Development of the Method of Crack Growth Analysis and Its Applications

点击翻译按钮获取中文摘要

A typical fracture of machines and structures is preceded by a propagation and coalescence of minute cracks that exist inside the body in advance or outbreak during life time. Therefore, in the prediction of the behavior of fracture, it is important to grasp a path of crack propagation and how to coalesce themselves during growth under given loading conditions.In order to realize an ideal simulation of crack propagation, the following two conditions are essential. The first is to use an adequate numerical scheme which can calculate the singular stress fields at the tip of an arbitrary shaped crack as accurately and effectively as possible.The second is to choose an adequate criterion that predicts the direction of crack propagation. In a conventional analysis, a maximum principle stress criterion or a local symmetry criterion is employed usually. The farmer enables relatively high-efficiency prediction but sometimes leads poor numerical results. On the other hand, the latter is reliabl … More e but too expensive to apply the crack propagation simulation among multiple cracks.In order to overcome the first condition, the Body Force Method, known as a powerful numerical method especially for crack problems is employed. The developed system can treat all two-dimensional crack problems essentially even in a case for extremely complex crack geometry where a number of branches and kink points are involved. In order to overcome the second condition, new prediction scheme for the direction of further crack propagation using a resultant force at the crack tip field is proposed. Through the numerical tests for many kinds of crack propagation problems, it was verified that the proposed criterion is much effective and provides highly accurate solution than ordinary methods.The developed crack propagation analysis system was applied many kinds of problems such as the crack propagation in a standard specimens, crack coalescence problem in a rectangular plates and failure simulation among multiple cracks in brittle materials under compressive stress. Less