镁合金表面冷喷涂防护技术研究

镁合金是目前最轻的金属结构材料,具有广阔的应用前景,但耐磨、耐蚀性差却制约着其广泛应用,可通过各种表面改性和表面涂覆技术拓宽其应用范围,介绍了镁合金的应用及其防护技术现状,重点介绍了冷喷涂技术在镁合金表面防护应用现状,分析了镁合金表面金属涂层的发展趋势,提出利用冷喷涂技术制备铝基非晶合金涂层,可望解决缺乏能为镁合金基体提供长效防护的单一涂层难题。     

臭氧净化处理对AZ91D镁合金表面微弧氧化涂层的影响

在AZ91D镁合金基体表面制备了微弧氧化涂层,开发出高效、环保的新型镁合金微弧氧化电解液并系统优化了微弧氧化的电源参数.利用SEM和×RD研究了AZ91D镁合金不同添加剂以及臭氧处理对微弧氧化涂层的厚度及组织的影响,并进行了基体和涂层的耐蚀性实验比较.     

镁合金磁控溅射镀铝耐蚀防护层研究

在AZ31镁合金表面进行了磁控溅射铝防护层的镀覆,并研究了镀层的成分分布、形貌、显微力学性能、防腐蚀性能及工艺条件对镀层的影响。结果表明：直径为1～2μm的细小晶粒均匀在镁合金基体表面沉积形成致密铝镀层,镀层和基体之间存在混融的过渡层;镀层表面粗糙度在2μm以下并与基体结合良好,其硬度、弹性模量等高于镁合金基体并具有一定韧性和弹塑性能;适当降低氩气压力,提高溅射电流,可改善镀层质量。镀层提高了镁合金基体的自腐蚀电位并降低了腐蚀电流,从而抑制了腐蚀倾向,但自腐蚀电位低于热喷涂铝电位且腐蚀电流高于微弧氧化处理电流。     

等离子喷涂ZrO2热障涂层的热冲击性能

利用ANSYS软件对铝、镍基体等离子喷涂ZrO2热障涂层在热冲击过程中的应力分布进行了数值模拟,并比较了不同金属基体对涂层热冲击行为的影响.结果表明:热冲击过程中产生的径向热应力最终导致涂层中垂直裂纹的出现,镍基体涂层的热冲击性能优于铝基体,有限元计算结果与试验结果吻合良好.     

AZ91D镁合金表面热喷涂陶瓷涂层研究

介绍在AZ91D镁合金表面热喷涂Al2O3+TiO2陶瓷涂层的组织、性能。该涂层和基体结合良好,涂层硬度可达 800HV以上,并有良好的耐短期热冲击能力。     

AZ91D镁合金表面热喷铝涂层研究

在镁合金表面热喷涂铝，而后经430－450℃保温1h，使镁、铝结合面产生熔融、扩散并形成冶金结合的防腐蚀层。试验和结果分析表明，热喷铝层和镁合金基体结合牢固，并具有良好的耐腐蚀性能。     

镁合金表面再制造AlCoTi非晶涂层组织及力学性能研究

采用高速电弧喷涂技术在AZ91镁合金表面制备了高非晶含量AlCoTi涂层,研究了涂层显微组织、力学性能、摩擦磨损及电化学腐蚀性能。结果表明,涂层呈典型的层状结构,其结构紧凑,与镁合金基体结合良好,孔隙率约为1.63%。涂层的组织主要由非晶相、纳米结构的α-Al和Al3Ti相组成。相比于AZ91镁合金,AlCoTi非晶涂层具有更高的显微硬度和耐磨性能：涂层的显微硬度约为511.3Hv0.1,远高于AZ91镁合金(62Hv0.1);在相同的磨损条件下,非晶涂层相对耐磨性约为晶体结构AZ91镁合金的3.9倍,其主要磨损机制为脆性剥落。在0.6 mol/L NaCl溶液中,非晶涂层自腐蚀电位、自腐蚀电流密度和电荷转移电阻分别为-0.696V、0.741 8μA/cm²和33 660?·cm²,明显优于AZ91镁合金的-1.392V、769.3μA/cm²和1 914?·cm²。通过对镁合金表面不同防护涂层的电化学腐蚀性能和显微硬度比较分析,本研究为镁合金提供一种低成本、高性能的涂层材料及再制造关键技术。     

铝基体上 ZrO2/NiCrCoAlY梯度涂层的研究

针对低散热发动机主要部件铝活塞顶部制备热障涂层的需要，用等离子喷涂法在铝基体上制备出梯度涂层，对其性能与显微组织结构进行了研究。     

HVOF中喷涂距离对AZ91D镁合金WC涂层性能影响研究

采用Jp—5000音速火焰喷涂(HVOF)技术在AZ91D镁合金表面喷涂WC—10Co4Cr涂层。利用扫描电子显微镜、X射线衍射仪、显微硬度计等设备和浸泡腐蚀实验来分析WC涂层的组织结构和性能。结果表明:WC涂层均匀、致密,孔隙较少,涂层与基体结合紧密,无裂纹,无剥离;经XRD检测分析,WC在高温环境中发生元素重组,生产了CW_3、W_2C,分解率与火焰作用时间有关;WC涂层提高了镁合金的耐腐蚀性。     

超音速火焰喷涂(HVOF)涂层的抗汽蚀性能研究

采用新型的超音速火焰喷涂（HVOF）技术,在铝青铜基体试件上喷涂了WC—Co、Ni60和NiCr三种抗汽蚀材料,通过振动汽蚀试验,研究涂层的抗汽蚀性能。试验表明,Ni60粉末喷涂层结构致密,与铝青铜基体结合较好,其抗汽蚀性能优于其它两种涂层。     

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.