非均匀载荷套管抗外挤能力分析

目前非均匀载荷引起的套管损坏现象越来越严重,在套管强度设计中就有必要考虑这些因素的影响。针对套管在非均匀载荷时的受力特点,建立了理想圆管非均布载荷作用下的内力计算模型,利用能量法原理,推导出了套管屈曲时抗挤强度计算的新公式,并对影响套管承载能力的两个敏感性参数进行了讨论分析。结果分析表明,外载荷的非均匀度是影响套管抗外挤能力的主要因素,套管的径厚比在外载荷非均匀度较小时对套管承载能力有较大的影响,当外载荷的非均匀度较大时,径厚比对套管承载能力的影响很小。     

石油套管偏磨后剩余强度的模拟分析

基于钻柱接头与套管磨损试验结果,采用Dawson和White的能量损失磨损理论计算得到套管磨损系数。运用ABAQUS建立钻柱接头-套管偏磨的三维有限元模型,采用二次开发的Umeshmotion子程序和Arbitrary Lagrange-Euler自适应网格技术准确模拟钻进过程中的套管局部偏磨过程,并对磨损后的套管的剩余抗挤和抗内压强度进行分析。结果表明：套管磨损后的形状为“月牙形”,且磨损最大深度与磨损时间呈非线性关系,而套管剩余强度与磨损最大深度近似呈线性关系;套管磨损对剩余抗挤强度影响最大,当剩余壁厚小于50%时,套管失去抵抗外挤作用的能力, 但仍然具有一定的抗内压强度;发生偏磨后的套管被外挤和内压载荷作用而破坏的形式分别为挤扁毁坏和拉断毁坏。     

非均匀磨损套管空间有限元分析

针对非均匀磨损套管进行了空间有限元分析,研究了磨损量、磨损长度、轴向拉力对套管抗内压强度的影响.计算结果表明非均匀磨损套管的抗内压强度随磨损厚度的增加而降低;不同的磨损长度对套管抗内压强度影响不明显,即抗内压强度主要受磨损厚度的影响;套管轴向拉力对其抗内压强度影响不大,并且这种影响随着磨损量的增加而逐渐减小.通过对磨损套管抗内压强度变化规律的研究,为合理制定井控措施提供了科学依据.     

月牙型磨损套管抗内压强度有限元计算

在油田钻井过程中,由于钻具在井中旋转及起下钻会对套管内壁造成磨损,导致其抗内压强度降低,对油井安全构成威胁。本文使用有限元分析软件ANSYS建立套管模型,简化为平面应力问题进行分析,研究当套管内壁取不同磨损量,对磨损后套管施加载荷,计算在不同磨损量下套管的抗内压强度。结果表明,在一定的内压力范围内,套管的抗内压强度与内壁的磨损量基本成线性关系。分析结果为油井管柱下套管提供理论指导。     

月牙形磨损缺陷套管的抗内压强度研究

套管磨损多呈"月牙形",其直接后果是降低套管的抗挤强度和抗内压强度,如何计算磨损套管的抗挤强度、抗内压强度制约着如何安全地设计套管柱。因此笔者对"月牙形磨损"套管在不同磨损程度时的周向应力进行研究,并重点对其抗内压强度的计算方法进行了探索。笔者以P110的95/8 in套管为例,建立了计算磨损套管周向应力的解析模型,并用弹塑性有限元方法建立了套管的有限元力学模型,通过有限元分析来验证解析模型的正确性,最后以此为基础得出了磨损套管的抗内压强度计算公式。     

非均匀挤毁测试研究C110套管的变形规律

为完善套管非均匀挤毁失效机理的理论研究,开展了C110套管的非均匀挤毁实验,通过精密的压力试验机给套管施加非均匀载荷,进而得到套管不同载荷下的径向位移。采用在套管外壁粘贴电阻应变片的方式来测量套管在挤毁过程中的应变,进而得到了套管的屈服载荷、失稳载荷以及套管在非均匀载荷下的变形规律和失效机理。     

