微波无损检测热障涂层下金属表面裂缝的参数优化

基于微波在介电材料中的传播理论及其对金属界面特性的敏感性, 利用CST-微波工作室(computer simulation technology-microwave studio)对微波检测热障涂层下金属的裂缝进行了仿真计算, 研究了热障涂层的厚度、 裂缝方向对检测结果的影响, 仿真计算了热障涂层厚度为400 μm、 裂缝长边方向平行于矩形波导探头长边的不同宽度的裂缝。结果表明: 热障涂层厚度不同时, 微波检测金属表面裂缝的敏感工作频率不同; 裂缝方向与波导口长边的夹角为50°～55°时检测敏感度低。裂缝宽度小于8 μm时用本研究中的频率范围无法检测, 裂缝宽度在10～30 μm时检测效果不明显, 裂缝宽度在30 μm～1 mm范围内, 裂缝越宽微波的反射系数相位差越大。因此, 在合适的工作频率下能利用微波无损检测技术对热障涂层下金属表面的裂缝进行无损检测。     

中间层碳纤维方向的微波无损检测实验研究

在研究多层媒介中的微波信号传播与反射机理的基础上,利用微波网络分析仪对3层复合材料中间层的纤维方向进行了检测研究。首先,根据N5225A网络分析仪记录的反射系数相位计算出反射系数相位差;然后,建立反射系数相位差与表示中间层纤维方向的β建立对应关系;最后,利用反射系数相位差表征纤维方向的变化。实验结果表明,矩形波导相对于复合材料纤维方向的角度(α)会对检测结果有一定的影响,反射系数相位差随工作频率的变化规律不同,并且对中间层的纤维方向的变化敏感范围也不同,波导口长边平行于第一层的纤维时,即α为0°时,对β为15~45°较敏感,波导口长边垂直于第一层的纤维时,即α为90°时,对β为45~75°较敏感;复合材料末端加一反射板可以增强检测效果,检测工作频率为33GHz,中间层纤维方向变化30°时,有反射板的反射系数相位差变化10°,而没有反射板的变化5°。     

EB-PVD制备热障涂层的反射光谱特性研究

为了研究航空发动机中涡轮叶片表面的热障涂层对辐射光谱的反射特性,本文使用真空电弧镀法在不锈钢基体上分别制备了NiCrAlYSi和NiCoCrAlYHf两种热障涂层的粘结层,并随后使用电子束物理气相沉积(EB-PVD)法制备了ZrO_2·Y_2O_3(YSZ)热障涂层的陶瓷面层,最后利用紫外-可见-近红外分光光度计测定了常温下热障涂层在0.3μm～2.5μm波段的反射率光谱并进行了分析研究。结果表明:金属粘结层和陶瓷面层厚度均相同时,不同的粘结层材料对热障涂层的光谱反射率影响不大,整个波段内NiCrAlYSi/YSZ和NiCoCrAlYHf/YSZ涂层的光谱反射率接近。当粘结层NiCrAlYSi的厚度相同,面层YSZ的厚度分别为20μm、100μm、170μm三种不同厚度时,热障涂层的光谱反射率表现出不同的特性,在0.3μm～0.45μm波段,厚度为20μm的YSZ的试样因表面呈蓝紫色反射紫光能力最强,而灰白色的其他两个试样反射紫光能力接近;在0.45μm～2.5μm波段,YSZ涂层厚度与光谱反射率正相关,涂层厚度越厚光谱反射率越高。通过调整电子束物理气相沉积工艺制备了YSZ微叠层,与相同厚度的传统柱状晶的YSZ相比,YSZ微叠层的光谱反射率提高了约一倍。     

8YSZ双层热障涂层缺陷演变与微裂纹水浸超声宏观检测

采用PASCAN-64型水浸超声设备并配合扫描电镜对8wt %Y₂O₃-ZrO₂(8YSZ)双层热障涂层热震过程中内部组织结构演变进行了检测。结果表明, 当超声波从垂直陶瓷层方向入射至粘结层反射所获得的回波信号影像主要反映了陶瓷层组织结构演变, 从垂直基底方向入射至粘接层/陶瓷层界面处反射所获得的回波信号影像主要反映了热生长氧化物层组织结构演变, 从垂直陶瓷层方向透射整个试片所获得的回波信号影像综合反映了整个涂层组织结构演变。当陶瓷层中均匀分布着孔隙率<11%、最大横向尺寸<50 μm的孔隙以及热生长氧化物层主要为致密的α-Al₂O₃时, 回波信号的幅值dB<0, 反映在影像中的信号分布均匀, 表明涂层处于良好状态。当陶瓷层中均匀分布着孔隙率>44%、最大横向尺寸>100 μm的孔隙以及热生长氧化物层主要为具有稀疏结构且厚度>5.2 μm的Cr、Co氧化物时, 回波信号的幅值dB>0的区域连接成片, 则预示着涂层即将失效或已失效。可见, 水浸超声技术能够较准确地反映热障涂层内部组织结构演变, 是一种较好的热障涂层内部缺陷的无损检测方法。     

平面电容传感器热障涂层缺陷检测系统

为有效检测热障涂层的缺陷,研究基于平面电容传感器的缺陷检测系统。该文对用于热障涂层缺陷检测的平面电容传感器的工作原理进行分析,结合热障涂层的结构,利用COMSOL有限元仿真软件对传感器结构进行优化设计,设计微小电容检测电路,并通过复导纳的方法提取检测信息,搭建热障涂层缺陷检测系统,并对系统的性能进行测试。实验测试中对3种不同厚度的氧化铝陶瓷片进行复导纳的检测,通过对检测结果进行数据分析更易区分不同厚度的陶瓷片,即基于平面电容传感器的缺陷检测系统可以有效检测出热障涂层的厚度变化缺陷。     

