组合型微织构化铝合金表面的摩擦学性能研究

为改善铝合金的摩擦学性能,运用有限元方法对单一方形凹坑、条形凹槽、方形凹坑和条形凹槽组合3种不同形貌织构摩擦副间润滑油膜承载能力进行仿真分析,并探究不同织构尺寸对油膜承载能力的影响。仿真结果表明：方形凹坑和条形凹槽组合织构润滑油膜承载能力最佳。采用脉冲Nd:YAG激光器在铝合金试件表面加工出具有规则形貌的方形凹坑和条形凹槽组合的织构阵列,借助CFT-I型高速往复摩擦磨损试验机进行摩擦试验,研究织构几何尺寸对摩擦副接触面间摩擦学性能的影响规律,并利用超景深显微系统对试件磨损表面的形貌进行观测。试验结果表明：组合织构化表面的平均摩擦因数与无织构表面相比明显减小,且波动幅度较小;当织构尺寸为80μm时,织构表面的摩擦因数最小,且试验得到的基体表面磨痕深度随织构尺寸的变化规律,与仿真计算得到的润滑油膜升力系数的变化规律相吻合,为微织构参数设计提供了一定的理论依据。     

表面微织构Al_2O_3-TiC陶瓷刀具的切削性能研究

研究了不同形状和不同结构尺寸的表面微织构陶瓷刀具切削45#淬火钢后,陶瓷刀具的前刀面月牙洼磨损形貌和后刀面磨损量,进而分析表面微织构对陶瓷刀具的作用机理和不同表面微织构的影响。其中,分别针对无微织构和三种不同形状,不同深度、宽度和间距的表面微织构陶瓷刀具做了单因素切削实验。实验结果表明,具有表面微织构的陶瓷刀具切削性能优于无微织构陶瓷刀具,过大的深度、宽度和间距反而不利于刀具前刀面的减摩。刀具表面微织构深度为10μm、宽度为25μm、间距为50μm时,与切削刃平行的横向微织构陶瓷刀具的切削性能最好,即该表面微织构的减摩效果最明显。     

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。     

表面织构排布形式对其润滑特性的影响

建立不同排布形式表面织构的几何模型,基于N S方程并采用CFD方法分析其油膜压力分布,并考察其流场流动情况和不同间距对承载能力的影响。结果表明,不同排布形式的表面织构对润滑特性有很大的影响,其中,交错排布的表面织构具有最高的承载力。微凹坑之间存在最优间距,使其所产生动压效应的作用发挥得最充分。交错排布的微凹坑织构最优面积率比均匀排布的微凹坑织构有了很大的提高。     

表面织构对水润滑径向滑动轴承湍流特性的影响

基于湍流理论,采用RNG k-ε湍流模型,研究水润滑径向滑动轴承轴瓦表面加工织构凹坑对轴承水膜压力、承载能力和湍流特性的影响,比较织构形状、分布位置、多尺度以及尺寸参数对轴承润滑性能的影响。结果表明:复杂形状织构加剧了水膜的湍流流动,导致更大的湍流动能,提高了水膜压力和承载力;织构棱边、尖角越多,越易形成二次涡;轴承收敛楔形入口处织构降低轴承承载能力,出口处织构提高承载力,且越靠近出口提升效果越明显;织构轴向尺寸与周向尺寸之比对轴承承载能力影响明显,并且存在最佳比值。     

一种刀具表面阶梯型微织构的作用机理分析

为了探究阶梯状微织构在刀具表面存在的作用及其相关机理,并获取最优的织构参数,利用激光加工设备在硬质合金刀具表面加工出不同参数的凹坑织构,利用摩擦磨损试验机进行销盘式摩擦磨损实验,并通过车床进行了切削铝合金的实验.结果 表明,当刀具表面凹坑织构的直径为65μm、凹坑深度为15μm时,与无织构表面相比,具有凹坑织构表面的摩擦系数降低了43.5％,与硬质合金相对磨的铝合金销的磨损量减小了40.2％,在切削加工中具有织构纹理的刀具的主切削力降低了10.4％.从上述结果来看,刀具表面的阶梯状微织构能够有效起到减摩降磨的作用,同时改变切屑类型,大幅提升刀具的使用寿命.     

