微观机制断裂理论在高强钢材料及钢结构断裂预测分析中的应用研究

发布时间：2018-04-25 04:29

  本文选题：微观机制断裂理论 + Q460高强钢　； 参考：《长安大学》2017年博士论文

【摘要】：高强度钢材由于其良好的性能近年来广泛应用于大型、超高层等重要性建筑中,其断裂力学行为关乎领域内结构的整体安全性能。目前,国内外对高强钢断裂性能的研究仍处于探索阶段,尚未有成熟有效的断裂力学方法供实际工程使用。因此,探索高强钢的断裂力学行为,提出合理的断裂力学方法将为高强钢结构的推广应用奠定重要的基础。微观机制断裂理论,作为目前力学领域中一种先进的材料失效理论,为解释结构钢材料的延性断裂问题提供了新的方法。与经典的断裂力学方法相比,这类新的断裂理论考虑了材料微观机制与复杂应力状态对材料断裂性能的影响,可准确地预测无初始缺陷金属材料的延性断裂起始与裂纹扩展,因此为高强钢结构断裂预测提供了新的途径。目前,有关微观机制断裂理论新方法的研究多局限在力学及其它工程领域中,而其在钢结构领域中的应用研究依然很少。在这种背景下,系统地考察这类断裂理论新方法在结构钢材料中的应用效果将为大型钢结构断裂预测提供重要的工程指导意义。本文以国产Q460高强钢及焊缝材料为研究对象,分别采用试验研究、理论分析与数值模拟相结合的方式,紧密围绕“材料性能→力学理论方法→工程应用”三个层次方面的内容,对微观机制断裂力学理论在我国高强结构钢断裂预测中的适用性进行了系统地考察,并将这些断裂力学方法推广应用于大型钢结构多轴复杂应力状态下的断裂预测分析中,从而为工程结构失效分析提供了有效的方法。本文的主要研究工作和成果如下:(1)率先对我国Q460高强结构钢多轴复杂应力状态下的断裂性能进行了系统地研究。利用四种类型切口试件获取了Q460高强钢不同应力状态下的断裂性能,采用电子显微镜观测了材料不同应力状态下的微观断裂机制,着重考察了应力三轴度与Lode角参数对Q460高强钢延性与微观断裂机制的影响,并将所得结果与其它牌号结构钢的断裂性能进行了对比,为高强钢结构选材、断裂模型校准及断裂预测提供核心的材性参数。(2)首次完成了三维非耦合型断裂理论在我国高强钢材料断裂预测分析中的可行性验证研究。基于Q460钢切口试件的试验结果,对9种Lode角依赖型非耦合型断裂模型进行了校准,并对各模型的断裂轨迹、固有特点及预测精度进行了系统地考察。通过对比分析得到了精度最高且最适合我国Q460高强钢的断裂模型,并利用切口试件试验结果对三维非耦合型断裂模型的应用效果进行了检验,从而为高强钢结构断裂预测分析提供了有效的方法。(3)系统地考察了临界距离理论在高强钢切口试件断裂预测分析中的适用性与应用效果。首先,利用切口圆棒试件对Q460高强钢的临界距离理论参数进行了校准。随后,利用校准的临界距离理论对平板槽口试件、剪切型与拉剪型平板切口试件的断裂性能进行了预测与评估。研究结果表明,临界距离理论可以准确地预测我国高强钢切口试件多轴复杂应力状态下的断裂起始位置与极限强度,这为该理论进一步在实际钢结构断裂预测分析中应用奠定了理论与试验基础。(4)完成了三维非耦合型断裂理论在高强钢焊接试件断裂预测分析中的推广应用。基于切口圆棒试件、平板槽口试件试验结果及Bridgman公式对高强钢焊缝材料的三维非耦合型断裂模型进行了校准,并将所校准的断裂模型应用于三种类型高强钢焊接试件的断裂预测分析中,分析了焊接试件加载过程中的损伤演化,并利用断裂模型模拟了试件上的裂纹扩展历程,考察了三维非耦合型断裂模型在高强钢焊接试件中的应用效果,从而为微观机制断裂理论在钢结构断裂预测分析中应用提供参考与指导。(5)提出一种全新通用且适合于钢结构工程应用的三维非耦合型断裂模型。该模型在Xue-Wierzbicki模型的基础上,结合工程实际情况,利用经典的Tresca破坏准则及Swift硬化法则简化得来。该模型优点在于模型中断裂参数可直接利用材料的应力-应变曲线进行校准。这使得模型的校准难度极大降低,并可直接用于预测不同牌号、不同类型钢结构的断裂问题。随后,本文将提出的断裂模型应用于大型钢管节点的断裂预测分析中,通过对比试验与数值模拟分析结果,对本文断裂模型的正确性进行了验证,所得研究成果为大型钢结构断裂预测提供了一种有效的方法。
[Abstract]:Due to its good performance, high strength steel has been widely used in large and super high rise buildings in recent years, and its fracture mechanics behavior is related to the overall safety performance of the structure in the field. At present, the research on the fracture properties of high strength steel at home and abroad is still in the exploration stage, and there is no mature and effective fracture mechanics method for practical use. Therefore, exploring the fracture mechanics behavior of high strength steel and putting forward a reasonable fracture mechanics method will lay an important foundation for the popularization and application of high strength steel structure. Micro mechanism fracture theory, as an advanced theory of material failure in the field of mechanics, provides a new method for explaining the problem of ductile fracture of structural steel materials. Compared with the fracture mechanics, the new fracture theory takes into account the effect of the material micro mechanism and the complex stress state on the fracture properties of the material. It can accurately predict the ductile fracture initiation and crack propagation of the metal material without initial defects. Therefore, it provides a new way for the fracture prediction of high strength steel structure. The research on the new method of crack theory is mostly confined to the field of mechanics and other engineering fields, and its application in the field of steel structure is still very few. Under this background, the application of this new method of fracture theory in structural steel materials will provide important engineering guiding significance for the fracture prediction of large steel structures. The research object of domestic Q460 high strength steel and weld material is the experimental study, the combination of theoretical analysis and numerical simulation, and the content of the three levels of "material properties, mechanics theory method and engineering application", and the applicability of fracture mechanics theory of micro mechanism to fracture prediction of high strength structural steel in China A systematic investigation is carried out and these fracture mechanics methods are applied to the fracture prediction analysis of large steel structures under multi axis complex stress state, which provides an effective method for the failure analysis of engineering structures. The main research work and results of this paper are as follows: (1) the multi axis complex stress state of our country's