Analysis on performance and test of a new type of ultra-high pressure pipe joint

Analysis as well as application of ultra-high pressure hydraulic system and elements has become a trend. The structure and operation principle of a new type of ultra-high pressure pipe joint is introduced. The structure of the new type of ultra-high pressure pipe joint is simple and is easy to be produced. The finite element model on two working conditions( preload condition with 30 N·m torque and static-loading condition with 70 MPa pressure) is built and computed. The width of contact area,the equivalent stress status,as well as the contact pressure status are plotted and analyzed. According to the national standard,test on air-tightness,blasting,and cyclic endurance is conducted and the results show that the new type of ultra-high pressure pipe joint has the sealability for ultra-high pressure up to 70 MPa,and the DN6 ultra-high pressure pipe joint can provide effective seal under70 MPa fluid pressure. The research can provide a thinking and method on designing ultra-high pressure pipe joint and push forward the development of ultra-high pressure hydraulic system.

Study on mechanical behaviors of double shoulder drill pipe joint thread

Double shoulder drill pipe joint(DSJ)is a novel thread structure which appears in recent years.Its strength reduced efficiently while the structure design is not appropriately,for the DSJ’s mechanical behaviors weren’t well studied.In this paper a 3D whole structure finite element model of DSJ was established based on the Principle of Virtual Work,and validated the model’s computing results by experimental results.The authors analyzed the stress and strain distribution with the 3D whole structure finite element model’s computing results under torque moment,compression force,tension load,and bend moment.And then acquired the DSJ’s mechanical behaviors under each load.The research works of this paper refer accordance to recognize and design the DSJ.

INTERFACIAL BEHAVIOR OF PIPE JOINTS UNDER TORSION LOADS

The interfacial behavior of pipe joints is studied in this paper. Firstly, through nonlinear fracture mechanics, the analytical expressions of interfacial shear stress and the load- displacement relationship at loaded end of pipe joints under torsion loads are obtained. Thus the shear stress propagation and the debonding process of the whole interface for different bond lengths can be predicted. Secondly, through the analytical solutions, the influences of different bond lengths on the load-displacement curve and the ultimate load are studied. The stress trans- fer mechanism, the interface crack propagation and the ductility behavior of the joints can be explained.

Elastoplastic pipe-soil interaction analyses of partially-supported jointed water mains

Water distribution networks are essential components of water supply systems. The combination of pipe structural deterioration and mechanics leads to the failure of pipelines. A physical model for estimating the pipe failure must include both the pipe deterioration model and mechanics model. Winkler pipe-soil interaction (WPSI), an analytical mechanics model developed by Rajani and Tesfamariam (2004), takes external and internal loads, temperature changes, loss of bedding support, and the elastoplastic effect of soil into consideration. Based on the WPSI model, a method to evaluate the elastic and plastic areas was proposed in the present study. An FEM model based on pipe-soil interaction (PSI) element was used to verify the analytical model. Sensitivity analyses indicate that the soft soil, long pipe and high temperature induced the axial plastic deformation more likely, which, however, may not occur in normal scenarios. The soft soil, pipes in small diameters, long unsupported bedding are prone to form flexural plastic area. The results show that the pipes subjected to the same loads have smaller stresses in the elastoplastic analysis than elastic analysis. The difference, however, is slight.

Transient out-of-plane distortion of multi-pass fillet welded tube to pipe T-joints

The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.

