导　　师： 方洪渊

学科专业： 080503

授予学位： 博士

作　　者： ;

机构地区： 哈尔滨工业大学

摘　　要： 为减轻结构重量并保证结构的承载能力，高强钢以其高的强度和良好的塑韧性广泛应用于桥梁、建筑、航空航天等领域。焊接作为一种高效的连接方法，广泛应用于工程结构领域。由于焊接过程的特殊性，使得焊接缺陷不可避免，导致焊接接头容易产生低应力脆断破坏，显著降低了接头的承载能力，给焊接接头设计带来一定的局限性。为提高易产生缺陷的焊接接头的承载能力，本文从断裂力学角度出发，提出了基于应力强度因子/(K因子/)的焊接接头等承载设计思想，并给出了接头含不同缺陷时的等承载设计准则，使用该准则可以设计出承载能力与母材相当的焊接接头。 对于焊缝和母材区都含缺陷的接头而言，提出了焊缝和母材区的K因子比值与焊缝金属和母材金属的断裂韧度比值相等时即可满足等承载要求的设计思想；对于焊缝区存在缺陷而母材区无缺陷的接头而言，提出了焊缝区裂纹失稳扩展的临界应力与母材的抗拉强度相等时即可满足等承载要求的设计思想；对于焊缝区无缺陷而母材区存在缺陷的接头而言，提出了母材区裂纹失稳扩展的临界应力与焊缝区峰值应力相等且不高于焊缝金属的抗拉强度时即可满足等承载要求的设计思想；本文主要针对前两种接头的等承载设计进行讨论和研究。 本文研究了接头形状参数对含中心裂纹和单边裂纹对接接头形状因子的影响规律，研究表明，使用不考虑余高影响的传统的形状因子表达式计算含缺陷接头的形状因子是不合理的。提出了一种获得含裂纹复杂结构形状因子表达式的新方法，即首先采用有限元法研究结构各形状参数对其形状因子的影响规律，再引入一个能够统一各形状参数对形状因子影响规律的几何不连续形状协调参数，最后对具有不同形状参数结构的有限元结果以� In order to reduce weight and ensure the load carrying capacity of structure,high-strength steel is commonly used in bridges, building, aerospace fields andso on due to its high strength and good ductility. As an efficient joining process,welding has been widely used in engineering field. Weld defects can not beenavoided because of the welding particularity. It has been found that weld defectscan significantly deteriorate the load carrying capacity of joint. Typical brittlefracture is often observed in the defect-existent joint. In order to increase loadcarrying capacity of defect-existent joint, equal load carrying capacity /(ELCC/)method based on stress intensity factor is proposed by using fracture mechanicstheory. ELCC design criteria of joint with different defects are given. In order to guarantee the load-carrying capacity of under-matched joint withdefect reach that of the base metal, four different conditions have beenconsidered. The influences of joint shape parameters on shape factor ofcenter-cracked or edge-cracked butt joint are studied. The results showed that itis unreasonable to calculate the shape factor of center-cracked or edge-crackedbutt joint without considering weld reinforcement. A new approach to obtainingshape factor expression for defect-existent complicated structures is introduced.Firstly, the influences of structural shape parameters on shape factor should beinvestigated by using finite element method. Secondly, a coordinated parameterwhich can unify all influences of shape parameters on shape factor must beintroduced. Then a modified coefficient function on the basis of the traditionalshape factor expression can be obtained with regression analysis of all finiteelement results by using the coordinated parameter as the independent variable.Finally, the accurate shape factor expression considering the effect of allstructural shape parameters can be obtained. The accurate shape factorexpressions for center-cracked and edge-cracked butt joint under tensile load aregiven in this paper

关 键 词： 断裂力学 因子 等承载焊接接头 静载 疲劳 等承载设计系统

领　　域： [金属学及工艺]