NVH Powertrain
Increasingly severe requirements for engine and gearbox noise emission motivate the use of advanced computer aided engineering simulation tools at the early design stage. Finite element methods are used to calculate the modal and frequency response characteristics of these ancillary component structures. In simulation, specific quantities such as local bearing stiffness and equivalent radiated power are used to assess the noise and vibration propensity. In addition, finite element tools may be used to generate accurate representation of the dynamic properties of engine structural components for use in multi-body engine dynamics simulations with special codes (such as AVL/EXCITE) to calculate the behavior of the engine and gearbox under a wide variety of in-service conditions. The purpose of these comprehensive numerical simulations is to engineer a structure with optimum noise and vibration characteristics.
Engine
In a reciprocating combustion engine both the fluctuating gas pressures in the cylinders and the inertia forces associated with the motion of the pistons excite vibrations and noise. Components and characteristics with a strong influence on the vibration and which are the subject of detailed CDH analyses include:
- Engine block: materials, stiffening rib structures, block wall and cylinder liner thicknesses, bearing housing and caps
- Oil pan: materials, stiffener structures, layout and shape
- Crankshaft: torsional und bending characteristics, vibration damper and counterweights
- Main bearings: axial and radial stiffness characteristics
Gearbox
A modern gearbox is a highly loaded complex component containing rotating shafts and planetary wheels mounted in a light aluminium-alloy case. The intermeshing of the gear teeth leads to multiple-frequency mechanical excitation that is transmitted through the bearings to the gearbox outer casing. This results in noise emission. CDH engineers assist clients to optimize the gearbox design using CAE simulations for:
- Stiffness, strength and durability analysis
- Vibration and radiated noise analysis
- Rib stiffening shape and configuration analysis
