【作者】 张鹏；

【导师】 杨志勇； 邢羽翔；

【作者基本信息】 武汉理工大学 ， 防灾减灾工程及防护工程， 2013， 硕士

【摘要】 在钢结构焊接和冷却过程中,由于局部短时间内高度集中的热输入使得焊缝区和母材区将产生残余应力和应变。焊接构件中的残余应力常常达到甚至超过母材和焊缝金属的屈服强度。焊接残余应力是结构应力腐蚀开裂、疲劳破坏和脆性破坏重要诱因之一。残余应力可以使得构件局部先于其它部分进入塑性状态,从而降低构件的稳定承载能力。目前,针对薄板的焊接残余应力开展的研究较多,但针对厚板和特厚板的相关研究很少。因此,对钢结构焊接残余应力特别是厚板焊接残余应力的研究显得至关重要。本文对焊接残余应力数值模拟领域的研究进展作了综述,讨论了焊接温度场和应力场的计算理论,并对有限元模型的建立作了详细介绍。本文研究对象为50mm厚的低合金高强度钢板(42级A572),焊接方法为自动埋弧焊,焊缝形式及尺寸参照纽约时报广场大楼角柱焊接加工工程。利用大型有限元软件ANSYS对“单道焊”和“双道焊”两种焊接工艺下构件的温度场和应力场分别进行了三维数值模拟。模拟过程中的关键技术有：(1)对焊接热源三维模型的简化处理；(2)单元生死技术被用来模拟焊缝金属的逐步填充过程；(3)接触单元被用来模拟钢板接触面的接触传热和可受压的特性；(3)利用间接法对焊接温度场和应力场进行耦合分析,成功获得了两种焊接工艺下钢板温度场和应力场的分布。计算结果与实际情况基本吻合,但精确度仍需通过实验进一步验证。通过不同时刻温度云图和多个采样点的热循环曲线来描述钢板温度场的变化情况；构件截面的应力分布情况通过应力云图和三维图像进行了对比分析。对比分析发现：(1)单道焊工艺对母材影响较严重,焊接热影响区范围较大,构件截面应力大幅波动的区域范围较大,角变形也较大；(2)双道焊工艺对母材影响相对较小,焊接热影响区范围大幅减小,构件截面应力大幅波动的区域范围明显减小,但是应力波动幅度相对较大,角变形有所减小。本研究成果对简化厚板焊接数值模拟和优化焊接工艺有一定的指导意义。此外,基于本课题研究成果,纽约时报广场大楼钢角柱整体焊接残余应力研究即将开展。更多还原

【Abstract】 In the welding process and after the welding, the residual stress and deformation will be generated in the weld and base metal due to the highly concentrated and transient thermal input. Residual stress in the welded structure often reached or even over the yield strength of base metal and weld. Residual tensile stress is a main factor resulting in stress corrosion cracking, fatigue damage and brittle fracture. And the residual stress enable partial structure entering plastic situation prior than other parts, which can decreasing the stable bearing capacity of the components. Until now, lots of researches have been carried on the thin plate residual welding stress, while few researches involved in the welding residual stress analysis of thick and super-thick steel plate. Therefore, it is necessary to investigate the feature of welding residual stress distribution of welding structures, especially for the thick steel plates.This paper reviewed the research development of welding residual stress numerical simulation field, discussed the calculate theory of welding temperature and stress, the numerical simulation model establishment process were also presented. The research object of this paper is two high strength low alloy steel plates which thickness is50mm(Grad42, A572), the welding method is automatic submerged arc welding, and the weld form and dimension is refer to the welding project of Times Square corner steel column. Three dimensional numerical simulations were carried out for Single-pass welding and Double-pass welding process respectively by finite element software ANSYS. The key techniques used in this simulation are:(1)The welding heat source simplification;(2) The element birth and death technique was adopted for the weld metal filling process simulation;(3)The contact element was used to fix the problem of thermal contact conductance and compressive property of the plates interface;(3)The indirect method was performed for the welding temperature field and stress field coupling analysis, and both temperature field and stress field were obtained successfully. The results were basically tallies with actual situation, but the experiment verification is also needed.The cloud atlases and cyclic curve of sampling points were used to represent the changing situation of plate temperature field, and the stress cloud atlases and three-dimensional picture were used for the stress field representation. Comparative analysis result shows:(1) for the single-pass welding, the welding influence on base metal is serious, the heat-affected zone is large, the cross section has large zone with large stress fluctuating, and the angular deformation is large.(2) for the double-pass welding, the welding influence on base metal is declined; the scale of the heat-affected zone decreased dramatically; the cross section has a small zone with large stress fluctuating, while the extent of the stress fluctuating is serious; the angular deformation is decreased slightly. The research result could offer reliable reference for the thick steel plate welding numerical simulation simplification and the welding technology optimization. Besides, this research provides a basis for the entire corner steel column welding stress simulation of Times Square in the further research.更多还原