Fracture Reliability Research On The Structure With Non-through Cracks

The non-through cracks exist widely in the engineering structures. The traditional methods for security evaluation and design are limited because of the uncertainty of factors such as material character, external load, and geometrical dimension. Hence, considering the randomness of the parameters, the fracture reliability analysis and research on the structure with non-through cracks have important practical significance and larger theoretical values. In this paper, the fracture reliability of structures with surface and embedded cracks is studied based on the line-spring model theory. The main achievements are summarized as follows:1. A reliability analysis method for fatigue propagation life of surface cracks is presented based on the line-spring model and Paris formula, with combining the Latin hypercube sampling method. The fatigue life is obtained with the given reliability and the reliability is obtained with the given fatigue life, in consideration of the uncertainty and correlation of parameters. The correctness of this method is demonstrated through comparing the results with those given in the literature.2. The analysis methods, which of reliability and reliability sensitivity for residually stressed structure with single surface crack and structure with multitudinous coplanar surface cracks, are stablished through combining the line-spring model with analysis methods of reliability and reliability sensitivity. The failure probability and reliability sensitivity are obtained and some conclusions are drawn. The efficiency and universal are demonstrated through comparing the results with those obtained by other methods.3. The line-spring model for a center embedded elliptical crack in non-uniform stress fields, which is along the thickness direction of the plate, is established based on the linear line-spring model for embedded cracks in this paper. The two dimensional weight function is used to transform the non-uniform stress field to an equivalent uniform one. The singular integral equations are formulated and the numerical results are gained by Gauss-Chebyshev method. The results are in good accordance with those given in the literature, and the rationality and reliability of this model are demonstrated.4. The reliability and reliability sensitivity for structure with embedded cracks are analyzed based on the line-spring model for an embedded crack in an infinite plate and the line-spring model for a center embedded crack in non-uniform stress fields established in the 4th chapter. The failure probability and reliability sensitivity are obtained and some conclusions are drawn.5. The software for analyzing the fracture reliability of the structures with non-through cracks is studied. The interface of the software is complied with VB and MATLAB connected by Active X technique, and good visualization of the input, processing and output of dates is obtained. This software has convenient operation and good stability and is worth to apply in engineering projects.