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Focus on the problem that fracture characteristic of integral structure is worse than composite structure, this paper studied the influence of anti-crack rib design parameters on the fracture characteristic of integral wing-spar through calculating the stress intensity factor and constructing support vector machine agent model. Results indicated that crack arresting rib could enhance the fracture characteristic of integral wing-spar well. When crack extended to crack arresting rib, residual strength of integral wing-spar will enhance for about 36%, crack growth life enhance about 13.5%; the best location of crack arresting rib is at 1/3 the height of wing-spar. Conclusions gained could provide reference for damage tolerance design of integral wing-spar. Introduction Recent years, integral structures are widely used in the territory of aerospace engineering for its simple process technology, lighter weight when bearing same stress, fewer potential crack origin and stress concentrate position . However, lacking “natural” anti-crack component like stringer and rivet hole, seriously influenced the fracture characteristic of integral structure. NASA had done some experiments on fatigue crack growth between integral structure and composite structure , their results indicated that crack growth rate of composite structure is slower than that of integral structure when crack cross through the skin. Therefore, how to improve the fracture characteristic of integral structure becomes a research hotspot among investigators. At present, researchers home or abroad had already done some experiments and simulations to study the fracture characteristic of integral structure . Their study achievements provided some guidance for integral structure design. For example with integral wing-spar, in order to improve its fracture characteristic, we can locate crack arresting rib on the webs of wing-spar. The investigation objective of this paper is crack arresting rib of integral wing-spar. Through calculating stress intensity factor (SIF) on crack tip, and combing support vector machine (SVM) agent model, we analyzed the specific influence of anti-crack rib design parameters on the fracture characteristic of integral wing-spar. Integral wing-spar Aircraft integral wing-spar consists of upper and lower flange, webs and crack arresting rib, sectional sketch map and parameters of it are shown in Fig. 1. The value of sectional parameters is shown in Table 1. Length of the spar is 5000mm. In order to analyze the influence of crack arresting rib design parameters to the fracture characteristic of integral wing-spar, the varied range of crack arresting rib design parameters is given in Table 2. We put forward the following supposes in our research: initial crack is located in the middle of the spar, the lower flange is complete break and crack extends 25mm on the webs; according to the design requirement, when the crack extends to anti-crack rib, we regard it as the critical crack; crack growth trajectory is straight line. The sketch maps of initial crack and critical crack are shown in Fig. 2. 5th International Conference on Information Engineering for Mechanics and Materials (ICIMM 2015) © 2015. The authors Published by Atlantis Press 1492 Material of the wing-spar is 7050-T7451, elastic modulus E=70GPa, material Poisson’s ratio v=0.33, ultimate strength 511 b MPa σ = , material fracture toughness 72 IC K MPa m = .

Influence of crack arresting rib on the fracture characteristic of integral wing-spar