Probability Of Aviation Engine Zero Component Life Test Evaluation Methods

For the problem of small sample experiments assessment of life reliability of aero-engine components, recently the method of life scatter factors was adopted more often inside and outside country. Two kinds of methods of life experiment assessment were introduced in DEF STAN 00-971 and JSGS-87231A, but only the few coefficients for several special conditions were given and could not satisfy the demand of engineering application. And no the theoretical formulas were provided. So in this paper, research work on the assessment methods of fatigue life reliability analysis of aero-engine components and its application were made.The life reliability experiment assessment method of the two-parameter Weibull distribution was studied. Then the theoretical formulas of reliability assessment based on the kth ordered failure time were deduced. And the coefficient table for the experiment design and life reliability assessment was given with the confidence 0.95, the reliability 0.9987 and the shape-parameter 3.6. The application of this method to evaluating probabilistic life of engineering components was demonstrated through several numerical examples.The life reliability assessment method of failure time following the logarithm normal distribution was studied. Then the theoretical formulas of the life scatter factors based on the any kth ordered failure time were deduced. And life scatter factors table was given with the confidence 0.95, the reliability 0.99865 and the ratio of maximum life and minimum life being six. The application of this method to evaluating probabilistic life of engineering components was demonstrated through a numerical example.The assessment method of the test for fatigue life experiment was further discussed, with the incomplete data on the fixed-failure-number experiments or fixed-truncation-time experiments.The influences of different regress methods on the scatter parameter of crack growth rate stochastic model were discussed through sets of the crack growthexperiment data of several metals. And the scatter parameters of crack growth stochastic model of several metals were given in the paper. The effect of material scatter parameters of crack growth rate on the probabilistic life of component crack growth was analyzed.