Effect of microstructure on the low temperature toughness of high strength pipeline steels

Microstructure observations and drop-weight tear test were performed to study the microstructures and mechanical properties of two kinds of industrial X70 and two kinds of industrial X80 grade pipeline steels. The effective grain size and the fraction of high angle grain boundaries in the pipeline steels were investigated by electron backscatter diffraction analysis. It is found that the low temperature toughness of the pipeline steels depends not only on the effective grain size, but also on other microstructural factors such as martensite-austenite （MA） constituents and precipitates. The morphology and size of MA constituents significantly affect the mechanical properties of the pipeline steels. Nubby MA constituents with large size have significant negative effects on the toughness, while smaller granular MA constituents have less harmful effects. Similarly, larger Ti-rich nitrides with sharp corners have a strongly negative effect on the toughness, while fine, spherical Nb-rich carbides have a less deleterious effect. The low temperature toughness of the steels is independent of the fraction of high angle grain boundaries.

Stress and Fracture Strength Analysis for Three-Way Pipes

Three-way pipes, T and Y pipes, are very important connecting components in pipeline systems, their strength are related to the safety of pipelines. In the case that crack is not detected in the three-way pipe, ANSYS finite element program version 5.6 is applied to study the stress distribution of the three-way pipe and to obtain the optimum fillet radius in the crotch region of the two pipes. The reasonable intersection angle of the two pipes is also obtained. In the case that a surface crack is detected in the three-way pipe, the maximum stress intensity factor (SIF) near the front of the surface crack is studied.

Strength differential effect and influence of strength criterion on burst pressure of thin-walled pipelines

In the framework of the finite deformation theory, the plastic collapse analysis of thin-walled pipes subjected to the internal pressure is conducted on the basis of the unified strength criterion （USC）. An analytical solution of the burst pressure for pipes with capped ends is derived, which includes the strength differential effect and takes the influence of strength criterion on the burst pressure into account. In addition, a USC- based analytical solution of the burst pressure for end-opened pipes under the internal pressure is obtained. By discussion, it is found that for the end-capped pipes, the influence of different yield criteria and the strength differential effect on the burst pressure are significant, while for the end-opened pipes, the burst pressure is independent of the specific form of the strength criterion and strength difference in tension and compression.

An Analytical Approach for Assessing the Collapse Strength of an Unbonded Flexible Pipe

这篇论文为预言一根灵活管子的倒塌力量论述一个分析计划，它考虑在相关的层之间的结构的相互作用。分析结果与一个 FEA 模型和很多个测试数据相比，并且显示出相当好的同意。理论分析证明压力盔甲层对弄弯提高了尸体的力量，尽管障碍削弱了这效果。管子的倒塌力量被象管子，层的厚度和材料的机械性质的内部半径那样的许多因素影响。例如，障碍的厚度的增加将增加接触压力并且接着减少批评压力。

Effect of strength matching on the reliability of welded pipe with circumferential surface crack

For different strength matching, the reliability index and failure probability of welded pressure pipe with circumferential surface crack were calculated using three dimensional stochastic finite element method. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The effects of external moment and the depth of the circumferential surface crack (a) on the reliability of pressure pipe were also calculated and discussed. The calculation results indicate that the strength matching has certain effect on the reliability of the welded pressure pipe with circumferential surface crack. The failure probability of welded pressure pipe with high strength matching is lower than that with low strength matching at the same conditions. The effects of strength matching on the failure probability and reliability index increased by adding external moment (M) and the depth of the circumferential surface crack (a).

Stress Corrosion Cracking of High-strength Drill Pipe in Sour Gas Well

In high sour gas reservoir drilling process, it happens occasionally that high-strength drill pipe suffers brittle fracture failure due to stress corrosion cracking, and poses serious hazard to drilling safety. To solve this problem, this paper studied the stress corrosion cracking mechanism and infl uencing factors of highstrength drill pipe in sour environment with hydrogen permeation experiments and tensile tests. We simulated practical conditions in laboratory and evaluated the stress corrosion cracking performance of the high-strength drill pipe under conditions of high stress level. For the problems occurring in use of high-strength drill pipe on site, the paper proposed a technical measure for slower stress corrosion cracking.

