离心铸造制备原位初晶硅和Mg_2Si颗粒增强铝基骤变复合材料的组织与性能

采用离心铸造工艺制备初晶硅和Mg2Si颗粒混合增强铝基骤变复合材料,采用光学显微镜、X射线衍射仪、硬度计等对此复合材料组织与性能进行了研究。结果表明:该复合材料分为增强层(内层)与非增强层(外层),两层之间存在明显的宏观界线,内层偏聚了大量的初晶硅与Mg2Si颗粒,而外层仅有极少量的颗粒;从内层到外层,硬度呈现先降低后升高趋势;在小载荷下,内层与外层耐磨性能差异显著,而在大载荷下,两者差异微弱;初晶硅颗粒显著提高了复合材料在小载荷下的耐磨性,Mg2Si颗粒提高磨损性能的作用次之。     

变质及热处理对过共晶铝硅合金组织与滑动磨损性能的影响

采用新型含TiC—RE—P的JHSM复合变质剂在850℃对过共晶Al-20％Si合金进行变质处理。研究结果揭示,经过变质处理后,初生硅的平均尺寸和形状由变质处理前100--250μm的不规则形状转变为变质处理后15～30μm的块状;变质处理后过共晶铝硅合金的硬度和耐磨性明显提高。     

等通道转角挤压Al-26%Si合金的组织和冲击性能

采用等通道转角挤压工艺(ECAP)细化了Al-26%Si合金中的组织,研究了该合金在不同温度下的冲击性能及断口形貌。结果表明:ECAP能有效细化该合金的晶粒,块状初晶硅尺寸明显减小且棱角钝化,针状共晶硅呈颗粒状弥散分布于基体中,300℃下挤压16道次后合金的室温(11℃)冲击功约为铸态的5倍;低温下,挤压16道次后合金的冲击性能随温度下降变化不大;当冲击温度由室温升高至100℃时,合金的冲击性能有所下降;铸态试样的断裂机制以脆性断裂为主,挤压后试样的断裂机制以韧性断裂为主。     

退火温度对形变铝硅合金组织和性能的影响

铝硅合金分别进行30%和70%的冷压缩变形,选取360℃、380℃、400℃、420℃及440℃对压缩试样进行退火处理,采用金相和硬度分析对材料微观组织及性能进行表征。结果表明：30%冷变形后基体组织与铸态组织保持一致,随着退火温度的升高,材料硬度呈缓慢下降趋势;70%冷变形后基体组织发生变化,随着退火温度的升高,材料硬度显著下降,共晶硅形态由板条状转变为颗粒状;退火温度高于380℃,70%冷变形试样发生再结晶。     

稀土变质处理对过共晶Al-18%Si-Mg合金组织和性能的影响

采用扫描电镜观察了不同稀土加入量变质处理过共晶Al-18％Si—Mg合金的组织变化,并分析了稀土对Mg2Si相结晶行为及合金性能的影响。结果表明：在未完全变质合金中Mg2Si相以网状或骨骼状形式存在,与共晶硅片之间存在附着生长关系;而在完全变质合金中,Mg2Si相以细小的颗粒相形式孤立地存在于共晶团边界上,数量极少。稀土的存在对Mg2Si相凝固结晶行为及合金性能产生了重要影响,这与初晶硅和共晶硅的变质程度有关。     

离心铸造铝梯度复合材料的组织与性能

针对传统铁质气缸套与铝合金气缸体匹配性差,长期使用导致漏油、漏气等问题,提出了一种制备铝基梯度复合材料气缸套的新思路。依此思路,采用Al-19Si-5Mg-1Cu-1Ni-1Ti-1Mn合金为毛坯材料,通过离心铸造的方式成功制备了初晶Si与Mg2Si颗粒互补增强的铝基梯度复合材料。从心部到外壁,该梯度复合材料具有两层结构,内层含有高体积分数初晶Si与Mg2Si颗粒,形成增强层;外层没有初晶颗粒,为非增强层。对两层结构的部分常温性能指标进行初步测试,结果显示,增强层具有高硬度、高耐磨性和良好热稳定性的特点。     

铁基自润滑梯度复合层的研究

采用金属涂覆铸造技术在铸钢件表面形成的５￣６ｍｍ厚的自润滑复合层中含有大量铬的碳化物和球状石墨。由表及里，其化学成分、铸态硬度、所含石墨及合金碳化物的数量和形态均呈梯度分布，并逐渐过渡到母体材料的水平。在重载干滑动磨损条件下，具有很好的耐磨性。     

热处理对激光选区熔化成形AlSi10Mg合金中共晶硅形貌与分布的影响

通过激光选区熔化(SLM)技术制备AlSi10Mg合金,分析了沉积态合金的显微组织,研究了3种热处理工艺(T6、T2、T6+T2)对共晶硅形貌和分布的影响。结果表明:沉积态合金表面熔池由中心向边界依次为细晶区、粗晶区和重熔区,合金中共晶硅呈短纤维状,尺寸为纳米级;热处理前后,AlSi10Mg合金均由铝、硅以及Mg_2Si相组成;热处理后共晶硅分布更加均匀,组织均匀性提高;沉积态合金依次经T6,T2工艺处理后,其共晶硅的硅元素含量增加,共晶硅纯度提高。     

熔体冷却制备过共晶Al-Si合金半固态组织

研究了熔体冷却对过共晶Al-18％Si合金微观组织的影响。将接近液相线的低温熔体通过冷却体流入薄壁铁型中，在580℃水冷时，获得初晶硅和共晶硅细小且有大量近球形α相的组织，为理想的半固态过共晶Al-Si合金组织，对其形成机理进行了分析。     

Al-Si 16%合金的过热温度与结晶行为

研究了不同过热温度对Ａｌ－Ｓｉ１６％结晶组织的影响，发现当过热温度超过９００℃后，试样中的初晶硅尺寸与数目大量增加，共晶硅的尺寸变小。ＤＳＣ分析表明，一定程度的过热增加了Ａｌ－Ｓｉ１６％的结晶潜热。液态Ｘ射线研究发现，在９００℃以下，Ａｌ－Ｓｉ１６％的平均配位数比相同温度纯铝低，而在９００℃以上，合金的平均配位数要高。１２５０℃温度过热后，合金熔体在液相线上方就已出现与硅晶态相对应的衍射峰。过热温度对结晶行为的影响可用Ａｌ－Ｓｉ１６％熔体中Ａｌ－Ｓｉ原子团在较高过热温度下向Ｓｉ－Ｓｉ原子集团转化的机制来解释。     

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。     

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.     

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....     

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.