大型壳体结构焊接变形及残余应力调控方法研究

发布时间：2018-07-12 18:12

本文选题：大型壳体结构 + 组合热源模型　；参考：《北京交通大学》2016年博士论文

【摘要】：核电安全壳钢衬里、船舶外壳等大型焊接壳体结构,由于其体积庞大,结构复杂,易产生焊接变形超差和残余应力过大等问题,这些问题是大型壳体结构焊接制造与施工过程中亟待解决的难题。焊接模拟技术可以预测焊接变形和残余应力,可为焊接变形应力的调整与控制提供理论依据和指导。然而焊接模拟的准确性受到焊接热源模型准确性的影响,制约了焊接模拟技术的有效指导作用。本文提出了基于多项式曲线拟合焊缝横截面轮廓的组合热源模型。该模型由旋转体和高斯面两部分构成,采用多项式曲线拟合焊缝横截面轮廓并将其作为旋转体边界,对旋转体内部施加热流密度建立熔池内部热流分布函数,焊缝表面采用高斯面热源模型建立电弧对熔池表面的热辐射关系。组合热源模型具有求解参数少、模拟准确性高特点,与传统双椭球、高斯体热源模型相比,焊缝横截面模拟准确度分别提高16.0%和19.0%,焊接变形模拟精度分别提高12.7%和1 5.9%。依据塑性应变区不均匀体积收缩引起的收缩力和弯矩与壳单元模型收缩力和弯矩分别相等的关系,建立了对焊等效壳单元模型。该模型可解决体单元模型单元数量过大及焊接大变形导致的热机耦合模拟不收敛问题,采用等效壳单元模型建立的安全壳钢衬里模拟变形与试验测试结果对比最大误差为21.3%。提出了高斯特性热源平行加热调控焊接应力方法。采用两束高斯特性氧乙炔火焰作为热源,平行加热焊趾两侧一定距离部位的母材,通过焊缝材料的塑性变形实现焊接拉应力的释放。该方法可实现大型壳体结构焊接应力的灵活调控。此外基于组合热源模型和高斯特性热源平行加热调控应力方法,开展了平行加热工艺参数对焊接应力的影响研究,建立了核电安全壳钢衬里焊接接头的残余应力调控工艺窗口。残余应力测试结果表明,平行加热处理后焊缝表面纵向残余拉应力降低45.0%,横向残余应力降低3.4%。本文针对核电、船舶等大型壳体结构焊接特点,开展了焊接变形及应力的模拟与调控方法研究。本研究对推动焊接模拟技术在大型壳体结构焊接中的推广应用、促进我国核电技术的发展具有重要的学术意义和工程应用价值。
[Abstract]:Large welded shell structures, such as steel lining of nuclear containment and ship shell, are easy to produce problems such as excessive welding deformation and excessive residual stress due to their large size and complex structure. These problems are urgent to be solved in the welding manufacture and construction of large shell structures. Welding simulation technology can predict welding deformation and residual stress and provide theoretical basis and guidance for welding deformation stress adjustment and control. However, the accuracy of welding simulation is affected by the accuracy of welding heat source model, which restricts the effective guidance of welding simulation technology. In this paper, a combined heat source model based on polynomial curve fitting for cross section profile of weld seam is proposed. The model consists of a rotating body and a Gao Si surface. The cross-section profile of the weld is fitted by polynomial curve and used as the boundary of the rotating body. The heat flux distribution function in the molten pool is established by applying the heat flux density to the body of the rotary body. The heat radiation relationship between arc and pool surface was established by Gao Si surface heat source model. The combined heat source model has the advantages of less solving parameters and high accuracy. Compared with the traditional double ellipsoid and Gao Si heat source model, the accuracy of weld cross-section simulation is increased by 16.0% and 19.0%, respectively, and the simulation accuracy of welding deformation is increased by 12.7% and 15.9%, respectively. The equivalent shell element model of butt welding is established according to the relationship between the contraction force and bending moment caused by inhomogeneous volume shrinkage in plastic strain region and the contraction force and bending moment of shell element model respectively. The model can solve the problem of non-convergence of thermo-mechanical coupling simulation caused by excessive number of elements in the model and large welding deformation. The maximum error between the simulated deformation of containment steel lining established by the equivalent shell element model and the test results is 21.3b. A method of controlling welding stress by parallel heating of Gao Si characteristic heat source is proposed. Using two Gao Si characteristic oxyacetylene flame as heat source, the welding tensile stress is released by plastic deformation of weld material by parallel heating of the base metal at a certain distance between the two ends of the weld toe. This method can realize the flexible control of welding stress of large shell structure. In addition, based on the combined heat source model and Gao Si characteristic heat source parallel heating control stress method, the effect of parallel heating process parameters on welding stress is studied, and the residual stress control process window of nuclear containment steel lining welded joint is established. The results of residual stress test show that the longitudinal residual tensile stress of weld surface decreases by 45.0 and the transverse residual stress decreases by 3.4after parallel heating treatment. According to the welding characteristics of large shell structures such as nuclear power and ships, the simulation and control methods of welding deformation and stress are studied in this paper. This study has important academic significance and engineering application value in promoting the application of welding simulation technology in welding of large shell structure and promoting the development of nuclear power technology in China.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG404

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