【作者】 付翀；

【导师】 张敏；

【作者基本信息】 西安理工大学 ， 材料加工工程， 2006， 硕士

【摘要】 焊接接头是一个力学和几何上极为复杂的不均匀结构体。为了深入研究焊接接头断裂性能及其评定工程化方法，本文对含Ⅰ+Ⅱ应力复合型裂纹焊接接头进行了深入的分析，并提出其安全性评价的工程化方法。 针对含Ⅰ+Ⅱ应力复合型裂纹的焊接接头，应用弹塑性有限元方法分析了其裂纹尖端应力场的分布规律。并对不同加载角度、不同组配焊接接头的COD断裂参量及其复合角进行了数值计算。进一步基于数值解的结果，讨论了加载角度和接头强度组配对焊接接头中应力复合型裂纹的断裂行为及其断裂参量的影响机制。研究结果表明，无论何种强度组配，焊接接头裂纹尖端应力场等值区的分布是不对称的。裂端上部发生锐化现象，而裂端下部发生钝化现象。断裂参量COD值的大小同时受到加载角度以及接头组配的影响。加载角度对焊接接头中复合型裂纹Ⅰ，Ⅱ型裂端场的主导性存在很大的影响，而接头强度组配对其影响不明显。因此，在进行含应力复合型裂纹的焊接接头的COD断裂参量的计算时，必须考虑这些因素的综合影响作用。 最后，本文结合工程实际，对含Ⅰ+Ⅱ应力复合型裂纹的焊接接头中，断裂驱动力的变化规律进行了讨论，并对安全性能评定的工程化方法进行了研究，提出了断裂参量COD及其复合角的工程估算公式。估算结果与有限元结果相比，吻合较好。更多还原

【Abstract】 It is very difficult to assess the integrity of welded joints because it is a complexity structure with mechanical heterogeneity and geometrical uncontinuity. In this paper, at first, the fracture behaviors of welded joints containing the mixed mode Ⅰ+Ⅱ crack is investigated, and then a new engineering treatment method to assess the integrity of welded structure containing defects is developed.By using elasto-plastic finite element method, the crack-tip field of welded joint, which containing the mixed mode Ⅰ+Ⅱ crack, are analyzed. Based upon, the fracture parameter COD and its mixity angles of mismatched welded joints are calculated under the different loading level and angle. However, the influences factors of the loading angles and the mis-matched strength of welded joints are analyzed in detail also. The simulation results show that, the crack tip stress-strain field is asymmetrical, the upper shape of crack-tip is sharpened, and the lower shape of crack-tip is blunted obviously. For the more, the fracture parameter COD changes with the loading angle and strength matching parameters of welded joints. The effect of loading angle on the domination of mode I or II of the mixed mode Ⅰ+Ⅱ crack is evident, and in the same time, the effect of strength matching is less than that of load angles. And the values of mixity angles depend on the loading angles and strength matching parameters respectively. As a result, the above factors must be considered during the calculation of the fracture parameter COD of welded joints containing the mixed mode Ⅰ+Ⅱ cracks.In the end, based upon the engineering appliance, the fracture driving forces of the mismatched welded joints containing the mixed mode I + II crack are investigated, and the engineering treatment formulation of fracture parameter COD and its mixity angles are obtained by the curves simulation methods also. It can be seen that the engineering estimation solution is in good according to the results of finite element analysis.更多还原