from measured frequency response functions under preloaded test conditions.This bench test enables manufacturers to conduct comprehensive design of experiments on the impact of powertrain vibration input while transmitting through the half shaft into the vehicle system. This method enables the study of the half shaft at the component level, because studying the half shaft at vehicle level is difficult…
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New Method for Decoupling the Powertrain Roll Mode to Improve Idle Vibration

FCA US LLC-Syed F. Haider, Ahmad Abbas, Francisco Sturla
Published 2019-06-05 by SAE International in United States
Modern engines have high torque outputs and have low RPM due to increased demand for fuel efficiency. Vibrations caused by such engines have to be mitigated. Decoupling the roll mode from the remaining five rigid body modes results in a response which is predominantly about the torque roll axis (TRA) and helps reduce vibrations. Therefore, placing the mounts on the TRA early in the design phase is crucial. Best NVH performance can be obtained by optimizing the powertrain mount parameters viz; Position, Orientation and Stiffness. Many times, packaging restricts the mounts to be placed about the TRA resulting in degradation in NVH performance. Assuming that the line through the engine mount (Body side) centers is the desired TRA, we propose a novel method of shifting the TRA by adding mass modifying the powertrain inertia such that the new TRA is parallel to and on top to the desired TRA. This in turn will decouple the roll mode and reduce vibrations. This problem is formulated as an optimization problem. The numerical examples presented in this paper…
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