基于磁記憶的油氣管道應力損傷檢測機理及應用研究
發(fā)布時間：2018-08-26 14:59
【摘要】：油氣管道運輸具有高效率、低成本及安全可靠等優(yōu)點,是能源運輸?shù)闹匾绞�。目前全世界已建成油氣輸送管道已超過250萬公里,而且這個數(shù)據(jù)每年仍在增長。我國地域遼闊,油氣資源分布不均,油氣的管道輸送成為關乎國民經(jīng)濟和社會發(fā)展的重要產(chǎn)業(yè)。由于管道具有高能高壓、易燃易爆、有毒有害、連續(xù)作業(yè)、鏈長面廣、環(huán)境復雜等特點,決定了管道安全管理的重要性。石油天然氣輸送管道所應用的鋼鐵材料具有良好的強度、硬度、塑性和韌性等機械性能以及良好的鐵磁性能,其發(fā)生破壞將經(jīng)歷由應力集中導致材料屈服進而發(fā)生塑性變形再到破壞的過程。管道在建設和使用過程中,會受到各種應力的作用,當管道局部存在缺陷或其他質量問題時,將會在局部產(chǎn)生應力集中,引起局部應力過大,甚至導致管道發(fā)生塑性變形或破壞。應力集中是威脅管道安全性的一個重要因素,由應力集中引起的塑性變形損傷被認為是材料的早期損傷。對管道應力集中及塑性變形的有效檢測可以預判危害的發(fā)生,并可作為評價管道應力集中程度的依據(jù),對保障管道安全意義重大。磁記憶檢測方法作為一種應力檢測方法已得到行業(yè)的認可,它具有設備簡單、操作方便、可實現(xiàn)在線大范圍無損檢測及對設備危險的早期判斷等優(yōu)點。但目前針對磁記憶信號形成的機理及特征尚無統(tǒng)一的定論,還不能明確在各種條件下的檢測信號特征。同時由于微弱的磁記憶信號亦受影響,對實驗研究方法的有效性具有較高要求,很多實驗方法具有一定局限性,不能有效說明磁記憶現(xiàn)象的真實情況,從而導致該方法在一些工程應用中的有效性受到質疑。鐵磁材料的磁性來源于原子磁矩,決定于微觀電子體系的運動及相互作用狀態(tài)。本文從量子力學微觀理論出發(fā),以密度泛函理論為基礎建立鐵磁材料力磁耦合磁記憶效應理論模型,通過第一性原理研究了鐵磁體系在力磁耦合過程中磁記憶信號特征,對應力損傷的磁記憶信號特征及檢測機理進行深入研究。通過拉伸和管道打壓實驗對理論研究結果進行了驗證。并開展了管道應力損傷磁記憶內(nèi)檢測技術的工程應用,對該檢測方法的工程應用可行性和有效性進行了研究。論文對鐵磁材料的力學和磁學特性進行了研究,明確了鐵磁材料應力損傷形成的微觀機理及磁性的微觀起源。以體系微觀電子密度分布函數(shù)為基礎,建立鐵磁材料力磁效應的量子力學密度泛函理論模型,通過第一性原理仿真軟件CASTEP計算了正常鐵磁晶體結構和塑性變形鐵磁晶體結構兩種鐵磁體系在不同應力作用下的能帶結構、電子態(tài)密度分布及原子磁矩。理論研究結果表明,鐵磁材料在單向拉伸和三向拉伸兩種應力狀態(tài)下,隨著應力的增大,體系能帶朝遠離費米能級方向移動,費米能級附近的電子分布數(shù)量減少,電子自旋態(tài)密度峰值逐漸下降,體系電子自旋間的交換相互作用程度減弱,軌道電子分布局域性增強,表明鐵磁體系的磁性在應力作用下逐漸減弱。通過原子磁矩的計算定量分析了鐵磁體系磁記憶信號的變化特征,得到磁記憶信號隨著應力的增大逐漸減小,應力與磁信號間存在線性對應關系。當材料發(fā)生塑性變形時,磁記憶信號發(fā)生突變,信號變化特征發(fā)生改變。塑性變形鐵磁體系的磁記憶信號隨應力變化的斜率小于正常鐵磁體系,表明材料在發(fā)生塑性變形后力磁耦合程度減弱。設計制作了不含人工缺陷及形狀效應的拉伸試樣和長距離實驗管道,建立了材料拉伸和管道打壓實驗平臺。實驗研究了鐵磁材料在單向拉伸和三向應力狀態(tài)下的磁記憶信號特征,得到鐵磁材料的應力與磁記憶信號的對應關系。分析了鐵磁材料在應力作用下由彈性變形轉變?yōu)樗苄宰冃螘r,磁記憶信號的變化特征。實驗研究表明,鐵磁材料在地磁和應力作用下將產(chǎn)生磁記憶信號,材料表面得磁感應強度隨應力的增大而減小,當材料屈服時,磁記憶信號發(fā)生突變,塑性變形后鐵磁材料力磁耦合程度減弱,磁記憶信號隨應力變化的趨勢變緩。實驗研究結果與理論研究結果具有一致性,驗證了理論研究的正確性。以Φ1219輸氣管道的磁記憶應力內(nèi)檢測為應用背景,對油氣管道應力損傷磁記憶內(nèi)檢測技術的工程應用進行研究。提出管道差異運行壓力下的二次應力內(nèi)檢測方法,對檢測結果進行分析和評價,對檢測到的危害點進行現(xiàn)場開挖驗證。研究結果表明了油氣管道應力損傷磁記憶內(nèi)檢測技術工程應用的可行性和有效性。
[Abstract]:Oil and gas pipeline transportation is an important way of energy transportation because of its high efficiency, low cost, safety and reliability. At present, more than 2.5 million kilometers of oil and gas pipelines have been built all over the world, and this data is still growing every year. The importance of pipeline safety management is determined by the characteristics of high energy, high pressure, inflammable, explosive, toxic and harmful, continuous operation, wide chain and complex environment. The steel materials used in oil and gas pipelines have good mechanical properties such as strength, hardness, plasticity and toughness, and good ferromagnetism. Performance, the occurrence of failure will undergo a process from stress concentration leading to material yield and then plastic deformation to failure. Pipelines in the construction and use process, will be subjected to various stresses, when there are local defects or other quality problems in the pipeline, will produce local stress concentration, resulting in excessive local stress, or even lead to failure. Plastic deformation or failure occurs in pipelines. Stress concentration is an important factor threatening the safety of pipelines. Plastic deformation damage caused by stress concentration is considered as early damage of materials. Magnetic memory testing method as a stress testing method has been recognized by the industry. It has the advantages of simple equipment, easy operation, on-line large-scale non-destructive testing and early judgment of equipment risk. However, there is no unified conclusion on the mechanism and characteristics of magnetic memory signal formation. At the same time, because the weak magnetic memory signal is also affected, the validity of the experimental research method is highly required. Many experimental methods have certain limitations, and can not effectively explain the true situation of magnetic memory phenomenon, which leads to the method in some engineering applications. The magnetism of