Aluminum Alloy Space Grid Structure Joint Performance And Overall Stable Research

As a lightweight,high-strength and corrosion-resistant material,aluminum alloy has been widely used in space structures.Due to the poor weldability of aluminum alloy materials,bolted connections are the most common form in aluminum alloy structures.At present,the joint design and structural analysis methods of aluminum alloy structures are consistent with steel structures in many aspects.However,the elastic modulus of aluminum alloys is only about 1/3 of that of steel.The internal force distribution of bolted and the overall spatial grid structure stability is closely related to the elastic modulus of the material.Many studies have also shown that the internal force distribution characteristics and structural stability of bolted joints of aluminum alloy space grid structures are significantly different from those of steel structures,and the joint force characteristics and structural stability analysis methods need to be further studied.Therefore,this paper studies the non-uniform characteristics of internal force distribution and overall stability analysis methods for bolted connections of aluminum alloy structures.The main contents include:(1)The problem of uneven shear force distribution of shear length connection of aluminum alloy bolts group is studied.Firstly,the internal mechanism of the uneven distribution of the shear force of the bolt group was revealed through theoretical analysis.It was found that the influence of the shear stiffness of the bolt,the material of the connection plate,the connection length,and the cross-sectional area of the connection plate would affect the uneven distribution of the shear force.In this paper,a large number of numerical simulations are carried out for the above influencing factors,and the results obtained from theoretical analysis are mutually verified.Finally,a practical calculation method for the shear force distribution of the bolt group is obtained through theoretical derivation.(2)The distribution characteristics of the axial force of the aluminum alloy bolt-sphere joint threads under tensile load are studied.Firstly,a refined finite element model was established,and parametric analysis was performed on all factors that may affect the axial force distribution of the thread.It was found that the sphere material and the screw depth of the bolt were the most important factors.Then,based on the simulation results,the distribution characteristics of the axial force of the thread under the elastic phase and the failure load were investigated.Finally,a simplified mechanical model of the joint was established and the theoretical derivation was established.The calculation formulas of the threads axial force distribution and tensile bearing capacity of the aluminum alloy bolt-sphere joint were obtained by combining the simulation results.(3)Research on the overall stability analysis method of aluminum alloy single-layer reticulated shells.This paper explores the modeling methods that can consider the overall defects of the reticulated shell,the defects of the members and the stiffness of the joints,and then studies the influence of the direction of the defect of the member and the amplitude of the defects on the overall stable bearing capacity of the reticulated shell.The reasonable defect amplitude of the aluminum alloy member is shown.Then,a large number of numerical simulations of aluminum alloy reticulated shells with different spans,vector-span ratios and cross-sections were carried out.Finally,based on the simulation results,a set of stability analysis methods for aluminum alloy structures considering member instability was proposed.