Surface contact analysis in axial thrust bearings based on different numerical interpolation approaches

Abstract

The simulation of moving parts in combustion engines and power trains by means of flexible multi-body dynamics requires complex computation techniques for the contact areas. Understanding surface interactions in detail is of great value for new products and can reduce the development time and costs significantly. Modelling of lubricated contacts, which exist in slider bearings (axial and radial) and in the cylinder kit (piston, rings, and cylinder liner) are challenging tasks. Here, the simulation models have rough discretizations of the body surfaces and fine oil-film discretizations. Although body surfaces are usually given by finite element method (FEM) meshes, the non-linear reaction force of the loaded oil-film is determined by integrating the lubricant pressure field on the hydrodynamic mesh. The pressure is commonly calculated by solving a type of Reynolds equation in the gap between the contacting surfaces. The combination of different types of meshes of the body surfaces and the oil-film highly affects the quality of the results. Interpolation and integration approaches have to be capable of dealing with the high sensitivity of algorithms used for elastohydrodynamic contacts. This paper presents an analysis of numerically simulated contacts in axial slider bearings for combustion engines. A surface contact algorithm with different numerical interpolation approaches for the clearance gap and its time derivative is utilized to investigate the elastohydrodynamic behaviour of axial thrust bearings. Thereby, the complete set of equations for moving and elastic bodies and oil-film reaction forces have to be solved in time domain to obtain the actual shape of the deformed clearance. The numerical interpolation approaches comprise the Fritsch-Butland interpolation with the Brodlie-derivative-formulation as well as generalized cubic spline functions. The investigations consider effects of inclined crankshafts as they occur in axial thrust bearings of combustion engines. Detailed results are shown applying linear and tetragonal FEM meshes for the surfaces of the contacting bodies.