磨削速度对碳化硅陶瓷磨削损伤影响机制研究

碳化硅陶瓷高速磨削过程中,磨粒对工件材料强力冲击,应变率剧增、复杂显微结构对应力波传送响应转变,材料力学行为发生变化,目前高速磨削对材料去除机制影响的物理本质认识还不清楚。为此,开展磨削速度对SiC陶瓷磨削裂纹损伤影响机制研究。通过单颗磨粒磨削SiC陶瓷试验,分析了磨削速度对SiC陶瓷磨削表面形貌、磨削亚表面裂纹损伤深度、磨削力和磨削比能的影响规律。试验结果表明,当SiC陶瓷材料以脆性方式去除时,磨削速度对裂纹损伤影响最为显著,随着磨削速度从20 m/s增加到160 m/s,磨削亚表面裂纹损伤深度从12.1μm快速降低到6μm。采用Voronoi法建立了金刚石磨削多晶SiC陶瓷有限元仿真模型,当磨粒切厚为0.3μm,磨削亚表面损伤以微裂纹为主;当磨粒切厚为1μm时,随着磨削速度增加,磨削亚表面裂纹损伤深度从14.7μm降低到4.6μm,磨削亚表面宏观沿晶裂纹逐渐变为微观裂纹。基于位错理论和冲击动力学理论,揭示了高速磨削过程中位错密度的增加和晶界反射应力波对应力场削弱作用是高速磨削SiC陶瓷裂纹损伤“趋肤效应”产生的机理。     

增材制造SLM工艺对Ti6Al4V表面织构成型质量的影响

为了探究增材制造SLM工艺对“一步法”制备Ti6Al4V表面织构实际成型尺寸和形貌等成型质量的影响,文章采用金属3D打印机在选择性激光熔化(SLM)工艺下制备表面具有不同理论织构直径和深度的Ti6Al4V钛合金试样,观察并分析得到凹坑织构边缘和底部的未熔物随着织构直径和深度的增大而增多。随着理论织构深度增加,D400试样凹坑织构的实际直径和平均直径误差均先增加后减小,平均直径误差最小为2.08%;D800试样凹坑织构的平均直径误差呈下降趋势,最小为2.84%。而D400试样凹坑织构的平均深度误差逐渐减小,最小为2.23%;D800试样凹坑织构深度方向成型精度较低。3D打印一体成型可以在Ti6Al4V钛合金表面制备较好的凹坑织构,且实际凹坑织构在直径方向的成型质量优于深度方向。     

织构参数对刀具表面摩擦系数的影响研究

研究了前刀面具有圆形凹坑阵列微织构的YT15硬质合金刀片对45钢工件进行切削试验时,其微织构参数与刀—屑界面平均摩擦系数的关系。通过单因素试验,获得各织构参数分别和刀—屑界面平均摩擦系数的关系:当凹坑直径小于200μm时,直径越大摩擦系数越小;接触区面积占有率在70%-75%时,摩擦系数较大,接触区面积占有率大于75%,时则可保证刀—屑界面摩擦系数较小;织构凹坑深度为4μm时,可以获得最小平均摩擦系数。验证了织构凹坑直径、接触区面积占有率以及凹坑深度等织构参数对刀—屑摩擦系数的关系,得出了在刀具前刀面加工出合适参数的微织构可有效降低刀—屑界面摩擦系数的结论。     

人工髋关节微织构减摩性能及织构参数优化

为改善钛合金TC4人工髋关节假体的耐磨性,用激光在钛合金试样表面构造出不同参数的圆形凹坑;采用单因素试验利用接触角测量仪以及摩擦磨损试验机,研究微织构参数对接触角和摩擦因数的影响;采用响应面法建立凹坑直径、深度、面积率与接触角、摩擦因数间的二次回归模型,得出最优织构参数。结果表明:在给定的织构范围内随着凹坑直径的增加、深度的减小、面积率的减小,钛合金的表面接触角均减小;在选取较小的凹坑深度、合适的凹坑面积率和凹坑直径时,可以有效降低钛合金的摩擦因数,且凹坑直径和凹坑面积率的交互作用对摩擦因数影响最显著;优化得到的织构最优参数为直径230μm,深度10μm,面积率14%。试验结果与二次回归模型预测值有较高的一致性,说明建立的二次回归模型具有较高的可靠性。     

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.     

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。     

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.     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type ...     

Research on key techniques of expendable conductivity temperature depth measuring system

This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.     

OPTIMIZATION METHOD ON IMPELLER MERIDIONAL CONTOUR AND 3D BLADE

An optimization method for 3D blade and meridional contour of centrifugal or mixed-flow impeller based on the 3D viscous computational fluid dynamics (CFD) analysis is proposed. The blade is indirectly parameterized using the angular momentum and calculated by inverse design method. The design variables are separated into two categories: the meridional contour design variables and the blade design variables. Firstly, only the blade is optimized using genetic algorithm with the meridional contour remained constant. The artificial neural network (ANN) techniques with the training sample data schemed according to design of experiment theory are adopted to construct the response relation between the blade design variables and the impeller performance. Then, based on the ANN approximated relation between the meridional contour design variables and impeller performance, the meridional contour is optimized. Fewer design variables and less calculation effort is required in this method that may be widely used in the optimization of three-dimension impellers. An optimized impeller in a mixed-flow pump, where the head and the efficiency are enhanced by 12.9% and 4.5% respectively, confirms the validity of this newly proposed method.     

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...