A Research On Assembly Tolerance Analysis Method Of Composite Elevator For Spring-in Deviation

Composite material has the advantages of high specific strength,high specific modulus,good fatigue performance and strong corrosion resistance.The composite elevator is a typical structural part of the aircraft.Its assembly accuracy and performance directly affect the flight performance of the aircraft.In this paper,the assembly tolerance analysis method of composite elevator is studied from three aspects: the maximal clamping force that can be applied to composite C beams,the tensile strength of countersunk bolts and the transmission of assembly deviation.The main research work includes the following three parts:(1)For the Spring-in deviation,a threshold range in which the C-beam can be applied with a variable thickness and opening feature can be applied.A finite element analysis model of composite C-beam is constructed.The user material(UMAT)subroutine is written based on the three-dimensional Hashin criterion in order to predict the failure mode of composite C-beam.Typical composite C-beam specimens with variable thickness and open-hole are designed and fabricated.The tensile fixtures are fabricated to carry out the mechanical test of composite C-beam specimens.The experimental data proves that the effectiveness of the proposed finite element analysis model of composite C-beam.Based on the proposed FEA model of composite C-beam,the threshold of clamping force at the geometrical features such as variable thickness and open-hole is obtained.It provides the reference for subsequent modification of composite C-beam assembly deviation.(2)Based on the FEA model and experimental data,the effect of the hole’s deviation on the mechanical properties of the countersunk bolted joint is obtained.The finite element analysis model of the countersunk bolted joint of the composite plate and the metal plate is constructed.The tensile experiments of composite material and metal countersunk bolted joints are carried out.The experimental data proves the effectiveness of the FEA model.Based on the design of experiment method,the effect of hole’s deviation on the mechanical properties of the countersunk bolted joint is obtained.Analysis of variance(ANOVA)method is used to investigate the interaction between depth and angle on the tensile strength of bolted joints.The results show that the depth deviation has a greater influence on the tensile strength of the bolted joint structure than the angle deviation.(3)An assembly tolerance analysis model for composite elevators is established.Assembly tolerance is optimized by the proposed model with the binary search method.Based on the assembly information of composite elevators,such as assembly sequence,part deviation and constraint relationship,assembly tolerance model of the composite elevator is constructed in 3DCS software.Inputting the initial tolerance of each component,the Spring-in deviation and other information is obtained.The modified density function is used to represent the effect of the clamping force on the assembly deviation of the composite elevator.The principal component analysis method(PCA)is used to determine the coordination scheme of multiple clamping forces.Based on the results of assembly tolerance analysis,the initial tolerance scheme is optimized with the binary search method.