Superelement Method On Mechanical Analysis Of Thin-walled Box With Changeable Cross-section

The thin-walled box is widely-used in aircraft.When analyzing the thin-walled box,if using engineering algorithm,it is low in precision;if adopting Finite Element Method(FEM),accuracy can satisfy the requirement of engineering,but a lot of data is needed to build a precise analysis model,at the same time,applying loads for every model is very troublesome,the model scale is very huge,so it leads to decreased effectiveness.Therefore,how to decrease the work consumption for modeling and reduce computational cost under acceptable accuracy becomes a real problem.Aimed at changeable cross-section thin-walled box,in this thesis is presented a new method called Superelement Method.Taking tansverse components as interfaces,this method divides wing or fuselage structure into several stages as super elements along the longitudinal direction.Each super element is composed of many rod elements and plate elements in plane stress.According to the characteristics of load and deformation of the thin-walled box,it is assumed that the cross-section is absolutely rigid in its self plane.Based on this hypothesis,suitable generalized displacements and generalized forces are defined on the interface of superelement,so it can reduce the degrees of freedom of structure.Firstly,stiffness matrix of superelement,which represents the relationship between generalized displacements and corresponding generalized forces is deduced.After that,computational program is written in Matlab language to calculate the stress-displacement status for thin-walled box.Several structure examples under mechanical and thermal load are calculated.By comparing the results from superelement method with those from analytical method?experiment and FEM software Abaqus,the validity of superelement method is verified.Meanwhile,affecting factors of calculation accuracy and results characteristics are analyzed and some useful conclusions are obtained.At last,dimension optimization of two thin-walled boxes is carried out using superelement method under full-stress criterion.It is shown that superelement method can be used to perform structure configuration.