Correlation of Test with CAE of Dynamic Strains on Transmission Housing for 4WD Automotive Powertrain

摘要

Reducing the vibrations in the powertrain is one of the prime necessities in today's automobiles from NVH and strength perspectives. The necessity of 4×4 powertrain is increasing for better control on normal road and off-road vehicles. This leads to bulky powertrains. The vehicle speeds are increasing, that requires engines to run at higher speeds. Also to save on material costs and improve on fuel economy there is a need for optimizing the mass of the engine/vehicle. The reduced stiffness and higher speeds lead to increased noise and vibrations. One more challenge a powertrain design engineer has to face during design of its transmission housings is the bending / torsional mode vibrations of powertrain assembly. This aggravates other concerns such as shift lever vibrations, shift lever rattle, rise in in-cab noise, generation of boom noise at certain speeds, etc. Hence, reducing vibrations becomes an important and difficult aspect in design of an automobile. Most of the solutions are directed at shifting the vibration frequencies out of normal engine operation range. This is accomplished by increasing the stiffness or by addition of external stiffeners bolted on the structure. The 4×4 powertrain modal frequencies generally fall within the operating range of excitation frequencies and may get excited during normal engine operation. To validate powertrains in early stage of design CAE plays a vital role. Correlation is necessary to validate the CAE method and apply it confidently for design iterations and improve the designs through optimization techniques, so that these virtual iterations will work in the field as well. Paper discusses on the correlation of frequencies of 4x4 powertrain and correlation for the dynamic strains measured on the high speed test track with CAE.