Grease life refers to the time it takes for the grease to lose its ability to keep the lubrication due to grease degradation. As grease life is generally shorter than fatigue life of bearing, the service life of greas...Grease life refers to the time it takes for the grease to lose its ability to keep the lubrication due to grease degradation. As grease life is generally shorter than fatigue life of bearing, the service life of grease-lubricated rolling bearings is often dominated by grease life. When designing a bearing systemolecular weightith grease lubrication, it is necessary to define the operating conditions limits of the bearing, for which grease life becomes a determining factor. Prolongation of grease life becomes an especially important challenge when the bearing is to be operated trader high-speed, high-temperature, and other severe conditions. Selecting a number of commercially sold greases composed of varying base oils, the author evaluated their properties and analyzed how each property affected the grease life by performing a multiple regression analysis. The optimum grease composition to best exploit each property was also examined. The results revealed among others that one would need to first determine the base oil type and then maximize ultimate bleeding while minimizing the evaporation rate.展开更多
Development of gas turbine oils that can be used in higher temperature conditions remains the greatest technological challenge. Though the maximum operating temperature of conventional lubricating oils is generally se...Development of gas turbine oils that can be used in higher temperature conditions remains the greatest technological challenge. Though the maximum operating temperature of conventional lubricating oils is generally set around 100 ℃, or 140 ℃ for scavenged oils, it is predicted that the future will require oils to function at 200 ℃ or above. To find a clue to developing oils that can be used at higher temperatures, this study attempted to estimate service lives and operating temperature ranges of certain oils, including oils conforming to MIL-PRF-23699, which are deemed promising candidates for high-temperature applications, by analyzing their reaction rates of degradation and degeneration by oxidation. Among a number of methods used in the analyses of reaction rates, this study chose thermo-gravimetry （TG）, with which estimations can be made relatively easily.展开更多
文摘Grease life refers to the time it takes for the grease to lose its ability to keep the lubrication due to grease degradation. As grease life is generally shorter than fatigue life of bearing, the service life of grease-lubricated rolling bearings is often dominated by grease life. When designing a bearing systemolecular weightith grease lubrication, it is necessary to define the operating conditions limits of the bearing, for which grease life becomes a determining factor. Prolongation of grease life becomes an especially important challenge when the bearing is to be operated trader high-speed, high-temperature, and other severe conditions. Selecting a number of commercially sold greases composed of varying base oils, the author evaluated their properties and analyzed how each property affected the grease life by performing a multiple regression analysis. The optimum grease composition to best exploit each property was also examined. The results revealed among others that one would need to first determine the base oil type and then maximize ultimate bleeding while minimizing the evaporation rate.
文摘Development of gas turbine oils that can be used in higher temperature conditions remains the greatest technological challenge. Though the maximum operating temperature of conventional lubricating oils is generally set around 100 ℃, or 140 ℃ for scavenged oils, it is predicted that the future will require oils to function at 200 ℃ or above. To find a clue to developing oils that can be used at higher temperatures, this study attempted to estimate service lives and operating temperature ranges of certain oils, including oils conforming to MIL-PRF-23699, which are deemed promising candidates for high-temperature applications, by analyzing their reaction rates of degradation and degeneration by oxidation. Among a number of methods used in the analyses of reaction rates, this study chose thermo-gravimetry （TG）, with which estimations can be made relatively easily.
