Three-dimensional finite element model of a bolted joint has been developed in the non-linear finite element code MSC.Marc and attempts were made to validate it by comparing results with those of experiments and other finite element. Issues in modeling the contact between the joint parts, which affect the accuracy and efficiency of the model, were presented. Experimental measurements of surface strains and load transfer ratio(LTR) were compared with results from finite element analysis. The results show that three-dimensional finite element model of bolted joint can produce results in close agreement with experiment. Three-dimensional effects such as bolt titling, seconding and through-thickness variations in stress and strain are well represented by such models. Three-dimensional finite element analysis was also used to study the effects of different parameters on the mechanical behaviour of single lap bolted joints. The results show that straight hole, small bolt diameter, and big hole pitch are selected first for bolted joint if other conditions allowed, and effect of bolt material on LTR of joint is small for small load. Interference and pre-stress should be strictly controlled for bolted joints in order to attain the best fatigue capability of lap joint.

Three-dimensional finite element model of a cracked bolted joint has been developed in the non-linear finite element code MSC.Marc and attempts were made to validate it by comparing results with those of experiments and other finite element. Issues in modeling the contact between the joint parts, which affect the accuracy and efficiency of the model, were presented. Experimental measurements of load transfer were compared with results from finite element analysis. The results show that three-dimensional finite element model of cracked bolted joint can produce results in close agreement with experiment. Three-dimensional effects such as bolt titling, seconding and through-thickness variations in stress and strain are well represented by such models. Three-dimensional finite element analysis was also used to study the effects of hole mod and crack on the load transfer behaviour of single lap bolted joints. The results show that hole mode has big effect on load transfer of cracked bolted joint. In the whole progress of crack growth, the load transfer through bolt 1 decrease, and almost all of the load duduction of bolt 1 transfer into blot 2 rather than into bolt 3.

The arresting landing of carrier aircraft is especial dynamic problem. During this process,the gear would bear the very big dynamic load,which does the biggest harm to gear .In this paper,it analyzed the landing gear shock strut in carrier aircraft arresting landing,and aiming at the runout of shock strut and the flexibility of the landing gear by using the Lagrange equation.Then it concluded the chaging of landing gear shock strut with symmetrical and straight arresting,3m of off-center distance arresting and 2°of rolling angle arresting after simulating.The conclusion showed that the landing gear shock strut would be stable after a short time concussion;rolling and unsymmetrical affected the shock strutmore severe than off-center and symmetrical arresting,and the qualities of concussion also being more acute.

A mathematical model was developed to correlate the amplitude of the pillowing deformation of lap joints to the degree of corrosion inside the joint. Based on mathematical model, finite element techniques were used to determine the effect of pillowing in the stress in fuselage lap joints. The stress caused by the internal pressure and riveting process was taken into account, and the fuselage curvature was ignored. The results show that pillowing can significantly increase the stress in a lap joint for material loss below the detection limit of current nondestructive inspection techniques, thus increasing the risk of premature cracking. In addition, the analyses show that pillowing resulted in a stress gradient through the skin thickness, which suggest that semi-elliptical cracks with a high aspect ratio can form. In the last, the stress correction curves at the critical rivet hole were used in the AFGROW crack growth rate program to predict the residual life of corroded lap joint and the analytical results were close to available test date.

Statistical analyses on fatigue crack growth threshold under three different stress ratios have been done. By the stratified random sampling theory and the weighted least square fitting method, the test data were analyzed based on Paris crack growth rate formulation. The statistical results of the fatigue crack growth threshold under different stress ratios were obtained by linear fitting method. The results show that the fatigue crack growth threshold is influenced by stress ratio R significantly. In the slow crack growth area near the threshold, the increase of stress ratio leads to the decrease of threshold and the increase of crack growth speed. The threshold results under different stress ratios satisfy the normal distribution.