铜基粉末冶金材料/铬青铜摩擦副中的电弧侵蚀机制

以铜基粉末冶金材料/铬青铜为摩擦副,在销-盘式摩擦磨损试验机上进行载流摩擦学特性研究。在多种条件下试验,探讨载流条件下铜基粉末冶金/铬青铜摩擦副中的电弧侵蚀机制。结果表明:载流摩擦下销试样磨损形式主要以机械磨损、电流和机械综合作用下的磨损、电弧侵蚀为主;电弧对铜基粉末冶金材料的侵蚀主要是熔融材料的黏着磨损、磨粒磨损,电弧作用下材料表层的疏松化、材料的蒸发与转移、材料的熔融积瘤。     

铜基粉末冶金刹车闸片磨损形貌演变研究

采用多功能销-盘摩擦磨损试验机，开展铜基粉末冶金/Q235-B摩擦副的摩擦磨损试验，在载流和无载流的工况下，研究接触压力(0.4、0.7、1.0和1.3 MPa)对铜基粉末冶金材料闸片磨损表面形貌的影响。结果表明：在无载流工况下，随着接触压力的增大，摩擦因数和磨损率均缓慢上升，试样表面损伤加剧，粗糙度升高，主要的损伤机制为磨粒磨损和剥层；在载流工况下，0.4 MPa时的摩擦因数和磨损率最大，损伤最严重，粗糙度最高，当接触压力增大到0.7 MPa后，表面形貌损伤的变化趋势与无载流工况一致，磨损机制在磨粒磨损和剥层的基础上增加了电弧烧蚀；载流工况下材料表面的粗糙度普遍高于无载流工况下，表面损伤更为严重。     

电流对铬青铜/紫铜摩擦学特性的影响

采用自制的销盘摩擦磨损试验机,在载流条件下对铬青铜QCr0.5/T2铜的摩擦学特性进行了研究,结果表明电流对摩擦因数和磨损率具有显著影响,电流越大,磨损率越高,摩擦副磨损越严重,摩擦因数越大。载流条件下,摩擦表面发生电点蚀,并出现局部熔化和雨滴状金属颗粒。     

铜-10%石墨合金的载流摩擦磨损性能

为提高铜基合金的载流摩擦磨损性能,采用粉末冶金方法制备了含10%石墨的铜基合金,并在自制的销盘式载流摩擦磨损试验机上进行了不同电流和滑动速度下的摩擦磨损试验.结果表明:与不含石墨的铜合金相比较,在不同电流和滑动速度下,加入10%石墨铜合金的摩擦因数和磨损率均降低,耐磨性能明显提高,摩擦因数稳定.     

铜基粉末冶金/Q235B摩擦副载流摩擦磨损性能*

磁浮列车中部分制动闸片在服役时一直处于受流状态,导致材料磨损加剧,影响闸片的服役寿命。为研究中低速磁悬浮列车制动闸片在受流工况下的摩擦磨损性能,以制动闸片使用的铜基粉末冶金材料和刹车盘使用的Q235B材料为摩擦副,研究不同制动速度下铜基粉末冶金/Q235B摩擦副的载流摩擦磨损行为。结果表明：无电流时随着滑动速度的增大,摩擦因数及磨损率整体呈现下降的趋势,载流时随着滑动速度的增大,摩擦因数整体呈现下降的趋势,而磨损率则整体呈现上升的趋势;无电流时磨损后的铜基粉末冶金材料表面覆盖着一层靛色的第三体层,该第三体层低速时主要以颗粒状为主,随着速度的增加逐渐被压实成连续致密状,高速时因黏着磨损加剧使得连续致密状第三体被破环,导致材料的摩擦因数和磨损率呈现反向增长的趋势;载流下磨损后的铜基粉末冶金材料表面出现了以机械磨损为主和以电弧烧蚀为主的2个区域,其中以机械磨损为主的区域依然是由靛色的第三体层组成,而以电弧烧蚀为主的区域表面则覆盖了一层金色熔融状物质,并且随着速度的增大,烧蚀区面积也逐渐增大。     

