TiC、TiB增强钛基复合材料的高温氧化性能及微观结构

针对钛基复合材料高温应用中的关键问题——高温氧化性能，从理论和实验上研究了不同增强体(TiC、TiB)对钛基复合材料氧化性能和微观结构的影响。结果表明：钛基复合材料的氧化规律为抛物线规律，TiB增强体比TiC增强体更能提高复合材料的高温抗氧化性能，TiB／Ti基复合材料表面氧化膜的状态较TiC／Ti基的致密、均匀，高温氧化后，基体元素Ti和Al会与氧发生反应生成TiO2、Al2O3。     

阳极氧化铝电路基板制备的研究

在添加羧酸和有机化合物的硫酸电解液中，采用阳极氧化的方法制备了电路铝基板衬底，研究了电流密度和氧化时间对氧化膜厚度和硬度的影响。利用X射线，SEM分析了氧化膜的物相组成和表面微观结构，并对其电绝缘性能进行了测试。结果表明，所获得的氧化膜是由非晶态的Al2O3以及少量晶态γ-Al2O3组成，呈致密的网状结构，其电学性能满足基板的要求。     

防冻液环境下PPS复合材料与不同配副材料的摩擦学行为

采用热压成型法制备短切碳纤维增强聚苯硫醚(PPS)复合材料,研究汽车专用防冻液环境中复合材料与4Cr13不锈钢、SiC陶瓷和Al2O3 陶瓷配副在不同载荷下的摩擦磨损性能;考察摩擦副在防冻液中的润湿性与耐腐蚀性;利用激光共聚焦显微镜和扫描电子显微镜对复合材料及对偶件磨损面进行观察,结合磨损面EDS和XRD分析探究材料的摩擦磨损机制。结果表明：防冻液环境中,SiC陶瓷耐腐蚀性能最强,Al2O3 陶瓷润湿性最好;在相同载荷下与4Cr13配副时复合材料的磨损率最低,但摩擦因数随载荷的增大上升最快,对偶件磨损率最大且磨粒磨损严重;与SiC或Al2O3配副时复合材料摩擦面呈现研磨特征;在相同载荷下与Al2O3 配副时复合材料磨损率最大,磨屑向对偶件表面沉积,与SiC配副时复合材料摩擦因数最小且对偶件磨损率最小。因此PPS复合材料与SiC配副宜作为防冻液环境下长耐久滑动轴承的优选材料。     

干摩擦条件下Al_2O_3基复合材料的摩擦磨损特性

以用SiC、Ti(CN)和ZrO2颗粒增韧的三种Al2O3基复合材料为研究对象,利用销盘式摩擦磨损试验机研究了它们的摩擦磨损性能,通过扫描电子显微镜对其磨损形貌进行了观察和分析.结果表明:在本试验条件下,Al2O3基复合材料的耐磨性能与添加剂的种类有关,其耐磨性能好坏顺序为Al2O3/Ti(CN)、Al2O3/SiC、Al2O3/ZrO2;Al2Os/SiC复合材料的磨损机理主要为疲劳磨损和脆性断裂,Al2O3/ZrO2和A12O3/Ti(CN)复合材料的磨损机理主要为磨粒磨损.     

原位反应结合热压烧结工艺制备Al_2O_3/Fe-28Al-5Cr复合材料的组织和性能

采用原位反应结合热压烧结工艺制备了Al2O3质量分数为10%和20%的Fe-28Al-5Cr基复合材料,研究了它们的物相、显微组织、力学性能,以及室温和200,400,600,800℃下的摩擦磨损性能,并与采用外加Al2O3方法制备的相同复合材料进行了对比。结果表明:原位合成Al2O3制备的复合材料由Fe3Al和Al2O3两相组成,Al2O3主要分布在晶界处;随着Al2O3含量的增多,复合材料的硬度逐渐增大,抗弯强度明显降低;当Al2O3质量分数为20%时,复合材料的耐磨性能得到了明显改善;与外加20%Al2O3制备的复合材料相比,原位合成Al2O3制备的复合材料具有较高的硬度和强度,在室温和200,800℃下的磨损率稍低。     

