Research of precise pulse plasma arc powder welding technology of thin-walled inner hole parts

The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion. The precise pulse plasma arc powder welding method is used for surface damage repairing of inner hole parts in this paper. The working principle and process of the technology are illustrated,and the microstructure and property of repairing layer by precise pulse plasma powder welding and CO2 gas shielded welding are tested and observed by microscope,micro hardness tester and X-ray residual stress tester etc. Results showed that the substrate deformation of thin-walled inner hole parts samples by precise pulse plasma powder welding is relatively small. The repair layer and substrate is metallurgical bonding,the transition zones( including fusion zone and heat affected zone) are relatively narrow and the welding quality is good. It showed that the thin-walled inner hole parts can be repaired by this technology and equipment.

Influence of polymer dispersants on dispersion stability of nano-TiO_2 aqueous suspension and its application in inner wall latex paint

The effects of SN5040 and polyethylene glycol（PEG） individually and in combination on the dispersion stability of nano-TiO2 aqueous suspension were investigated by ultraviolet-visible absorption spectroscopy. The adsorption mechanism of these dispersants was detected by zeta potential, isothermal absorption and FTIR analysis. It is found that SN5040 is superior for stabilizing nano-TiO2 in aqueous suspension to PEG in basic region, and the optimum mass fraction of SN5040 addition is 3%. In the case of NaCl addition, the optimum value increases with .the increase of NaCl concentration in the solution. When the mixture of SN5040 and PEG is employed, the antagonism appears preponderant. When SN5040 and PEG are added sequentially, the synergistic reaction takes place. The synergistic reaction can be attributed to the mechanism that PEG adsorption decreases the electronic repulsion between SN5040 molecules, which results in the increase of SN5040 adsorption density. PEG is adsorbed by the interaction with the pre-adsorbed SN5040 layer. Furthermore, the modified inner wall latex paint with well dispersed nano-YiO2 suspension is endowed with excellent ultraviolet absorption and antibacterial properties.

Calculation on inner wall temperature in oil-gas pipe flow

Based on the energy equation of gas-liquid flow in pipeline,the explicit temperature drop formula for gas-liquid steady state calculation was derived.This formula took into consideration the Joule-Thomson effect,impact of terrain undulation and heat transfer with the surroundings along the line.Elimination of temperature iteration loop and integration of the explicit temperature equation,instead of enthalpy energy equation,into the conjugated hydraulic and thermal computation have been found to improve the efficiency of algorithm.Then,the inner wall temperature of gas-liquid flow was calculated by using explicit temperature equation and inner wall convective heat transfer coefficient of mixed flow which can be obtained by liquid convective heat transfer coefficient and gas convective heat transfer coefficient on the basis of liquid holdup.The temperature results of gas-liquid flow and inner wall in the case example presented both agree well with those in professional multiphase computational software OLGA.

Finite element modeling of power spinning of thin-walled shell with hoop inner rib

A 3D elasto-plastic finite element(FE)model of power spinning of thin-walled aluminum alloy shell with hoop inner rib was established under software ABAQUS.Key technologies were dealt with reasonably.The reliability of the FE model was verified theoretically and experimentally.The forming process was simulated and studied.The distribution of the thickness and stress,and the variations of spinning force were obtained.The workpiece springback was analyzed with ABAQUS/Standard.The results show that the FE model considering elastic deformation can not only be used to analyze the workpiece springback in the complex spinning process,but also serve as a significant guide to study the local deformation mechanism and choose the reasonable parameters.

Inner and outer pressure forming of nickel based super-alloy thin-walled part with variable diameter sections

A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.

Viscous Inner and Outer Pressure Forming Method of Thin-walled Tube and Its Application

Aiming at overcoming the difficulties in integral forming of thin-walled tubes with complex shapes, a novel forming method by inner and outer pressure through viscous was proposed. In this method, by dividing large deformation of the part into inner and outer pressure forming deformations, the limit deformation of tube part can be increased by several times. Meanwhile, the principle of viscous inner and outer pressure forming was provided, and key problems during the forming process such as reduction of the wall-thickness and instability wrinkling were analyzed. Thereby, the complex curved surface super-alloy GH3044 thin-walled tube with varying diameter ratio of 1.35（the ratio between the maximum and minimum diameters of the part） can be integrally formed by this method. The experimental surface of the formed part is superior in quality and the wall-thickness distribution is uniform. The results show that the viscous inner and outer pressure forming can provide a new approach for integral forming of thin-walled tubes with complex shapes.

Atomic layer deposition of copper thin film and feasibility of deposition on inner walls of waveguides

Copper thin films were deposited by plasma-enhanced atomic layer deposition at low temperature,using copper(I)-N,N′-di-sec-butylacetamidinate as a precursor and hydrogen as a reductive gas.The influence of temperature,plasma power,mode of plasma,and pulse time,on the deposition rate of copper thin film,the purity of the film and the step coverage were studied.The feasibility of copper film deposition on the inner wall of a carbon fibre reinforced plastic waveguide with high aspect ratio was also studied.The morphology and composition of the thin film were studied by atomic force microscopy and x-ray photoelectron spectroscopy,respectively.The square resistance of the thin film was also tested by a four-probe technique.On the basis of on-line diagnosis,a growth mechanism of copper thin film was put forward,and it was considered that surface functional group played an important role in the process of nucleation and in determining the properties of thin films.A high density of plasma and high free-radical content were helpful for the deposition of copper thin films.