Theoretical and experimental study of the thermal strength of anticorrosive lined steel pipes

Bimetallic lined steel pipe （LSP） is a new anti-corrosion technology. It is widely used to transport oil, gas, water and corrosive liquid chemicals. At present, the hydroforming pressure for LSP has been investigated theoretically and experimentally by most researchers. However, there are a few reports on the thermal strength of bimetallic LSP. Actually, the bimetallic LSP will be subjected to remarkable thermal load in the process of three layer polyethylene （3PE） external coating. Reverse yielding failure may occur on the inner pipe of the bimetallic LSP when it suffers from remarkable thermal load and residual contact pressure simultaneously. The aim of this paper is to study the thermal load and strength of the bimetallic LSP. A mechanical model, which can estimate the thermal strength of the bimetallic LSP, was established based on the elastic theory and the manufacture of the bimetallic LSP. Based on the model, the correlation between the thermal strength of the bimetallic LSP and residual contact pressure and wall thickness of the inner pipe was obtained. Reverse yielding experiments were performed on the LSP （NT80SS-316L） under different thermal loads. Experiment results are consistent with calculated results from the theoretical model. The experimental and simulation results may provide powerful guidance for the bimetallic LSP production and use.

航空液压管路轴向挤压式接头组件连接强度的数值分析

针对目前航空液压管接头无法满足高工作压力要求的问题,以Φ12 mm的钛合金轴向挤压式接头为研究对象,利用Abaqus平台建立了轴向挤压连接成形与拉脱试验过程的有限元模型,通过同参数条件下的拉脱试验验证了有限元模型的准确性。结果表明,有限元模型计算误差仅为3.4%,接头组件连接强度是由导管与管套凹槽的轴向对抗阻力和导管与管套径向接触力共同决定的。系统研究了管套材料力学性能、凹槽结构、摩擦因数对接头组件连接强度的影响规律,管套材料屈服强度越高,连接强度越强;管套凹槽宽度每增长0.2 mm,连接强度提高约2.4%;摩擦因数每增加0.01,接头连接强度平均提升18%左右。

冲击力下薄壁内衬复合管界面黏结强度效应分析

【目的】研究薄壁内衬复合管在受冲击力作用下的界面黏结强度对层间剥离屈曲的影响。【方法】建立薄壁内衬复合管在弹性阶段的非线性分析模型,对薄壁内衬复合管材模态试验与分析模型的分析结果进行对比,验证有限元分析模型可靠性。通过改变衬层与原基层管壁间的界面黏结强度,研究复合管在冲击力下的动态特征。【结果】研究结果表明,当冲击荷载较小、管道变形处于弹性阶段时,薄壁内衬复合管的损伤大都集中在层间界面处。界面黏结强度对层间剥离屈曲有较大的影响,随着层间界面黏结强度的增加,外基层管与内衬层的最大等效应力差值减少。此外,外基层管和内衬层的变形协调性能力随着黏结强度增加而增大,径向层间位移减小,增加了复合管的整体性和连续性。【结论】研究结果可为薄壁内衬修复管道设计方法及层间界面效应分析提供参考。

高强钢管超高性能混凝土短柱轴压承载力性能试验研究

为研究高强钢管内填超高性能混凝土(UHPC)的钢管混凝土短柱轴压性能,该文设计22根高强钢管UHPC短柱进行轴压试验,从破坏模式、荷载-纵向应变关系对试件的轴压性能进行对比分析,旨在通过径厚比、混凝土强度、截面类型等变化来探究高强钢管UHPC短柱的实际承载力性能差异.试验结果表明:高强钢管UHPC短柱的轴压性能受径厚比、混凝土强度影响较大;试件承载力随钢管壁厚增加而增加,但相同钢管直径和不同钢管直径增幅呈现不同规律.该文从延性、核心混凝土强度提高程度两个角度进行分析并提出高强钢管混凝土试件的相关参数设计建议.最后,将高强钢管UHPC短柱的轴压试验承载力结果与国内外规范GB 50936—2014、AIJ计算承载力结果进行对比,并基于极限平衡理论推导出高强圆钢管UHPC试件的轴压承载力计算公式,同时结合该文试验数据对其进行验证,证明了公式的准确性.

