双辊薄带连铸高速钢铸带中碳化物的形成及演变

采用光学显微镜观察了在工业双辊薄带连铸机上制备的M2高速钢铸带中的碳化物,利用二次枝晶间距计算了铸带的凝固速率;并用扫描电镜和透射电镜研究了高温热处理后铸带中亚稳相M2C碳化物的演变情况。结果表明：双辊薄带连铸高速钢工业铸带的凝固速率为1．7×10^3K·S^-1,比实验室铸带的5．4×10^2K·S^-1高一个数量级,远远高于工业铸锭的2×10^1K·S^-1;双辊薄带连铸工艺可以细化高速钢铸带中的共晶碳化物,并获得较多的亚稳相M2C碳化物,在高温热处理过程中M2C碳化物与部分奥氏体反应生成稳定相M6C和MC碳化物,使碳化物分布更加均匀弥散。     

双辊连铸薄带辊速控制模型参考自适应

为解决国内双辊连铸薄带辊速控制系统薄带成品率低、裂纹、易断带和轧卡等问题,对辊速与熔池温度场分布相互关系进行了研究:辊速与铸机出口处薄带表面温度近似线性关系。辊速越大,薄带表面温度越高且易断带;辊速越小,薄带表面温度越低且易裂纹或轧卡。通过采样薄带表面温度,建立凝固终点模型和温度反馈修正铸辊主速度给定数学模型,解决凝固终点不能测量及因干扰致其波动而不能实时修正主速度给定的问题;通过建立模型参考自适应系统解决系统实时性和鲁棒性差的问题。     

双辊薄带铸轧纯铝凝固组织模拟与性能分析

基于CAFE原理,建立双辊薄带连铸数学模型求解纯铝在铸轧机熔池区晶粒生长演变以及枝晶分布情况.结果表明:金属液与弯月处铸辊接触后开始凝固,铸辊表面形成大量细小等轴晶,晶粒数目逐渐减少且粗化,晶粒延<001>取向择优生长,等轴晶演化为柱状晶.Kiss点位置高度对晶粒细化有关键作用.     

K4202镍基铸造高温合金的组织研究

系统研究K4202镍基铸造高温合金的组织.研究表明,K4202合金在热处理后合金的组织为:在γ基体上分散着沉淀强化相γ',晶界有少量的M23C6碳化物,主要沿晶界呈链状析出,晶内有块状的MC型碳化物,同时由于合金成分中含有一定量的B,因此在枝晶间边上也有少量的硼化物(M3B2)存在.通过1170℃×4h固溶 840℃×10h时效处理后,γ'相数量达到10%左右.     

1Cr18Ni9Ti不锈钢双辊薄带的铸态组织特征研究

通过双辊薄带连铸试验和组织成分分析,对1Cr18Ni9Ti不锈钢双辊薄带的铸态组织特征进行了研究。结果表明：1Cr18Ni9Ti不锈钢双辊薄带的铸态组织和传统薄板坯没有本质区别,但薄带坯组织较为细密,柱状晶区呈不严格的对称分布;一次枝晶和二次枝晶间距小,并且均随离薄带表面距离的增加而增大;柱状枝晶的生长比较紊乱,没有严格的方向性;在薄带厚度方向上元素铬和镍没有明显的成分偏析。     

双辊薄带熔池凝固模拟分析中的关键问题

由于双辊薄带连铸工艺复杂,工序高度凝聚,应用计算机数值模拟技术辅助或代替常规物理实验对凝固过程进行仿真分析,借此获得优化的工艺参数以指导生产具有重要意义。通过对双辊薄带凝固模拟分析中的关键参数进行研究,针对不同问题建立相应的计算模型,对涉及的湍流模型、凝固模型、对换热系数、结晶潜热、导热系数、粘度等相关问题进行研究确定并开发编写UDF,为数值模拟成功及工艺参数的确定打下坚实基础。     

基于VOF的双辊薄带熔池凝固模拟研究

根据双辊薄带连铸工艺特点,应用Fluent软件建立基于VOF多相流及凝固模型的二维熔池钢液凝固分析模型,在设定参数下进行kiss点的预测分析;建立能够合理描述双辊薄带铸轧过程中的湍流流动及凝固过程的控制模型,对有效导热系数、有效粘度及有效换热系数等关键问题进行合理化处理,编写开发UDF以满足自定义需求,调节控制参数以获得收敛有效的物理解,最后通过多核并行计算得到kiss位置,为后续工艺参数制定提供技术参考。     

轧辊用高速钢铸态组织分析

利用XRD、SEM和EDS等方法对几种轧辊高速钢铸态组织中碳化物的类型、形态和分布等进行了研究,并对碳化物的体积分数进行了测定。分析了碳化物对铸态组织的影响以及合金成分与碳化物类型、体积分数之间的关系。结果表明：轧辊高速钢铸态组织主要由马氏体基体和少量的残余奥氏体以及MC型、M6C型和M2C型碳化物组成,其中MC型碳化物是影响轧辊高速钢铸态组织的重要因素。碳化物的体积分数随合金碳含量的增加而增加,并在一定程度上受到钨当量的影响。     

高速工具钢中碳化物的形态

<正> 在高速工具钢中存在着M6C、M2C、MC三种类型的初生碳化物。这些碳化物都是在凝固过程中从钢液中结晶出来,成为最终产品中的未溶碳化物残存在钢中,起着增加耐磨性、防止奥氏体晶粒粗化的作用。但是,这些碳化物的硬度均大于HV1500,几乎没有塑性,因而存在形态、粒度及其分布、相对量等对材料的机械性能都有极大的影响。其中具有Fe3(W,Mo)3C～Fe4(W,Mo)2C 成分的M6C 型碳化物在高速钢工具钢的初生碳化物中构成比例最大,必须在浇铸时尽量地进行细化。照片1(a)是SKH2(18W—4Cr—1V)     

Co-Cu-Pb三元合金的快速凝固组织及电学性能研究

采用单辊快速凝固技术研究Co-Cu-Pb三元难混溶合金薄带的快速凝固组织特征及电学性能,并通过将金属熔体热传导方程与Navier-Stokes方程相耦合,理论计算合金薄带的冷却速率。结果表明:在急冷快速凝固条件下,Co-Cu-Pb三元难混溶合金薄带的凝固组织由优先生长的Co(Cu)相枝晶骨架和枝晶间的富Pb相组成。随着冷却速率的增大,Co(Cu)相枝晶尺寸明显减小,凝固组织均匀性得到改善;而随着Pb含量的增大,少量的Pb相析出存在于Co(Cu)相枝晶干上。冷却速率的增大,合金薄带组织均匀性引起电子散射源减少,导致自由电子的散射作用减弱,使得合金薄带的电阻率减少。而合金中Pb含量的增大,减少了导电的有效电荷数,使得合金薄带的电阻率增大。快速凝固技术有效地改善了Co-Cu-Pb难混溶合金薄带的凝固组织均匀性和电学性能。     

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.     

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....     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.