扩散应力对圆筒结构中渗C的影响

运用数值方法模拟C浓度和扩散应力沿壁厚方向随扩散时间的演变规律,研究圆筒结构在平面应变情况下扩散应力对渗C的影响.结果表明:扩散应力增大了C的有效扩散系数,从而加速了质量传递的过程;当扩散时间一定时,C浓度和平均浓度随着圆筒外径与内径比值的增大而减小.圆筒中内表面渗C导致径向应力从内壁到外壁始终为压应力,周向和轴向应力在内壁附近为压应力,在外壁附近为拉应力.     

不等厚P92弯头的应力分析

本文采用有限元方法，分析了不等厚P92弯头在工作压力下的应力分布。结果表明，弯头轴向截面沿环向，在内壁位于内弧侧的应力最大，中性层的应力最小；弯头轴向截面沿环向，在外壁侧位于中性层的应力最大，外弧侧的应力最小。弯头0°环向截面沿轴向，在内壁整体应力分布最大，90°环向截面沿轴向，整体应力分布最小；弯头0°、45°、90°环向截面沿轴向，在内壁整体应力分布最大，180°环向截面沿轴向，在外壁整体应力分布最小。通过上述分析了解了不等厚P92弯头在工况下的应力分布情况，为该类弯头的受力分析及寿命评估提供了一定的理论基础。     

内压圆筒组合应力校核问题的探讨

国标GB150-89《钢制压力容器》中规定,当考虑温差应力时,组合应力应满足σ_B≤2·[σ]~t·φ。本文论证在满足σ_B≤2·[σ]~t·φ的条件下,(1)内壁温度高于外壁温度的单层内压圆筒,内外壁温差Δt≤2.3p,℃;(2)外壁温度高于内壁温度单层内压圆筒,外内壁温差Δt≤0.9p,℃时,均可不做组合应力校核。(3)在GB150-89标准规定的适用范围内,单层圆筒热应力可用σit=2·Δt,MPa;σot=1.6Δt,MPa 来估算。     

锅炉汽包热应力的产生及控制研究

就锅炉汽包壁温度变化引起的热应力进行讨论,详细分析了汽包上下壁、内外壁温差的产生原因、温差引起的热应力的产生过程和热应力对汽包寿命的各种影响因素,提出了控制汽包壁温差的措施,以保证汽包安全运行。     

自增强圆筒的最佳弹塑性半径

<正> 一、前言经过自增强处理的厚壁圆筒,内壁处于塑性状态,外壁处于弹性状态;具有应力分布均匀,平均应力低,承载能力大,弹性操作范围广,疲劳寿命高等优点,现已在石化工业上得到广泛应用。近年来,不少的科学工作者对厚壁圆筒的弹塑性半径进行了理论和实验的研究,由     

换热器壳体不均匀温度场的热应力解析分析

为了评估固定管板式换热器壳程圆筒体的安全强度,针对换热器壳体中的周向、轴向和径向三维不均匀温度场,总结了根据各自一维温度场模型由相应的解析式求解其热应力的方法。该方法简单易行、安全可靠,可便捷地得到比通常有限元应力分析方法更经济合理的设计结果。案例分析表明,一般的换热器圆筒体周向温差引起的轴向热应力大于轴向温差引起的轴向热应力,且该轴向应力可能出现拉应力和压应力交替间隔分布的状况。     

压力载荷作用下非圆截面管件的应力分析

采用有限元方法,分析了含椭圆度的直管、弯头在内压或内压与轴向载荷共同作用下的应力分布.考察不同载荷方式与椭圆度条件下,直管、弯头的应力分布和大小.结果表明:在两种加载方式下,含椭圆度直管的应力集中区域在长轴端部的内壁侧与短轴端部的外壁侧;仅内压作用下,弯头应力最集中的区域为弯头与直管交界处的内壁侧;当内压与轴向载荷共同...     

