耐热聚乙烯管材专用树脂的性能

研究了耐热聚乙烯管材专用树脂QHM22F的常规物性、长期热稳定性、加工性能、静液压强度等,并在管材生产厂家进行了不同口径的管材加工应用试验。结果表明:QHM22F的简支梁缺口冲击强度在70 kJ/m2以上;200℃氧化诱导期大于120 min;熔体强度在0.24 N以上;加工性能良好,可满足高速牵引的加工需要。采用QHM22F生产的管材内外表面光滑、壁厚均匀,性能满足用户要求。     

聚乙烯管道热熔接头可靠性评价方法研究

介绍了目前国内外聚乙烯管道熔接接头可靠性评价的短期力学性能和长期耐慢速裂纹拓展的主要检测方法及其适用性研究.近年来,超声波相控阵被广泛应用于熔接接头可靠性无损检测,其自动化检测和结果智能化判定是一个重要的研究方向.目前我国标准中对熔接接头可靠性检测的项目较少,为使聚乙烯承压管道向厚壁、大口径、高耐压、耐高温、长寿命和更...     

聚乙烯及其复合管道安全检测与评价方法

聚乙烯及其复合管道广泛应用于油气输送、城市燃气等能源领域,其安全性至关重要。焊接接头的安全检测及评价是聚乙烯及其复合管道系统安全的关键技术。介绍了聚乙烯管道焊接接头的无损检测原理及方法、冷焊检测技术以及缺陷分类与失效模式三方面内容。对电熔和热熔焊接接头分别采用超声相控阵和耦合聚焦技术进行超声检测,并给出了缺陷剖切与检测结果的对比图。提出了物理概念清晰、工程应用方便的冷焊超声检测方法。将电熔接头中的缺陷分为熔合面缺陷、孔洞、结构畸变和过焊。分别对含不同类型和大小缺陷的电熔接头进行力学性能测试,发现电熔接头存在三种典型的失效模式,即沿电熔套筒壁贯穿裂纹失效、熔合面失效以及沿电阻丝所在平面贯穿裂纹失效。根据试验测试与理论分析结果,提出了相应的安全评定方法。所提出的方法,填补了国内外在聚乙烯管道安全检测与评价方法方面的技术空白,提高了燃气管道的本质安全性。     

高密度聚乙烯管耐氯氧化试验系统设计

为了研究高密度聚乙烯(PE-HD)管的耐氯氧化性能,基于ASTM F2263标准,设计了一种封闭循环试验系统,可在流动状态下通过改变温度、压力和有效氯含量加速试样的氧化失效.结果表明,该系统可独立测试24根DN 20的PE-HD管状试样,可编程逻辑控制器(PLC)作为控制主机可以控制管路的压力、温度和流量,再加上耦合各...     

Effect of rotation extrusion and molecular weight on ductile failure of polyethylene pipes under hydrostatic pressure

ABSTRACT

In this study, two kinds of polyethylene (PE) with different molecular weight were processed into the pipes via rotation extrusion and the failure behaviours under hydrostatic pressure as well as molecular relaxation were investigated. The experimental results showed that the high molecular weight PE exhibited slower relaxation behaviour with higher relaxation activation energy to facilitate the formation of shish-kebab under flow field, while for the low molecular weight one, the stretching molecules easily relaxed back coil state and spherulites were prone to form. Therefore, the low molecular weight PE pipes via convention and rotation extrusions had similar isotropic spherulite morphology and short failure times. In the case of high molecular weight PE, during the convention extrusion, polymer melts flowed along the axial direction to induce the alignment of shish-kebab accordingly, which went against to the hoop stress in hydrostatic pressure. With the rotation of mandrel and die, the direction deviated from the axis so that PE pipe exhibited better resistance to the hoop stress. The failure time was 182?h, 264% longer than the convention-extruded one. Accordingly, a new strategy to prepare high hydrostatic pressure PE pipe under cooperative effects of rotation extrusion and long molecular relaxation time was proposed.     

聚乙烯电熔接头管材熔融区深度与焊接性能关系研究

在聚乙烯管道电熔焊接过程中,形成接头强度主要取决于套筒和管材界面聚乙烯高分子链的扩散缠结阶段经历的时间,该时间与熔焊区扩展到管材内部的熔融区深度存在一定的对应关系。为探索聚乙烯电熔接头管材熔融区深度与接头焊接性能的关系,提出了一种管材熔融区深度的超声测量方法,开展了管材熔融区深度测量和焊接性能试验。结果表明,管材熔融区深度与界面焊接强度有明确的关联,管材熔融区深度在一定范围内时,就能保证基本的剥离强度值和界面韧性;在此基础上提出一种以管材熔融区深度确定电熔接头焊接时间的新方法,该方法充分考虑到环境温度、焊接电压、电阻丝电阻等各种偏差,更能适应实际工程。     

