本文選題：微觀機(jī)制斷裂理論 + Q460高強(qiáng)鋼��； 參考：《長安大學(xué)》2017年博士論文

【摘要】：高強(qiáng)度鋼材由于其良好的性能近年來廣泛應(yīng)用于大型、超高層等重要性建筑中,其斷裂力學(xué)行為關(guān)乎領(lǐng)域內(nèi)結(jié)構(gòu)的整體安全性能。目前,國內(nèi)外對高強(qiáng)鋼斷裂性能的研究仍處于探索階段,尚未有成熟有效的斷裂力學(xué)方法供實際工程使用。因此,探索高強(qiáng)鋼的斷裂力學(xué)行為,提出合理的斷裂力學(xué)方法將為高強(qiáng)鋼結(jié)構(gòu)的推廣應(yīng)用奠定重要的基礎(chǔ)。微觀機(jī)制斷裂理論,作為目前力學(xué)領(lǐng)域中一種先進(jìn)的材料失效理論,為解釋結(jié)構(gòu)鋼材料的延性斷裂問題提供了新的方法。與經(jīng)典的斷裂力學(xué)方法相比,這類新的斷裂理論考慮了材料微觀機(jī)制與復(fù)雜應(yīng)力狀態(tài)對材料斷裂性能的影響,可準(zhǔn)確地預(yù)測無初始缺陷金屬材料的延性斷裂起始與裂紋擴(kuò)展,因此為高強(qiáng)鋼結(jié)構(gòu)斷裂預(yù)測提供了新的途徑。目前,有關(guān)微觀機(jī)制斷裂理論新方法的研究多局限在力學(xué)及其它工程領(lǐng)域中,而其在鋼結(jié)構(gòu)領(lǐng)域中的應(yīng)用研究依然很少。在這種背景下,系統(tǒng)地考察這類斷裂理論新方法在結(jié)構(gòu)鋼材料中的應(yīng)用效果將為大型鋼結(jié)構(gòu)斷裂預(yù)測提供重要的工程指導(dǎo)意義。本文以國產(chǎn)Q460高強(qiáng)鋼及焊縫材料為研究對象,分別采用試驗研究、理論分析與數(shù)值模擬相結(jié)合的方式,緊密圍繞“材料性能→力學(xué)理論方法→工程應(yīng)用”三個層次方面的內(nèi)容,對微觀機(jī)制斷裂力學(xué)理論在我國高強(qiáng)結(jié)構(gòu)鋼斷裂預(yù)測中的適用性進(jìn)行了系統(tǒng)地考察,并將這些斷裂力學(xué)方法推廣應(yīng)用于大型鋼結(jié)構(gòu)多軸復(fù)雜應(yīng)力狀態(tài)下的斷裂預(yù)測分析中,從而為工程結(jié)構(gòu)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)率先對我國Q460高強(qiáng)結(jié)構(gòu)鋼多軸復(fù)雜應(yīng)力狀態(tài)下的斷裂性能進(jìn)行了系統(tǒng)地研究。利用四種類型切口試件獲取了Q460高強(qiáng)鋼不同應(yīng)力狀態(tài)下的斷裂性能,采用電子顯微鏡觀測了材料不同應(yīng)力狀態(tài)下的微觀斷裂機(jī)制,著重考察了應(yīng)力三軸度與Lode角參數(shù)對Q460高強(qiáng)鋼延性與微觀斷裂機(jī)制的影響,并將所得結(jié)果與其它牌號結(jié)構(gòu)鋼的斷裂性能進(jìn)行了對比,為高強(qiáng)鋼結(jié)構(gòu)選材、斷裂模型校準(zhǔn)及斷裂預(yù)測提供核心的材性參數(shù)。(2)首次完成了三維非耦合型斷裂理論在我國高強(qiáng)鋼材料斷裂預(yù)測分析中的可行性驗證研究�；赒460鋼切口試件的試驗結(jié)果,對9種Lode角依賴型非耦合型斷裂模型進(jìn)行了校準(zhǔn),并對各模型的斷裂軌跡、固有特點及預(yù)測精度進(jìn)行了系統(tǒng)地考察。通過對比分析得到了精度最高且最適合我國Q460高強(qiáng)鋼的斷裂模型,并利用切口試件試驗結(jié)果對三維非耦合型斷裂模型的應(yīng)用效果進(jìn)行了檢驗,從而為高強(qiáng)鋼結(jié)構(gòu)斷裂預(yù)測分析提供了有效的方法。(3)系統(tǒng)地考察了臨界距離理論在高強(qiáng)鋼切口試件斷裂預(yù)測分析中的適用性與應(yīng)用效果。首先,利用切口圓棒試件對Q460高強(qiáng)鋼的臨界距離理論參數(shù)進(jìn)行了校準(zhǔn)。隨后,利用校準(zhǔn)的臨界距離理論對平板槽口試件、剪切型與拉剪型平板切口試件的斷裂性能進(jìn)行了預(yù)測與評估。研究結(jié)果表明,臨界距離理論可以準(zhǔn)確地預(yù)測我國高強(qiáng)鋼切口試件多軸復(fù)雜應(yīng)力狀態(tài)下的斷裂起始位置與極限強(qiáng)度,這為該理論進(jìn)一步在實際鋼結(jié)構(gòu)斷裂預(yù)測分析中應(yīng)用奠定了理論與試驗基礎(chǔ)。(4)完成了三維非耦合型斷裂理論在高強(qiáng)鋼焊接試件斷裂預(yù)測分析中的推廣應(yīng)用�；谇锌趫A棒試件、平板槽口試件試驗結(jié)果及Bridgman公式對高強(qiáng)鋼焊縫材料的三維非耦合型斷裂模型進(jìn)行了校準(zhǔn),并將所校準(zhǔn)的斷裂模型應(yīng)用于三種類型高強(qiáng)鋼焊接試件的斷裂預(yù)測分析中,分析了焊接試件加載過程中的損傷演化,并利用斷裂模型模擬了試件上的裂紋擴(kuò)展歷程,考察了三維非耦合型斷裂模型在高強(qiáng)鋼焊接試件中的應(yīng)用效果,從而為微觀機(jī)制斷裂理論在鋼結(jié)構(gòu)斷裂預(yù)測分析中應(yīng)用提供參考與指導(dǎo)。(5)提出一種全新通用且適合于鋼結(jié)構(gòu)工程應(yīng)用的三維非耦合型斷裂模型。該模型在Xue-Wierzbicki模型的基礎(chǔ)上,結(jié)合工程實際情況,利用經(jīng)典的Tresca破壞準(zhǔn)則及Swift硬化法則簡化得來。該模型優(yōu)點在于模型中斷裂參數(shù)可直接利用材料的應(yīng)力-應(yīng)變曲線進(jìn)行校準(zhǔn)。這使得模型的校準(zhǔn)難度極大降低,并可直接用于預(yù)測不同牌號、不同類型鋼結(jié)構(gòu)的斷裂問題。隨后,本文將提出的斷裂模型應(yīng)用于大型鋼管節(jié)點的斷裂預(yù)測分析中,通過對比試驗與數(shù)值模擬分析結(jié)果,對本文斷裂模型的正確性進(jìn)行了驗證,所得研究成果為大型鋼結(jié)構(gòu)斷裂預(yù)測提供了一種有效的方法。
[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.

【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TU391;TU511.3
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本文編號：1799774