轴力对预应力高强混凝土管桩抗震性能的影响

目的研究轴力和往复荷载作用下预应力高强混凝土管桩的抗震性能,为预应力高强混凝土管桩的设计和实际工程应用提供参考依据。方法应用ABAQUS有限元软件对预应力高强混凝土管桩进行有限元模拟,并与已有试验结果对比,两者吻合良好,验证了模型的准确性。在此基础上,研究轴压比和有无普通钢筋及普通钢筋直径对预应力高强混凝土管桩滞回曲线、骨架曲线、刚度退化、延性及耗能能力的影响。结果配置普通钢筋可以提高预应力高强混凝土管桩的承载能力和延性,对刚度影响不大;随着轴压比的增加,预应力高强混凝土管桩的承载能力逐渐提高,但延性变差,轴压比为0.45时,预应力高强混凝土管桩发生脆性破坏。结论配置普通钢筋可以有效改善预应力高强混凝土管桩的抗震性能,预应力高强混凝土管桩的轴压比不宜超过0.3。

基于磁各向异性的管壁应力集中区域检测方法

针对应力集中导致管壁发生屈服失效的问题,提出了利用磁各向异性检测管壁应力集中区域的方法。从能量角度出发,研究了应力导致管壁产生磁各向异性的机理,建立了管壁当量应力与磁各向异性探头输出电压信号的数学模型,通过计算管壁的当量应力判断其是否发生屈服失效,搭建了应力检测实验平台。实验结果表明,应力会导致管壁产生磁各向异性,磁各向异性检测方法能够检测出管壁当量应力的变化趋势和主应力方向所在延长线的角度,进而判断管壁是否产生应力集中区域。

宝钢高强度气瓶管的开发与组织性能研究

开发抗拉强度1100 MPa及以上的高强度高韧性无缝气瓶管是实现气瓶轻量化的重要基础。在传统34CrMo4气瓶钢的基础上,通过采用增Mo、加Ni辅助微合金化控制以及控制夹杂物等级和N含量等技术手段,成功开发了抗拉强度≥1100 MPa,延伸率≥14%,-50℃低温横向冲击韧性≥60 J/cm^(2)的高强度高韧性气瓶管,并在国内首次实现批量商业化应用。热处理试验结果表明,随着回火温度的升高,高强度气瓶钢的强度逐渐降低,塑性和低温韧性逐渐改善,这主要与组织中板条粗化和析出相发生粗化、聚集等的变化有关。为获得良好的强韧性匹配,推荐淬火温度为860℃,回火温度为520~560℃。

间断级配散粒土侵蚀过程及强度演变机理研究

旨在探究相同应力条件下不同密实度间断级配散粒土管涌侵蚀机理及其侵蚀后强度变化特性,制备干密度为1.80,1.84,1.88 g/cm^(3)的3种土体试样,通过管涌三轴试验深入地探讨了干密度对其破坏临界水力梯度、累计涌砂量、体积变化量及侵蚀后强度变化的影响规律。研究表明:试样破坏临界水力梯度随其干密度增大而增大,且利用Terzaghi公式(F1)、毛昶熙公式(F2)及水利水电科学研究院公式(F3)对其渗流临界水力梯度进行分析,发现在该应力环境下各公式计算结果与试验结果均较接近(优劣度为F2>F3>F1)。试样累计涌砂量与体积变化量均与其干密度呈负相关性变化趋势,其涌砂速率随管涌侵蚀不断发展而逐渐衰减;土的强度受干密度与侵蚀率二者影响,表现为侵蚀后土体强度折减程度随侵蚀进行而逐渐增加,随干密度增大而减小。

石油钻杆的发展趋势分析

随着钻井工况的复杂化、钻井深度加深以及其他特殊钻井的需求,钻杆定制化生产的要求越来越多,如抗硫钻杆、超高强度钢级钻杆、特殊螺纹钻杆等高端石油钻杆。目前,国内石油钻杆生产厂家都以生产API标准的石油钻杆为主,同质化竞争严重,针对深井、深海井、高腐蚀性井等领域发展所需的抗硫钻杆、超高强度钢级钻杆、特殊螺纹钻杆等高端石油钻杆产品目前涉足厂家较少,在特殊用途钻杆市场内还未形成竞争力。石油钻杆未来发展趋势一定是以满足特殊用途的定制化钻杆为前提的高端石油钻杆。本文立足于国内市场现状,放眼石油钻杆发展趋势,为今后我国钻杆的发展方向提出建议。

