Establishment of method to observe EHL film thickness and its behavior in commercial steel rolling bearing by ultrasonic interference method

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For the stable operation of a roll bearing operated with severe condition, it is important to observe an EHL film thickness and its behavior under the condition that solid contact slightly occurs. Therefore, it is insufficient only by conventional optical observation and must clarify the lubrication conditions of EHL region for real roll bearing which does not transmit the light.The purposes of this study were proposal of a new measurement method of oil film thickness for the EHL film less than 100 nm by ultrasonic pulse reflection method, and establishment of the new measurement system which can observe the EHL film thickness and its behavior for commercial steel bearing.Relations of reflection characteristic of ultrasonic wave, measured under atmospheric pressure with 50MHz probe, and the oil film thickness accord with the theory result which is made echo height average in ultrasonic wave irradiation area.In addition, the relations of echo height for a known film thickness were measu … More red and calibration curves were made. When the estimation of a film thickness under the static condition with this calibration curve was done, it became clear that film thickness estimation of less than 100nm can be possible.The distribution of the shape in echo height observed by a ultrasonic wave method with the monocyte type EHL apparatus, which consisted of optical glass and a steel ball, agreed with the shape of EHL film observed by light interference method qualitatively. When the similar experiment using steel disc was performed, the horseshoe-shaped oil film, which is generally observed by light interference method, was able to observe. In addition, the influence of speed and load for the formation of the EHL film accorded with a general tendency, and the possibility of the EHL film thickness measurement by a ultrasonic wave method was confirmed.Furthermore, the behavior of a film thickness until direct solid contact start with a thrust bearing apparatus, which has a function stopping the revolution of balls and can evaluate lubrication conditions of a commercial roll bearing, was observed. As a result, it was confirmed that the behavior of EHL film thickness distribution of a commercial bearing was same with the behavior observed by a flat steel disc.As mentioned above, the possibility of the evaluation of EHL lubrication conditions for the commercial bearing by an ultrasonic wave method was confirmed, and the base for technology development was established. Less