考虑焊接影响的空间结构承载力精细化有限元分析

发布时间：2019-04-19 19:33

【摘要】：大跨度空间结构具有自重轻、结构受力合理、造型变化形式多样的优良特点，使得近年来大跨度空间结构在我国取得了广泛的应用。其中管桁架结构和网壳结构是空间结构中比较常用的结构形式，而组成构件的关键在于连接方式。在焊接过程中，由于焊接热源能量的集中输入，不均匀的温度分布，导致在焊接结构中产生比较大的焊接残余应力和变形，这种应力和变形的产生不但对结构的尺寸稳定和加工精度产生一定程度的影响，还威胁结构的局部稳定性和整体稳定性。因此本文通过对管桁架结构、网壳结构焊接过程的数值模拟，为合理的预测和考虑焊接残余应力的对管桁架结构，网壳结构的极限承载力的影响，以及实际设计和施工中考虑焊接残余应力这一因素提供必要的参考。为达到研究目标，本文采用精细化的建模方法，通过ANSYS中实体单元建立了焊接球节点和相贯节点的计算模型，通过对模型施加生热率的加载方法，模拟焊接热源，并通过间接耦合法，最终计算出了这两类节点在焊接过程中，温度场和应力场的变化情况。研究了残余应力的分布范围及变化趋势，结果表明在焊缝附近区域会产生接近材料屈服强度的残余应力。本文采用多点约束方法分别建立平面管桁架和K6（2）网壳的多尺度有限元模型，节点位置采用实体单元，杆件位置则用梁单元模拟以减少计算耗时，并与全部采用壳单元建立的模型计算结果进行了对比，验证了利用实体—梁单元的多尺度方法计算结果的有效性。通过对管桁架多尺度有限元模型，施加焊接数值模拟过程中计算获得的残余应力作为初始荷载，获得了考虑残余应力的管桁架多尺度模型，同时与不考虑残余应力的管桁架多尺度模型计算结果进行对比，结果表明残余应力的产生将导致所取平面管桁架模型极限承载力降低11.8%。利用上述同样的方法，分析了焊接残余应力对K6（2）网壳极限承载能力的影响，计算结果表明由于球节点的存在，结构的破坏是由于杆件的首先破坏所导致的，，节点刚度强于杆件，残余应力并不会显著影响结构的承载力。
[Abstract]:Long-span spatial structure has been widely used in China in recent years, because of its advantages of light weight, reasonable structural force and various forms of modeling change, which makes the long-span spatial structure have been widely used in China in recent years. Pipe truss structure and reticulated shell structure are more commonly used in the spatial structure, and the key to make up the members is the connection mode. In the welding process, due to the centralized input of the welding heat source energy and the uneven temperature distribution, the welding residual stress and deformation in the welding structure are caused by the large residual stress and deformation. This kind of stress and deformation not only affects the dimensional stability and machining precision of the structure, but also threatens the local stability and global stability of the structure. Therefore, through numerical simulation of the welding process of tube truss structure and reticulated shell structure, in order to reasonably predict and consider the influence of welding residual stress on the ultimate bearing capacity of pipe truss structure and latticed shell structure, As well as practical design and construction to consider the factor of welding residual stress to provide a necessary reference. In order to achieve the research goal, this paper adopts the refined modeling method, establishes the calculation model of the welded ball node and the intersecting node through the solid element in ANSYS, and simulates the welding heat source by applying the heat generation rate loading method to the model. The change of temperature field and stress field in the welding process of these two kinds of joints is calculated by indirect coupling method. The distribution range and variation trend of residual stress are studied. The results show that the residual stress close to the yield strength of material will occur in the area near weld seam. In this paper, the multi-scale finite element model of planar tube truss and K6 (2) reticulated shell is established by multi-point constraint method. The node position is based on solid element, and the member position is simulated by beam element to reduce the calculation time. The effectiveness of the multi-scale method based on solid-beam element is verified by comparing with the results of all the models established by shell element. Based on the multi-scale finite element model of pipe truss, the multi-scale model of pipe truss considering residual stress is obtained by applying the residual stress calculated during welding numerical simulation as the initial load. At the same time, the results are compared with those of multi-scale model without residual stress. The results show that the generation of residual stress will reduce the ultimate bearing capacity of the plane truss model by 11.8%. Using the same method, the influence of welding residual stress on the ultimate bearing capacity of K6 (2) reticulated shell is analyzed. The calculation results show that the failure of the structure is caused by the first failure of the bar due to the existence of spherical joints. The stiffness of the joint is stronger than that of the member, and the residual stress will not significantly affect the bearing capacity of the structure.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU399;TU312.1

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