某电厂316L不锈钢输氨管腐蚀开裂原因

某电厂316L不锈钢输氨管道在运行过程中发生开裂现象。采用宏观观察、化学成分分析、金相检验、扫描电镜及能谱分析等方法分析了管道开裂的原因。结果表明：管道裂纹由内壁向外壁扩展,呈穿晶开裂特征,裂纹呈树枝状形貌,符合应力腐蚀开裂特征;腐蚀产物中存在Cl元素,在拘束拉应力和腐蚀介质的共同作用下,管道发生了应力腐蚀开裂。     

热交换器不锈钢管束断裂失效分析

采用宏观分析、金相检验、断口宏观及微观分析以及能谱分析等方法,对某炼油厂裂化车间4台热交换器不锈钢管束先后发生大面积断裂的性质及原因进行了分析。结果表明:该热交换器管束断裂是由在交变载荷和腐蚀介质作用下发生的由外向内的腐蚀疲劳开裂引起的;腐蚀疲劳裂纹起始于管外壁的点蚀坑等应力集中处,促进腐蚀疲劳裂纹扩展的管束外部介质主要是Cl^-和H₂S;裂纹先以腐蚀疲劳开裂方式扩展,而后又呈典型的应力腐蚀开裂方式继续扩展,当应力腐蚀裂纹扩展达到管束断裂强度时便发生断裂。最后提出了预防管束断裂的措施及建议。     

DN50不锈钢波纹软管开裂失效分析

通过宏观检验、扫描电镜观察以及X射线能谱分析等手段,对某304奥氏体不锈钢DN50波纹软管开裂原因进行了分析。结果表明:软管开裂是由于腐蚀疲劳所致,软管的管壁内、外表面在腐蚀介质和外界应力的综合作用下产生沿晶微裂纹和蜂窝状腐蚀形貌,并受到交变应力作用,因而发生双向多源疲劳开裂失效。     

流量计导压管断裂失效分析

某化工厂工艺管线上的316不锈钢材质的孔板流量计导压管断裂,导致介质泄漏发生火灾。为查明其失效原因,对断裂的仪表管进行成分、硬度、金相、断口形貌和腐蚀产物分析,确认仪表管发生断裂的原因是在安装应力、震动和环境中Cl元素的共同作用下,先发生了应力腐蚀形成裂纹源,裂纹达到门槛值后又以疲劳形式扩展,最终导致开裂。     

铁路轮对用轴承外圈开裂失效分析

某型铁路轮对用轴承在运行约6×105 km后发现轴承外圈开裂,采用化学成分分析、金相检验、硬度测试以及断口分析等方法对轴承外圈开裂原因进行了分析。结果表明:该轴承外圈开裂主要是因为其外表面在环境腐蚀性介质作用下产生腐蚀坑,形成缺口效应和应力集中,在机械应力和残余应力的作用下,腐蚀坑处萌生微裂纹并不断疲劳扩展,最终导致轴承外圈开裂失效。     

火电厂汽轮机叶片开裂原因分析

某火电厂汽轮机末级动叶片在停机检修时发现端部进汽侧背弧面上存在一段裂纹,运用宏观观察、化学成分分析、硬度测试、金相检验、断口扫描及能谱分析等方法,对汽轮机叶片的开裂原因进行了分析。结果表明:汽轮机末级动叶片上的裂纹形成于进汽侧背弧面上的水蚀坑处,动叶片承受的拉应力以及氯离子腐蚀的工作环境,导致叶片发生了晶间应力腐蚀开裂。     

锅炉水冷壁管横向裂纹形成原因分析

某锅炉在运行期间发生水冷壁管泄漏事故,检查发现数十根管材外壁存在横向裂纹。通过宏观检查、化学成分分析、力学性能测试、金相检验和扫描电镜分析,对锅炉水冷壁管横向裂纹的形成原因进行了分析。结果表明:在壁温波动导致的热疲劳应力和腐蚀气氛的共同作用下,锅炉水冷壁管向火侧管壁发生了腐蚀疲劳开裂,形成了密集的横向裂纹,最终导致水冷壁管泄漏。     

滤清器外壳开裂分析

滤清器外壳安装在汽车发动机台架上试验500 h后出现裂纹,采用宏观和微观分析、化学成分分析和金相检验等方法对开裂原因进行了分析。结果表明:滤清器外壳的外壁局部区域在拉延时产生了微裂纹,在交变应力作用下形成疲劳裂纹,并导致早期疲劳开裂。     

列车车轮辐板断裂原因分析

通过化学成分分析、宏观及微观检验、力学性能测试、有限元分析等方法对列车车轮辐板断裂的原因进行了分析。结果表明:车轮辐板内侧面存在明显的点腐蚀,在辐板表面交变应力的作用下发生疲劳开裂,当疲劳裂纹扩展到一定长度时车轮发生断裂。点腐蚀不仅破坏了辐板表面喷丸加工所形成的高硬度残余压应力层,并在点蚀坑内部造成应力集中,形成疲劳裂纹源。因此车轮在运输、存放及使用过程中应注意防护,避免腐蚀的发生。     

热交换器不锈钢管泄漏原因分析

通过宏观检验、化学成分分析、力学性能试验、腐蚀试验、断口分析、能谱分析以及金相检验等手段对某项目6号机组3号高压加热器热交换器换热管发生泄漏的原因进行了分析。结果表明:该热交换器不锈钢管发生泄漏失效主要是因为介质中存在氯和氧元素(启停机凝结水),在遮热板钻孔内壁和失效管外壁之间产生点蚀和缝隙腐蚀,破坏了换热管表面的钝化膜并形成点蚀坑(孔),在热应力、冲击应力和振动应力作用下逐渐萌生微裂纹,最终发生应力腐蚀开裂和振动疲劳开裂,并导致泄漏。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。