ferromagnetic materials originates from the magnetic moments of atoms and is determined by the motion and interaction state of the micro-electronic system. Based on the microscopic theory of quantum mechanics and the density functional theory, a theoretical model of magnetic memory effect in ferromagnetic materials with force-magnetic coupling is established. The characteristics of magnetic memory signal during the coupling process are studied. The theoretical results are verified by tensile and compression tests. The engineering application of magnetic memory inner detection technology for pipeline stress damage is carried out. The feasibility and feasibility of the method are verified. In this paper, the mechanical and magnetic properties of ferromagnetic materials are studied, and the micro-mechanism of stress damage and the micro-origin of magnetism are clarified. Based on the micro-electron density distribution function of the system, the quantum mechanical density functional theory model of ferromagnetic materials is established, and the first primitive is used. The energy band structure, electron density distribution and atomic magnetic moment of two ferromagnetic systems, normal ferromagnetic crystal structure and plastic deformed ferromagnetic crystal structure, are calculated by CASTEP. The theoretical results show that the system of ferromagnetic materials under uniaxial and triaxial tensile stress states increases with the increase of stress. The band moves away from the Fermi level, the number of electrons near the Fermi level decreases, the peak value of electron spin density decreases, the exchange interaction between electron spins decreases, and the locality of orbital electrons increases, indicating that the magnetism of the ferromagnetic system gradually weakens under stress. The variation characteristics of magnetic memory signals in ferromagnetic systems are analyzed quantitatively and numerically. It is found that the magnetic memory signals decrease with the increase of stress and there is a linear relationship between stress and magnetic signals. The slope of stress change is smaller than that of normal ferromagnetic system, which indicates that the coupling degree of force and magnetism decreases after plastic deformation. Tensile specimens and long-distance experimental pipes without artificial defects and shape effects are designed and manufactured. The experimental platform of material tension and pipe compression is established. The uniaxial tension and three-dimensional stress of ferromagnetic materials are experimentally studied. The characteristics of magnetic memory signals under stress state are obtained, and the corresponding relationship between stress and magnetic memory signals of ferromagnetic materials is obtained.The characteristics of magnetic memory signals are analyzed when ferromagnetic materials are transformed from elastic deformation to plastic deformation under stress.The experimental results show that ferromagnetic materials will produce magnetic memory signals under the action of geomagnetic and stress. The magnetic induction intensity on the surface decreases with the increase of stress. When the material yields, the magnetic memory signal mutates, the coupling degree of the ferromagnetic material weakens after plastic deformation, and the magnetic memory signal slows down with the change of stress. Based on the application background of magnetic memory stress detection in gas pipeline, the engineering application of magnetic memory stress damage detection technology in oil and gas pipeline is studied. The secondary stress detection method under differential operating pressure of pipeline is put forward, the detection results are analyzed and evaluated, and the dangerous points detected are verified by field excavation. The feasibility and effectiveness of engineering application of stress memory magnetic memory testing technology for oil and gas pipelines are presented.
