Design-allowable Value Statistical Estimation Method And Software Development Of Aviation Material Mechanics Performance

Aviation materials and structures require excellent performance, which is often characterized in A basic value and B basic value. A basic value is the lowest value of the upper99%of a specified population with95%cofidence.B basic value is the lowest value of the upper90%of a specified population with95%cofidence.Paper gives the calculation methods of A basic value and B basic value that adapts to different sources and sample sizes according to the characteristics of sample, including the normal distribution basic value calculation method, lognormal distribution basic value calculation method, the three parameters of weibull distribution basic value calculation method and the non-parametric method. Because of the small sample sizes in the aviation materials, this paper also introduces bootstrap method, making the calculation of three parameters weibull distribution basic value in small sample more precise.According to the main failure mechanism of the mechanical equipment, the paper gives the calculation of fatigue limit basic value based on staircase method. This method does not require closed test or data in pairs, which is more convenient and in wide range of application.Considering the staircase method cannot reflect the variance of different stress, this paper also gives the statistical processing methods of experimental data of grouping method. Including the C-P-S-N curves fitting method and the calculation of fatigue strength basic value in a given life.The grouping method take the variance of different stress into account, the C-P-S-N curve makes a sudden changge in the fatigue limit strength.and the fatigue limit strength is generally back stepped by the C-P-S-N curve, thus the result of the fatigue limit strength will departure from the true value in a great possibility. So the paper also gives a method based on the mixed method of the above two methods. In view of the different test purpose the paper gives different error coefficient calculation methods.The demand of the aviation materials on the performance is greater; most fatigue is high cycle fatigue. Sometimes in order to save time can’t wait until all the specimens are failure, so the paper gives the basic value calculation method of censored data and data processing method of data with no failure.