海上平台导管架腿柱结构强度和稳定性分析

根据南海北部大陆西区气田的分布情况,为更经济和绿色地增加气田的产量,需要新增立管连接2个气田平台。以支撑平台导管架的腿柱结构为研究对象,采用7套复合材料背负式管卡安装立管,并考虑腿柱实际受载工况,分析当管卡在不同位置时导管架腿柱结构强度和屈曲稳定性。借助所构建的SACS计算模型,验证在水深88 m下,采用7套复合材料背负式管卡时,海洋平台导管架腿柱结构的安全性和可靠性,为在相同工作环境下平台腿柱结构的设计提供参考。

极地钻探用铝合金双壁钻杆结构强度的有限元分析及试验研究

为了实现钻穿冰盖、直接获取冰下基岩样品的科研目标,本文设计了一种极地钻探用铝合金双壁钻杆,使钻杆可以满足极地上覆积雪层、冰层、冰岩夹层和冰下基岩等不同地层的空气反循环、水力反循环、绳索取心钻进相配合等钻进需求。依据铝合金双壁钻杆在极限拉伸、极限拉扭组合工况下的受力情况,开展了双壁钻杆的有限元分析,并对双壁钻杆外管与钢接头连接试样进行了拉伸试验与扭转试验。双壁钻杆有限元分析结果表明:在极限拉伸和极限拉扭组合工况下铝合金双壁钻杆中产生的最大应力分别为183.8 MPa与161.9 MPa,均小于铝合金材料的屈服强度489.99 MPa。双壁钻杆外管与钢接头连接试样强度试验结果也表明:拉伸试样破坏时的极限可承载拉力为399.5 kN,远大于提升1000 m双壁钻杆所需的拉力(208.11 kN);扭转试样破坏时的极限可承载扭矩为8264.7N·m,同样大于钻杆在正常钻进过程当中所承受的最大扭矩(1990.56 N·m)。上述结果表明,极地钻探用铝合金双壁钻杆设计方案可以满足极地钻探使用要求。

基于强度和经济性相统一的锅炉承压管选材方法研究

针对锅炉设计中承压管的经济合理选材问题,从强度计算的角度出发,分析了不同材料管子壁厚、质量与许用应力的关系,结合各原材料的单位价格,给出了以许用应力、原材料单价为函数的承压管选材经济性评价模型,并用评价模型对20G、SA-106C、15Ni1MnMoNbCu3种材料做了验证对比分析,结果显示:当设计温度大于220℃时,管道、集箱优先选用15Ni1MnMoNbCu,受热面小管优先选用SA-210C,即选择使用温度上限相近、许用应力高的材料。评价模型为承压管经济选材提供了新的方法,可进一步降低原材料的成本,提高产品的竞争力。

浇注工艺对高强度抗硫管内壁带状组织的影响研究

内壁带状组织的控制是高强度抗硫管的生产难点之一。在高强度抗硫管电炉冶炼过程中,开展不同浇注工艺(钢水过热度、结晶器电磁搅拌、末端电磁搅拌和连铸拉速等)的对比试验,通过金相显微镜、扫描电镜等分别对连铸坯、热轧态管和调质态管进行微观组织分析,研究了高强度抗硫管内壁带状组织的形成机理及演变规律,探索了不同浇注工艺对高强度抗硫管内壁带状组织的影响。

钢铁企业自备电厂管道支吊架间距计算标准分析

文章对比分析了钢铁企业自备电厂单元内外热力管道支吊架间距计算相关的规范,梳理了相应的计算公式及合格判定条件,并以典型的能源介质管道为例,列举了管道支吊架间距计算的三种情况,分析了造成计算值差异的原因;同时还指出了各规范在固有频率校核以及DL/T 5054-2016强度条件计算简化公式的不完善之处。