Experimental and Numerical Studies on Sea Sand Concrete Filled Stainless Steel Tube with Inner FRP Tube Subjected to Axial Compression

Since fibre-reinforced polymer(FRP) and stainless steel(SS) offer advantages of corrosion resistance and hybrid confinement, this study proposed a new type of composite column: sea sand concrete(SSC)-filled SS tubular columns with an inner FRP tube(CFSTFs) to help exploit abundant ocean resources in marine engineering. To study compressive behaviours of these novel members, eight CFSTFs and two SSC-filled SS tubular columns(CFSTs)were tested under axial compression. Their axial load-displacement curves, axial load-strain curves in SS or FRP tubes were obtained, and influences of key test parameters(the existence of glass FRP(GFRP) tubes, steel tube shapes, and GFRP tube thicknesses and diameters) were discussed. Further, specimen failure mechanism was analyzed employing the finite element method using ABAQUS software. Test results confirmed the excellent ductility and load-bearing capacity of CFSTFs. The existence of GFRP tubes inside can postpone SS tube buckling, and the content of inner FRP tubes, particularly increasing diameters, was found to improve compressive behaviours. GFRP contents helped develop the second elastic-plastic stage of the load-displacement curves. Furthermore, the bearing capacity of CFSTFs with a circular cross-section was approximately 26% higher than that with a square cross-section, and this difference narrowed with the increase in GFRP ratios.

Deformation behaviors of 21-6-9 stainless steel tube numerical control bending under different friction conditions

For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.

Effect of Pipe Diameter on Electrochemical Behavior of Stainless Steel Type 304 Pipes in Tap Water

We investigated the effects of pipe diameter on the corrosion resistance of stainless steel type 304 pipes using electrochemical measurements. Compared to plate steel, pipes have harder physical properties and tend to be harder and showed greater permeability with decreasing inner diameter. We found that the maximum corrosion current density in the secondary active state, which is the starting point of secondary passivation, appeared in the polarization curve measurement in tap water. Similar to the Vickers hardness and the maximum current density in the secondary active state, the permeability tended to increase as the diameter decreased. This is thought to increase the amount of deformation-induced martensitic and increase corrosion susceptibility. The peak of the secondary active current density was clearly seen as the potential sweep speed was increased. In addition, potential sweep speed dependence was observed in the corrosion susceptibility evaluation of deformation-induced martensite. In comparison with acid treatment, the formation of deformation-induced martensite was considered to occur in the extreme surface layer. The maximum corrosion current density in the secondary active state is expected to be a new susceptibility evaluation method for evaluating the deformation-induced martensitic transformation.

Application of Compactness Detection to Complicated Concrete-Filled Steel Tube by Ultrasonic Method

An example of using ultrasonic method to detect the compactness of complicated concrete-filled steel tube in certain high-rise building was discussed in this study.Because of the particularity of the complicated concrete-filled steel tubular column,the plane detection method and embedded sounding pipe method were adopted in the process of effectively detecting the column.According to the results of the plane detection method and embedded sounding pipe method,the cementing status of steel tube and concrete can be concluded,which cannot be judged by the hammering method in the rectangular steel tube-reinforced concrete.

The Ratcheting Behaviour of Stainless Steel Pressurized Piping Elbows Subjected to Dynamic Out-of-Plane Moments

In this paper the ratcheting behavior of four pairs of stainless steel elbows is studied under conditions of steady internal pressure and dynamic conditions that induced out-of-plane external moments at frequencies typical of seismic excitations. The finite element analysis with the nonlinear kinematic hardening model has been used to evaluate ratcheting behavior of the piping elbows under mentioned loading condition. Material parameters have been obtained from several stabilized cycles of specimens that are subjected to symmetric strain cycles. The direction of maximum strain is at about 45° between the hoop and axial directions. The results show that the direction of highest ratcheting is along the hoop direction rather than the direction of maximum principal strain. Also, the initial rate of ratcheting is large and then it decreases with the increasing cycles. Also, the FE method gives over estimated values compared with the experimental data.