内牙水管接头的注塑模具设计及CAE仿真

针对一端带有内螺纹和另一端为光孔的水管接头,设计了一套带有齿轮传动+抽芯液压缸的自动脱螺纹机构和斜导柱侧抽芯机构的三板式注塑模具。首先,结合塑件的结构特点,确定了点浇口进胶以及浇口位置和直流循环式的冷却回路,利用模流仿真分析软件moldflow对确定的模流分析模型进行注塑成型工艺过程模拟分析。结果表明,塑料熔体的充填时间、缩痕指数、气穴分布以及翘曲变形量等成型工艺参数都在合理范围之内,验证了浇注系统和冷却系统设计的合理性。其次,对模具结构进行设计,将主分型面取在塑件的轴心面上,其余两个分型面顺序分型实现浇注系统凝料的自动脱落。由于塑件为带内螺纹的管状零件,针对内螺纹脱模难的问题,设计了齿轮传动机构驱动螺纹侧型芯旋转和抽芯液压缸的直线移动的两套运动机构实施自动脱螺纹,塑件光孔部分的成型和抽芯采用斜导柱侧抽芯机构来实现。通过模流分析,验证了模具结构的合理性,并且缩短了模具设计的开发周期,有效地提高了塑件的成型质量。

Ultimate Bearing Capacity of Hollow Spherical Joints Welded with Circular Pipes under Eccentric Loads

The hollow spherical joints welded with circular pipes applied to the National Swimming Center of China are subjected to large bending moments, but the influence of bending moments is not considered in the design equations in Technical Specification for Latticed Shells. Based on the von Mises yield criterion, multilinear isotropic hardening rule and associated flow rule, the elasto-plastic finite element model is put forward to analyze the behavior of the joints, and a calculation method for the joints under bending moments or eccentric loads is proposed. It is shown by the analytical results of joint that the stiffening rib can improve the ultimate bearing capacity by 10% for joints under axial tensile load, by 40% for joints under axial compressive load, and by 50% for joints under bending moment. The unified calculation equations for joints with or without stiffening rib are put forward, which can be applied to calculating the ultimate bearing capacity of the hollow spherical joints with circular pipes under eccentric loads.

复合载荷作用下矿用定向钻杆接头的三维力学特性分析

煤矿钻杆在严苛的服役环境和复杂的受力状态下易失效,不仅影响正常生产,而且还因打捞困难致使事故恶化。针对上述问题,以煤矿φ73 mm外平定向钻杆为研究对象,对不同载荷下钻杆接头进行了受力分析,并通过单轴拉伸试验获得了接头材料的力学性能参数,构建了接头材料的本构模型。在此基础上,应用虚功原理、Von Mises屈服准则和接触非线性理论建立了钻杆接头螺纹的弹塑性有限元分析模型,分析了不同工况载荷作用下接头部位的受力状态及应力场分布规律。研究结果表明:在预紧扭矩为2000 N·m时,该钻杆接头具有良好的密封性能和联接强度;单扭和拉扭载荷下,靠近主台肩的第一螺纹牙为主要失效部位;在压、弯、扭载荷下,主台肩为主要失效部位;在钻机最大扭矩与推进力的作用下,接头的抗弯能力达到3°/3 m。

大型钢结构多向钢节点电弧增材制造工艺

多向钢节点作为连接大型钢结构的关键构件,承载钢结构建筑各方向的力,对其安全性起至关重要的作用。基于七向钢节点结构特点,文中研究了电弧增材制造钢结构建筑的七向钢节点,采用分区成形、平曲面切片及摆动填充的路径规划方法,将其分为直臂圆管区、相贯区和支管延长区3个区域,相贯区包括两管相贯、三管相贯和四管相贯3种类型。直臂圆管区和支管延长区采用摆动工艺进行堆积,两管相贯、三管相贯和四管相贯区分别采用曲面切片的路径规划进行堆积。对堆积完成的构件进行成形精度检测、微观组织的观测和力学性能的测量。结果表明,七向钢节点构件成形尺寸偏差为±1.32 mm,成形精度较高。微观组织为铁素体和珠光体,构件的抗拉强度和屈服强度相对于同成分铸件分别提高了约30%和105%,电弧增材制造的七向钢节点满足使用要求。