【學位授予單位】：沈陽工業(yè)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TE973.6
[Abstract]:Oil and gas pipeline transportation is an important way of energy transportation because of its high efficiency, low cost, safety and reliability. At present, more than 2.5 million kilometers of oil and gas pipelines have been built all over the world, and this data is still growing every year. The importance of pipeline safety management is determined by the characteristics of high energy, high pressure, inflammable, explosive, toxic and harmful, continuous operation, wide chain and complex environment. The steel materials used in oil and gas pipelines have good mechanical properties such as strength, hardness, plasticity and toughness, and good ferromagnetism. Performance, the occurrence of failure will undergo a process from stress concentration leading to material yield and then plastic deformation to failure. Pipelines in the construction and use process, will be subjected to various stresses, when there are local defects or other quality problems in the pipeline, will produce local stress concentration, resulting in excessive local stress, or even lead to failure. Plastic deformation or failure occurs in pipelines. Stress concentration is an important factor threatening the safety of pipelines. Plastic deformation damage caused by stress concentration is considered as early damage of materials. Magnetic memory testing method as a stress testing method has been recognized by the industry. It has the advantages of simple equipment, easy operation, on-line large-scale non-destructive testing and early judgment of equipment risk. However, there is no unified conclusion on the mechanism and characteristics of magnetic memory signal formation. At the same time, because the weak magnetic memory signal is also affected, the validity of the experimental research method is highly required. Many experimental methods have certain limitations, and can not effectively explain the true situation of magnetic memory phenomenon, which leads to the method in some engineering applications. The magnetism of ferromagnetic materials originates from the magnetic moments of atoms and is determined by the motion and interaction state of the micro-electronic system. Based on the microscopic theory of quantum mechanics and the density functional theory, a theoretical model of magnetic memory effect in ferromagnetic materials with force-magnetic coupling is established. The characteristics of magnetic memory signal during the coupling process are studied. The theoretical results are verified by tensile and compression tests. The engineering application of magnetic memory inner detection technology for pipeline stress damage is carried out. The feasibility and feasibility of the method are verified. In this paper, the mechanical and magnetic properties of ferromagnetic materials are studied, and the micro-mechanism of stress damage and the micro-origin of magnetism are clarified. Based on the micro-electron density distribution function of the system, the quantum mechanical density functional theory model of ferromagnetic materials is established, and the first primitive is used. The energy band structure, electron density distribution and atomic magnetic moment of two ferromagnetic systems, normal ferromagnetic crystal structure and plastic deformed ferromagnetic crystal structure, are calculated by CASTEP. The theoretical results show that the system of ferromagnetic materials under uniaxial and triaxial tensile stress states increases with the increase of stress. The band moves away from the Fermi level, the number of electrons near the Fermi level decreases, the peak value of electron spin density decreases, the exchange interaction between electron spins decreases, and the locality of orbital electrons increases, indicating that the magnetism of the ferromagnetic system gradually weakens under stress. The variation characteristics of magnetic memory signals in ferromagnetic systems are analyzed quantitatively and numerically. It is found that the magnetic memory signals decrease with the increase of stress and there is a linear relationship between stress and magnetic signals. The slope of stress change is smaller than that of normal ferromagnetic system, which indicates that the coupling degree of force and magnetism decreases after plastic deformation. Tensile specimens and long-distance experimental pipes without artificial defects and shape effects are designed and manufactured. The experimental platform of material tension and pipe compression is established. The uniaxial tension and three-dimensional stress of ferromagnetic materials are experimentally studied. The characteristics of magnetic memory signals under stress state are obtained, and the corresponding relationship between stress and magnetic memory signals of ferromagnetic materials is obtained.The characteristics of magnetic memory signals are analyzed when ferromagnetic materials are transformed from elastic deformation to plastic deformation under stress.The experimental results show that ferromagnetic materials will produce magnetic memory signals under the action of geomagnetic and stress. The magnetic induction intensity on the surface decreases with the increase of stress. When the material yields, the magnetic memory signal mutates, the coupling degree of the ferromagnetic material weakens after plastic deformation, and the magnetic memory signal slows down with the change of stress. Based on the application background of magnetic memory stress detection in gas pipeline, the engineering application of magnetic memory stress damage detection technology in oil and gas pipeline is studied. The secondary stress detection method under differential operating pressure of pipeline is put forward, the detection results are analyzed and evaluated, and the dangerous points detected are verified by field excavation. The feasibility and effectiveness of engineering application of stress memory magnetic memory testing technology for oil and gas pipelines are presented.
【學位授予單位】：沈陽工業(yè)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TE973.6
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