基于选择性激光烧结PS原型的 快速铸造工艺研究

针对传统熔模精密铸造工艺中熔模制作过程复杂的问题,以某典型零件为研究对象,开展了基于选择性激光烧结技术的熔模精密铸造工艺研究。首先采用SolidWorks建立了零件的三维模型,将模型导入激光烧结设备中,调整并优化了烧结设备的工艺参数,以PS(聚苯乙烯)粉末为原材料进行了激光烧结成型,制得了零件的PS原型;然后,以该PS原型与蜡浇注系统结合后的整体模型作为熔模替代了传统压制蜡模,进行了熔模精密铸造,制得了目标零件的精密铸件;最后,测量并分析了铸件的尺寸精度和表面质量。研究结果表明:通过该快速铸造工艺制得的铸件质量较好,尺寸精度可达CT6级,表面粗糙度可达Ra6.3μm。     

快速精密铸造技术及应用

快速精密铸造技术是一门迅速发展的高新精密金属铸件制造技术,具有其他铸造技术无法比拟的优点,拥有广泛的应用市场。文中根据国内外最新的研究资料,对快速精密铸造技术的工作原理、优点及应用进行了较为详实的介绍和论述。     

大型涡轮转子叶片熔模精铸特点

阐述了用熔模精密铸造制作大型涡轮转子的工艺。介绍了以模料选择、采用冷蜡芯工艺制模、浇注系统设计、合理选择浇注温度和铸型温度等措施，来避免缩松和防止叶片的弯扭变形，并对叶片铸件采用静压矫正。     

铸件加工工艺探索

铸造种类繁多,随着铸造技术水平的提高,采用精密铸造技术直接获得高精度的工件成品已成为可能。但考虑到制作成本等方面的因素,铸造主要还是作为一种毛坯制作方法被制造业广泛采用。绝大多数铸件都是通过机械加工最后才成为成品工件的。一般来说,铸件的尺寸精度不高,所以分析探索怎样将铸件最终加工成合格成品的工艺方法,不仅必要,而且具有很重要的现实意义。下文对目前普遍采用的砂型铸件机械加工工     

金属型真空重力精密铸造技术的研究及在铝硅系合金铸造上的应用

总结了传统金属型铸造的特点，综合创新研发了金属型真空重力精密铸造技术，开展了真空环境中铝液流动充型和快速凝固过程的研究，并投入批量生产。生产实践证明，该技术在增加铸件致密度、强度，提高尺寸精度和金属利用率，以及减少废品和降低生产成本等各方面都有明显的优势，具有较大的推广应用价值。     

基于SL原型的消失法精密铸造工艺研究

研究用快速成型技术制作出树脂模型,实现消失法精密铸造的方法和工艺。提出采用SL方法制作精密铸造型壳的方法,进行了理论分析和试验,得到影响型壳所受应力的原因,优化了铸造工艺。     

基于3D打印技术的离心泵叶轮快速精铸工艺研究

以具有典型复杂型面的离心泵叶轮为应用范例,开展了基于3D打印技术的快速精铸工艺研究。首先基于Pro/E软件建立离心泵叶轮三维模型并进行CAD优化设计,基于RPData软件对叶轮模型进行前处理,然后通过3D打印机制作叶轮树脂模型并进行后处理,最后以叶轮树脂模型作为熔模进行熔模精密铸造,最终得到离心泵叶轮精密金属零件。经测量知制得的叶轮铸件的尺寸精度可达CT4级,表面粗糙度可达Ra6.3um以下。     

快速成型技术在熔模精密铸造中的应用

快速成型技术是具有高柔性的先进制造技术,无需任何专用工具,由零件的CAD模型直接完成零件或零件原型的成型制造。将快速成型技术与铸造技术结合起来,采用快速成型技术制造铸型或铸模,可极大提高铸造的柔性和生产效率,满足新品试制和小批量生产的需求,这也是快速成型技术的一个主要发展方向。本文通过几种快速成型模在熔模精密铸造中的实际应用和试验得出,采用SLA法制作的蜂窝结构快速成型模在尺寸波动方面满足精铸需要,并能实现铸件的快速制造。     

大型复杂薄壁铝合金铸件调压成形精密铸造技术

西北工业大学周尧和院士等针对大型复杂薄壁部件的铸造生产难题而发明了一种大型复杂薄壁铝合金铸件调压成形精密铸造技术。采用该技术生产大型复杂薄壁铸件，能够在金属液平稳进入铸型型腔的同时保持优异的充型能力和补缩能力，在保证大型复杂薄壁铸件成形精度的同时获得优异的冶金质量，使铸件晶粒细化，致密度提升，铸件性能提高。     

大型薄壁复杂铝件铸造技术的现状与发展

随着航天、国防、汽车等工业的不断发展，对铸件的要求向小余量、薄壁、高精度、高性能方向发展：介绍了大型薄壁铸件的特征，叙述铝合金复杂薄壁铸件的发展特点，提出复杂薄壁铸件对先进的精密成形技术及铸造工艺的要求.     

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.