固定管板釜式再沸器壳程斜锥应力分析

以某固定管板釜式再沸器为例,忽略局部结构,建立整体应力分析模型,利用ANSYS软件对各工况下的应力进行了计算;同时,仅取设备壳程筒体建立局部应力分析模型,对比分析了斜锥最大倾角路径上的轴向应力和薄膜应力.结果显示：前者的最大应力强度位于斜锥大端内壁处,而后者的最大应力强度位于斜锥小端外壁处;对比同时表明采用整体模型分析所得斜锥各项应力强度水平均远低于局部模型分析结果,以此为基础进行设计可大大降低斜锥壁厚.     

焦炭塔热机棘轮效应的安定性分析

利用常用的安定性分析和有限元安定性分析两种方法对焦炭塔进行安定性分析,结果表明,焦炭塔塔壁存在径向、轴向和周向的应力,且热应力占主要成分,影响较大。采用安定性准则进行评价,得出焦炭塔满足安定性条件的结论。并对两种方法进行了比较,得出有限元安定性分析法是一种较好的安定性校核方法。     

焦炭塔筒体和裙座连接部位热力耦合分析

本文以中石油独山子石化分公司某焦炭塔的结构和原始操作参数为依据,以焦炭塔筒体和裙座连接部位为研究对象,应用ANSYS和Workbench有限元分析软件建立有限元模型,模拟分析主要操作阶段的瞬态温度场变化及相对应下的热力耦合应力。结果表明:焦炭塔筒体和裙座连接部位热应力主要由轴向温差变化引起,整个循环周期中的峰值应力均出现在筒体和裙座连接处。     

Surface Diffusion

Advances in instrumentation have made it possible in recent years to study the microstructure of inorganic materials at atomic resolution using the technique of high-resolution electron microscopy (HREM). Details of instrumentation have been described elsewhere [l], and applications and trends for HREM have recently been reviewed [2]. Although HREM is primarily a technique for studying bulk defects, it is increasingly also being applied in the profile-imaging mode to derive information about surfaces [3]. The high spatial resolution of the electron microscope makes it a valuable tool for the characterization of heterogeneous catalysts. This is evidenced by the growing number of studies wherein electron micrographs are being used to describe the morphology of a particular catalyst. Profile imaging is proving particularly useful in this regard for following changes in surface structure as a function of treatment conditions [4].     

表面粗糙度

从固体材料表面粗糙度在表面处理技术中的重要性出发,介绍了表面粗糙度的含义.应用最普遍的表面粗糙度的表示方法,即轮廓算术平均偏差Ra,以及另外两种表面粗糙度的表示方法:轮廓10点高度值Rz和轮廓最大高度值Rg.     

Variations of Surface Tension with Body and Surface Concentrations

Mathematical derivatives of surface tension with body concentration and with surface concentration are examined analytically for solutions in which the activity coefficient of the solute is taken as a linear function of solute concentration in the body, and as fixed at unity in the surface. As an approximation, the surface concentration is taken as a uniform value maintained throughout a surface domain extending from the geometrical surface to a fixed depth into the solution, at which the concentration changes as a step function to the body concentration. The writer accepts previous experimental and theoretical conclusions that for an ionic solute the increment of surface tension per surface ion increases with decreasing ionic radius. The Debye-Hückel equation for the activity coefficient of electrolytes predicts that the activity coefficient of an ionic solute increases with increasing ionic radius. Experimentally, this predicted dependence and its reverse are observed about equally often. For those solutes which behave according to the Debye-Hückel prediction it is found that a negative derivative must exist between the derivatives of surface tension with body and with surface concentration at sufficiently high values of the increment of surface tension per surface ion.     

Acoustic Surface Wave Measurements of Surface Cracks in Ceramics

Acoustic surface wave techniques were devised for detecting and characterizing surface cracks in ceramics. These techniques detect cracks at least as small as 60 μm deep on polished samples. The crack detectability was diminished by surface grinding, because of a background effect, attributed to backscattering from surface microcracks. Preliminary experiments conducted on turbine blades indicated that the techniques can be applied to components of complex shape.     

