基于Weibull分布的电磁脉冲损伤函数Bayesian分析技术

Weibull分布是电磁脉冲易损性分析常常用到的一种分布.论文采用Weibull分析方法运用Gibbs抽样技术求取了基于Weibull分布的固态继电器电磁脉冲损伤函数.     

中子吸收涂层/斩盘界面应力的有限元分析

中子吸收涂层/斩盘界面的结合强度直接影响转盘式中子斩波器的性能。本文基于有限元计算软件ANSYS,对高速离心载荷下中子吸收涂层/斩盘界面的应力分布进行计算分析,考察涂层的弹性模量、泊松比、涂层厚度等参数对界面应力分布的影响。结果表明,采用软而韧的涂层可有效降低涂层/斩盘界面的应力峰值;减小涂层厚度有助于避免高速离心载荷下斩盘开口处的塑性破坏。     

不锈钢管道焊缝金属随机循环应力幅的良好统计模型

与现有确定性分析方法不同，考虑材料循环变形的分散性，应用确定不锈钢管道焊缝金属随机循环应力幅统计模型的方法研究了1Cr18Ni9Ti不锈钢焊缝金属循环应力幅的良好统计模型。综合考虑了总体拟合效果、与疲劳失效机制的一致性和分析结果的安全性三要素，分析比较了三参数Weibull、两参数Weibull、极小值、极大值、正态、对数正态和指数分布对试验数据的拟合效果。结果表明，极小值、极大值、正态和对数正态分布可作为良好假设分布，以极小值和正态分布最好。其余分布因不符合三要素之二或三项，不适于表征循环应力幅数据。     

固态继电器电磁脉冲损伤阈值概率分布的选取

由固态继电器电磁脉冲损伤阈值数据的频率直方图可初步选择Normal分布和Weibull为数据的总体分布,分别采用适用于判断小子样数据分布类型的拟合优度检验法、Bootstrap方法和Bayesian方法,确定了数据的总体分布为Weibull分布.     

CrTiAlN复合涂层硬质合金刀具的制备与切削性能研究

利用多弧离子镀技术在YT14硬质合金刀具上制备了CrTiAIN复合涂层,对不同偏压条件下CrTiAIN复合膜的表面形貌、硬度、结合性能进行了系统研究,采用X射线衍射分析技术(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)等现代材料分析技术对CrTiAIN复合涂层的微观组织结构进行了分析表征,结果表明:CrTiAIN复合涂层的主要成分为Cr、Ti、Al、N、O,相组成为Cr、CrN、Cr2N和TuN晶体相与AIN非晶相.在干式切削条件下,不同涂层刀具的切削寿命的排序依次为:CrrnAlNTiAINTiN未涂层,同时对不同涂层刀具的耐磨损特性进行了讨论分析.     

核电厂压力容器安全评估的新方法——主曲线简介

新的主曲线方法对反应堆压力容器完整性的评估在美国被称为革命性的改进。本文从保证核电安全的反应堆运行限值曲线出发,说明主曲线的由来、根据和标准;从对微观组织很敏感的脆性断裂特点,阐述主曲线的理论和它的统计规律性及其Weibull分布统计模型和实验方法;从断裂韧性数据库对该模型的拟合式,理解主曲线的含义、优点和应用以及主曲...     

基于粗糙基底的W/316L不锈钢第一壁系统热应力的研究

第一壁系统中热应力的大小是决定聚变堆安全运行的关键因素之一。本文通过Ansys Workbench有限元软件，对具有粗糙基底的W/316L不锈钢系统中的热应力分布，以及影响热应力大小的诸如温度、涂层厚度、基底厚度等因素进行了深入分析。同时从系统中交界面剪切应力入手，研究了粗糙基底对涂层结合强度的影响。结果表明：粗糙基底系统中热应力随着温度、基底厚度的增加而增加，随着涂层厚度的增加而降低。除此之外，粗糙基底提升了系统中热应力的极值，在一定程度上提高了涂层与基底的结合强度。研究结果为后期高结合强度第一壁涂层系统的研发提供了一定的参考价值。     

中子辐照对Cr涂层锆合金力学性能的影响

为研究中子辐照对Cr涂层锆合金力学性能的影响,获得Cr涂层锆合金的辐照性能数据,本文针对多弧离子镀技术制备的Cr涂层锆合金开展了中子辐照考验,通过拉伸试验过程实时观测试样力学行为变化并对试验后断口微观形貌进行分析,研究了辐照后Cr涂层锆合金的力学性能以及涂层与基体的结合能力。结果表明：中子辐照导致Cr涂层锆合金的抗拉强度和屈服强度升高,断后伸长率下降,表现出与商用锆合金相似的辐照强化效应。同时Cr涂层与无涂层锆合金相比,其屈服强度和抗拉强度升高但塑性变形能力降低。另一方面,Cr涂层在拉伸变形量较大时产生环向裂纹,但未从基体表面剥落,中子辐照未对涂层结合强度产生明显的影响,受力过程中涂层仍保持了完整性。     

