结构陶瓷体内微缺陷的高频超声无损检测

采用人工引入夹杂粒子的方法,制得含缺陷的热压陶瓷样品(Si_3N_4,SiC 和 ZrO_2)。籍助200MHz 的高频超声手段,研究了适用于陶瓷缺陷无损检测的技术参数和影响缺陷检测的陶瓷材质的特性条件,以及导至声波衰减的技术和材质因素。分析了缺陷的大小、方位和特性与反射波的强度,亦即示波器上的缺陷波幅之间的关系。证实了200MHz 高频超声技术用于检测致密陶瓷体内微缺陷(80～100μm 尺寸的 Pt,W,Si,MgO 和 MoSi_2夹杂粒子)的合适性。确定了欲达到良好检测效果必需具备的陶瓷材质条件:1.致密度>95%理论密度;2.显微结构参数(晶粒,气孔径,第二相粒子)的尺寸比被检缺陷小1～2个数量级;3.表面光洁度≈V_(?);4.有效检测深度5～10mm(取决于陶瓷基体材质);5.陶瓷基体和缺陷的声阻抗差别要大。     

高频超声技术用于陶瓷零部件的无损评价和寿命预测

设计复合制作了工作频率在20～100MHz的纵波、横波以及曲面超声换能器．以延迟块直接耦合的方式对陶瓷零部件进行声参数和缺陷尺度的超声技术检测.以纵波（对气孔较灵敏）和横波（适于检测裂纹）换能器交替使用提高了可信度．在广泛检测的基础上,建立AVN（距离、波幅、当量）关系曲线,供作缺陷尺度的查判之用.基于无损的检测结果,根据断裂力学的基本原理,对陶瓷零部件作质量评价和级别判断以及取／舍裁决．     

陶瓷及陶瓷基复合材料微缺陷的超声检测

为研究陶瓷及陶瓷基复合材料微缺陷的超声检测能力，针对一些人工缺陷试样进行了超声检测试验。试验主要采用了纵波垂直入射法和泄漏瑞利波法。通过试验结果，比较了两种方法的检测能力。     

高频超声技术用于陶瓷坯体制备过程中的逐段检测

以20～50MHz的工作频率范围,藉助于延迟块（平面、曲面）直接耦合方式,有效地开展了陶瓷坯体（生坯、素坯、毛坯）的超声无损检测．声参数（声速和声衰减）对陶瓷制备过程中各阶段的坯体内显微结构异常有灵敏的响应．适当选取工作频率和耦合条件,可以有效地进行素坯、毛坯超声技术缺陷检测．     

100t钢包耳轴深厚焊缝超声相控阵的CIVA仿真与检测

针对钢包耳轴深厚焊缝实际检测存在的难题,定制了耳轴试块(内置两个Ф4mm横通孔缺陷),通过CIVA仿真技术对耳轴试块检测参数的设置进行了探究,利用超声相控阵探伤仪对耳轴试块进行了实验,对比了不同波形的检测效果,研究了超声相控阵技术对钢包耳轴深厚焊缝中缺陷检测的可行性.结果表明,在设定检测面、扇形扫查方式和10°~30°扫查角度等参数下,对耳轴试块进行检测可获得较好的扫查结果,且超声相控阵横波检测结果的信噪比高、杂波干扰少,实际现场100t钢包耳轴深厚焊缝的检测结果证实了超声相控阵技术对耳轴深厚焊缝中缺陷的检测具有可行性.     

超声Δ法与TOFD法在薄壁电子束焊缝上的检测结果对比分析

采用超声Δ衍射法和TOFD法对模拟缺陷进行检测,得出了缺陷检测波形图和B/C扫描图。对比分析了超声Δ衍射法与TOFD法的检测结果。实验表明利用超声Δ衍射法能够识别近表面垂直表面的面状缺陷,有效地对缺陷进行定位,能够很好地克服表面盲区,对缺陷的检测识别能力不受缺陷方向限制。从检测结果数据可以看出超声Δ衍射法的检测灵敏度和缺陷识别能力优于TOFD法。     

The Comparison Analysis of Test Result of Ultrasonic △ Technique and TOFD Method

采用超声△衍射法和TOFD法对模拟缺陷进行检测,得出了缺陷检测波形图和B/C扫描图.对比分析了超声△衍射法与TOFD法的检测结果.实验表明利用超声△衍射法能够识别近表面垂直表面的面状缺陷,有效地对缺陷进行定位,能够很好地克服表面盲区,对缺陷的检测识别能力不受缺陷方向限制.从检测结果数据可以看出超声△衍射法的检测灵敏度和缺陷识别能力优于TOFD法.     