聚乙烯管焊接接头相控阵超声检测的优化设计

在管道工程应用中,由于良好的耐腐蚀性和韧性,聚乙烯(PE)管与其他材料相比具有显着优势,已广泛地应用在核电、油气输送领域;PE管焊接过程中,焊接参数、人员操作和环境等因素会影响聚乙烯管道的焊接情况,可能致使焊接接头内部形成缺陷,影响管道安全运行,而相控阵超声检测技术能够实现聚乙烯管道焊接接头内部结构的无损检测及评估;因此开展PE管焊接接头的相控阵超声实际检测工作,研究了聚乙烯材料的声衰减规律及声频散效应,优化了焊接接头的超声相控阵检测工艺,基于CIVA仿真软件实现了聚乙烯管道相控阵超声检测的声场模拟和缺陷仿真,通过研究检测参数及声学参量变化对检测结果的影响,获得了PE管焊接接头的最优检测工艺;通过加工带有典型缺陷的聚乙烯热熔对接接头试样,对前期基于仿真结果设计的检测工艺以及针对焊接接头相控阵检测研发的楔形耦合组件进行可靠性测试和工艺试验;研究结果为PE管接头缺陷的超声相控阵检测提供了工艺设计的理论支持和可靠的研究方法。

强震作用下跨断层管道柔性接口抗震加固研究

强烈地震引起的地面永久性大变形是导致埋地供水管线损坏的主要威胁之一。该研究借鉴链式结构的设计思想,基于传统承插式管道接口形式,研发了一种新型管道抗震接口,其可支持一定的轴向伸缩自由变形。当接口变形量达至极限状态时,接口发生自锁现象并能提供较高的抗拉承载力,进而带动相邻管道滑移,以抵消断层错动引起的变形量。针对新型抗震接口开展了轴向力学性能试验,并建立了跨断层下的管线数值模型;同时,数值结果与相关全尺寸试验进行对比验证。该研究以土体压实条件和断层穿越管道位置作为关键变量,研究了加固前后断层错动下承插式管道的力学响应。研究结果表明:提出的抗震接口能够有效地提高管道抵抗地面大变形能力,并且提高接口的轴向抗拉拔能力是提升管道抗断层错动能力的关键;对于松砂土跨断层下的承插式管道接口震损较为严重;断层穿越管道不同的位置会造成不同的接口变形规律;国内规范中管道接口的转角限值过于保守,不利于对跨断层承插式管道安全性能进行合理验算。

油气田用工业纯钛管道TIG焊焊接接头组织与性能研究

选用工业纯钛管道TA2、TA3进行钨极氩弧(Tungsten Inert Gas,TIG)焊接工艺研究。通过金相分析、力学性能试验和腐蚀试验,焊缝均能取得满足要求的金相组织,TA3接头的抗拉强度在室温和高温下都优于TA2。冲击试验均为韧性断裂,焊缝在硫化氢酸性环境中的抗应力腐蚀开裂性能优异,可满足油气田服役要求。

核安全3级高密度聚乙烯管道热熔对接工艺实践

高密度聚乙烯(HDPE)管道因具有良好的耐海水腐蚀能力,在压水堆核电厂服务水系统和部分设备冷却水系统核安全3级管道中逐渐得到了应用。为了有效提升HDPE管道热熔对接工艺的质量,根据ASME BPVC规范,对核安全3级HDPE管道的材质性能、热熔对接工艺评定、热熔对接工艺实践等进行了分析。通过合理控制热熔对接压力、端面吸热压力、端面加压加热时间、最小吸热时间等参数,可以显著提升HDPE管道热熔对接工艺的质量。