聚乙烯及其复合管电熔接头的失效模式与爆破压力研究

通过Abaqus有限元分析软件,建立聚乙烯（PE）及其复合管电熔接头受内压和轴向力作用下的有限元模型,分析电熔接头的应力分布规律,研究管材种类、强度对电熔接头的失效模式与爆破压力的影响规律,结合电熔接头短时爆破实验验证模型的有效性。结果表明,PE管电熔接头的失效模式是管材韧性破坏;增强热塑性复合管（RTP）电熔接头的失效模式和爆破压力受管材强度影响,随强度增加,失效模式由管材破坏转变为电熔套筒破坏,爆破压力随RTP管材强度增加先升高,随后趋于稳定。     

Morphology of extruded high-density polyethylene pipes studied by atomic force microscopy

Atomic force microscopy (AFM) was used to study the structure of extruded polyethylene (PE) pipe. During extrusion, the outer surface of the pipe was cooled with water. Two cross sections, parallel and transverse to the extrusion direction, were examined in order to spatially follow the structural development during extrusion. The morphology revealed was spherulitic, and the spherulites had a mostly banded appearance when viewed under the AFM. We were not able to distinguish an oriented skin layer at the surface of the pipe, either by AFM or polarizing microscopy. The changes in the pipe's structure resulting from the cooling conditions were found to be rather gradual, and no clearly defined zones were observed. A slight orientation towards the extrusion direction was detected only in the area of the pipe crystallized under the lowest degree of undercooling. Measured spherulitic size, band period, and lamellae thickness showed a gradual increase in their values from the cooled to the noncooled surface of the pipe. Transmission electron microscopy (TEM) was used to verify the band period and lamellae thickness measurements done by AFM. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 515–523, 1997     

基于抗剪机构和破坏模式的RC剪力墙极限承载力分析

以建立基于抗剪机构和破坏模式的钢筋混凝土(RC)剪力墙极限承载力的分析模型为目的,根据RC剪力墙破坏模式,剪力墙的抗剪机构可简化成倾角为θ的混凝土压杆、纵向及横向分布钢筋3部分。基于该抗剪机构,推导了RC剪力墙的极限承载力的计算公式,并编制了计算程序,对15片不同配筋、不同几何尺寸和受力状态的RC剪力墙进行了承载力分析,理论计算结果和试验结果吻合较好,该分析模型能够较好地反映RC剪力墙的极限承载力特性,可供RC剪力墙抗剪强度验算参考。     

耐热聚乙烯管材专用树脂QHM22F的性能及加工应用

研究了工业化生产的耐热聚乙烯(PE-RT)管材专用树脂QHM22F的常规物性、加工稳定性、加工性能等,并在不同管材生产线上进行了加工应用试验。结果表明:QHM22F的简支梁缺口冲击强度在70 k J/m2以上;200℃氧化诱导期大于120 min;耐压等级达到PE-RTⅡ型;QHM22F的加工性能良好,可满足高速牵引(36.1 m/min)的加工需要;采用QHM22F生产的管材内外表面光滑、壁厚均匀,性能满足用户要求。     

炭黑对给水用聚乙烯管材物理性能的影响

采用不同炭黑比例的聚乙烯(PE)管材,研究了炭黑对PE管材物理性能的影响.结果表明,炭黑对PE管材的氧化诱导时间(OIT)、拉伸性能、密度均有一定的影响;相同的原料和工艺下,密度与炭黑含量呈线性关系,随着炭黑含量的增加,密度也随之增大;在炭黑含量为1.43％～3.51％区间内,随着炭黑分散等级的增大,OIT变小,并且与...     

基于应变硬化模量方法评价聚乙烯管材耐慢速裂纹增长性能研究进展

概述了聚乙烯（PE）管材3种典型失效破坏模式（韧性破坏、脆性破坏、热氧老化破坏）,简述了慢速裂纹增长的分子机理和断裂力学机理,详细介绍了应变硬化模量（SH）方法的测试原理和试验过程,介绍了目前SH法测试与材料微观结构相关性的研究进展,综述了国内外关于SH法评价管材耐慢速裂纹增长性能的可靠性研究以及应用SH法评价材料耐环境应力开裂性能的研究进展,并对应用SH法在控制产品质量方面提出展望。     

基于粒子滤波联合估计的气相聚乙烯质量指标在线估计

针对气相聚乙烯生产中各种复杂的工况造成在线估计精度下降的现象,基于乙烯聚合机理并利用特征建模方法建立了聚乙烯质量指标预测模型,结合扩展卡尔曼滤波,提出了粒子滤波联合估计方法,即将状态和修正系数组成增广状态向量,实现对质量指标预测模型的在线滤波修正,并分析了基于粒子滤波估计的收敛性。所提方法在中石化某气相聚乙烯装置的长周期运行结果证实了所提方法的可行性和有效性,为实施聚乙烯装置的先进控制奠定了基础。     

Effect of vibration extrusion on the structure and properties of high‐density polyethylene pipes