金属材料缺陷的电磁超声/涡流复合检测技术研究

电磁超声检测和涡流检测因其非接触、检测速度快、对试件表面要求低等优点而被广泛应用于金属材料的缺陷检测中,但电磁超声检测存在近表面的检测盲区,涡流检测对内部深层缺陷灵敏度不高。基于电磁超声和涡流的复合检测方法,设计了能同时满足电磁超声检测和涡流检测的复合式探头,建立了电磁超声和涡流复合检测有限元模型,并对金属试件中不同类型的缺陷进行了检测实验。仿真和实验结果表明,该复合探头不仅能快速检测表面裂纹,而且可激发出具有明显指向性的纵波,一定程度上削弱了波形转换产生的干扰波,可实现对内部缺陷的准确定位、识别,为电磁超声和涡流复合式检测技术在板材的复杂缺陷检测中的应用提供了基础。     

缺陷偶极子调控铅基钙钛矿压电陶瓷性能的研究进展

压电陶瓷作为一种可以实现机械能和电能之间相互转换的功能陶瓷材料,广泛应用于传感器、制动器、超声换能器、医学超声成像及发动机燃油喷射系统等领域.在压电陶瓷中,元素掺杂可以有效调控陶瓷的电学性能,伴随掺杂而产生的缺陷偶极子对压电陶瓷性能有着显著而独特的影响.因此研究缺陷偶极子对压电陶瓷性能的调控机理,有助于理解压电陶瓷诸多物理现象的内在成因,譬如老化、疲劳等.通过元素掺杂引入的氧空位会导致钙钛矿结构的压电陶瓷产生缺陷偶极子,而缺陷偶极子与自发极化之间的耦合效应会影响陶瓷的铁电响应行为,从而使得压电陶瓷出现束腰电滞回线和偏移电滞回线等特征.另外由于陶瓷中氧空位的扩散速率很低,使得缺陷偶极子极化方向趋于稳定,进而抑制极化旋转和限制畴壁运动,有助于提高压电陶瓷的机械品质因数.尽管有大量研究通过缺陷偶极子调控压电陶瓷的宏观性能使其能够满足不同的应用需求,然而由于压电陶瓷为多晶材料,其内部晶粒取向各异且存在复杂的铁电畴结构,压电陶瓷中缺陷偶极子在形成过程中的微观机理与其具体形态以及缺陷偶极子对压电陶瓷性能的具体作用机理仍有待深入研究.此外,压电陶瓷在高驱动场下的高功率特性对机电设备的实际设计具有重要意义,因此缺陷偶极子对压电陶瓷高功率特性的影响也值得关注.本文从氧空位诱导缺陷偶极子的形成及其表征手段、缺陷偶极子对铅基压电陶瓷电滞回线的影响和不同受主掺杂对铅基压电陶瓷机械品质因数的影响出发,论述了缺陷偶极子与压电陶瓷自发极化耦合效应引发的偏移和束腰奇异电滞回线特征,揭示了缺陷偶极子主要通过抑制极化旋转和限制畴壁运动提高机械品质因数的机理.然而关于缺陷偶极子的形态、与非四方相间的耦合关系以及缺陷偶极子对压电陶瓷高功率特性的影响等问题仍需进一步的研究.     

ZnO薄膜换能器在高频超声无损评价中的应用

本文主要研究 ZnO 薄膜换能器在无损评价中的应用。ZnO 薄膜的体波换能器已经研制成功。本工作的目的是把超声脉冲回波测量技术用到150～400MHz 的高频范围。用这种测量技术可以测定精细陶瓷(如 SiC、Si_3N_4、ZrO_2)中100μm 的缺陷,并可定量地确定缺陷的位置和形状。与 X 射线及激光扫描超声显微镜相比有其独特的优点。     

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.……     

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...     

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.     

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.……     

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.     

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.     

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 ...