飞机生保系统氧气导管接头腐蚀原因分析

[目的]飞机生保系统氧气导管接头装机后多次发生腐蚀问题,为保证飞机质量安全,亟需明确其腐蚀原因。[方法]针对小平管嘴与外套螺母配合面及附近区域均出现腐蚀的现象进行了形貌、组织及成分分析,并通过模拟实验来验证腐蚀成因。[结果]确定了表面腐蚀产物为不规则及泥纹花样的Cu、Zn氧化物,且存在较高含量的K、Ca、Na异常元素。氧气导管小平管嘴沟槽处容易残留中性钾皂液,在表面浸润的情况下形成了大片不规则的钾皂残留物;其余开放表面接触过中性钾皂后,在未洗净的情况下易产生不规则及泥纹花样的Cu、Zn氧化物颗粒。另外,由于焊接后小平管嘴表层脱锌形成了疏松多孔组织,因此其表面更容易吸附钾皂成分,从而加速腐蚀。[结论]氧气导管在气密试验后表面残留中性钾皂成分是导致其腐蚀的根本原因。建议气密试验后将导管彻底洗净或更换气密试验检测剂。

基于有限元的K型管节点快速建模方法研究

管节点是现代工程结构设计与强度分析中的重点。分析ANSYS参数设计语言的优势与局限,确定利用VB.net开发自动建模程序实现参数化建模总体设计方案。以K型管节点为研究对象,对单元类型的选取、网格划分的原则及方法等方面展开研究,通过VB.net一键生成K型管节点有限元模型命令流,实现K型管节点有限元快速建模,此研究方法可推广至其他形式管节点。

沉管隧道管节接头钢剪力键制作及安装工艺

随着我国海底隧道工程建设的快速发展,沉管法海底隧道施工技术得到更多应用。沉管隧道管节接头作为沉管连接的关键部位,也是薄弱部位,管节接头止水与剪力键体系对沉管隧道结构的安全性有重要影响。为高质量完成管节接头施工,保证沉管的安全性,文章通过大连湾海底隧道管节接头钢剪力键施工,总结钢剪力键制作及安装技术的具体操作步骤及施工要点,积累沉管隧道管节接头剪力键施工经验,为后续施工提供参考。

过活断层倒虹吸地面压力管结构型式比较研究

以往对过活断层倒虹吸地面压力管道研究,往往只单独研究钢衬钢筋混凝土管和明钢管两种结构型式,具体哪种管型更为合适尚无比较。采用有限元方法,通过建立地面钢衬钢筋混凝土管和明钢管两种管道有限元模型,对比分析了两种管道型式过活断层倒虹吸在断层蠕滑变形、黏滑变形以及地震作用下的位移和应力。研究结果表明:①钢衬钢筋混凝土管和明钢管管线中布置多个波纹管伸缩节后,均能较好适应断层蠕滑变形;②两种管道结构位于主断层范围的波纹管伸缩节在断层黏滑变形作用下变形均在100 mm以上,设计难度大;③地震作用下,在主断层范围内的钢衬钢筋混凝土管虽然位移大,但地震引起的应力较小,而明钢管在固定支座处的受力情况明显恶化;④综合多种工况的计算结果,钢衬钢筋混凝土管的受力情况比明钢管更优秀,但明钢管具备运行期检修复位的条件,两种管道方案各有优劣,应根据工程具体需求合理选择管道结构型式。

城市地下综合管廊预制管接缝纤维增强混凝土性能试验研究

为提升城市地下综合管廊预制管接缝混凝土的力学性能,文中从纤维掺量和纤维长度入手,研究了预制管接缝纤维对混凝土裂缝面积、抗折强度、抗压强度及抗渗性能的影响。结果表明,纤维掺量从0、6%、10%增加至14%,掺加6 mm纤维的混凝土裂缝面积降幅分别为31.8%、46.3%、62.7%,7 d抗折性能增幅分别为29.6%、14.3%、11.1%;掺加10 mm纤维的混凝土裂缝面积降幅分别为36.3%、52.7%、59.9%,7 d抗折性能增幅分别为25.9%、18.5%、14.8%,确定最佳纤维掺量为10%。当纤维长度从0增加至6 mm时,再增至10 mm时,混凝土的最大渗透高度降幅分别为50.1%、65.3%。