Mode Buried Elliptical Crack In Thick Wall Pipe Finite Element Analysis And Research

Thick-walled pipe is vital component of the industrial pressure pipe. For a long time, there are many flaws in the pipe processing, which has not been the perfect solution.Compared with undefective pipe, adverse working condition gives the defective pipe much greater chance of fatigue cracking. Considering the importance of the pipe and the actual needs of fracture safety assessment, this article gives a detailed and in-depth finite element analysis to the thick-walled pipe with burial elliptic crack and obtains some useful research results:1. After trying kinds of three-dimensional crack modeling method, this article develops a more convenient one. At the same time, the corresponding command stream files are built up. Using these files, you can get access to your desired results easily.2. Under internal pressure, this article studies the equivalent stress distribution and finds that there are many difference between smooth pipe and defective pipe. At the same time, the linear elastic stress intensity factor K, is calculated. And then, this paper studies the variation law of K, with various parameters, including c/a、c/t、Ro/Ri、 P.3. Under just one loads of internal pressure, this article studies the expanding law of plastic zones and the final failure mode. After initial loading, the vicinity of the crack free surface yields firstly but does not form plastic hinges. With further increase of internal pressure, redistribution of stress and strain occurred. And the axial expansion of plastic zones is much faster than the expansion along thickness direction. When the internal pressure reaches the limit state, the inner surface of pipe are completely yielding and the plastic zones are fully penetrating pipe wall, which leads to pipe failure. So the failure mode is overall failure.4. Under just one loads of internal pressure, this article calculates plastic limit load and studies the law of changes with influential factors. And then it comes to the conclusion that we can get much greater PL values with greater K、greater Ro/Ri、lower c/t、greater c/a.