BACKGROUND: The axial strength of a plastic pipe is much higher than its circumferential strength due to the macromolecular orientation during extrusion. In this work, a custom‐made electromagnetic dynamic plasticating extruder was adopted to extrude high‐density polyethylene (HDPE) pipes. A vibration force field was introduced into the whole plasticating and extrusion process by axial vibration of the screw. The aim of superimposing a vibration force field was to change the crystalline structure of HDPE and improve the molecular orientation in the circumferential direction to obtain high‐circumferential‐strength pipes. RESULTS: Through vibration extrusion, the circumferential strength of HDPE pipes increased significantly, and biaxial self‐reinforcement pipes could be obtained. The maximum increase of bursting pressure and tensile yield strength was 34.2 and 5.3%, respectively. According to differential scanning calorimetry and wide‐angle X‐ray diffraction measurements, the HDPE pipes prepared by vibration extrusion had higher crystallinity, higher melting temperature, larger crystal sizes and more perfect crystals. CONCLUSION: Vibration extrusion can effectively enhance the mechanical properties of HDPE pipes, especially the circumferential strength. The improvement of mechanical properties of HDPE pipes obtained by vibration extrusion can be attributed to the higher degree of crystallinity and the improvement of the molecular orientation and of the crystalline morphology. Copyright © 2008 Society of Chemical Industry     

Effect of temperature on the performance of laterally constrained dielectric elastomer actuators with failure modes

This article analytically investigates the temperature influence on the performance of laterally constrained dielectric elastomer actuators. The effects of both temperature and stretches on the permittivity are taken into consideration. The governing equations of state are established by modeling the actuator as a thermodynamic system of three degrees of freedom. Various failure modes, including electromechanical instability, electric breakdown, loss of tension, and tensile rupture are considered to restrict the operation state and to determine the region of allowable state. Numerical calculations are performed to depict the variations of some important physical quantities with generalized coordinates and to gain insight on the influence of temperature on the critical curves of failures. It is shown that the temperature has obvious effects on the operation state and the allowable region. The present results can be used for designing and optimizing an actuator, and the present approach can be extended to other kinds of dielectric elastomer actuators with complex geometries.     

国内聚乙烯管材专用料生产现状及市场分析

综述了国内聚乙烯（PE）管材专用料的生产情况;研究并分析了今后5～10年国内PE管材专用料的市场需求及发展方向,提出了我国PE管材专用料开发领域存在的问题和建议。     

聚乙烯管道热熔对接焊接头性能的分析

测试和分析了聚乙烯管道热熔对接焊接头的结晶度、硬度、拉伸性能和冲击性能，并与基材的性能进行了比较。结果发现，焊接接头区域内的结晶度高于基材部分的结晶度。焊缝的拉伸强度和硬度也均高于基材，而冲击强度低于基材。     

国内外耐热聚乙烯管材专用料的发展概况

介绍了耐热聚乙烯管材的分类,概述了国外耐热聚乙烯管材专用料的发展现状以及主要Ⅰ型和Ⅱ型树脂的性能,同时阐述了国内耐热聚乙烯管材专用料新标准的制定情况和开发情况,并针对国内的研发和生产现状,对存在的问题和发展方向提出了相应的建议。     

Effect of substrate curvature on residual stresses and failure modes of an air plasma sprayed thermal barrier coating system

A set of aerofoil shaped air plasma sprayed thermal barrier coated (APS-TBC) specimens were adopted in this paper to investigate the stress distributions in the ceramic top coat (TC) and the thermally grown oxide (TGO), the mechanism of local crack generation and propagation at the TC/BC (bond coat) interface. The failure mode of the TBC system, the distribution of asperities at TC/BC interface, thickness of the TC and BC, and the TC microstructure were found to be influenced by substrate curvature. Residual stress was therefore measured across the thickness of the TC, along the undulating TGO and mapped at locations of asperities where failure tended to occur to interpret the initiation of local failure. The role of the TGO was investigated via its chemical bonding with the TC and the decohesion occurring at the TGO/BC interface. The crack propagation at the interface has been discussed with respect to the macro-failure of the TBC system.     

高温内压环境下聚乙烯燃气管道老化性能评价研究

将一批聚乙烯燃气管道试样置于80 ℃、1.1 MPa水浴环境下进行老化试验,老化时间分别为0、165、500、1 000 h,并通过差示扫描量热法（DSC）、热失重分析（TG）、傅里叶变换红外光谱分析（FTIR）和拉伸试验分别测试各老化试样对应的氧化诱导时间（等温OIT）、热分解温度（T_s）、官能团组成和断裂伸长率（ε）,模拟分析高温内压环境下聚乙烯管道的老化性能变化规律。DSC、TG和拉伸试验结果显示,随着老化时间增加,聚乙烯管道的等温OIT、T_s和ε都逐渐降低,老化程度逐渐增加,并且管内壁的老化速率明显大于外壁;FTIR结果显示,随着老化时间增加,聚乙烯管材料的官能团谱图中1 720 cm^-1和3 400 cm^-1处分别出现了C=O和O—H的振荡峰,进一步证实了聚乙烯管材料分子链中引入了氧化反应产物。