發(fā)布時間：2018-04-22 14:27

  本文選題：大變形管線鋼 + 多相鋼��； 參考：《北京科技大學》2016年博士論文

【摘要】：油氣輸送管道在通過凍土層、海底、地震帶以及塌陷和滑坡等地區(qū)時常承受一定塑性變形,從而發(fā)生彎折、扭曲和斷裂等破壞,引發(fā)失效事故。開發(fā)能承受大變形而不發(fā)生失效的大變形管線鋼已成為高性能管線鋼發(fā)展的一個重要方向。大變形管線鋼的形變能力與多相組織應變硬化行為和失效行為密切相關(guān)。多相鋼中“軟-硬”相的合理搭配是實現(xiàn)高塑性的重要技術(shù)路線。本文通過對多相鋼的力學行為進行實驗研究和數(shù)值模擬計算分析,揭示了多相鋼組織選擇和體積分數(shù)調(diào)控對應變硬化能力／行為、應力比及塑性損傷行為的影響,可為大變形管線鋼的工程化應用提供實驗和理論依據(jù)。組織特征及其本構(gòu)關(guān)系影響著鐵素體／貝氏體(F/B)多相鋼的應變硬化能力,控制成分和相變可以獲得不同強度及應變硬化能力的組織。提高F/B多相鋼中組織之間強度差可降低屈強比。F/B多相鋼的應變硬化行為呈現(xiàn)出與貝氏體體積分數(shù)相關(guān)的特性。通過修正C-J分析方法對多相鋼的應變硬化過程進行分段以及對各階段應變硬化能力表征,合理地解釋了應力比、屈強比、應變硬化指數(shù)及均勻伸長率隨貝氏體體積分數(shù)變化的規(guī)律。并分析了應力比、應變硬化指數(shù)、屈強比及均勻伸長率之間的關(guān)系及適用條件。相關(guān)結(jié)論得到了工業(yè)化大生產(chǎn)和實驗數(shù)據(jù)的驗證,具有較高可靠性。F/B多相鋼中組織分數(shù)和組織形態(tài)(形貌和分布)對其強度和塑性損傷有明顯的影響。鑒于這種影響通常很難通過實驗測量,本文通過微觀力學數(shù)值方法計算并分析了體積分數(shù)和組織形態(tài)對多相鋼強度和塑性損傷的影響。結(jié)果表明,組織體積分數(shù)對多相鋼強度和塑性損傷的影響顯著,其損傷機制與形變機制密切相關(guān),均呈現(xiàn)出與組織分數(shù)相關(guān)的特性。而組織形態(tài)對強度影響不明顯,但對塑性損傷有較大的影響。最后,論文結(jié)合一種F/B多相鋼,對其拉伸過程中的微觀應變分布進行了數(shù)值模擬分析和預測,并對形變組織和損傷進行了實驗觀察,其結(jié)果與實驗吻合。
[Abstract]:Oil and gas pipelines are often subjected to plastic deformation in frozen soil, seabed, seismic zone, collapse and landslide, which results in bending, twisting, fracture and so on, which lead to failure accidents. The development of large deformation pipeline steel which can withstand large deformation without failure has become an important direction in the development of high performance pipeline steel. The deformation capacity of large deformation pipeline steel is closely related to the strain hardening behavior and failure behavior of multiphase microstructure. The reasonable collocation of "soft-hard" phases in multiphase steels is an important technical route to achieve high plasticity. Based on the experimental study and numerical simulation analysis of the mechanical behavior of multiphase steel, the effects of structure selection and volume fraction control on strain hardening capacity / behavior, stress ratio and plastic damage behavior of multiphase steel are revealed in this paper. It can provide experimental and theoretical basis for engineering application of large deformation pipeline steel. The microstructure and its constitutive relation affect the strain-hardening ability of ferrite / bainitic F / B multiphase steel. The microstructure with different strength and strain-hardening ability can be obtained by controlling the composition and transformation. The strain hardening behavior of F / B multiphase steel can be reduced by increasing the strength difference between the microstructure of F / B multiphase steel. The strain-hardening behavior of F / B multiphase steel is related to the volume fraction of bainite. The strain hardening process of multiphase steel is segmented by modified C-J analysis method, and the strain hardening ability of each stage is characterized. The stress ratio and the yield strength ratio are explained reasonably. The variation of strain hardening index and uniform elongation with the volume fraction of bainite. The relationships among stress ratio, strain hardening index, flexural strength ratio and uniform elongation are analyzed. The results are verified by industrial production and experimental data. The microstructure fraction and microstructure morphology (morphology and distribution) of F- / B multiphase steel have obvious influence on the strength and plastic damage. In view of the fact that this effect is usually difficult to be measured experimentally, the effects of volume fraction and microstructure on the strength and plastic damage of multiphase steel are calculated and analyzed by means of micromechanics numerical method. The results show that the microstructure volume fraction has a significant effect on the strength and plastic damage of multiphase steel, and the damage mechanism is closely related to the deformation mechanism. However, the effect of microstructure on strength is not obvious, but it has great influence on plastic damage. Finally, the microscopic strain distribution in the tensile process of a kind of F / B multiphase steel is numerically simulated and predicted, and the microstructure and damage of the steel are observed experimentally. The results are in good agreement with the experimental results.
【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TG142.33

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