月牙形磨损套管抗内压强度计算

将内壁磨损套管月牙模型简化为偏心圆筒模型,通过直角坐标向双极坐标的转换和选取曲线坐标中表示应力的复势,得出了偏心磨损套管等效应力和剩余抗内压强度计算方法。磨损套管等效应力解析解和数值解对比分析表明,随着磨损深度的增加和作用在内表面压力的增大,磨损套管危险截面内、外表面的等效应力呈指数增大;磨损套管抗内压强度随磨损深度线性减少。采用双极坐标公式计算偏心磨损套管等效应力与有限元分析结果相差小于0.9%。偏心磨损套管抗内压强度理论解和月牙形磨损套管抗内压强度试验值之间相对误差小于10%。将月牙形磨损套管简化为偏心圆筒模型,采用偏心磨损套管抗内压强度公式计算月牙形磨损套管抗内压强度是可行的。     

CO_2腐蚀对套管强度动态影响分析

针对腐蚀对套管强度时变性影响,采用双重迭代试算法结合压力温度耦合作用,计算井筒内压力、温度沿井深方向分布情况,依据Norsok模型得到全井套管柱CO2腐蚀速率计算预测模型。依据试井理论利用现场录测井口压力数据回归得到气井稳产阶段井口压力随时间变化函数关系,将定产降压阶段内的压力温度时变规律引入腐蚀速率预测模型,建立CO2腐蚀环境下全井套管柱剩余强度时变性分析系统,通过对均匀腐蚀套管强度实例计算结果表明:腐蚀引起的壁厚减薄使得套管柱剩余强度随时间增加逐年降低,稳产阶段初期下降最快,随时间增加下降趋势逐渐减缓,其沿井深分布规律与腐蚀速率变化规律相似;套管极限抗挤毁强度受均匀腐蚀影响显著,其降低程度高于套管极限抗内压强度和管体抗拉强度。     

现场工况条件下含点蚀缺陷套管抗外挤强度分析

套管一旦发生点蚀，其表面可能出现孔洞，甚至穿孔现象，这严重削弱了套管的剩余强度，对井场的生产和安全构成了重大威胁。为了评估点蚀后套管的抗外挤强度，提出了一种模拟现场工况对套管抗外挤强度进行分析的方法。首先模拟现场工况下压力和温度条件，严格配比井下腐蚀液体作为介质对套管全尺寸试样和挂片样件进行腐蚀；然后对腐蚀后套管进行抗外挤试验，测量出其被挤毁时的失效压力；接着观察腐蚀后挂片的表面点蚀规律，并计算和测出其平均腐蚀速率、最大点蚀深度和点蚀密度，为有限元分析提供数据支撑；最后使用ABAQUS对不同条件下套管的抗外挤强度进行分析。结果表明：在一定温度和压力范围内，温度和压力越高，套管失效压力越高；平均腐蚀速率、最大点蚀深度和点蚀密度随温度和压力升高而增大，其中平均腐蚀速率增长率为112.5%，增长最为显著；套管的抗外挤强度随腐蚀时间增长而降低；点蚀密度会影响套管的应力分布情况和承载能力。     

内压对射孔套管强度影响的有限元分析

射孔对套管抗挤强度的影响程度取决于多种因素.主要研究内压对射孔套管强度的影响.建立未射孔套管、不带水泥环射孔套管、外裹水泥环射孔套管有限元模型,并应用ANSYS有限元软件分析计算了未射孔、射孔及孔边开裂三种情况下套管的最大应力,同时研究了水泥环对射孔套管强度的影响.结果表明:射孔套管最大应力比未射孔套管增大了64%,孔...     

