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Study on Contact Fatigue Life Based on Grease Variation with Temperature

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Tutor: SongBaoYu
School: Harbin Institute of Technology
Course: Mechanical Design and Theory
Keywords: rolling contact fatigue,temperature field,lubricating grease,friction moment
CLC: TH117.22
Type: Master's thesis
Year:  2008
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Abstract:
Bearing is widely applied in aviation, astronautics, machinery and national defense. The performance of machinery equipment is directly affected by bearing’s life. Rolling contact fatigue is one of the main inactivation types of bearing. Research and improvement of lubricating property of grease are important ways to increase the bearing service life and reliability. With the development of modern industry , bearing always works at variable temperature environment. So, it both have theoretical significance and practical value to research the variation of contact fatigue life which is caused by lubricating property of grease at different temperatures.In this paper 3# general purpose lithium lubricating grease is selected as experimental grease., and the temperature of contact zone is measured respectively under different ambient temperature with improved experimental bench. And then the heat generation rate caused by friction and boundary condition are figured out. Simulation results of contact zone’s temperature have also been calculated in ANSYS software. Comparing the measurement results with simulation results, operating temperature of lubricating grease is got.Using Weibull slope k, rated life L10, and median life L50 as evaluating indicator, results of contact fatigue experiment indicate that contact fatigue life decreases with the increment of temperature. Within the bounds of experimental temperature, contact fatigue life reflects grease’s lubricating property directly. Research results show that evaporated quantity of base oil increases with temperature rise, and lose more base oil at high temperature. At the same time, viscosity will decrease drastically that causes much sum of grease bleeding and declining bearing capacity of oil films. Besides, strength limit of lubricating grease decreases with the increase of temperature as well, which gives an edge to amount of grease bleeding and weakens adhesive ability of lubricating grease. The integrated effects of these factors deteriorate the lubricating property of lubricating grease. It is identical with the result of contact fatigue experiment.
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