电弧能量对铜基粉末冶金/铬青铜摩擦副载流效率及载流稳定性的影响

以铜基粉末冶金/铬青铜为摩擦副,在销-盘式摩擦磨损试验机上进行载流摩擦学特性研究,探讨电弧能量对铜基粉末冶金/铬青铜摩擦副载流效率、载流稳定性的影响。结果表明:载流效率、载流稳定性与电弧能量的大小是密切相关的,电弧能量越大,载流效率、载流稳定性越差;频率相对均匀和瞬间电弧能量密度小的电弧可以维持电流的连续性,有较好的载流稳定性及较高的载流效率,而瞬间较高的电弧能量使载流效率急剧降低,载流稳定性变差;电弧发生及能量大小的随机性与不确定性及电弧对试样表面的侵蚀都导致了销试样间电压与电阻的波动,是载流效率和载流稳定性变差的主要原因。     

铝含量对铜基粉末冶金材料性能的影响

从一系列铜基粉末冶金材料配方中选出几种具有代表性的配方进行实验,研究铝含量对铜基粉末冶金材料密度、抗压强度、摩擦磨损等性能的影响。结果表明:在铜基粉末冶金材料中添加铝元素后,材料的密度、抗压强度和摩擦因数都降低,磨损率明显下降;随着铝含量的增加,材料的磨损率大幅下降,但摩擦因数变化不明显;在铜基粉末冶金中加入铝元素后,在显微组织中有新相生产,使基体组织细化,因而铜基粉末冶金的整体材料性能得到提高。     

铜基粉末冶金/铬青铜摩擦副载流摩擦磨损的电弧侵蚀特性研究

在销/盘式载流摩擦磨损试验机上,对铜基粉末冶金/铬青铜摩擦副载流摩擦磨损的电弧侵蚀特性进行了研究,探讨了电弧对铜基粉末冶金材料的载流摩擦学特性的影响.利用方差分析表,采用F检验法对电流、载荷、速度3种因素进行了显著性检验.结果显示电流对电弧能量的大小有影响,载荷、速度对电弧能量有显著影响;随着速度的增加,电弧的强度和发生频率均增大;低速下,主要是磨粒磨损和粘着磨损,高速下,主要是电弧侵蚀和粘着磨损.     

室温及气氛条件下铜基自润滑复合材料的摩擦磨损性能研究

采用粉末冶金法制备了3种铜基自润滑复合材料,分别考察了它们在室温及气氛条件下的摩擦磨损性能,通过对复合材料的力学性能和磨痕表面形貌、成分的分析,探讨其摩擦磨损机制.结果表明:Cu-9%石墨、Cu-4.5%石墨-4.5%MoS2、Cu-9%MoS2复合材料的密度、硬度和抗弯强度值都依次增大;室温条件下,因石墨与Cu的硫化物协同润滑作用,Cu-4.5%石墨-4.5%MoS2复合材料的摩擦磨损性能最好;气氛条件下,因Cu的硫化物发挥了其自润滑作用,Cu-9%MoS2复合材料表现出最佳的减摩耐磨性能,而Cu-4.5%石墨-4.5%MoS2复合材料次之;铜基自润滑材料的基体强度与固体润滑膜的覆盖率,是影响摩擦磨损机制转变的关键因素.     

表面粗糙度对铜基粉末冶金/铬青铜摩擦副载流摩擦磨损性能影响的研究

以铜基粉末冶金/铬青铜摩擦副为对象,应用销盘式摩擦磨损模拟试验,研究载流条件下摩擦副的表面粗糙度对摩擦学特性的影响规律.结果表明:表面越粗糙,越易起弧,形成更高的电弧能量,磨损形式主要是磨粒磨损、电弧侵蚀;表面越光滑,燃弧时间越长,电弧能量越高,摩擦因数越低,磨损形式主要是黏着磨损、电弧侵蚀;表面粗糙度有一个最佳值,在这个表面粗糙度下电弧能量最小、质量磨损率也最小.     

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...     

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。     

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。     

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.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

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。     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

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...