| Abstract:Modern aircraft is becoming large-scale device. Safety, comfort, pursuing aircraft reduction operating costs and environmental-friendly are the aims of designers. In order to reaching the goal, light-aircraft is one of important ways besides environmental-friendly and high-efficieny engineer. On the other hand, it becomes important that how to improve safety and fatigue property of aircraft. Researchers in the world are studying new lighter materials and fatigue of material since plane born at the beginning of the last century. A lot of design ideas were put up to improve fatigue life of structure. Selective reinforcement structure is one of important technologies.This paper was funded through major project of state major project ’Research on the integrated design technology of aluminum lithium alloy’. Research work went on the crack inhibition mechanism of the aluminum lithium alloy by theoretical calculation, experiment and finite element simulation methods. The work is mainly including bonding technology, optimization of bonding methods and research of selective reinforcement structure, which including internal stress, crack propagation mechanism. This will offer the reference for aircraft structure design and manufacture of China. The main content includes:(1) Key process of aluminum alloy bonding is broken through in technical field. The optimized parameters are determined to handle surface of the alloy.Anodization process are optimized by orthogonal experimental method; The aim is to explore the best alloy surface treatment technology improving bonding properties to fit the alloy studied in paper; this will provide a process for selective reinforcement structure of aluminum lithium alloy.(2) Cohesive zone model of mixed failure on the bonding specimens is founded by commercial analysis software MARC.MSC, basing on the boundary layer theory. Singularity of stress on the bonding edge of bonding sample are analyzed and put forward optimized formula to improve bonding joint stress calculation estimating the joint edge peak stress. On base of these analyses, parameters of material and dimension (thickness, length of overlap, elastic modulus and thickness of adhesive, and so on) were researched, all these work will provide useful reference for improving bonding process.(3) Thermal residual stress of aluminum lithium alloy selective reinforcement structure during curing is studied by finite element model method, and theoretical calculation and experimental methods is used to verify the validity of the finite element method.(4) Crack growth rate of aluminum lithium alloy selective reinforcement structure with two different reinforced patches (Titanium alloy and GLARE composite plate) under varied cyclical loading is studied. Effect on crack growth rate of reinforced plate dimensions of Ti alloy plates was researched. In addition, crack growth rate of selective reinforcement structure by titanium alloy bolted and bonding was studied. At the same time, preliminary study was carried out on the relationship of matching between aluminum alloy and reinforced plate, connective mode. All these work will provide effective reference to the selective reinforcement design.(5) Experimental data and finite element method are used to study relationship between crack growth rate of crack, crack length and stress of crack tip in selective reinforcement strength structure in this paper. The mechanism of crack inhibition in reinforcement structure was revealed. A new formula was put forward based on the classical Paris formula which fit selective reinforcement structure fatigue crack propagation in this paper, using the method of experiment and finite element method, and validity of the predicting formula is verified by experimental results. |
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