0Cr18Ni9Ti不锈钢表面渗锆合金层的耐腐蚀性能及抗高温氧化性能

采用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备渗锆合金层,然后将其分别置于在0.5mol·L-1 HCl溶液、3.5%NaCl溶液、0.5mol·L-1 NaOH溶液中进行电化学腐蚀试验,另在静态空气中进行了1 000~1 150℃的高温氧化试验,研究了渗锆合金层的耐腐蚀性能及抗高温氧化性能,并与不锈钢基体进行了对比。结果表明:在三种溶液中,不锈钢基体的相对腐蚀速率分别为渗锆合金层的24.43倍、2.44倍、1.90倍,不锈钢基体表面发生了较为严重的腐蚀,而渗锆合金层只出现了局部腐蚀坑,这是因为在腐蚀过程中其表面形成了一层致密的ZrO2钝化膜;不锈钢基体和渗锆合金层的氧化质量增加曲线都基本遵从抛物线规律;在1 150℃氧化20h后,不锈钢基体表面氧化严重,而渗锆合金层的表面形貌较好,存在少量孔洞,组织相对致密。     

γ-TiAl合金表面粉末包埋渗铝改性层的组织与高温抗氧化性能

采用粉末包埋渗金属技术在γ-TiAl合金表面制备出一层渗铝改性层,对改性层的表面形貌、元素分布规律及相组成进行了检测与分析,并试验研究了改性层在850℃静态空气中的抗氧化性能。结果表明:改性层均匀致密,无明显的贯穿裂纹,主要组成相为TiAl3;在850℃静态空气中恒温氧化100h后,表面氧化层主要由Al2O3、TiAl3、TiAl2相组成,改性层显著提高了γ-TiAl合金的高温抗氧化性能。     

钼基高温合金表面包埋渗法制备渗铝层的组织与性能

采用包埋渗法在TZM钼基高温合金表面制备抗氧化的渗铝层,渗铝温度为1 050℃,渗铝时间为12 h;采用SEM、EDS和XRD等分析了渗层的显微组织、物相组成和元素分布等,并对渗层的硬度和抗高温氧化性能进行了研究。结果表明:渗层的相组成为Al_5Mo、Al_3Mo和Al_4Mo;渗层均匀致密,厚度达到130μm,具有双层结构,与基体形成了冶金结合;渗层表面呈颗粒状,其显微硬度达到了8 000 MPa;在800℃×80 h高温氧化下包埋渗铝层具有较好的抗氧化性能。     

γ-TiAl合金表面双层辉光等离子铬钨共渗层的高温氧化行为

采用双层辉光等离子表面技术在γ-TiAl合金表面制备铬钨共渗层,用SEM、EDS和XRD分析等方法结合高温氧化试验,研究了该共渗层在高温下的氧化(共100h)行为。结果表明:γ-TiAl合金经双层辉光等离子铬钨共渗后,共渗层表面形貌完好,组织均匀,与基体连接紧密,结合处无孔洞及裂纹等缺陷存在;铬钨共渗层在高温下可形成保护性氧化膜,有效降低了氧化速率,与γ-TiAl合金基体相比,氧化增重降低,抗氧化能力明显提高;随氧化温度升高,铬钨共渗层的氧化增重明显增大,但氧化机制不变;在氧化过程中,除了铬、钨发生内扩散外,基体中的钛、铝元素均发生了显著的外扩散。     

TC4钛合金表面渗锆层的显微组织与摩擦磨损性能

采用双层辉光等离子渗金属技术在TC4钛合金表面制备渗锆层,研究了渗锆层的显微组织、相组成以及摩擦磨损性能,并与TC4钛合金基体的摩擦磨损性能进行了对比。结果表明:TC4钛合金表面的渗锆层厚度约为10μm;渗锆层的组织连续、均匀、致密,与基体结合良好,锆含量由表层向基体内部呈梯度分布;渗锆层的摩擦因数和比磨损率约为TC4钛合金基体的45.9%和13.6%,摩擦磨损性能明显提高。     