The current situation and prospect of oil steel pipe in China

The oil steel pipe in the petroleum industry is very important for its high price, large consumption volume and great effect on the development of petroleum industry. The oil steel pipe mainly includes oil well pipe (drill pipe, drill collar, casing and tubing etc.) and oil-gas transportation pipe. This paper is an attempt to make a comprehensive review on the current situation and prospect of the oil steel pipe in China, presenting the past , today and future of the China oil pipe. The first section is a historical review of the China oil pipe. The developing course and progress of the oil steel pipe products are presented. The second section is about the current situation of the China oil pipe. The general situation of the China’s steel pipe corporation and their products types, capability, etc. is introduced. The third section is about the prospect of the China oil pipe. This part mainly describes the new product research and development in China steel pipe corporations, which are facing more and more strict technical requirements of the petroleum industry in oil pipe, and reveals the prosperity of China’s steel pipe corporations.

通气孔对新型不锈钢芯管平压性能影响分析

不锈钢芯管作为不锈钢桥面芯板的重要传力构件,其平压力学性能与桥面板承载能力息息相关。因钎焊工艺要求,不锈钢芯管壁上开设有双通气圆孔。为研究双通气圆孔对不锈钢芯管平压性能的影响,开展2组不同厚度不锈钢芯管平压性能试验与有限元非线性屈曲分析。通过试验结果验证采用Riks弧长法进行不锈钢芯管非线性屈曲分析方法的正确性。并考虑圆孔直径d、偏心距e、芯管壁厚t等因素,建立不同规格不锈钢芯管模型,开展非线性屈曲分析,探究多参数协同作用下对不锈钢芯管平压性能的影响分析。研究结果表明:不锈钢芯管平压试验曲线表现出明显的非线性特征,分为弹性阶段、弹塑性阶段与塑性破坏阶段;通气孔、管端扳边处转角及管脚10 mm处易优先出现局部屈曲破坏;不锈钢芯管极限荷载Pu及其对应的压缩位移δ_(u)随孔径d、偏心距e的增加而减小,随壁厚t增加而增大;芯管极限荷载Pu受孔径d的影响大于受偏心距e的影响,增大孔径使芯管极限荷载Pu下降6.00%~15.51%,而增大偏心距使芯管极限荷载Pu下降0.64%~9.22%,芯管应规避在管身中部(e/H=0.5)开孔;当孔径比d/D≯0.04、偏心比e/H≯0.3时,通气孔对芯管极限承载力影响较小,对极限荷载下的压缩位移δ_(u)不产生影响,建议将其作为通气孔设计取值。研究中获得的临界值及变化规律可用于新型不锈钢桥面芯板结构设计与优化研究。

圆中空夹层不锈钢管水泥砂浆短柱轴压性能研究

海洋工程平台塔架结构中,圆形截面中空双钢管是主要受力构件,工程界十分关注其受压性能和耐腐蚀性能。为研究圆中空夹层不锈钢管水泥砂浆短柱的轴压力学性能,以外不锈钢管壁厚、内碳素钢管直径和是否含夹层水泥砂浆为试验变量,共设计了12个短柱试件。分析各试件的破坏情况、荷载-位移曲线、承载力、变形能力及应变特征,研究不同变量对极限承载力的影响规律。结果表明:试件破坏形态为外钢管端部或中部局部屈曲破坏;随着不锈钢管壁厚的增大,试件的轴压承载力近似呈线性增长;夹层水泥砂浆对试件力学性能影响较大,可有效提高试件承载力,抑制外不锈钢管的变形,提高试件延性;对于含夹层水泥砂浆的试件,承载力随空心率增大而减小,不含夹层水泥砂浆的试件,承载力随空心率增大而增大。根据国内外规范以及相关学者提出的理论公式,计算了试件的极限承载力,并与试验承载力进行了对比分析,给出了设计建议。

新型不锈钢管固废混凝土构件受弯性能研究

进行了6个不锈钢管混凝土试件的纯弯试验研究,分析了在弯曲荷载作用下,混凝土类型和截面形状对新型S35657奥氏体不锈钢管混凝土构件的破坏模态、荷载-变形关系、抗弯刚度与承载力的影响规律。试验结果表明:固废混凝土对新型不锈钢管混凝土纯弯构件的整体破坏模态影响不大,但固废混凝土有利于提高构件的抗弯承载力与刚度。随后建立了不锈钢管固废混凝土纯弯构件有限元模型并验证了既有材料模型的适用性,最后分析了各规范抗弯承载力计算方法的适用性和预测精度。

