基于电场驱动熔融喷射聚合物基复合材料高分辨率3D打印

针对当前聚合物基复合材料（Polymer matrix composites,PMC）成型存在打印分辨率低、打印材料受限、成型结构较为简单、工序复杂等方面的不足和局限性,尤其是还面临难以实现宏/微结构跨尺度高效制造的挑战性难题,提出一种基于电场驱动熔融喷射PMC高分辨率3D打印新工艺。阐述了基于电场驱动熔融喷射PMC高分辨率3D打印的基本原理和工艺流程。通过试验,揭示了主要工艺参数（碳填料含量、施加电压、螺杆转速、打印速度、加热温度等）对于打印件分辨率（精度）和质量的影响及其规律。利用自主搭建的试验平台,并结合试验优化的工艺参数和提出的两种打印模式,实现了多层石墨烯/聚乳酸（Polylactic acid,PLA）和多壁碳纳米管/PLA复合材料微尺度三维网格、多层石墨烯/PLA大高宽比薄壁圆环、多壁碳纳米管/PLA复合材料柔性导电网格以及其他聚合物复合材料3D结构典型工程案例的制造。研究结果表明,提出的电场驱动熔融喷射3D打印能实现高分辨聚合物基复合材料成型（使用内径300 μm喷嘴,实现了分辨率为40 μm的PMC特征结构制造）,而且还具有大面积宏/微结构跨尺度集成制造的优势。     

电磁致动式微滴按需喷射装置的设计及实现

针对现有商业化微滴按需喷射装置需根据喷射材料性质定制而较难直接用于研究不同材料喷射行为的现存问题,设计并实现了一种基于电磁致动器的机械振动式低成本微滴按需喷射装置。该装置由激振系统,喷射坩埚及相应的低氧环境保护系统,加热及温度控制调节系统组成。采用该微滴喷射装置进行试验,通过调整电磁致动器激励电压脉宽成功实现了不同喷射频率下水和石蜡微滴的按需可控喷射,试验结果证明了该装置的稳定性以及实现不同材料微滴喷射的可行性。     

微域保护气对金属微滴喷射过程影响机制研究

金属微滴喷射3D打印过程需在低氧环境(氧含量低于50 ppm)下进行,现有设备常采用带除氧系统的密闭手套箱来维持低氧环境,但因其空间受限,操作不便,很难适应该技术向应用领域拓展。在微滴喷射出口处构建微域低氧环境,既可保护微滴喷射时不被氧化,又能扩大该技术应用范围并提高操作灵活性,是促进金属微滴喷射3D打印技术工程化应用的一个关键。但施加保护气会产生气流扰动,不利于微滴稳定喷射和精确沉积。为解决现有微域保护技术不足,设计开发一种新型环形射流微域保护装置,结合微域保护下的锡合金微滴喷射试验与微域气流流场模拟,揭示氧化和气流动力学对微滴喷射过程作用机制。研究发现当保护气供应不足时,金属射流由于氧化表面张力降低、黏度增大(即Oh数增大),会断裂为带锥形拖尾的单颗熔滴;当保护气供应过大时,气流在射流根部产生二次涡,使射流二次断裂,并生成多颗熔滴。最终在合适参数下打印出较长沉积距离熔合良好、堆叠整齐的锡合金立柱和尺寸均匀、落点准确的凸点阵列,证实环形射流微域保护装置的有效性。研究成果可为金属微滴喷射3D打印技术的推广应用提供关键技术支持和理论基础。     

FDM大型3D打印机的制作与工艺分析

随着行业的发展,3D打印技术在工业领域的应用已成为不可阻挡的趋势。但是目前大多数3D打印机仍停留在桌面级,并不能真正推动制造业的大型化和工业化。因此,大型3D打印机的设计制作将会成为未来3D打印技术的研究方向。以北京通州区某机械公司一遗弃的数控机床为三维平台,制作了可打印大型铸造模具的工业级3D打印机,其中包括熔融挤出系统、三维移动系统、三维控制系统、基板加热系统等。以玻纤含量为20%的ABS为材料,初步探究了其打印可行性。研究了不同计量螺杆转速和压力对熔体挤出质量流量的影响;研究了不同打印速度、计量螺杆转速、层高对堆叠后单丝宽度的影响。通过对实验数据的分析,得到了不同工艺参数对质量流量和丝宽的影响规律,解决了熔体堆积过程中流量分布不均及溢料问题,并为后续打印提供了数据依据。对打印机进行模具打印测试,验证了其打印可行性。     