Q460 high strength structural steel is first. The fracture performance was systematically studied. The fracture properties of Q460 high strength steel under different stress conditions were obtained by four types of notch specimens. The micro fracture mechanism under different stress states was observed by electron microscope, and the stress three axis and Lode angle parameters were emphatically investigated for the ductility and micro fracture machine of Q460 high strength steel. The results are compared with the fracture properties of other brands of structural steel, which provide the core material parameters for high strength steel structure selection, fracture model calibration and fracture prediction. (2) the feasibility verification of three-dimensional uncoupled fracture theory in the fracture prediction analysis of high strength steel in China is completed for the first time. Based on Q46 The test results of 0 steel incisional specimen are calibrated for 9 Lode angle dependent non coupling fracture models, and the fracture trajectory, inherent characteristics and prediction accuracy of each model are systematically investigated. The fracture model of the highest precision and most suitable for our country's Q460 high strength steel is obtained by comparison and analysis, and the result of the notch test is used. The application effect of the three-dimensional uncoupled fracture model is tested, which provides an effective method for the fracture prediction analysis of high strength steel structure. (3) the applicability and application effect of the critical distance theory in the fracture prediction analysis of high strength steel incisional specimen are systematically investigated. First, the critical value of the notch round bar test on the critical value of Q460 high strength steel is made. The distance theory parameters are calibrated. Then, the critical distance theory is used to predict and evaluate the fracture properties of the plate notch specimen, the shear and the tensile shear plate notch specimen. The results show that the critical distance theory can accurately predict the fracture in the multi axis and complex stress state of the high strength steel incisional specimen in China. The initial position and ultimate strength have laid the theoretical and experimental foundation for further application of the theory to the actual fracture prediction analysis of steel structures. (4) the application of the three-dimensional uncoupled fracture theory to the fracture prediction analysis of high strength steel welded specimens. The three-dimensional uncoupled fracture model of high strength steel welds was calibrated, and the fracture model was applied to the fracture prediction analysis of three types of high strength steel welded specimens. The damage evolution during the loading process was analyzed, and the crack propagation process on the specimen was simulated with the fracture model, and three was investigated. The application effect of the non coupling fracture model in the welded specimens of high strength steel is provided, which provides reference and guidance for the application of micro mechanism fracture theory in the prediction and analysis of steel structure fracture. (5) a new and general non coupling fracture model for steel structure engineering application is proposed. The model is based on the basis of the Xue-Wierzbicki model. In connection with the actual situation of the engineering, the classical Tresca failure criterion and the Swift hardening rule are simplified. The advantage of the model is that the model interruption parameters can be calibrated directly by the stress-strain curve of the material. This makes the calibration difficulty of the model greatly reduced, and can be used to predict the different grades and different types of steel structures. Then, the fracture model proposed in this paper is applied to the fracture prediction analysis of large steel pipe joints. Through the comparison test and numerical simulation analysis, the correctness of the fracture model is verified. The results of the study provide an effective method for the fracture prediction of large steel structure.

【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TU391;TU511.3
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本文编号：1799774