Test Study And Validation Of Structure Details Fatigue Rating Of Aircraft

The quality of detailed fatigue design has a significant impact on fatiguestrength of the entire airplane structure, detailed design proficiency and service life.Since the development strategy of civil aircraft has just been established in China,the DFR method from Boeing Company and the material data manual from overseasare usually adopted in the design and analysis process. As the design philosophy andtechnology has made a great progress in recent years, some new structures, processesand new materials progressively emerge in the aircraft structure. These technologybreakthroughs encourage us to newly develop a more systematic, scientific andreliable structure detail design methodology with independent intellectual property,which will lay a solid foundation for the future research and a rapid enhancement ofdesign ability for civil airplanes.Fatigue evaluation procedure, DFR method, is supported by enormous andmulti-sources fatigue data. The parameters are determined according to the servicedata and the materials test data from huge data base of Boeing in the late1960s. Butthere are more new data and advanced statistic model in used. In this report thevariation of DFR values are analyzed, which is influenced by the shape parameter,the slope standard S-N curve, parameter σm0of equal life curve and the numbers ofstructure details. Therefore,Currently according to the key parameters to determinethe DFR, established the statistical analysis model of DFR(α),analysising theinfluence of shape parameters on DFR, in order to providing the basis for selectingmaterial.According to the aviation standard(HB) and ASTM standards for domesticmaterial fatigue test, establishing a reliably,engineering standard providing thesupport for the related field of DFR test.Through the experiment on18groups of495aluminum alloy specimens know the fatigue life distribution,the shape parameter. Using the method of linear regression for each fatigue life analysis.At the sametime the paper analysis the influence of few details on DFR,obtained the probabilitystatistic model of estimating more details, and analysis DFR of the specimens ondifferent materials direction and different the roughness.The analysis result iscompared with the results and the allowable values.