Abstract:In this study, the lubrication performance of the crank pin bearing in a marine two-stroke diesel engine is evaluated to investigate the adhesional failure on the crank pin bearing. A numerical algorithm for the lubrication analysis considering motion analysis of the crank pin system is developed. The film pressure and thickness for three clearances and three lubricant temperatures are calculated. The results show that the lubricant temperature has a higher effect on film thickness than clearance. In terms of the film parameter, the operating condition that can result in solid-solid contact is investigated. We also suggest the desirable operating conditions of clearance and lubricant temperature to prevent the solid-solid contact.

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The influence of oil quantity supplied and contact bulk temperature on micro-pitting lifetime is estimated using two-roller contact machine. The failure criterion is set as 4% micro-pitting on contact surfaces, which is adopted from precedent researches. To quantify the failure rate of damaged surfaces of micro-pitting occurrence, DBR(Dark and Bright Ratio) technique was effectively implemented for observing not a sudden emergence of macro-pitting but the transition of micro-pitting growth. The change of damaged surface area was measured and calculated by the use of dark and bright ratio of test specimen pictures taken by optical microscope. The optimum oil quantity was determined to obtain the minimum oil quantity with no change in bulk temperature despite of increasing the inlet oil quantity. In conclusion, the influence of supplied oil quantity and contact bulk temperature considering film parameter on micro-pitting lifetime and the surface contact strength by the S-N curves of failure rate are quantitatively reported and expressed as empirical formulas.