陶瓷浆料按需喷射打印沉积系统设计与实验

针对陶瓷零件脆性大、硬度高、复杂形状受限、生产周期长、成本高等问题,提出了一种将微滴按需喷射技术应用到陶瓷零件打印成形的新方法。通过分析陶瓷浆料按需喷射打印沉积成形工艺原理,完成了试验系统总体结构、喷射装置和运动控制系统的设计开发,并利用该系统进行了陶瓷浆料单个微滴按需喷射,以及点阵、线条、平面和实体的打印沉积实验。实验结果表明:该系统可满足陶瓷浆料微滴的按需喷射和打印成形,验证了所开发的按需喷射打印系统的可行性与正确性。     

高性能电加热玻璃3D打印与微转印复合制造工艺

为了解决透明电加热玻璃制造技术难以兼顾电加热玻璃加热线的透光率、导电性以及附着力的问题,开发了一种可低成本、批量化实现高性能电加热玻璃制造的复合工艺。该工艺采用电场驱动熔融喷射沉积(Electric-field-driven Fusion Deposition,EFD)3D打印和UV辅助微转印复合制造透明电加热玻璃。根据复合制造工艺原理,选择及配制了EFD 3D打印、UV辅助微转印介质以及加热线材料。通过具体实验揭示了主要工艺参数对制造透明电加热玻璃加热线结构参数的影响以及规律,并确定了复合制造工艺的最佳工艺窗口。依据最优工艺参数实现了有效图案化面积为60mm×70mm,线宽为15μm,高宽比为0.7,周期为1 000μm,透光率为88%,方阻为0.5Ω/sq,附着力为4B级,加热线为线栅结构的透明电加热玻璃制造。实验结果表明:利用EFD 3D打印和UV辅助微转印复合工艺制造的透明电加热玻璃具有透光率高、方阻低及附着力高等优势。该复合工艺为实现低成本、高性能的电加热玻璃的批量化制造提供了全新的解决方案。     

砂型3D打印技术的实践应用

基于传统砂型铸造工艺过程复杂、生产效率低的问题,提出基于微滴喷射原理的砂型3D打印技术。其能快速获得精密铸型技术,可以实现复杂砂型（芯）的快速制造。砂型3D打印技术可实现铸件组织、性能和铸造缺陷的可控性,降低3D打印成本提高生产效率,符合智能化和绿色化的发展方向。     

电场驱动μ-3D打印蜡基微流控模具

提出了一种基于电场驱动微尺度3D打印制备蜡基材料微结构的工艺。通过脉冲直流产生自激发静电场驱动皮升级体积石蜡微滴喷射沉积成形;研究了打印参数如气压、电场强度、脉冲频率及占空比等因素对于蜡模打印的影响;优化实验参数,制作了可用于PDMS转印的石蜡微模板,模板线宽为61.25 μm,高度为44.13 μm;结合微转印技术和等离子改性技术制作了微米级微流道芯片样件,并通过实验验证了其具备微流控芯片的基本特征。     

基于FDM成型工艺的3D打印机的创新设计

3D打印是一种增加型制造，通过数字建模等方式获取扫描数据，基于数据将打印产品分割成截面，将这些截面逐层堆积成型。FDM工艺生产简单，操作安全，基本无污染，可打印材料种类多，且成型速度较快，精度较好，制造成本较低，因此FDM是3D打印成型技术中普及率最高的。为提高其打印质量与精度，对打印装置整机设计及其工艺参数的影响进行研究，主要根据市场上现有FDM成型工艺的3D打印机的机型与结构提出整体设计，完成装机后对创新设计的3D打印机采用正交实验进行工艺参数测试，得出该设计的最优工艺参数组合。     

利用多材料3D打印制造功能梯度材料的研究

针对目前功能梯度材料制造方法的单一和不足,文中提出一种新的聚合物功能梯度材料生产工艺——利用多材料3D打印工艺制造功能梯度材料零件。首先介绍了多材料3D打印的工作原理;其次,通过制作两个功能梯度零件:变密度材料和变刚度材料,验证了利用多材料3D打印技术制造聚合物功能梯度材料的可行性,对于后续研究具有重要的指导意义。     

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.     

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....     

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.     

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.