Simplified motion and loading compared to physiological motion and loading in a hip joint simulator

Two wear tests were conducted using the Durham Hip Joint Wear Simulator to investigate the effects of simplified motion and loading on ultra-high molecular weight polyethylene (UHMWPE) acetabular cup wear rates. Bovine serum was used as a lubricant and a gravimetric technique was used to measure wear. The first wear test duration was 7.1 x 10(6) cycles and investigated the effect of simplified loading. This was achieved by using full physiological motion and loading for the first 5 x 10(6) cycles of the test, then physiological motion with simplified loading for the final 2.1 x 10(6) cycles of the wear test. The UHMWPE acetabular cup wear rates using full physiological motion and loading were 32.2 and 51.7 mm3/10(6) cycles against zirconia and CoCrMo femoral heads respectively. Using simplified loading the cup wear rates were 30.1 and 49.2 mm3/10(6) cycles against zirconia and CoCrMo respectively which was not significantly different from wear rates with physiological loading. The effect of simplified motion was investigated in a second wear test of 5.0 x 10(6) cycles duration. Physiological loading was applied across the prosthesis with physiological motion in the flexion/extension plane only. Mean wear of the acetabular component dropped to 0.197 mm3/10(6) cycles. The surfaces of all the acetabular cups were subject to gross examination, optical microscopy and scanning electron microscopy. No notable difference was observed between the cups subjected to physiological motion and loading and those subjected to simplified loading. The cups worn with a single plane of motion had a much smaller worn area and a notable difference in surface features to the other cups. Simplifed loading is therefore an acceptable simplification in simulator testing but simplifying motion to the flexion/extension plane axis only is unacceptable.     

四种牙科高分子修复材料摩擦学行为的对比研究

在往复滑动摩擦磨损试验台上以TA2纯钛为对摩材料,研究和比较了4种我国口腔临床常用牙科高分子修复材料在人工唾液介质中的摩擦磨损行为。结果表明在人工唾液介质中,3种成品树脂牙的摩擦因数、磨痕深度均较小,磨损表面主要呈现犁削效应;光固化树脂修补材料的摩擦因数大,耐磨性较差,磨损形貌以剥落为主,伴随犁削。     

聚醚醚酮复合材料的转移膜研究

用物理共混-模压法制备了Ekonol／PEEK和Ekonol／石墨／MoS2／PEEK复合材料，通过摩擦磨损实验方法对材料的耐磨件能进行了研究，并用SFM对对偶件表面进行了观察和分析，以探讨对偶面上转移膜的特性对复合材料耐磨性能的影响，结果表明：PEEK能在对偶面上形成不连续、厚薄不均的转移膜；Ekonol的加入能促进转移膜的形成；Ekonol和固体润滑剂能协同改善PEEK所形成转移膜的质量，从而提高PEEK的耐磨性能；复合材料在其对偶面上形成的转移膜质量的好坏对其耐磨性能产生直接影响。     

PCBN刀具的磨损机理和干切削GCr15时的磨损与寿命

研究了PCBN刀具的磨损机理和磨损形式。通过对干切削GCr15轴承钢时刀具的磨损形式及寿命进行试验研究 ,得出了工件硬度、切削速度对PCBN刀具磨损的影响规律以及工件硬度在临界硬度附近时刀具磨损速度最快的结论。加工两种硬度工件时的刀具寿命方程表明 ,切削速度对PCBN刀具寿命的影响小于对硬质合金及陶瓷刀具寿命的影响。     

Correlations between two-body and three-body abrasion and erosion of metals

The effects of various variables on the wear resistance of different pure metals are compared for two-body abrasion, three-body abrasion and erosion. The variables studied are the annealed hardness of the worn metal, the increase in hardness of the worn metal before the wear process due to work hardening and heat treatment, the applied load, the distance travelled, the abrasive particle size and the abrasive hardness. It was found that the effects of most of these variables are similar for the three different wear processes.     

