【作者】 姚荣荣；

【导师】 雷毅；

【作者基本信息】 中国石油大学 ， 材料加工工程， 2008， 硕士

【摘要】 油井管是石油钻采工业中必不可少的重要物资,其质量安全关系着整个采油作业的顺利进行,无论是新产品出厂及使用前还是旧产品的修复过程中都需要进行无损检测。接口螺纹部位是油井管最薄弱的环节,油井管表面损伤、滑脱、断裂裂纹往往发生在该处。选取P110油管接头为研究对象,在弹塑性力学的基础上对处于机紧状态下相互啮合的内外螺纹各扣牙的力学行为进行分析,通过建立数学模型的解析法和有限元分析的数值模拟方法,对该接头内外螺纹各扣牙表面的受力情况及力学分布规律进行研究,分析表明各螺纹牙上受力分布很不均匀,两端的几个扣牙受力最大,危险首先发生在该扣牙处,因此,对油井管的检测重点应在接口两端数牙。选择磁化方式及参数,采用有限元分析方法对P110油管接口螺纹区域的磁场分布进行模拟,在接口顶端加10 mm厚的垫块同时线圈长度往油管内部延长15 mm后,得到了竖直方向的沿螺纹各扣牙表面均匀分布的电磁场,以检测螺纹表面的横向裂纹;同时对油管接口部位中心导体法磁化过程进行模拟,得到了以导体为中心,沿螺纹牙走向分布的环形磁场,以检测螺纹表面的纵向裂纹。此外,为研究缺陷的尺寸参数对漏磁场的影响,以磁偶极子理论为依据,建立了螺纹表面裂纹以及近表面孔洞型缺陷的磁荷模型,分析了缺陷各尺寸参数对漏磁场的影响,得出在裂纹深宽比比较大的情况下,裂纹深度越大或裂纹宽度越大,漏磁场信号均越大,缺陷越容易检出,而且,缺陷的检出存在一定的范围;对于孔洞型缺陷,缺陷尺寸越大,距离表面位置越近,漏磁信号越明显,缺陷越容易检出,缺陷的检出同样存在一定的检测范围。由于油井管螺纹表面大多为沿螺纹牙走向分布的横向裂纹,采用有限元分析法重点对螺纹表面根部横向裂纹的漏磁场分布进行了模拟,分别建立了不同位置、不同尺寸参数的裂纹,对缺陷周围的漏磁场进行模拟,得出在模拟过程中施加的磁化电流作用下,只能检测裂纹中心距离螺纹根部0.45 mm之内的裂纹。裂纹大小、形状均对漏磁信号有重要的影响,裂纹越大越容易检出,在距离螺纹牙底0.45 mm处的裂纹,当深度为0.6 mm时,宽度小于0.6 mm的就可能造成漏检。此外,裂纹深宽比或者宽深比在1/2和1/1时,漏磁信号最明显,这种形状的裂纹最容易被检出。更多还原

【Abstract】 Oil well tube is the absolutely necessary material in the petroleum drilling industry,and the whole production work depends on its quality safety.So nondestructive testing should be implemented on new products before being used and old ones during repairing process.Oil well tubing thread is the weakest link,surface injury spondylolisthesis and fracture crack usually occur firstly.P110 tubing joint is selected as the study object and mechanical behavior of meshing thread under the compact status is analyzed based on plastoelasticity.Mechanical behavior of the joint thread surface and distribution law are researched by establishing mathematical model and finite element analysis.It turns to be that the stress distribution of thread teeth is quite uneven,and stress on the several thread teeth of the two ends of the tubing joint is quite large.Invalidation occurs there firstly.Therefore nondestructive testing should be implied mainly on the several thread teeth of the two ends of the tubing joint . Suitable magnetization mode and parameters are selected and magnetic field distribution of P110 tubing joint thread is simulated by using finite element analysis method.Vertical electromagnetic field uniformly distributed along each thread tooth surface is obtained by applying a cushion block with 10 mm depth and a coil 15mm longer than before.Transverse crack on the thread surface can be found out by using this kind of magnetic field.Meanwhile,center conductor magnetization process is simulated and annular magnetic field along thread surface is obtained.Vertical crack on the thread surface can be found out by using this kind of magnetic field.In addition,in order to research defect size parameters effect on leakage magnetic field,crack magnetic charge model on the thread surface and hole type defect magnetic charge model under the thread surface are established based on the magnetic dipole theory.Each defect size parameter effect on leakage magnetic field is analyzed,and it turns to be that when the ratio of depth to width of the crack is large,the leakage magnetic field signal increases when the depth or the width of the crack increases.But also,there exists a range of the defect detection.For hole type defect,the leakage magnetic field signal increases when the size of the defect is bigger or it is nearer to the thread surface,and then,it is easier to be found.And also,there exists a range of the defect detection.As most of the defects on the thread surface are transverse cracks,leakage magnetic field of transverse crack in the bottom of the thread tooth is mainly simulated and cracks with different positions and size parameters are made.The leakage magnetic field of each kind of crack is simulated and it turns to be that under the magnetization current during the simulation only cracks in 0.45 mm range from the bottom of the thread tooth can be found.In addition,the size and shape of the crack have a big effect on the leakage magnetic signals.The bigger the crack is,the easier it is to be found.When the crack with a depth of 0.6 mm is 0.45 mm far from the bottom of the thread tooth it cannot be found when its width is smaller than 0.6 mm.Moreover,when the ratio of depth to width or width to depth of the crack is 1/2 or 1/1,the leakage magnetic field is much more obvious and it is easier to find this kind of crack.更多还原