Flexible multi-body dynamics simulation - A powerful method for prediction of structure borne noise of internal combustion engines

The numerical simulation of contacting engine pans is a challenging target during the engine development process. Contrary demands like increasing use of light weight materials and tighter limits of admissible stress and strain increase the difficulty of designing low vibrating and low noise engines. The appropriate simulation too] has to meet conflicting demands in efficiency and accuracy, in addition. Moreover the prediction method must be capable to represent engines with arbitrary size and application area at all operating and loading conditions. Various excitation effects have to be covered. Besides the combustion, the excitation that results from impacts of body surfaces is an important source of structure borne noise and makes an accurate representation in a simulation methodology necessary. In addition to the vibro-acoustic excitation, these oil lubricated contacts between the surfaces mainly influences also friction and wear. This paper outlines a flexible multi-body dynamics simulation methodology that considers linear elastic bodies considering highly non-linear contacts. The contact models are both non-linear spring damper approaches and advanced mixed lubrication models that consider effects of mass, elasticity, surface roughness and hydrodynamics. The numerical integration of the resulting non-linear mathematical model is done in time domain. The first part of the paper discusses the mathematical formulation of the flexible multi-body simulation model. Both the representation of the linear elastic bodies and the highly non-linear contacts are outlined. In the second part, the paper focuses on the comparison of simulation results and measurement results to show the wide range of applications and the achievable result quality. In particular results on piston slap excitation, valve train and timing drive excitation, crankshaft motions, engine mount vibrations and structure borne noise simulation considering all excitation effects are considered.