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。     

TiB2/Cu复合材料的电火花加工电极

粉末冶金法制备的颗粒增强TiB2/Cu被首次用作电火花加工电极材料,经试验验证为优良的电极材料.不同电流、脉宽下的试验表明：TiB2体积分数为5%的电极耐损耗性能优于40%的电极.脉宽100μs下时,加工速度和电极损耗率的变化均比较剧烈,而当脉宽达到100μs以上时,变化相对平缓.分析表明TiB2/Cu电极电加工特性与其他铜基复合材料电极类似.同时环境扫描电镜和能谱分析系统记录下的电极表面形貌和元素变化反应了该电极的腐蚀机理和对碳、氧及工件中的重金属元素的吸附作用.     

喷丸处理对S31035奥氏体耐热钢抗高温水蒸气氧化行为的影响

对S31035钢进行喷丸处理，再在665℃下进行高温蒸汽氧化试验，研究了喷丸处理对该钢抗高温水蒸气氧化行为的影响。结果表明：未喷丸试样在氧化100 h后即出现明显的氧化物衍射峰，氧化3 000 h后形成双氧化物层，氧化膜厚度约为8.07μm;喷丸试样在氧化1 000 h后才出现微弱的(Fe, Cr)₂O₃衍射峰，在氧化3 000 h后表面氧化膜仍然较薄，厚度仅为0.45μm;在氧化过程中，喷丸试样的氧化速率常数比未喷丸试样低3个数量级，抗水蒸气氧化性能较好；喷丸处理细化了表层晶粒，为铬元素扩散提供了更多通道，使表面形成Cr₂O₃保护膜而提高了该钢的抗高温水蒸气氧化性能。     

Haynes 282镍基合金在600～700℃超临界水中的氧化特性

在600~700℃、25 MPa超临界水中对Haynes 282镍基合金进行氧化,研究了不同温度和时间下合金的氧化动力学曲线以及氧化膜的表面形貌、微观结构和物相组成等。结果表明:Haynes 282合金的单位面积氧化质量增加随着温度的升高和时间的延长而增大;600℃时合金的氧化动力学曲线遵循抛物线规律,650,700℃时的氧化动力学曲线介于抛物线和直线规律之间;合金表面的氧化膜具有双层结构,外层为呈松散的多面体形状的微米尺寸氧化物颗粒,内层为由细小晶粒组成的致密氧化膜;600℃氧化后氧化膜内层主要为Cr_2O_3,外层则为TiO_2;650℃氧化后氧化膜外层由TiO_2与MnCr_2O_4组成,而内层由Cr_2O_3和少量的MnCr_2O_4组成;700℃氧化后氧化膜外层由NiCr_2O_4与MnCr_2O_4组成,而内层由Cr_2O_3和少量的MnCr_2O_4组成。     

含硼杂环化合物在菜籽油中的性能研究

合成了一种含硼杂环化合物,采用四球及环块摩擦试验机研究了其在菜籽油中的摩擦学性能,并考察了其抗腐蚀性能、氧化安定性和热稳定性.结果表明:含硼杂环化合物使菜籽油基础油的抗磨性能和承载能力都得到明显提高,减摩性能也有所改善;该添加剂还具有良好的抗腐蚀性能、优良的氧化安定性和热稳定性.采用X-射线光电子能谱分析了摩擦表面的元素化学状态,结果表明:氮和硼元素以吸附的形式存在于摩擦表面,而硫则与金属表面反应生成了含硫酸盐和FeS2的反应膜.吸附膜与反应膜的共同作用提高了基础油的减摩抗磨性能及承载能力.     

磷酸盐溶液钛合金微弧氧化膜影响因素的研究

采用脉冲电源于NaH2PO4＋NaF溶液中对Ti6Al4V进行微弧氧化.于Ti6Al4V表面形成了氧化物陶瓷膜.综合研究了电解液浓度、电压、氧化时间对膜厚的影响,利用扫描电镜、X射线衍射研究了陶瓷膜的组织结构.结果表明：在恒定的电参数下,随电解液浓度提高,电压升高,膜层粗糙度加大,由亚稳态的锐钛矿相TiO2向高温稳定的金红石相TiO2转变;随氧化时间的延长,膜厚逐渐增加,达到一定时间后膜厚趋于平稳.     

新型碳纤维海洋电场电极的制备及性能研究

针对传统碳纤维电极易受电容容抗效应影响而无法响应低频信号的问题,采用浓硝酸氧化+硅溶胶涂覆的改性方法,制备了一种新型的碳纤维海洋电场电极。实验结果证明,改性后碳纤维表面引入了大量氮氧官能团,使得电极比表面积和亲水性得到大大提高,同时电极受容抗效应的影响减小。在电场响应性能方面,改性后电极能够正确响应低至1 m Hz的低频信号,相较于改性前,响应的准确性和灵敏度也得到大大提高,改性后电极对10和1 m Hz信号响应的线性度分别为3. 3%、2. 1%,灵敏度分别为0. 048 2,0. 050 3。     

固体铁氧化物与CO2-CO气体间18O交换的质谱研究

为掌握冶金反应过程中氧在气-固两相间的迁移动力学,采用氧同位素交换技术研究了1373 K时固体铁氧化物与CO₂-CO气体的氧同位素交换反应,考察了气相氧分压（CO₂/CO比值）对氧同位素交换反应的影响。结果表明：在氧同位素交换反应前期,反应速率随时间急剧下降,后期缓慢下降,反应前期和后期的控制性环节分别为界面化学反应和氧在铁氧化物内的扩散;氧分压的提高有利于氧同位素交换反应的进行。     

钢/玻璃的摩擦磨损性能动态观测研究

本实验在自行设计的摩擦磨损动态观测实验机进行,摩擦副之间的接触采用球一盘式接触。研究表明：当以较低速度滑动时,钢球表面的氧化物起到抗磨作用;滑动速度达到一定值时,氧化膜的生成速度小于氧化膜的磨损速度,摩擦表面为粘着磨损;当滑动速度继续升高时,摩擦表面的活化能增加,氧化加速．又出现氧化磨损;而滑动速度过高时,粘着磨损成为主要磨损形式,同时由于磨粒的作用,表面也发生疲劳磨损和磨料磨损．致使磨损急剧增加;表面层在摩擦热导致的高温条件下,氧化膜的生成速度又有所增加,氧化磨损为主要形式。     

不锈钢表面等离子喷涂热障涂层高温氧化性能的研究

利用等离子喷涂技术在不锈钢表面喷涂，由底层（NiCrAl）和面层（ZrO2＋Y2O3）组成的梯度涂层。用SEM和XRD方法表征了梯度涂层的显微组织和相结构。对喷涂后试样在800℃进行了高温氧化试验，给出了氧化动力学曲线。结果表明不锈钢表面等离子喷涂NiCrAl＋（ZrO2＋Y2O3）梯度涂层的厚度约为530μm。不锈钢表面喷涂梯度涂层后，提高了高温抗氧化的性能，降低了氧化速率，喷涂后的氧化膜致密，对继续氧化有阻碍作用。     

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...     

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.     

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.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

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....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.