AZ91D镁合金电子设备耐腐蚀性复合表面处理工艺技术

镁合金耐腐蚀性差,易氧化,严重影响了其使用寿命。针对镁合金单独零件的微弧氧化、钝化和镀镍等表面处理,开展了一系列防腐蚀性试验研究。结果表明:单独零件在先微弧氧化后油漆的复合表面处理方式下可通过GJB150A中规定的96 h盐雾试验考核。与镁合金单独零件相比,镁合金电子设备还会出现电偶腐蚀和间隙腐蚀的情况。因此,有针对性地开展了镁合金材料电子设备的防腐蚀性结构设计。结果表明:在采用微弧氧化、喷漆和Parylene气相沉积复合工艺表面处理的电子设备,成功通过GJB150.11A中规定的96 h盐雾试验考核。     

镁合金的特点及加工要点

在介绍了镁的理化性质及镁合金诸多优点的基础上,阐述了镁合金切削加工时必须注意的工件易变形、镁屑易燃烧等要点,最后深入细致地阐述了镁合金切削加工过程中防燃的措施、防腐蚀措施以及减少零件加工过程中防止变形的措施。     

镁合金及其低温切削加工的研究进展

由于镁合金具有密度小、比强度高、生物相容性好和可降解性等特点,在轻量化材料领域和医用金属材料领域潜力巨大,但由于其燃点较低、线性膨胀系数较大,导致镁合金在加工时易出现切屑燃烧、加工变形等问题。本文介绍了镁合金的分类与应用、镁合金在切削过程中存在的问题以及镁合金低温切削加工研究进展,对镁合金的加工和应用具有指导意义。     

镁合金在高温下的流动模拟

对于镁合金AZ31和AZ91的高温加工时流变应力的评估,可以用一个公式来表示,该公式是通过分析镁合金在不同的温度和不同的应变速率作用下流变应力的变化得出的。该公式通过温度补偿应变速率即Zener-Hollomon参数（Z参数）可以简单地表示出来。已经证明Z的对数线性方程适用于高温时的合金流变应力。     

空冷对镁合金切削加工表面质量的影响

通过对镁合金在采用压力冷空气或干切削加工时的试验对比,分析压力冷空气对镁合金切削加工的影响,研究表明在采用空气冷却情况下,铣削加工的工件表面粗糙度减小,提高了表面质量。在某些条件下,采用压力冷空气冷却对工件表面质量的改变效果虽不明显,但避免了镁合金在干切削加工过程中切削易燃烧,采用水基润滑液易产生化学反应的缺点,对镁合金加工具有较强的应用价值。     

镁合金钻削及其钻头刃磨

广东读者孙新生来信反映,他们厂最近遇到一批镁合金零件,在加工中遇到不少困难,特别是在钻削加工中问题更为突出,望介绍有关经验。在金属钻削中镁合金钻削资料寥寥无几,本文根据多年镁合金钻削的实践体会,介绍几点经验以供参考。一、镁合金切削状况镁合金具有刚度低、变形大、易腐蚀、切削时不宜用冷却润滑液等特点,当切削温室超过480℃时会产生燃烧。由于这些特殊性质,钻削工作困难很大。镁合金切屑为针状碎屑,当钻削到一定深度时,碎屑容易堆积填满钻头的螺旋槽不易排出;随着切削温度     

等温模锻对AZ91D镁合金性能的影响

镁合金作为最有潜质的轻质结构材料，具有高比强度、高阻尼、良好的锻造性，以及易回收利用等一系列优点。由于镁是密排六方结构，室温塑性差，如何经济地得到组织性能稳定的镁合金变形材一直是摆在广大研究者面前的重大课题。已有研究结果表明，镁合金的塑性变形能力对温度高度敏感，在高于523K时，棱柱滑移面启动，合金塑性大幅改善。因此，研究镁合金在高温变形下组织性能的演变对实际生产具有指导意义。     

半固态AZ91D合金暂态流变特性的研究

文中以Chen-Fan模型为基础对其表达式中关于解聚率和碰撞率的表达式做出符合实际的修改,并将修改后的模型应用于半固态AZ91D镁合金暂态过程的研究。首先将半固态A Z91D镁合金浆料静置一段时间后,分别从浆料中各固相粒子之间发生聚合和解聚两个方面观察其处于暂态过程时的表观黏度变化。然后通过研究发现当再次施加某一剪切速率时,半固态浆料的表观黏度值会急剧下降直至稳定到某一固定数值,表现出典型的剪切变稀即触变性。这对于半固态金属浆料的充型十分重要。     

Al-Ti和Al-Ti-C中间合金对消失模铸造AZ91镁合金显微组织的影响

A l-Ti和A l-Ti-C中间合金对消失模铸造AZ91镁合金组织的试验研究表明,与常用变质剂C2C l6相比,加入A l-Ti和A l-Ti-C中间合金对消失模铸造AZ91镁合金具有更好的组织细化效果和更高的力学性能,而加入A l-Ti-C中间合金的作用效果最佳。A l-Ti-C及A l-Ti中间合金的加入提高了共晶反应的离异化程度,晶界上的β相由连续网状变为不连续块状和孤立的粒状结构且分布均匀。A l-Ti-C中间合金对消失模铸造AZ91镁合金晶粒细化是其晶粒生长抑制作用和引入形核质点综合作用的结果。     

AZ91D镁合金加工工艺的应用研究

在分析AZ91D镁合金化学成分、物理力学性能的基础上,通过试验对比了切削速度在66.819m/min、107.388m/min、169.434m/min时的切屑断屑性能、切屑形态及其表面质量。试验表明:在背吃刀量恒定的前提下,随着切削速度的提高,切屑变形减小。切屑形态由C形挤裂切屑变成带状连续切屑,断屑能力变差,结构表面质量变差;在背吃刀量0.06mm时,切削形成粉末状切屑,堆积在卷屑槽内,易引起镁合金燃烧。总结了镁合金切削加工中对刀具、切削参数、切削液以及切削过程的要求,介绍了工序间防腐措施。分析了AZ91D镁合金的固溶时效作用,从零件结构、设备及防火等方面提出了热处理过程的要求。从冶金和环境方面综述了镁合金的腐蚀因素,并对比分析了AZ91D镁合金切屑在空气和水中的腐蚀现象。最后,重点介绍了镁合金的微弧氧化工艺。研究成果对镁合金加工工艺的推广应用提供了技术参考。     

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...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

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.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

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...