钼基体上钼-硅-氮涂层的制备与高温抗氧化性能

采用氨解渗氮法和熔盐渗硅法在钼基体上制备了钼-硅-氮涂层,利用SEM、XRD研究了涂层的微观结构、元素分布及物相组成,并分析了其在1 600℃的抗高温氧化性能。结果表明:钼基体上的钼-硅-氮涂层由MoSi2和Si3N4相组成,高温氧化时表面可形成致密的SiO2膜,在1 600℃循环氧化寿命达48h。     

ZG45铸钢表面Ni/ZrO_2复合铸渗层的组织与耐磨性能

采用负压铸渗技术在ZG45铸钢表面制备了Ni/ZrO_2复合铸渗层,并对其显微组织、硬度以及常温摩擦学性能进行了研究。结果表明:铸渗层的主要相组成为ZrO_2,Cr_2B,NiB化合物和Fe(Ni)固溶体相;其表面硬度可达60～64 HRC,显微硬度由铸渗层表面至基体呈梯度变化,最大硬度在铸渗层的次表层,最大值为8.5GPa;在100 N和250 N载荷下基体的磨损率分别是铸渗层的22.6倍和21.9倍。     

浸铝硅石墨复合材料氧化及滑动磨损性能研究

为研究浸铝硅石墨材料在高温下动态密封性能,采用环块式磨损试验机考察浸铝硅石墨材料在高温下的抗氧化性能及室温下的干滑动磨损性能,通过光学及电子显微镜、X射线衍射表征浸铝硅石墨氧化表面及磨损表面形貌及组成,探讨浸铝硅石墨的氧化及磨损机制。结果表明, 与石墨材料相比,浸铝硅石墨在300~500 ℃范围内具有较好的抗氧化能力;由于铝的浸渗,提高了基体材料的强度及承载能力,而其中的石墨在磨损过程中可在磨损表面形成一层摩擦层,因而显著提高了材料的抗磨性能。     

激光熔覆原位自生Ti-Al-Si复合涂层的微观组织和高温抗氧化性能

为提高钛合金的高温抗氧化性能,采用激光熔覆原位自生技术,在TC4钛合金表面自行设计并制备了原子百分比为Ti∶Al∶Si=41∶41∶18和Ti∶Al∶Si=35∶35∶30的两种涂层。通过XRD、OM、SEM表征了涂层的微观组织和物相组成;借助管式电阻炉测试了涂层和基体试样在800℃×24h×5次循环氧化条件下的高温抗氧化性能;结合氧化增重和氧化动力学曲线分析了涂层的高温抗氧化机理。结果表明,涂层主要由Ti5Si3、Ti7Al5Si12、Ti3Al、TiAl和TiAl3等物相组成。涂层中没有出现一般激光熔覆所产生的外延生长柱状晶组织,全部为细小等轴晶。在800℃×24h×5次循环氧化条件下,TC4基材单位面积的氧化增重约为35.1mg·cm-2,涂层的约为2.8mg·cm-2和3.3mg·cm-2。两种涂层的高温抗氧化性能较钛合金基材分别提高了12.5倍和10.6倍。激光熔覆原位自生Ti-Al-Si复合涂层能明显改善TC4钛合金的高温抗氧化性能。涂层抗氧化性改善的机理,一方面是表面生成了连续致密的TiO2、Al2O3、SiO2氧化层,阻碍了氧扩散;另一方面是提高了氧化层的黏附性,使氧化层不易从涂层表面剥落,对涂层未氧化部分起到了很好的保护作用。     

浸铝硅石墨复合材料氧化及滑动磨损性能

为研究浸铝硅石墨材料在高温下动态密封性能,采用环块式磨损试验机考察浸铝硅石墨材料在高温下的抗氧化性能及室温下的干滑动磨损性能,通过光学及电子显微镜、X射线衍射表征浸铝硅石墨氧化表面及磨损表面形貌及组成,探讨浸铝硅石墨的氧化及磨损机制。结果表明,与石墨材料相比,浸铝硅石墨在300~500℃范围内具有较好的抗氧化能力;由于铝的浸渗,提高了基体材料的强度及承载能力,而其中的石墨在磨损过程中可在磨损表面形成一层摩擦层,因而显著提高了材料的抗磨性能。     

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.