Ball-cratering abrasion tests of high-Cr white cast irons

The application of a ball-cratering method to test three-body abrasive wear of bulk materials in the presence of large abrasive particles has been investigated. Three high-Cr white cast irons (WCIs) with different material properties were used as wear samples. Abrasive slurries contained two types of abrasive particles, silica sand and crushed quartz. Silica sand and crushed quartz particles have similar chemical composition and hardness but differ in sharpness. Wear rates of WCI samples were determined and the worn surfaces were examined by optical microscopy, SEM and Talysurf profilometry.It was found that the ball-cratering test can differentiate between the wear resistances of materials with similar properties. The wear resistance of WCIs in the presence of silica sand increased with increasing the hardness of the wear sample and decreasing the size of carbides in the microstructure. Smaller silica sand particles caused less wear damage than larger silica sand particles, even though the smaller particles were slightly sharper than the larger ones. When silica sand and quartz particles of the same size were used, the angular quartz particles caused much higher wear than the rounded silica sand particles. Surface morphologies of the wear craters on the WCI samples were examined in an SEM and then compared with the morphologies of the worn surfaces from slurry pumps. It was found that the silica sand particles generated surface morphologies similar to those found in the worn slurry pumps. In these surfaces the matrix was preferentially worn out and hard carbides were protruding. Wear surface morphologies produced by the angular quartz particles were different. They consisted of numerous superimposed indents and the microstructure phases were not distinguishable. This indicates that the type of abrasive particles used in ball-cratering testing significantly affects the test outcomes in terms of wear rates and wear surface morphology.     

高锰钢和贝氏体钢辙叉失效机理及其磨面组织

以实际铁路线路上过早失效的高锰钢辙叉和贝氏体钢辙叉为研究对象,利用金相、扫描电镜、透射电镜和MÖssbauer谱等分析方法研究两种失效辙叉残体磨面组织结构的变化,并探讨其失效机理。结果分析表明,两种辙叉在服役过程中表面组织都发生纳米化反应,高锰钢辙叉在服役过程中表面奥氏体内产生少量碳原子聚集的现象,其失效形式是磨损、压溃变形和疲劳剥落;贝氏体钢辙叉失效的原因是磨损和氢致脆性剥落。从而提出增加辙叉使用寿命和提高铁路运行安全的方法和途径。     

介稳奥氏体锰钢耐冲击磨粒磨损性能及磨面组织

利用冲击磨粒磨损试验结合扫描电镜、透射电镜和穆斯堡尔谱等分析手段研究了介稳奥氏体锰钢的耐磨性和磨损机制。结果表明,介稳奥氏体锰钢在某一冲击功下具有最佳耐磨性。在磨损过程中磨面诱发生产两类马氏体,无碳马氏体和合金马氏体。最耐磨时的磨面组织为合金奥氏体和无碳马氏体的混合组织。     

Analysis on collapse strength of casing wear

Carrying capacity of the casing will reduce after the casing is worn, which seriously affects the subsequent well drilling, well completion, oil extraction and well repair. A lot of researches on calculation of casing wear collapse strength have been done, but few of them focus on collapsing failure mechanism, and influencing factors and law of collapse strength. So, significant difference between estimated value and actual value of collapse strength comes into being. By theoretical analysis, numerical simulation and actual test, the collapsing failure mechanism of casing wear as well as the influencing factors and laws of collapse strength are investigated, and the investigation results show that collapse of crescent casing wear belongs to "three hinged" instability. The severely-worn position on the casing is yielded into the plastic zone first then deformed greatly, which causes the plastic instability of the whole structure. The casing wear collapse strength presents changes of exponent, power function and linear trend with the residual casing wall thickness, wear radius and axial load, respectively. When the flexibility is less than 10°/30 m, the borehole bending has less impact on casing collapse strength. Thus, the computation model for the casing wear collapsing strength is established by introducing wear radius coefficient and casing equivalent yield strength, at the same time, the model is tested. The test results show that the relative error for the computation model is less than 5%. The research results provide a basis for design of the casing string strength and evaluation of down-hole safety.