A woman's Inner World in“the Mark on the Wall”

As is known to all, Virginia Woolf's concern with feminist thematics are dominant in A Room Of One's Own (1929), however, her another short story —— "the Mark on the wall"also best presents us a woman's world at the beginning of 20th Century.

The spanwise spectra in wall-bounded turbulence

The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation （DNS） of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the nearwall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Rer can be as low as 1000. The properties of the inner and outer peaks in the spanwise spec- tra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.

用brick-wall方法计算MRN黑洞内视界的熵

利用薄层模型brick-wall方法计算了MRN黑洞内视界的熵,得出了黑洞熵与视界面积成正比的结果。

Strength of Wall-Slab Junction with New Form of Shear Reinforcement in a Laterally Loaded Tall Shear Wall Building

Very high concentration of flexural, shear and torsional stresses occurs at the wall-slab junctions in a laterally loaded tall building consisting of planar walls and coupling slabs. Due to this concentration of stresses and their interaction, there are great chances of failure to occur at the junction. Also the flexural stresses are not uniformly distributed and have the highest intensity near the periphery of inner walls but are reduced drastically as we move away from the wall-slab junction. Numerous attempts have been made to strengthen the wall-slab junction by using various types of shear reinforcement to ensure that shear failure should not occur. Various methods including fibre reinforcement consisting of twins of twisted steel couplets have already been used. This paper describes a new method of placing 2 inch wide flange I-sections at appropriate locations to improve the shear strength of the wall-slab junctions. Based on systematic research, a new procedure has also been developed to assess the strength of wall-slab junction using the new reinforcement method. Test results showed that a substantial increase, up to 57%, in the shear strength of specimens was obtained by using the new method of shear reinforcement in a laterally loaded tall building.

压缩天然气用环缠绕复合气瓶泄漏原因分析

针对某压缩天然气缠绕复合气瓶在使用不久后发生泄漏,采用化学成分分析、力学性能检验、金相检验、电镜观察等手段,分析了泄漏原因。结果表明:气瓶泄漏的原因是在充装使用过程中混入了水分,天然气中混有的H_(2)S、CO_(2)和氯化物溶于水滴后形成酸性溶液与瓶壁金属发生了电化学腐蚀,形成局部点状腐蚀,加上腐蚀和应力损伤持续进行,最终导致气瓶内壁穿孔失效,引起泄漏。

蒙陕矿区内钢板-钢筋混凝土钻井井壁非均匀受力特性研究

以蒙陕矿区某煤矿风井为工程背景,利用双向不等压模型推导出水平地应力下井壁的受力形式,并得出了非均匀系数k的计算公式,确定了蒙陕矿区地层的不均匀系数范围为0.06~0.20,研判了钻井井壁全深受力关键横断面的受力破坏特征。根据有限元软件ANSYS模拟非均匀荷载条件下的井壁受力规律,井壁混凝土外缘环向应力为控制应力,井壁应力呈现非均匀分布,90°位置的不均匀程度大于0°位置,外荷载较小的90°位置受拉,而外荷载较大的0°位置受压。通过对井壁压力试验台对内钢板-钢筋混凝土进行非均匀加载试验分析,非均匀荷载对钻井井壁受力影响极为明显,在k=0.15时模型的峰值应力仅为均匀荷载条件下的23.1%~33.3%;在k=0.20时模型的峰值应力为均匀荷载条件下的20%左右,且破坏形式为混凝土先受拉破坏,随后钢筋和钢板屈服。研究结果表明,内钢板-钢筋混凝土钻井井壁对非均匀荷载较为敏感,在蒙陕矿区使用钻井法应该考虑非均匀系数的影响,且需要在井壁设计阶段重点关注井壁外荷载较小位置的受力。

高性能井筒超声脉冲回波扫描成像测井仪研制

多功能超声成像测井仪采用超声脉冲反射法对套管腐蚀及固井质量做定量评价。利用从井眼内壁反射波形提取的幅度及到时实现井眼内壁高分辨率成像;提取套管共振波的共振频率计算套管厚度;采用全波反演方法反演套管后环空介质的声阻抗。通过优化采集模式、研制高性能换能器并建立固井质量评价模版确保仪器性能优于同类产品。现场实测资料表明,仪器可准确测量套管壁厚,识别射孔层段和射孔孔眼,识别套损缺陷,为套管找漏及侧钻点选择提供重要的决策依据,并准确评价双层套管情况下的内层套管固井质量,同时还可以在裸眼井中获取井壁表面裂缝、层理、孔洞等地质构造信息。

