基于微观机理的高强钢结构材料与节点的断裂性能研究

发布时间：2018-03-31 13:27

  本文选题：高强度钢材　切入点：焊接节点　出处：《清华大学》2015年博士论文

【摘要】：高强度钢材以其显著的优势在国内外实际工程中得到了成功应用,但应用中仍面临低温冷脆、屈强比增大、延性降低和焊接连接等问题。本文基于高强度钢材的断裂微观机理,以大量的试验研究为基础,结合数值计算和理论分析,从材料材性、典型构造和梁柱节点三个层面对高强度钢材钢结构的断裂性能展开了系统研究,主要研究工作和成果如下:(1)对国产高强度结构钢材及其对接焊缝共计120个材性试件进行了一系列的低温拉伸、冲击、三点弯断裂韧性及电镜扫描试验,系统研究了高强度焊接钢材在低温下的力学性能、韧性性能及断裂微观机理,分析了钢材强度对其断裂性能的影响,为高强钢结构选材和考虑低温的防脆断设计提供了丰富的材性数据。(2)基于微观机理提出断裂预测模型,通过54个缺口圆棒和12个光滑圆棒的单调拉伸和低周疲劳试验,结合有限元分析,建立了460MPa高强度钢材及其焊缝的单调拉伸及循环本构模型,标定了微观机理模型中的材料韧性参数,以及循环荷载下的损伤退化系数。结果表明韧性参数与屈强比没有明显关联,而与塑性指标存在一定关系。研究为后续高强钢结构节点的断裂性能分析提供了必要基础。(3)选取代表实际梁柱节点局部焊接构造的典型十字型焊接接头试件,采用对接熔透焊和角焊缝两种焊缝类型,完成了20个高强度钢材典型焊接节点在单调拉伸和往复加载下的断裂性能试验,探讨了焊缝类型、荷载类型及钢材强度对其断裂性能的影响,为发展高强度钢材焊接节点的断裂分析模型提供了依据。(4)完成了4个高强钢框架栓-焊混接梁柱节点足尺试件的往复加载试验,包括4种不同的构造细节,分析了焊接工艺细节及节点局部构造对高强钢框架梁柱节点低周疲劳断裂性能的影响,得到相应节点试件断裂性能指标,为发展适用于强震作用下高强度钢结构梁柱节点的高应变低周疲劳断裂预测模型提供了依据。(5)基于本文中高强钢典型焊接接头和高强钢框架梁柱节点的试验研究,建立了节点精细化有限元模型,应用微观机理模型和结构多尺度模型相结合的断裂预测模型对高强钢梁柱节点的低周疲劳断裂性能进行了分析。研究验证了微观机理模型对于高强钢梁柱节点延性断裂预测的有效性,以及模型对于不同几何构造的普遍适用性,为高强钢结构节点的低周疲劳断裂分析提供了一种有效分析方法。
[Abstract]:High strength steel has been successfully applied in practical engineering at home and abroad with its remarkable advantages. However, the application still faces the problems of low temperature cold embrittlement, increasing yield ratio, decreasing ductility and welding connection, etc. This paper is based on the fracture microscopic mechanism of high strength steel. Based on a large number of experimental studies, combined with numerical calculation and theoretical analysis, the fracture properties of high strength steel structures are systematically studied from three aspects: material properties, typical structures and Liang Zhu joints. The main research work and results are as follows: (1) A series of low-temperature tensile tests, impact tests, three-point bending fracture toughness and scanning electron microscopy tests were carried out on 120 domestic high strength structural steels and their butt welds. The mechanical properties, toughness properties and fracture micromechanism of high strength welded steel at low temperature were studied systematically. The influence of steel strength on fracture properties was analyzed. This paper provides abundant material data for material selection of high strength steel structure and brittleness resistance design considering low temperature. Based on microscopic mechanism, a fracture prediction model is proposed. Through monotonic tensile and low cycle fatigue tests of 54 notched round rods and 12 smooth round bars, Combined with finite element analysis, the monotone tensile and cyclic constitutive models of 460MPa high strength steels and their welds are established, and the material toughness parameters in the microscopic mechanism model are calibrated. And the damage degradation coefficient under cyclic load. The results show that there is no obvious correlation between the toughness parameter and the yield ratio. The study provides a necessary basis for the subsequent analysis of fracture properties of high-strength steel structure joints. The typical cross-welded joint specimens, which represent the local welding structure of Liang Zhu joints, are selected. The fracture behavior tests of 20 typical welded joints of high strength steel under monotonic tensile and reciprocating loading were carried out by means of butt penetration welding and fillet weld, and the weld types were discussed. The effect of load type and steel strength on the fracture properties of high strength steel welded joints provides a basis for the development of fracture analysis model of high strength steel welded joints. The reciprocating loading tests of four full-scale specimens of high strength steel frame bolt-welded mixed Liang Zhu joints have been completed. Including four different structural details, the effects of welding process details and joint local structure on the low cycle fatigue fracture properties of Liang Zhu joints of high strength steel frames are analyzed, and the fracture performance indexes of the corresponding joints are obtained. In order to develop a prediction model of high strain and low cycle fatigue fracture for Liang Zhu joints of high strength steel structures under strong earthquake, the experimental study on typical welded joints of high strength steel and Liang Zhu joints of high strength steel frames in this paper is presented. The fine finite element model of node is established. The low cycle fatigue fracture behavior of Liang Zhu joints of high strength steel was analyzed by using the fracture prediction model combined with micro mechanism model and multi scale structural model. The validity of sexual fracture prediction, The universal applicability of the model to different geometric structures provides an effective analysis method for low-cycle fatigue fracture analysis of joints of high-strength steel structures.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU511.3
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本文编号：1690935