Catalytic Aluminas: Surface Models and Characterization of Surface Sites

Aluminas have been used extensively as adsorbenu and active catalysrs and catalyst supponsm the pas. Already in 1197 the aluminadyzed dehydration of ettllnoi was dtscavered by Dutch chermsts: and S;rbatier [3] remewed the use of dumlnas as active cazaiysrs far vanous reacttons UI the second decade of thu century. She that time the applicazions of aluuuas m dycic pmcesses have mcreased tremendously. In tndustrral cualytic pmcesses, alumuus are mostiy used as catalyst suppons [4]. Oxides a d mued oxides ap well as tracuuion mauls and noble meare supported oa alumma. Thuscb. romaa-elumana catalysts are ktng used for the conversion of parafdns to olailnrc hydrocarbons, 10 hydrodealkplation of aromatics. and to a lesser exzm in catalyzic reforming. The larter process LS also caralyzed by molybdena-alumina, a cavlyst system whid is also active for malang toluene and ocher aromatics from satwed hydrocarc bons. It also dyzes the Isomerhation of pm. Great efions are presently be-made to nudy the surface chemlstry of these molybdena-alumma ysfs [5, 6]. The great mterest LD. ttuS catalyst and its detailed nature and properties are certadp reiated to the enormous imnortance of cobalt oxade-molybdenum omde-nlumlna as a widely u5ed Caulytic system for hydrodesuUunzaim, hydmdeoirrogemion, and hydmcracklng reacttans. Cenaialy one of the most imporrant appllcations of alumbas is its use as a support for nobie met tn cazalpzic reformtng, My, dunsinas may also be used as supports for the immobilt.? tioa of mommuclear complexes and of polynucieu me clusters, a fleld which hs recently begun to attraa the Wrest of cacaiytic chamlsts [7, 8].     

材料表面改性技术

本文论述了材料表面改性技术各类型方法，包括工艺原理、特点及应用。     

聚烯烃表面氧化处理的研究

研究了以高锰酸钾或重铬酸钾／水／浓硫酸＝５∶８∶１００（质量比）或２０％（质量分数）的过硫酸铵水溶液及氯化铁或硫酸铜作为催化剂对聚烯烃进行的表面氧化处理,并通过熔点和红外光谱及光电子能谱等方法对氧化反应和产品的结构进行了表征。研究表明,最佳氧化温度和时间分别为４５℃～６０℃与４５ｍｉｎ;用ＫＭｎＯ４／Ｈ２ＳＯ４／ＦｅＣｌ３／ＣｕＳＯ４,Ｋ２Ｃｒ２Ｏ７／Ｈ２ＳＯ４／ＦｅＣｌ３,Ｋ２Ｃｒ２Ｏ７／Ｈ２ＳＯ４／ＣｕＳＯ４体系对聚乙烯的氧化中,氧化深度依次减小,Ｃ原子的摩尔分数由未氧化时的８０．８０４％,分别降低为３１．９０７％、６９．９０５％和７８．６６９％;在ＦｅＣｌ３催化下,产品中Ｃｌ的含量普遍增加,而以ＫＭｎＯ４／Ｈ２ＳＯ４／ＦｅＣｌ３／ＣｕＳＯ４氧化时增加最多,但对Ｋ２Ｃｒ２Ｏ７／Ｈ２ＳＯ４／ＦｅＣｌ３氧化体系,Ｏ含量的增加相对较多     

Catalytic Aluminas: Surface Models and Characterization of Surface Sites

Abstract

In recent years polyurethanes have been confronted with several challenges. Some of these challenges have been overcome with the development of new catalysts. This review article covers recent developments in the field of polyurethane catalysis. An overview of the different types of catalysts, their applications, and their actuation mechanisms, followed by a general survey of the stability of one‐component polyurethane systems in which the latent catalyst is already incorporated is presented.