基于蒙特卡洛方法的油田管道内腐蚀状态安全评价及预测

随着管道长时间运行,油气管道内壁会出现不同程度的腐蚀、凹点、裂纹、结垢及磨蚀等缺陷,需要及时维修或者更换。针对油田管道内壁腐蚀特点,提出了一种新的基于蒙特卡洛方法的管道安全评估模型。首先用管道内检测仪器对目标管道进行内检测,获取相关缺陷的具体数据,然后在分析数据的基础上预测腐蚀缺陷生长规律,最后基于安全预警模型对管道内腐蚀进行安全评价,预判管道失效年限。

磁信号检测高温合金内外壁缺陷分类研究

为区分高温合金内外壁缺陷,采用高精度弱磁传感器对高温合金人工槽型缺陷进行检测。从有缺陷的一面检测为正面(即外壁缺陷),从另一面检测为反面(相当于内壁缺陷),发现单侧表面缺陷检测信号出现极性相反的情况,无法通过极性相反这一特征区分内外壁缺陷。针对这一现象,基于支持向量机中的分类功能,对采集到的弱磁信号进行特征提取获得面积、幅值和占宽3种特征量建立分类数据库,进行内外壁缺陷分类识别,并采用不同的核函数建立分类模型进行比较,最终发现径向基核函数分类模型正确率最高,为84.37%,且经过样本库外的试件验证后正确率仍有81.25%。结果表明该算法能够有效地对高温合金缺陷信号进行分析和辨识,具有一定的实用价值。

PCCP管芯混凝土防裂控裂技术研究进展

预应力钢筒混凝土管(PCCP)在我国引调水工程中发挥着重要作用,PCCP运行的安全性对水资源的配置至关重要,关系国计民生。当管芯混凝土内表面产生有害裂缝后,在水压力的作用下会引起内管芯混凝土破坏,导致钢筒被锈蚀,形成安全隐患,因此,针对管芯内壁混凝土裂缝预防和控制的研究对水资源的合理利用具有重大意义。为了预防和减少PCCP内壁出现有害裂缝,根据国内外学者的研究成果,概述了PCCP管芯内壁混凝土裂缝的种类和形式,即纵向裂缝、螺旋裂缝和插口端裂缝;总结了干燥收缩、沉降收缩、温度收缩、焊缝、缠丝应力、吊装运输等因素与PCCP内壁混凝土裂缝的关系;分别从PCCP设计、原材料、配合比、养护制度、焊缝、钢筒、插口和裂缝自愈合、纤维增强材料等方面总结了PCCP管芯内壁裂缝的预防和控制方法。最后,对PCCP管芯混凝土内壁裂缝的控制和预防进行了展望,为继续研究提供思路。

地连墙内撑支护体系支撑有效刚度计算方法

针对地连墙内撑支护体系,综合考虑内支撑的初始挠曲、支撑杆件压弯二阶效应、支撑与地连墙的相互作用和地连墙变形等因素,建立内支撑的有效刚度计算方法.以北京地铁某车站基坑工程为背景,在ABAQUS有限元建模中分别引入现行规范支撑刚度和支撑有效刚度,进行基坑开挖与支护的数值模拟,并将模拟结果与实测结果进行对比分析.研究结果表明:内支撑有效刚度计算方法能更真实地反映基坑支护体系的实际受力、变形状态.

内壁扩张角度对冲压旋转爆轰燃烧室工作特性影响的数值研究

为研究内壁扩张角度对冲压旋转爆轰燃烧室工作特性的影响,构建了内壁扩张角度从0°~6°变化的5种扩张型燃烧室,基于乙烯-空气对带有凹腔结构的冲压旋转爆轰燃烧室进行三维数值模拟,分析了不同扩张角度下燃烧室的流场特征。计算结果表明:采用扩张型流道可有效减弱新鲜燃料层内的提前燃烧现象,随着扩张角度增大,爆轰波波头高度增加,爆轰波传播稳定性增强;扩张型流道对爆轰波后燃烧产物起到整体加速作用,并未起到整流作用;凹腔结构中涡核中心随着扩张角度的增大逐渐向凹腔后缘壁面移动,回流进入凹腔底部的新鲜燃料增多,凹腔对主流区新鲜燃料卷吸作用增强;采用扩张型流道后,燃烧室凹腔段总压增益和燃烧室出口总压均随扩张角度的增大而降低。

在役油管内壁腐蚀缺陷脉冲涡流检测方法

为实现采油管柱中的在役油管内壁腐蚀缺陷高精度离线检测,本文提出了一种基于双磁场传感的脉冲涡流外检测及深度定量评估方法。在试验研究中,以检测信号下降沿对数曲线斜率作为信号特征。在建立信号特征与油管剩余壁厚间映射关系的基础上,通过分析感应涡流在油管内分布范围与成像检测所识别腐蚀缺陷区域间的互相关关系,引入腐蚀缺陷深度评估补偿系数β。结合所建立映射关系,形成油管内壁腐蚀缺陷深度高效可视化定量评估方法。通过对缺陷成像及深度定量评估结果与真实情况的对比分析发现:所提方法不仅可实现对油管内壁腐蚀缺陷的三维形貌重现,且对其深度的定量评估具有较高的精度,满足工程实际在役油管的检测精度要求。