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In this paper we present a time-domain dynamic analysis of a helical gear box with different housing models using a unique finite element-contact mechanics solver. The analysis includes detail contact modeling between gear pairs along with the dynamics of gear bodies, shafts, bearings, etc. Inclusion of the housing in the dynamic analysis not only increases the fidelity of the model but also helps estimate important NVH metrics, such as dynamic load and vibration transmission to the base, sound radiation by the gearbox, etc. Two different housing models are considered. In the first, the housing is represented by a full FE mesh, and in the second, the housing is replaced by a reduced model of condensed stiffness and mass matrices. Component Mode Synthesis (CMS) methods are employed to obtain the reduced housing model. Results from both the models are successfully compared to justify the use of reduced housing model for further studies.

The main goal of this paper is to extend the acoustic boundary element analysis to the high frequency regime. At higher frequencies, the surface boundary element mesh of the radiator must be sufficiently fine to capture the rapid spatial variations of the sound field. Traditional BEM implementations have had difficulty in dealing with large number of unknown variables and thus are limited to low frequency analysis of small bodies. In a typical boundary element analysis, computation of the coefficient matrix constitutes a major portion of the total analysis time and total memory usage. The key to obtaining rapid solutions of large problems using BEM is to completely bypass the coefficient matrix computation. We have developed a new Direct Boundary Element Variational formulation that is used in conjunction with iterative solvers from the Krylov family, and a new Multilevel Fast Multipole Method (MLFMM) that facilitates extremely fast matrix-vector product computation.