Uncertainty Quantification And Propagation Methd Researching For The Complex Structural System And Its Application

In the practical engineering, aviation equipments, such as wingstructure, aircraft engines and other mechanical parts, have very complex mechanical structures, for example, the wing structure working in large load, in which structural failure in the key components including nine boxes structure, three boxes structure and the connected parts between wing skins and stringers may lead to a plane crash, causing casualties and significant economic losses. Owing to the increasing complexity of the working environment and equipment, many parameters associated with equipment, including material properties and geometric characteristics, commonly exhibit various uncertainties, which gives challenges to reliability analysis of such complex structures. Therefore, it is significant to study uncertainty quantification and propagation for complicated engineering structures. This paper will study efficient numerical integration methods for uncertainty quantification and propagation of practical complex structures including wing rib structure and turbine blades, which are subjected to various uncertainties.The main work of this paper includes:(1) Three numerical integration methods of uncertainty analysis and their application.Firstly, the numerical integration methods are applied to several numerical examples, and in order to verify the accuracy and efficiency of the methods, the result is compared with that of MCS method. Then, the numerical integration methods combined with finite element analysis software(NASTRAN, ANSYS) are applied to wing rib segments three boxes, wing nine box section structure and aircraft engine turbine blade structure. Finally, the probability density function(PDF) of the output response of complex structural system can be further estimated by using Pearson and Johnson methods, and the structural reliability is accordingly evaluated.(2) Uncertainty analysis and their application under correlated random variables.The numerical integration methods and probability density estimation methods, combining with the uncertainty transformation, are applied to the uncertainty analysis of the complex structures with correlated input variables. Numerical examples are employed to verify the accuracy of the methods, and then the methods are utilized to estimate the PDF of the output and the structural reliability for turbine blades, wing three boxes and wing nine box structure.(3) Structural uncertainty analysis and their application under fuzzy random mixed variables.The numerical integration methods and probability density estimation methods, combining with the entropy theory transforming fuzzy variables into random variables, are applied to the uncertainty analysis of the structures with fuzzy random mixed variables. Numerical examples are utilized to verify the accuracy of the methods, and then the methods are applied to estimate the PDF of the output and the structural reliability for turbine blades, wing three boxes and wing nine box structure.(4) Importance measurement analysis of uncertainty structure and its application.We have studied the methods of sensitivity analysis based on variance and the probability density function, and apply numerical examples to verify the accuracy of the methods. And then we apply the methods to wing rib segments nine box structure.(5) Uncertainty analysis of bolted composite structure.FFNI and UDR numerical integration methods are not employed here due to the fact that they are computationally intensive and unstable for high-dimensional structure of complex system problems. A connected part between wing skins and stringers is first simulated as bolted composite material structure, which is modeled by ABAQUS software. Then, the efficient sparse grid numerical integration method is applied to estimate the output response and structural reliability.