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This paper describes rheological properties of hydrodynamic and elastohydrodynamic lubrication (EHL) film under various contact pressure conditions using the fluorescence measurement method. In this measurement method, the viscosity and the information about the state of the lubricant (liquid or solid) can be obtained via the analysis of fluorescence spectrum of a pyrene excimer emission. Previous research revealed that the intensity of excimer emission decreased with increasing of viscosity. In addition, the intensity ratio between the excimer peak and lubricant 5P4E fluorescence peak was introduced for the analysis, and the ratio decreased with increasing viscosity of lubricant. In this study, the viscosity profile obtained from the relationship between the intensity ratio and viscosity showed that the state of lubricant in the lubrication film corresponded almost exactly to the lubrication regime proposed in previous researches. It is concluded that the viscosity measurement technique proposed in this study is useful method for practical uses in hydrodynamic and elastohydrodynamic conditions, while in the high viscosity range, the measured viscosity varies widely due to the variation of intensity ratio.

Elastohydrodynamic lubrication of a journal bearing has been usually calculated with bearing deformation. In this study, crank-pin deformation is included in addition to the bearing deformation of con-rod big-end. The calculated results are shown with and without the crank-pin deformation and the effects of the crank-pin deformation on calculated results are discussed. The effects of the crank-pin deformation appear after compression TDC during low speed operation and near suction TDC during high speed operation.

As vehicle engines become lighter, smaller, and more powerful, stress prediction of the main bearings has become an important aspect of strength design measures for the cylinder block. To predict the stress of the engine main bearings under actual working conditions, a flexible multibody dynamics (FMBD) solver was developed with a built-in elastohydrodynamic lubrication solver for the main bearings. The dynamic behavior of the engine system under actual working conditions was then calculated and the results were used to calculate the stress. To reduce the stress calculation cost, rather than inputting the actual working load into a finite element model (FEM) of the whole engine as a boundary condition, the stress was calculated by inputting the dynamic behavior into a small FEM consisting only of the main bearing as a displacement boundary condition. Verification of the test results confirmed that this model is capable of highly precisely predicting the actual working strain of main bearing portions susceptible to fatigue-related fractures. It was confirmed that the developed model could predict the actual working strain if the highest natural frequency of the eigenmode utilized by the FMBD analysis was set to 50kHz or higher.