等离子喷涂Fe-Ni-B屏蔽涂层的结构与性能研究

采用大气等离子喷涂技术在1Cr18Ni9Ti钢基体上制备了Fe-Ni-B涂层,并对涂层进行了重熔处理.采用扫描电子显微镜(SEM)、X射线荧光光谱仪(EDX)对重熔前后涂层的显微组织及界面结构进行了微观分析,并对重熔前后涂层的显微硬度、热疲劳性能、结合强度进行了试验研究.结果表明,重熔处理对涂层显微结构有明显改善,涂层更为致密.涂层与基体界面处已发生相互扩散并有新相生成,涂层热疲劳性能更好,结合强度也有所提高.     

316L不锈钢基材功能梯度Al涂层残余热应力分析

涂层材料的功能性和可靠性在很大程度上受残余热应力的影响,为降低残余热应力防止涂层开裂以及提高其热机械性能,利用有限元方法对Al/316L系梯度功能材料在制备过程中产生的残余热应力分布进行分析,详细讨论了成分分布指数、涂层厚度和梯度层数目对应力大小和分布的影响.分析结果表明成分分布指数的增大不但影响涂层和基体界面的应力大小,还影响涂层中热应力峰值所处位置;涂层残余应力随着梯度层厚度的增加而减小;梯度层数的增多,有利于涂层中残余热应力的缓和,但当梯度层数达到9时,缓和效果并不明显.     

脉冲偏压对贫铀表面磁控溅射离子镀铝结合强度的影响

采用磁控溅射离子镀技术在不同偏压下于贫铀表面制备铝镀层，用扫描电镜和俄歇电子能谱仪对镀层形貌和界面元素分布进行分析，用拉伸法对镀层的结合强度进行测定。结果表明：在-900V脉冲偏压下所得镀层与铀基体结合良好，镀层与基体之间存在较为明显的“伪扩散区”；与直流偏压相比较，脉冲偏压所得镀层结合强度明显增强，镀层的致密性显著改善。     

Properties of tungsten coating deposited onto copper by high-speed atmospheric plasma spraying

Tungsten (W) coatings were fabricated on copper (Cu) by high-speed atmospheric plasma spray (HAPS) technique. The properties of the porosity, oxygen content, bonding strength and microhardness were measured. The results obtained indicated that the HAPS-W coating showed good properties particularly in terms of porosity and oxygen content. The porosity of the HAPS-W coating was 2.3% and the distribution of pore size diameter was mainly concentrated in the range of 0.01-1 μm. The oxygen content of the coating measured by means of Nitrogen/Oxygen Determinator was about 0.10 wt.%. These initial results suggest that the HAPS-W coating has achieved the reported properties of the vacuum plasma spray (VPS) W coating. Compared with VPS, HAPS-W technique could provide a convenient and low cost way to obtain adequate W coatings for fusion applications.     

1Cr17Ni4不锈钢等离子体喷涂金属涂层的摩擦磨损特性研究

研究了1Cr17Ni4马氏体型不锈钢表面等离子体喷涂FeCrA1Y、NiCrAlY2O3和NiCrAlY金属涂层的组织结构和小位移滑动的摩擦磨损特性。采用拉伸方法进一步分析了各涂层的结合强度、结果表明,在该等离子体喷涂工艺下,3种涂层摩擦系数相当,均明显低于ICr17Ni4不锈钢基材的值;Ni基涂层耐磨性能有所提高,其中NiCrAlY金属涂耐磨性能最好．但FeCrAlY涂层耐磨性能不及基体材料。3种涂层的磨损机制主要为磨粒在磨损中的塑性变形机制和疲劳磨损机制。     

The development and prospect of fabrication of W based plasma facing component by atmospheric plasma spraying

The possibility and development of fabrication of W coating by atmospheric plasma spraying (APS) is summarized and reported. SEM was used to investigate the surface and cross-section morphology of fabricated coatings, while EDS and XRD were used to investigate the compositions and phase of these coatings. Through controlling the condition and parameters of the APS, the oxidation of the W coating can be reduced significantly. The W coatings with different initial particle sizes resulted in different microstructures. The finer the particle size of the spraying powders, the lower the porosity will be. The effects of different interlayers on bonding strength were studied. The W coating deposited directly onto the copper substrate presented the highest bonding strength compared with coatings with different interlayers, while the coating with a graded W/Cu interlayer shows the best thermal shock resistance. The feasibility of fabrication of thick W coating by APS was also investigated. Pure W coating with a thickness of 2–3 mm and porosity less than 2% can be fabricated by APS.     

