Abstract
A study on life distribution and reliability for a roller guide with cage type is carried out with total number of 90 test samples of two lots (Ns=38 and 52) and fatigue life distribution functions, such as two and three parameters Weibull distribution and log-normal distribution, are used for discussion. The basic dynamic load rating formula standardized by ISO in 2004 is also compared with the life test data in relation to the effect of crownings of carriage raceway end portions. As a result, (1) the best fit for the life test series is obtained by 3-parameter Weibull distribution introduced a minimum life as a third parameter, having Weibull slope m=27/20 and load life exponent p=10/3, followed by the log-normal distribution as second, and 2-parameter Weibull distribution as the third. (2) The 2-parameter Weibull distribution with Weibull slope m=9/8 as used in ISO linear bearing standard dose not fit with the experimental results. (3) The fatigue failures of roller guide is initiated near the crowning start points of carriage raceway both end portions, and almost 70% of test specimen are uneven and inclined contact situations of rollers. (4) The basic dynamic load ratings between theory and life test result fit well each other, and λbm factors are also fallen into suitable value range.
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