三维网络结构SiC-Fe复合材料制备及腐蚀性能研究*

传统钢铁材料难以满足深井开采严苛的腐蚀环境,亟需开发具有良好耐蚀性的新材料。SiC陶瓷具有优异的耐蚀性,因此探讨了以SiC为原材料的复合材料的制备及耐蚀性。以SiC、Al2O3、SiO2为原材料采用有机泡沫浸渍法制备出三维网络结构SiC陶瓷,并采用浇铸工艺制备三维网络结构SiC-Fe复合材料,采用扫描电子显微镜、X射线衍射仪等对SiC-Fe复合材料组织结构及物相进行分析,通过电化学试验、浸泡试验对SiC-Fe复合材料的耐蚀性进行表征,并分析其耐腐蚀机制。结果表明：SiC-Fe复合材料中SiC陶瓷增强体与高铬铸铁基体之间未发生元素扩散,界面结合方式为机械结合,基体中主要物相有奥氏体和碳化物,陶瓷增强体中主要为六方结构SiC和Al2O3;SiC陶瓷增强体的加入使高铬铸铁的腐蚀电流由4.189×10-3 A/cm2降至3.353×10-3 A/cm2,电荷转移电阻从7.309 Ω·cm2增大至11 881 Ω·cm2,电容值从1.994×10-4 F/cm2降至1.974×10-5 F/cm2,使整体的耐蚀性得到了提高。浸泡试验表明,SiC-Fe复合材料的腐蚀主要发生在高铬铸铁基体部分,界面及SiC陶瓷增强体处不易发生腐蚀;与纯高铬铸铁材料相比,SiC-Fe复合材料点蚀产生的时间较晚且腐蚀程度相对较轻。研究成果为复合材料在煤矿深井开采装备的应用提供重要理论依据。     

共沉淀法制备纳米Al2O3强化铜基复合材料微动磨损研究

采用共沉淀法制备了纳米Al2O3／Cu基复合材料,研究了不同Al2O3含量对铜基复合材料摩擦磨损性能的影响。结果表明,复合材料的耐磨性能明显优于基体材料,随着Al2O3含量的增加,复合材料的耐磨性能先升高后下降,以Al2O3含量2％为最佳,相对耐磨性为3．13。纯铜的磨损表现为粘着磨损,而复合材料则逐渐转变为磨粒磨损,并伴有一定的氧化磨损。     

TiC／（Al2O3／Y-TZP）纳微米复合陶瓷材料的性能及显微结构研究

采用热压烧结制备了TiC/(Al2O3/Y-TZP)纳微米复合材料,用SEM观察了复合材料断口形貌和微观结构,研究了纳米TiC含量对复合材料的力学性能的影响,结果表明:20%TiC(15%Al2O3/5Y-TZP)复相陶瓷抗弯强度和断裂韧性高达620MPa、6.8MPa·m1/2.     

等离子喷涂NiAl/Al2O3梯度陶瓷涂层的结构与组织特征

利用等离子喷涂方法制备了NiAl/Al2O3梯度陶瓷涂层,并对涂层的组织分布、相结构、硬度和孔隙率进行了研究.结果表明:梯度涂层的组织表现出宏观不均匀性和微观连续性的分布特征,是由α-Al2O3、γ-Al2O3、δ-Al2O3、Ni、NiO以及镍铝金属间化合物等多种相组成的复合材料;梯度涂层中NiAl合金层的孔隙最少,表面纯陶瓷层孔隙率最高;随着Al2O3含量的增加,涂层的硬度逐渐增大.     

钻杆用铝基复合材料中SiC/Al界面润湿性研究进展

SiC增强铝基复合材料可显著提高铝合金耐磨性,可用于制备新型的高强耐磨轻质石油钻杆;但SiC/Al界面润湿性差,致使在真空熔炼时SiC颗粒加入困难,且在铸锭中分布不均,从而无法获得组织、性能均匀的优质钻杆。在概述SiC/Al界面润湿行为及界面反应的基础上,系统介绍了SiC高温氧化、SiC化学镀镍和基体合金化等3种常用的改性方法,及其对SiC/Al界面润湿性的作用机理。综合比较后指出,采用SiC化学镀镍法可有效改善SiC/Al的界面润湿性,且在界面生成的中间化合物稳定,在制备石油钻杆用铝基复合材料时可优先考虑使用。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....