Big Bearings Research Articles

A study of lubrication mechanisms using two-phase fluids with porous bearing materials

A potential, novel lubrication mechanism involving two-phase fluids and porous bearing materials is examined in this study both theoretically and experimentally. Lubricating oils with a secondary particulate phase have been considered operating in oil-saturated porous media with the elements of the particulate phase acting as one-way valves on the pores, blocking and unblocking them, depending on the direction of contact load. The goal is to enhance the lubrication, mainly in starved contacts and in some ‘difficult’ applications, as for example in big end bearings for marine engines. The theoretical part of this work deals with the mathematical analysis of an oil-saturated, porous slab, in contact with a solid sphere and lubricated with a two-phase oil containing thin and soft platelets. The problem is analysed using Biot's theory of consolidation in porous media. A subsequent study deals with the effects of the maximum contact load, size, and number of pores of the porous medium, elastic modulus of the medium, and the viscosity of the oil used to carry the particulate phase, on the lubrication performance of the system. Furthermore, a rig was built to study the concept on a macroscale and the results are reported in the paper. Both the theoretical and the experimental work gave good indications that the concept works, at least in some cases. Potential problems with application of this lubrication mechanism have also been identified and are briefly discussed in the paper.

Analysis of diverse simulation models for combustion engine journal bearings and the influence of oil condition

The paper deals with the comparison of different models, from simple to complex, for the simulation of non-stationary response of the journal bearings used in combustion engines. The variety of simulation models covers classical methods from Holland, Butenschoen and numerical methods based on the Hydrodynamic (HD), Elasto-hydrodynamic (EHD) and Thermo-elasto-hydrodynamic (TEHD) lubrication theory. Several crankshaft main bearings and connecting rod big end bearings are investigated. The comparison includes the following bearing parameters: Peak Oil Film Pressure (POFP), Minimum Oil Film Thickness (MOFT) and oil flow. Calculation time is compared, too. Estimation of oil viscosity is discussed over a typical temperature and pressure range found in combustion engines, including the influence of the fuel dilution as an example of the oil aging phenomena.

Vibration Analysis of Connecting Rod Big End Bearings

The aim of the work described in this paper was to compare 'finite bearing' and 'short bearing' models of connecting rod big end bearings with measured practical performance. The effects of bearing shell distortion were also to be investigated, and an assessment made of a novel approach to collecting experimental data from a running internal combustion engine. Theoretical results were obtained for models based both on a 'finite bearing' solution and on the 'short bearing' approximation. Results were calculated for both a circular bearing profile and also for a distorted bearing profile, such as might be caused by the interference 'nip' between the bearing shell and the connecting rod. Experimental data was collected from a single cylinder diesel engine. The results of the work show that a 'full' bearing analysis predicts smaller values of minimum oil film thickness than those obtained when the short bearing approximation is used, and that bearing shell distortion leads to smaller values of minimum oil film thickness. Values of minimum oil film thickness inferred from practical measurements were generally found to be larger than those predicted by theory however, probably because of further bearing shell deflection caused by the oil film forces. The experimental procedure investigated proved useful for measuring changes in oil film thickness, but less useful for measuring absolute oil film thickness.

Load-free sliding overplate for highly loaded big end bearings

Lead has always been an important metal in plain bearing technology. Completely lead-free solutions for high-end engine applications are still not considered to be technically achievable. Therefore, the European End of Life Directive (2000/53/EC), which took effect on 1 July 2003, lists copper-based lead/bronze bearings as an exception. The bearing group of Federal-Mogul has now announced its exit from the lead industry and addresses the issue layer by layer. A recently introduced adaptive bearing offers a lead-free overplate for high-performance internal combustion engine applications. This new bearing changes its technical characteristics during the running-in phase.

Finite Element Analysis of Dynamically Loaded Journal Bearings: Influence of the Bolt Preload

An improved FEM model was developed to simulate the elastic behavior of a connecting rod bearing, accounting for the displacements caused by the tightening torque applied to the bolts that join the cap and the rod. These initial displacements are added to the pressure induced displacements, to enhance the solution of the elastohydrodynamic bearing lubrication problem. The big end bearing of a marine diesel engine was modeled and analyzed under combustion process loads and inertia loads using the Newton-Raphson method together with the Murty’s algorithm. Some important differences between these results and other results published for the same bearing without the bolt preload are identified and discussed.

An Evaluation of Eight-Node Quadrilateral Finite Elements for the Analysis of a Dynamically Loaded Hydrodynamic Journal Bearing

A comparative study is presented for the finite element analysis of a dynamically loaded journal bearing showing the improvement in solution accuracy and decrease in computer time achieved when using eight-node quadilateral, rather than three-node triangular, elements. Results are presented for medium size diesel engine big end bearings using a wide variety of mesh gradings.

Changes in the structure and composition of automobile big-end bearing materials and their relation to bearing failure

Changes in the composition and structure of automobile big end bearings during operation were examined by X-ray diffraction and electron probe X-ray microanalysis. It was found that evolution of heat and severe plastic flow of the surface layer caused diffusion of Sn into Cu, resulting in the formation of intermetallic compounds such as ε-Cu 3Sn. Similar changes were obtained by heating an unused bearing at 170°C for 120 h. It is suggested that the formation of intermetallic compounds such as ε-Cu 3Sn is a contributory factor in bearing failure.