【作者】 盛燕；

【导师】 孙建刚；

【作者基本信息】 大庆石油学院 ， 防灾减灾工程及防护工程， 2007， 硕士

【摘要】 随着断裂力学理论的不断成熟以及计算机技术的飞速发展,断裂力学在工程实际中得到了广泛的应用。目前,应用断裂力学理论对在役压力管道进行安全评定,具有十分重要的实际意义。但是,对于一些特殊的含有裂纹缺陷的结构进行安全评定仍然缺乏可以直接利用的断裂参数结果。本文以断裂力学为基础,采用有限元分析方法,借助ANSYS有限元分析软件,建立了不同情况下的含有穿透裂纹的直管道有限元模型。进行分析计算,给出在线弹性条件下不同情况穿透裂纹的应力强度因子K I值;进一步换算为工程实际中易于应用的应力强度因子修正系数F,采用回归拟合技术,给出了修正系数F的表达式。并依据本文方法,对含裂纹缺陷的压力管道进行剩余强度评价,与相关文献进行比较分析,说明了本文方法的可行性。本文工作的主要内容包括:1.依据断裂力学的理论只是,分析研究平面裂纹尖端的应力强度因子的求解方法,应用ANSYS有限元分析软件,建立平板有限元模型,验证本文所要采用Shell63单元和建模方法的准确性和可靠性,为本文以后工作打下坚实的基础。2.以ANSYS提供的APDL语言编写相应程序,建立不同情况下的含有穿透裂纹直管道有限元模型,在内压载荷作用下,分析研究裂纹周围应力、应变场的分布,计算出线弹性条件下的应力强度因子K I值。3.提取有限元计算结果,利用MATLAB数据处理软件绘制出应力强度因子随着不同影响因素的变化关系图,分析讨论其变化规律。4.进一步求解应力强度因子修正系数F值,利用MATLAB数据处理软件绘制成曲线图,总结讨论其变化规律,并利用非线性最小二乘估算法进行回归分析得到应力强度因子修正系数F的表达式。5.初步对含穿透裂纹缺陷的压力管道结构进行剩余强度评价,通过分析研究,进一步验证本文公式的准确性。更多还原

【Abstract】 Fracture mechanics is applied widely in the practical engineering along with the theory of fracture mechanics mature as well as the computer technology developed rapidly. At present, it has practical significance that the theory of fracture mechanics is used in the safety assessment of pipes which in service. However, the result of the fracture parameters is can’t be used directly to make safe estimation for the structure which has the especial cracks. In this paper, based on fracture mechanics, the straight pipe which contained through-wall cracks are analyzed by the finite element analysis (FEA) method and ANSYS software. Finite element models are established for straight pipe which contain through-wall crack in different situations. They are analyzed and calculated. The stress intensity factor ( K I) which contained the through-wall cracks in different situations in linear-elasticity is calculated, and is transformed to correction coefficient F of stress intensity factor. Fitted method is adopted, and expression of correction coefficient F of stress intensity factor is given. According to the method in this paper, residual strength assessment of pressure-pipes which contained cracks is did. Compared with corresponding papers, the feasibility of this method is expressed.The main contents in this paper include:1 According to the theory of fracture mechanics, the way for solution of plane crack top’s stress intensity factor is analyzed and studied; the ANSYS software of finite element analysis is applied to set up plane finite element model;the accuracy and the reliability of modeling as well as the application of the Shell63 unit is confirmed in this paper, and foundation is built stably for later work.2 APDL is applied to write corresponding procedure; models for through-wall crack of straight pipeline in different situations are established by FEA; stress around crack and distribution of strain field under inner- pressure are analyzed, K I in linear-elasticity is calculated.3 The result of the finite element is picked up, charts of K I changing along with the different influence factors are plotted, and rule of change is analyzed and discussed.4 The stress intensity factor shape correction coefficient F is solved further, graphs are drawn up by MATLAB, its change rules are summarized and discussed, the correction coefficient of K I is obtained through non-linear the least square estimation method.5 The residual strength assessment of the pressure pipes which contained the through-wall crack is did initially. Through analyzing and studying, the accuracy of formulas in this paper are confirmed further.更多还原