沉积入射角度对热障涂层形貌和性能的影响

采用真空电弧镀（ARC）技术在DZ125合金基体上制备NiCrAlYSi(HY3)金属粘结层,然后采用电子束物理气相沉积（EB-PVD）技术,分别以0°、20°、40°、60°和80°五种入射角度沉积氧化钇稳定氧化锆（6～8YSZ）陶瓷涂层,研究了入射角度对涂层形貌和性能的影响。结果表明：五种入射角度的热障涂层均能形成柱状晶结构,随着入射角度增加,孔隙率和柱状晶倾斜角度均逐渐增加,涂层厚度逐渐减小;对带涂层试样进行结合强度测试,入射角度0°～40°时涂层的结合强度均在55MPa以上,入射角度增加到80°时,结合强度降低到15.7MPa;热冲击条件下,陶瓷面层和基体之间形成TGO,由于不同入射角度下涂层孔隙率不同,TGO生长速度不一致,导致其热冲击寿命存在明显差异,入射角度为0°～40°时涂层的热冲击寿命均超过4000次,入射角度为60°时涂层的热冲击寿命为3371次,入射角度为80°时涂层的热冲击寿命最短,仅为1836次。     

物理气相沉积热障涂层批量生产用球坑仪快速测厚法研究

为了满足热障涂层批量生产时对厚度快速、准确检测的需要,本文选用球坑测厚法对物理气相沉积热障涂层厚度进行了测量研究。首先在GH3039高温合金基体上分别制备厚约120μm的NiCrAlYSi涂层和Zr O₂·Y₂O₃(YSZ)涂层,研究了研磨液粒径、研磨时间等参数与磨坑直径的关系,随后根据试验结果对高温合金试片涂覆的NiCrAlYSi/YSZ热障涂层使用球坑测厚法进行了厚度测量,并与金相测厚法结果进行了对比。结果表明：NiCrAlYSi涂层和YSZ涂层磨坑直径与研磨时间均满足抛物线增加关系;相同条件下,所用研磨液粒径为5μm和10μm时获得的磨坑直径相当,均比1μm时的大;针对同一涂层,球坑测厚法与金相测厚法测量结果吻合度高,误差在6%以内。     

高温热处理对等离子体喷涂的纳米氧化锆热障涂层的影响

热障涂层已广泛用于燃气发动机燃烧室等高温零部件上。纳米热障涂层韧性改善,厚度可以增加,能够提高零部件使用温度和使用寿命。首先利用低压等离子体在镍基体上喷涂制备NiCoCrAlYTa金属中间结合层和大气等离子体喷涂制备Y_2O_3部分稳定的ZrO_2纳米陶瓷面层,然后将纳米氧化锆热障涂层样品在大气中于1050～1250℃温度范围内煅烧处理2～20h。通过扫描电镜和X射线衍射仪分析纳米氧化锆热障涂层高温煅烧前后的组织结构变化和相组成变化,并与常规微米氧化锆热障涂层进行比较。研究结果表明:经高温煅烧后,纳米氧化锆热障涂层中晶粒大小和在陶瓷面层/金属中间结合层界面上形成的TGO的厚度随煅烧温度升高和时间的延长而增大;纳米热障涂层中TGO的增长速度比常规微米热障涂层快;纳米热障涂层经高温煅烧空气中冷却后,主要由四方相组成;与常规微米热障涂层的相组成比较,纳米氧化锆热障涂层中的四方相为低稳定剂四方相。     

等离子喷涂热障涂层隔热性能分析方法

热障涂层材料已成为现代高性能航空发动机的关键材料,而隔热性能一直是评价热障涂层性能的一个重要指标。首先基于傅里叶导热定律,推导出一维稳态温度场的解析表达式,并讨论了陶瓷层厚度、陶瓷层上表面工作温度和金属基底下表面工作温度对热障涂层系统隔热性能的影响。设计了一种比较新颖的实验测试方法,成功实现了对热障涂层系统内部不同位置的温度进行实时测试和保存实验数据。结果表明,各个温度采集点的实验测试结果与理论预测结果吻合很好,说明提出的实验测试方法可以有效评估不同类型的热障涂层材料体系的隔热性能。     

X射线测量高速钢上不同厚度氮化钛涂层残余应力

采用多弧离子镀在AISIM2高速钢(HSS)上沉积了TiN硬涂层,试样中基体厚度为1mm,涂层厚度分别为3.0、5.0、7.0、9.0和11.0μm.应用X射线衍射(XRD)分析了TiN涂层中残余应力,测量了TiN(220)衍射晶面在五种不同倾斜角(Ψ=0°,20.7°,30°,37.8°和45°)下的X射线衍射峰.结果表明:在3～11μm涂层厚度范围内,TiN涂层中均表现出残余压应力且残余压应力值较大.TiN涂层中残余应力大致分布在-3.22～-2.04GPa之间,本征应力分布在-1.32～-0.14GPa,热应力约为-1.86～-1.75GPa.TiN涂层中残余应力值随涂层厚度变化是非线性增加的,随厚度增加表现出先增大后减小的变化趋势,多项式拟合后发现约在8.5μm厚时残余应力达到最大值.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...