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Reducing Radiated Structural Noise from AIS Surfaces using Several FEM Optimization Methods
Abstract:
Two finite element optimization techniques are presented for minimizing automotive engine air induction structural radiated noise and mass. Air induction systems are generally made of thin wall plastic which is exposed to high levels of pulsating engine noise. Weak air induction system walls vibrate excessively creating noise that can be heard by the driver. The conventional approach is to add ribs (many times through trial and error) which increase part weight or by adding “kiss-offs,” which restrict air flow.
The finite element optimization methods considered here are shape optimization and topometry optimization. Genesis, a fully integrated finite element analysis and optimization package by Vanderplaats Research & Development, was used to perform finite element optimization. Choice of optimization method is primarily dependent on several factors which are appearance, part interference and flow restriction requirements. “GT Power” was used to model the complete engine air flow system and calculate local acoustic pressure levels for modal frequency response analysis. Node velocity results of the structural analysis were applied to an external BEM acoustic model. “LMS Virtual Lab” was used to calculate the surface radiated sound power.
A shape optimized duct radiated significantly less noise but assembly interference requirements were increased for the duct which led to the use of topometry or part thickness optimization. Finite element structural optimization is shown here to be an effective design tool for minimizing radiated air induction shell noise. Shell noise is also shown to be significantly reduced by reducing the forcing acoustic pressure.