Crushing behaviour of high temperature reactor coated fuel particles

This paper examines in detail the crushing behaviour of high-temperature reactor fuel particles with pyrolytic carbon or silicon carbide outer coatings and discusses their failure mechanisms, in an attempt to relate crushing failure loads to coating strengths, and provide a simple, quick testing technique for quality control or performance assessment. Failure occurs by a series of mechanisms, in varying sequence, initiated by Hertzian cracking. Because the first event detected in a crushing test load/deflection curve is not the formation but the propagation of the Hertzian crack, the crushing load cannot be related to the coating strength; instead, it is governed by the fracture surface energy of the outer coating. A crushing test is therefore not a suitable technique for measurement of the strength of particle coatings. However, through measurement of the size of the contact surface, reliable estimates of the Young's modulus of the outer coating can be made by application of the Hertz theory of contact.     

Fracture toughness transition curve estimation from a notched round bar specimen using the local approach method

The local approach method for the brittle or transition region describes the fracture probability of specimens or structures using Weibull statistics. Many papers have discussed the characteristics of the Weibull parameter using notched tensile specimens and the applicability to fracture toughness scatter evaluation using CT specimens. However few papers have made clear whether the Weibull parameter of the Weibull stress is a material property or not. In this paper the distribution of Weibull stress in the brittle fracture region using notched round bar specimens and CT specimens were investigated and it was confirmed that both distributions agreed well. Furthermore the estimation method for the fracture toughness transition curve including its scatter from notched round bar tensile tests was proposed based on the relation between the Weibull stress and the Wallin's fracture toughness transition curve. As a result, the estimated fracture toughness curve in the brittle and lower transition region from the notched round bar specimens coincided with the measured fracture toughness curve from CT specimens. This method will be applicable to fracture toughness curve estimation under plane strain conditions even if there is no possibility of obtaining thick enough CT specimens from a structure because of geometry or some other restrictions.     

Ion beam modification of metals

Energetic ions beams may be used in various ways to modify and so improve the tribological properties of metals. These methods include: — ion implantation of selected additive species; — ion beam mixing of thin deposited coatings; — ion-beam-assisted deposition of thicker overlay coatings.

The first of these techniques has been widely used to modify the electronic properties of semiconductors, but has since been extended for the treatment of all classes of material. Tool steels can be strengthened by the ion implantation of nitrogen or titanium, to produce fine dispersions of hard second-phase precipitates. Solid solution strengthening, by combinations of substitutional and interstitial species, such as yttrium and nitrogen, has also been successful. Both ion beam mixing (IBM) and ion-beam-assisted deposition (IBAD) use a combination of coating and ion bombardment. In the first case, the objective is to intermix the coating and substrate by the aid of radiation-enhanced diffusion. In the latter case, the coating is densified and modified during deposition and the process can be continued in order to build up overlay coatings several μm in thickness. The surface can then be tailored, for instance to provide a hard and adherent ceramic such as silicon nitride, boron nitride or titanium nitride. It is an advantage that all the above processes can be applied at relatively low temperatures, below about 200° C, thereby avoiding distortion of precision components. Ion implantation is also being successfully applied for the reduction of corrosion, especially at high temperatures or in the atmosphere and to explore the mechanisms of oxidation. Ion-assisted coatings, being compact and adherent, provide a more substantial protection against corrosion: silicon nitride and boron nitride are potentially useful in this respect. Examples will be given of the successful application of these methods for the surface modification of metals and alloys, and developments in the equipment now available for industrial application of ion beams will also be reviewed.     

Properties of Electrodeposited Tungsten Coatings on Graphite Substrates for Plasma Facing Components

Tungsten coating on graphite substrate is considered as one of promising candidate materials of plasma facing components. In this study, tungsten coatings on graphite substrate were successfully prepared by direct current (DC) and pulse current (PC) electrodeposition methods in Na₂WO₄–WO₃ molten salt under the air atmosphere. Pores were found on the surfaces of the tungsten coatings produced by DC electrodeposition method. For the coatings fabricated by PC method, compact and smooth tungsten coatings were successfully obtained. The crystal structure, morphology, density, microhardness, adhesive strength, oxygen content and the thermal conductivity of the coatings fabricated by PC method were investigated. The obtained tungsten coatings had a body centered cubic structure. After electro-deposition for 100 h, the thickness of the tungsten coating reached 810.02 ± 10.40 μm and the oxygen content was 0.03 wt%. The thermal conductivity of the tungsten coating was 134.29 W m^?1 K^?1. The density of the tungsten coating was 18.83 g cm^?3. The hardness of the coating was 492.0 ± 7.8 HV. After deuterium plasma irradiation, the tungsten coatings were prone to blistering.