复合工艺制备的表面微凹坑织构的摩擦性能研究

在构建的激光电化学复合微加工系统上,采用皮秒脉冲激光辐照与电解刻蚀复合加工方法在7075铝合金表面制备出不同尺寸的阵列凹坑微织构。采用共聚焦显微镜观测复合加工织构试样表面形貌,采用MFT-5000型RTEC摩擦磨损试验机研究润滑条件下凹坑织构的摩擦学性能,并探讨直径、深度、面积密度对减摩性能的影响。结果表明:复合加工工艺制备的表面微织构具有良好的表面形貌;润滑条件下材料表面的凹坑型织构能显著改善其摩擦学性能,相比光滑表面最高可降低摩擦因数30%;在实验参数范围内,凹坑的直径与面积密度对材料表面摩擦性能影响较大,凹坑深度对摩擦性能影响较小。     

材料表面不同微形貌对润滑摩擦性能的影响分析

对汽车发动机的汽缸套所用的铸铁材料进行激光表面微造型加工,通过对激光脉宽、加工数目、加工速度、激光功率、激光频率以及微造型的形状等参数的改变加工出数组表面具有不同几何参数的微造型样件,分别进行润滑往复直线摩擦实验,研究了激光参数和微结构的形貌参数对摩擦性能的影响规律。     

45号 钢表面微凹槽织构激光加工工艺

为优化激光表面织构技术加工微凹槽的工艺参数,采用声光调Q二极管泵浦Nd:YAG激光器在45#钢表面开展工艺试验研究。通过WKYO NT1100三维形貌测量仪获得织构形貌,应用单因素法分析泵浦电流、脉冲重复频率、扫描速度工艺参数对织构形貌的影响。结果表明,随着泵浦电流的增加,微凹槽织构的宽度和深度均随之增大;随着重复频率的增加,微凹槽织构的宽度逐渐变小,而深度先变大后变小;随着扫描速度的增加,微凹槽织构的宽度逐渐增大,而深度逐渐减小。通过对上述参数的优化可以获得较为理想的微凹槽形貌,较佳工艺参数范围为：泵浦电流15～17 A,重复频率1 500～2 500 Hz,扫描速度10～20 mm/s。     

单晶硅表面微结构纳秒脉冲激光加工研究

以单晶硅为对象,使用波长355 nm、脉宽15 ns的纳秒激光对单晶硅进行烧蚀加工试验研究.基于单因素法设计并完成了单晶硅纳秒脉冲激光直线刻蚀试验,探究了激光输出功率、激光脉冲重复频率、激光扫描速度和扫描次数对纳秒脉冲激光加工单晶硅表面形貌的影响规律.基于优化的加工工艺参数,在单晶硅表面制备出方形阵列的微结构.     

45~#钢表面微凹槽织构激光加工工艺

为优化激光表面织构技术加工微凹槽的工艺参数,采用声光调Q二极管泵浦Nd:YAG激光器在45~#钢表面开展工艺试验研究。通过WKYO-NT1100三维形貌测量仪获得织构形貌,应用单因素法分析泵浦电流、脉冲重复频率、扫描速度工艺参数对织构形貌的影响。结果表明,随着泵浦电流的增加,微凹槽织构的宽度和深度均随之增大;随着重复频率的增加,微凹槽织构的宽度逐渐变小,而深度先变大后变小;随着扫描速度的增加,微凹槽织构的宽度逐渐增大,而深度逐渐减小。通过对上述参数的优化可以获得较为理想的微凹槽形貌,较佳工艺参数范围为:泵浦电流15~17 A,重复频率1 500~2 500 Hz,扫描速度10~20 mm/s。     

激光参数对钛合金薄板毛化形貌的影响

为了提高钛合金薄板与复合材料之间的粘结性能,需要对钛合金薄板进行激光毛化处理,重点在于找到合适的激光加工工艺参数。对各个参数采用单因素轮换法进行实验,结果表明,在选取适当的保护气体侧吹角度、气压的情况下,激光输入电流、脉冲宽度、离焦量对毛化点微观形貌的影响最直接;重复频率、加工速度的影响次之。此外通过在显微镜下研究毛化点的微观结构,总结出各个激光参数对毛化点平均直径、微凸起高度及材料的表面粗糙度的影响,并得出了相关的规律。     

钛合金疏水表面微坑阵列的掩膜电解加工仿真与分析

为改善钛合金疏水性能,获得较高的接触角,使用掩膜电解技术对钛合金进行了凹坑阵列表面微织构的加工。首先,建立微坑阵列掩膜电解加工的数学模型并进行多物理场耦合仿真;其次,分析掩膜电解加工参数对微坑阵列的作用,并借助润湿理论模型获得微坑阵列的固-液接触面积比;最后,以该面积比为因变量,以电解质质量分数、电解电压和掩膜尺寸为自变量,进行正交试验仿真和极差分析,获得最佳工艺参数组合。与仿真预测值相比,微坑阵列单元体直径、间距、深度、固-液接触面积比和表面接触角的测量值误差均小于8%,从而表明该方法在未经低表面能材料修饰的情况下,成功制备了接触角约为140°的微坑阵列。     

硬质合金刀具表面微结构的激光加工研究

硬质合金刀具常用来加工难加工材料,通过刀具表面织构化技术可以提高硬质合金刀具的耐磨性和加工性能。激光加工技术作为一种快速非接触自动化加工技术,可以在硬质合金刀具表面上加工出微结构。本文主要研究平均功率、扫描速度、脉冲频率、离焦量、扫描次数这五个工艺参数对硬质合金刀具微结构尺寸及形貌的影响,从而选定最优的激光加工工艺参数。实验结果表明:随着平均功率的增大,微沟槽的深度和宽度都在增加,但功率过大导致严重烧蚀使底侧面形貌不平整;扫描速度和脉冲频率的增加都会使得微沟槽的深度和宽度呈现减小的趋势,过大的扫描速度使得底面形貌不连续,随着脉冲频率和扫描次数的增加,沟槽底面形貌变得平整;离焦量从0mm变化到-1. 2mm时,微沟槽的宽度缓慢增大,深度则先增大后减小,底面形貌由连续变成稀疏的孔洞。通过优选出的激光加工硬质合金刀具工艺参数,制备出了良好的刀具表面单一型和混合型微结构。     

基于激光加工的微米级平行沟槽表面润湿性实验研究

生物医用材料表面润湿性是影响其生物相容性的一个重要影响因素。通过改变激光加工工艺参数,在钛合金基底上制备不同微结构尺寸的平行沟槽结构,采用白光干涉的方法测量钛合金表面平行沟槽的轮廓形貌,分别从平行和垂直纹理方向上对静态接触角、前进角和后退角进行测量,分析材料表面微结构对润湿性的影响,并探讨微结构尺寸与能量壁垒之间的关系。     

摩擦副表面圆形微凹坑特种加工工艺设计与试验

摩擦副表面一定规则形貌的微凹坑可以改善表面摩擦学特性,提高润滑耐磨性能.根据摩擦学理论,设计圆形微凹坑;用组合电加工方法制作阵列微细轴工具电极;采用多种微细特种加工方法加工出微凹坑,并进行微凹坑加工工艺分析.     

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.     

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.     

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.