基于生产过程的多规格不锈钢管自动封箱装置设计

针对6种不同规格的不锈钢管和企业对产品的包装需求,为实现3~6箱/min的自动包装效率,设计了一种自动封箱装置,该装置由夹箱机构、纸箱拍齐装置、折箱装置、顶升机构和机架5部分组成,通过分析每个机构的结构特点和工作原理,阐述了夹箱机构、纸箱拍齐装置、折箱装置的运动过程,重点分析了折箱机构中针对不同规格的不锈钢管如何设计其短边折箱机构及其主要技术参数的计算方法。实践证明:该封箱装置结构设计合理,整体运行稳定可靠,产品包装速度达到生产要求,减少了单条生产线所需要工人的数量,改变了传统的人工包装方式,提高了生产效率,降低了生产成本,具有较好的推广价值。

爆炸荷载作用下不锈钢管混凝土构件工作机理研究

本文进行不锈钢管混凝土构件在爆炸荷载作用下力学性能的试验研究,试验参数包括钢管截面形式(圆形、方形)、比例距离及有无填充混凝土。建立爆炸荷载作用下不锈钢管混凝土构件动态响应的有限元分析模型,模型计算结果得到试验结果的验证。基于验证的有限元计算模型,对比分析不同条件下不锈钢管混凝土和普通钢管混凝土构件的破坏形态、动态响应和耗能规律。试验和有限元分析结果均表明:随着比例距离减小,构件的破坏程度由弹性变形到弯曲破坏或剪切破坏;混凝土的填充能够有效延缓钢管发生局部屈曲和破坏,构件的承载能力、变形能力和耗能能力得到有效提升,进而提高构件的抗爆性能。在近场爆炸范围内,不锈钢管混凝土和普通钢管混凝土构件均出现三种可能的整体破坏形态,即弯曲破坏、弯剪破坏和剪切破坏,另还伴随有较明显的局部破坏形态;在条件相同包括名义屈服强度相同的情况下,不锈钢管混凝土构件的抗爆性能优于相应普通钢管混凝土构件。

AISI-304不锈钢薄壁管滚珠旋压工艺参数的正交优化研究

针对小直径不锈钢薄壁管滚珠旋压参数不当引发的一系列问题,选取φ6 mm×0.5 mm×10 mm的AISI-304不锈钢管为研究对象,建立其有限元模型,运用Abaqus软件对其成形过程进行仿真,分析了不同工艺参数(减薄量、进给比、旋压角)对其等效应力和均匀塑性应变的影响,最后运用正交试验法对工艺参数进行优化。结果表明:优化后的工艺参数组合为:减薄量0.2 mm、进给比0.05 mm/r、旋压角25°。在此工艺参数组合下,AISI-304不锈钢管的等效应力值和均匀塑性应变值达到最优,其值分别为642.22 MPa和0.06。

海洋平台换热器橇海水系统超级双相钢耐蚀分析

集合国外行业标准和国内使用经验,对海洋石油平台管壳式换热器橇内海水系统超级双相钢管线频繁泄漏进行研究,探析冶金状态、海水温度、焊接特性、材料污染为超级双相钢在海水系统中腐蚀泄漏的主要原因。从系统工艺、冶金、焊接、运行等方面分别提出减少泄漏风险的方法,并在后续设备改造中得到良好的应用。

工艺参数对不锈钢管切割表面质量的影响研究

不锈钢管切割质量主要受到切口断面毛刺的影响,对不锈钢管切割时毛刺的形成过程及工艺参数对切口质量的影响规律进行分析。首先,建立解析模型描述切口毛刺的产生过程,分析切口毛刺形成的影响因素;其次,运用有限元仿真软件,建立奥氏体不锈钢316L材料的三维切削仿真模型,模拟切削加工过程,分析切削完成后切口毛刺的形貌特征;最后,针对切口毛刺形成的影响因素,对切削过程进行单因素仿真。对减少切口毛刺的形成和优化工艺参数提供理论指导。

