A Synthesis Method On Wing Structural Durability/Damage And Reliability And Application Software Research

Along with the improving of the requirements for aircraft performance, especially the higher maneuverability and economic capability for the advanced fighter plane, the existing aircraft structure design system which based on durability analysis and damage tolerance design can't meet all expectations very well. Designing with the durability and damage tolerance method independently tends to enhance the structural weight and its maintenance cost. Under this circumstance, the theory of combined design and analysis of durability and damage tolerance for aircraft structure is talent showing itself and provides novel approaches for the solution of above problem. So in this paper, based on the existed achievement of durability and damage tolerance, the investigation can mainly be described in three areas:Firstly, the conception and objectives of combined design and analysis for aircraft structure have been modified. The combined analysis model based on the durability analysis method PFMA and the probability damage tolerance analysis model is established to solve the problem that the existing model could not carry through the durability and damage tolerance analysis synchronously. The model is built on the basis of initial fatigue quality (IFQ) of structure. Using random crack propagation formula gets a crack random propagation distribution after time t.Secondly, building a safe margin expression based on the TTCI to obey the three-parameter Weibull distribution, two-parameter Weibull distribution and lognormal distribution, and solve the curves of reliability versus time. Methods used in solving are the first order second moment, the reliability index can be directly obtained calculated by this method through the mean and standard deviation and solving the complicated triple integral by theoretical derivation is avoided After solving reliability versus time curve, under the specified reliability requirements structure economic life and crack propagation cycles are predicted respectively by durability and damage tolerance. It makes both equal through improving the structure design and that could pave the way for structural optimization in the future. Thirdly, with object-oriented programming method, some durability methods and durability/damage tolerance integrated model, which are probability fracture mechanics of durability analysis,improved crack initiation method and deterministic crack growth approach and durability/damage tolerance integrated model have compiled into software by Visual Basic language. In the integrated model solution module, except of using the Losm method, the Monte Carlo method is joined, which can get more accurate results.This dissertation improves the idea of aircraft structural design and the durability/damage tolerance analysis methods. Its theoretical achievements not only offer technical support for the research and design of advanced aircraft, but also offer a new method to assess aircraft structural life and safety. It must have a good perspective.