Variation Modeling And Analysis For The Assembly Of Low-rigidity Aeronautical Structures

Most of aeronautical structures fall into low-rigidity sheet metal.Not only is it difficult to guarantee high dimensional accuracy in the processing and forming,but also cause the spring-back of during assembly,which results in the dimensional deviation of the final assembly.Assembly variation modeling and analysis is an effective way to deal with the issue of assembly variation control.In this paper,variation source characterization,assembly variation modeling and analysis with respect to low-rigidity aeronautical structures are studied,based on the differences between variation source information obtained in different aircraft production stages.The main research content and innovations are given as follows:The technology development of aircraft digital assembly is introduced,and the state of the art in the field of assembly variation modeling and analysis is stated.Among them,the research status of assembly variation analysis regarding aeronautical structures is emphatically analyzed.After that,current problems in the assembly variation analysis of low-rigidity aeronautical structures are clarified,which is the inducement of the research contents of the thesis.Three methods used to represent uncertain parameters,based on the interval model,fuzzy model and statistical model,are comparatively analyzed.Based on the methods,combining with the types of variation source information obtained in different aircraft production stages,the variation-source-estimation methods of aeronautical structures in prototype production,small-batch production and mass production stages are explored.The variation-source-estimation methods are methods based on the interval number,fuzzy number and mean-variance representation.The assembly process of the low-rigidity aeronautical structures is analyzed,and the influence factors of the assembly variation are discussed.Then an assembly variation model,integrating positioning coordinates errors and deformation of parts as well as merging the rigid and flexible factors,is constructed.Aiming at different variation source information,the assembly variation model of aeronautical structures is extended using the interval analysis and fuzzy interval analysis.Also,the solving of assembly variation of aerospace structures based on Monte Carlo Simulation was given.The assembly process of the outer-wing-box skeleton of an aircraft is briefly analyzed.A rigid-flexible hybrid assembly variation model of a simulant wing-box skeleton is constructed.Considering the differences between variation source information obtained in different production stages,assembly variation prediction methods for the wing-box skeleton was pertinently proposed based on the interval analysis and fuzzy interval analysis.Meanwhile,the assembly variation prediction method based on the Monte Carlo Simulation was given.Thus,variation modeling and analysis methods with respect to low-rigidity aeronautical structures are developed.Finally,the content of the thesis are summarized,and future works are discussed.