电力火灾后圆端形不锈钢管混凝土柱轴压性能研究

进行了14根电力火灾后圆端形不锈钢管混凝土短柱的轴压试验,分析截面高宽比、受火时间和含钢率对其火灾后剩余承载力的影响。试验表明:该类短柱的破坏模态均为局部屈曲、焊缝开裂和混凝土被压碎;试件的剩余承载力随着受火时间或高宽比的增加而降低,受火120 min后该类试件的承载力降低了7.8%~13.9%。接着建立了有限元模型,该模型可很好地模拟实测结果。基于有限元模型开展了理论分析,结果表明初始荷载对该类组合柱的剩余承载力影响较小。参数分析表明当混凝土强度从30 MPa增加到90 MPa时,其强度折减系数降低了15.8%;当截面周长从1 228 mm增加到4 913 mm时,其强度折减系数提高了20.5%;当受火时间从0 min增加到180 min时,其强度折减系数降低了8%;但含钢率、高宽比和钢材强度对其强度折减的影响较小。最后给出了电力火灾后圆端形不锈钢管混凝土短柱的剩余承载力的设计方法。

SRPE管-混凝土-钢双壁空心短柱轴压性能试验研究

针对西部盐渍土地区钢筋混凝土桥柱的腐蚀问题,提出“SRPE管-混凝土-钢双壁空心柱”。为研究其轴心受压力学性能,设计制作了6根SRPE管-混凝土-钢双壁空心短柱并进行轴压试验,获得了试件的破坏形态和荷载-位移曲线,进而分析了SRPE管压力等级、空心率和钢管径厚比对试件轴心受压力学性能的影响规律。研究结果表明:试件的破坏形态为中下部剪切破坏;试件极限承载力随SRPE管压力等级提高而增大,随空心率和钢管径厚比增大而减小,且空心率影响大于钢管径厚比。最后给出了SRPE管-混凝土-钢双壁空心短柱的轴心受压承载力计算式,计算结果与试验值吻合良好。

通风管三通相贯线处焊接坡口自动切割机的研究与设计

通风管三通焊接前需要切割相贯线处的坡口,焊缝坡口的准备对后续焊接工作至关重要。同时,还设计了以液压传动及其控制系统为核心的通风管三通相贯线处焊接坡口自动切割机。其具有钢管夹紧力可控,快、慢速运动有效结合,提高了生产效率,保证了坡口切割质量,改善了工人劳动条件。液压传动及其控制系统的应用为钢管自动切割提供了必要条件,方案合理可行,机构简单紧凑,将具有广阔的应用前景。

法国核电应力腐蚀问题对我国核电技术发展的启示

2022年,法国电力公司(EDF)大量核电机组因一回路管道应力腐蚀开裂(SCC)问题而停堆检修,对法国甚至欧洲的生产生活造成巨大影响。针对该事件,在总结国内外核反应堆类似失效案例及材料老化研究成果的基础上,对反应堆不锈钢部件的SCC问题的机理、影响因素、抑制措施开展了分析,并结合我国核电机组服役时间逐渐延长,材料老化、设备失效问题日益突出的现状,提出我国核电运维改进措施,如优化残余应力、加强监督和检查,研发更有效的无损检测技术等。同时,探讨了我国在反应堆材料老化研究方面的发展方向。

双不锈钢管约束海水海砂混凝土柱轴压试验及承载力计算模型

目的 研究双不锈钢管约束海水海砂混凝土柱(DSTSCC)试件的轴压性能、破坏形态和轴压承载力计算模型,为该类构件的轴压承载力计算提供试验和理论研究参考。方法 对24个DSTSCC试件进行轴压试验,分析外管壁厚、芯管壁厚和芯管直径等参数对其破坏形态、应力-应变曲线和承载力的影响规律。结果 双不锈钢管约束试件的破坏形态以腰鼓型破坏为主;由于不锈钢受拉本构无明显的屈服台阶,可以持续地约束核心混凝土,试件应力-应变曲线无明显的下降段,表现出较好的延性特征;随外管壁厚增大,轴压承载力可提高6%~25%;随芯管壁厚增大,轴压承载力可提高3%~20%;随芯管直径增大,轴压承载力呈现为先提高后降低的趋势。结论 基于试验破坏机理分析和理论分析,所建立DSTSCC试件的轴压承载力计算模型相较于既有承载力计算模型,具有更好的适用性。