基于SYSWELD管板焊结构焊接变形的数值模拟
发布时间：2019-05-19 17:20
【摘要】：固定式管板换热器在压力容器、石油、化工、暖通等各行业中得到了广泛应用。众多换热管和管板之间的焊缝导致换热器产生较大的焊接变形,如果控制不当,会恶化管板的受力状态,导致密封不严,甚至管子拉脱等严重后果。因此预测和控制换热器的焊接变形具有重要的工程应用价值。本文设计组装了旋转焊接装置,在此基础上搭建了基于国产机器人的管板换热器自动化焊接试验平台,实现了单换热管与管板的自动焊接,获得了良好焊缝成形的接头;采用热电偶测温仪测量了焊趾附近指定点的温度,获得了这些点的热循环曲线;利用盲孔法测量了焊缝附近应力。采用Sysweld软件建立了单换热管与管板焊接的局部模型,对热源进行了校核。局部模型的计算结果表明,单换热管焊接时,残余应力呈中心对称分布;在焊缝附近切向残余应力为拉应力,随着距焊缝距离增加逐步过渡为压应力;在焊缝附近径向应力为拉应力,随着距离焊缝越远径向残余应力逐渐减小,在边缘处径应力趋近于0。残余塑性应变主要分布在焊缝及热影响区内,确定了以热影响区边界为准,确定宏单元尺寸。为了提高计算效率,根据换热器的实际情况,提出缩小局部模型尺寸的方法。利用总散热能量相等的原理计算并修正得到了等效散热系数,最终确定等效散热系数为440W/(m2 · K)。利用逐步缩小范围的方法确定了实际的弹性拘束大小,通过对不同影响因素的综合分析,确定了轴向温度力、拉压刚度和弯曲刚度三个主要影响因素,以此为基础拟合出了不同条件下的弹性拘束计算公式,并对公式进行了验证。利用"局部-整体"映射有限元法对管板换热器整体变形进行预测,研究了不同焊接顺序对焊接变形的影响,通过对5种焊接顺序下的整体变形对比,得出:由内向外对称分布的焊接顺序下,管板换热器整体变形量最小。通过对比不同局部模型下管板换热器的整体变形,验证了本文提出的缩小局部模型尺寸的方法的可行性。
[Abstract]:Fixed tubesheet heat exchanger has been widely used in pressure vessel, petroleum, chemical industry, HVAC and other industries. The welding seam between many heat exchanger pipes and tubesheet leads to large welding deformation of heat exchanger. If it is not controlled properly, it will deteriorate the stress state of tubesheet, resulting in lax sealing and even tube pulling off and so on. Therefore, it is of great engineering application value to predict and control the welding deformation of heat exchanger. In this paper, the rotating welding device is designed and assembled, on the basis of which the automatic welding test platform of tubesheet heat exchanger based on domestic robot is built, the automatic welding of single heat exchanger and tubesheet is realized, and the good weld forming joint is obtained. The temperature of the specified point near the welding toe was measured by thermocouple thermometer, and the thermal cycle curves of these points were obtained, and the stress near the weld was measured by blind hole method. The local model of welding between single heat exchanger pipe and tubesheet is established by Sysweld software, and the heat source is checked. The calculation results of the local model show that the residual stress is centrally symmetrical in the welding of the single heat exchanger pipe, and the tangential residual stress near the weld is tensile stress, which gradually changes to compressive stress with the increase of the distance from the weld. The radial stress near the weld is tensile stress, and the radial residual stress decreases gradually as the distance weld gets farther away, and the radial stress approaches to 0 at the edge of the weld. The residual plastic strain is mainly distributed in the weld and the heat affected zone, and the macro element size is determined based on the boundary of the heat affected zone. In order to improve the calculation efficiency, according to the actual situation of the heat exchanger, a method to reduce the size of the local model is put forward. Based on the principle of equal total heat dissipation energy, the equivalent heat dissipation coefficient is calculated and modified, and the equivalent heat dissipation coefficient is determined to be 440W/ (m2 K). The actual elastic restraint size is determined by the method of gradually narrowing the range. through the comprehensive analysis of different influencing factors, three main influencing factors, axial temperature force, tension and compression stiffness and bending stiffness, are determined. On this basis, the formulas for calculating elastic restraint under different conditions are fitted, and the formulas are verified. The "local-global" mapping finite element method is used to predict the overall deformation of tubesheet heat exchanger, and the influence of different welding sequence on welding deformation is studied. The global deformation under five welding sequences is compared. It is concluded that the overall deformation of tubesheet heat exchanger is the smallest under the welding sequence distributed symmetrically from inside to outside. By comparing the overall deformation of tubesheet heat exchanger under different local models, the feasibility of the method proposed in this paper to reduce the size of local model is verified.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG404
[Abstract]:Fixed tubesheet heat exchanger has been widely used in pressure vessel, petroleum, chemical industry, HVAC and other industries. The welding seam between many heat exchanger pipes and tubesheet leads to large welding deformation of heat exchanger. If it is not controlled properly, it will deteriorate the stress state of tubesheet, resulting in lax sealing and even tube pulling off and so on. Therefore, it is of great engineering application value to predict and control the welding deformation of heat exchanger. In this paper, the rotating welding device is designed and assembled, on the basis of which the automatic welding test platform of tubesheet heat exchanger based on domestic robot is built, the automatic welding of single heat exchanger and tubesheet is realized, and the good weld forming joint is obtained. The temperature of the specified point near the welding toe was measured by thermocouple thermometer, and the thermal cycle curves of these points were obtained, and the stress near the weld was measured by blind hole method. The local model of welding between single heat exchanger pipe and tubesheet is established by Sysweld software, and the heat source is checked. The calculation results of the local model show that the residual stress is centrally symmetrical in the welding of the single heat exchanger pipe, and the tangential residual stress near the weld is tensile stress, which gradually changes to compressive stress with the increase of the distance from the weld. The radial stress near the weld is tensile stress, and the radial residual stress decreases gradually as the distance weld gets farther away, and the radial stress approaches to 0 at the edge of the weld. The residual plastic strain is mainly distributed in the weld and the heat affected zone, and the macro element size is determined based on the boundary of the heat affected zone. In order to improve the calculation efficiency, according to the actual situation of the heat exchanger, a method to reduce the size of the local model is put forward. Based on the principle of equal total heat dissipation energy, the equivalent heat dissipation coefficient is calculated and modified, and the equivalent heat dissipation coefficient is determined to be 440W/ (m2 K). The actual elastic restraint size is determined by the method of gradually narrowing the range. through the comprehensive analysis of different influencing factors, three main influencing factors, axial temperature force, tension and compression stiffness and bending stiffness, are determined. On this basis, the formulas for calculating elastic restraint under different conditions are fitted, and the formulas are verified. The "local-global" mapping finite element method is used to predict the overall deformation of tubesheet heat exchanger, and the influence of different welding sequence on welding deformation is studied. The global deformation under five welding sequences is compared. It is concluded that the overall deformation of tubesheet heat exchanger is the smallest under the welding sequence distributed symmetrically from inside to outside. By comparing the overall deformation of tubesheet heat exchanger under different local models, the feasibility of the method proposed in this paper to reduce the size of local model is verified.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG404
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相关期刊论文 前10条
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2 蔡志鹏,赵海燕,鹿安理;提高弹性能模型方法预测焊接变形实用性的研究[J];机械工程学报;2003年07期
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