基于功能参数的渐进成形件表面质量表征研究

目的 以圆锥台成形件为例，基于粗糙表面的区域支承率曲线，进行了用功能参数表征表面几何形貌的研究，以全面、准确、定量地表征渐进成形件的表面质量，预测表面性能。方法 用渐进成形工艺加工成形角分别为35°、45°和55°的圆锥台件，将各圆锥台的成形面分为顶部、中部和底部三个区域，并使用三维表面轮廓仪，在上述三个区域中随机测量各4个样本。根据ISO 25178-2:2012，将各样本表面的区域支承率曲线分为峰区、核心区和谷区，选用部分功能参数——核心区高度Sk、峰区材料体积Vmp、核心区材料体积Vmc和谷区空隙体积Vvv表征表面，并与常用的高度表征参数——Sa、Sq、Ssk和Sku进行比较。结果 成形件表面的Ssk和Sku的计算值极不稳定，变异系数（标准偏差与均值之比）最高值分别可达127.67%和39.11%，Sa、Sq的最大变异系数分别为4.41%和4.26%，虽然它们的参数计算值较为稳定，但常无法体现表面形貌的实际差异。功能参数独立表征不同功能区，Sk和Vmc的最大变异系数分别为9.32%和7.73%，说明同一表面各处，在长期工作阶段具有较为一致的表面性能，Vmp和Vvv的最大变异系数分别为60.53%和31.25%，说明表面各处峰、谷区的形貌有所不同，因而在磨合时间、磨粒存储等方面会有不同的表现。结论 粗糙表面的三维本质要求用三维表征参数才能全面表征其几何形貌。高度参数虽然计算简单，但常难以解读它们的物理意义，无法定量评价表面性能；功能参数具有明确的物理意义，可为表征表面质量、预测表面性能提供定量、实用的方法。     

铍铜合金断续切削后刀面磨损机理研究

目的研究断续切削过程温度变化对刀具粘结现象、涂层剥落和刀具磨损的影响。方法搭建了仿铣削加工的断续车削实验平台,采用热电偶法测量了断续切削过程中刀具后刀面在不同速度下的切削温度,利用带有能谱仪(EDS)的扫描电镜(SEM)观察后刀面随速度变化的磨损形貌并分析后刀面磨损区域的元素组成,阐述了后刀面温度和刀具磨损之间的联系,研究了Ti AlN涂层硬质合金刀具断续切削铍铜合金C17200时的后刀面磨损机理。结果随着切削速度的增加,刀具温度在v=500 m/min出现峰值,温度越高,后刀面的涂层剥落和粘结磨损现象越严重,涂层剥落和粘结磨损现象在切削速度为500 m/min时最严重,而后随着刀具温度的降低而减缓,切削速度600 m/min时的涂层剥落和粘结磨损现象相比500 m/min时有所减轻。结论断续切削过程中,刀具持续性地经受"负载-卸载"、"升温-降温"产生的高温、冲击和加工环境的不稳定性,是引起粘结现象、涂层剥落和刀具磨损的主要原因。涂层剥落和粘结磨损是导致铍铜合金断续切削刀具失效的主要磨损形式。     

Monocular-vision-based method for online measurement of pose parameters of weld stud

With the rapid development of stud welding technology, weld studs are extensively used in automobile industry. A weld stud differs from a regular stud in that it has special external features. This study develops a novel non-contact, fast, and high-precision method based on monocular vision for measuring the position and attitude parameters of a weld stud. Under this method, the measuring principle for the weld stud’s position and attitude parameters is derived and an accurate mathematical model is set up. Based on this mathematical model, a precise calibration method for the projective transformation’s corresponding relationship parameters is developed and an optimal observation condition is then introduced as the constraint into the measurement process so as to enhance the location precision. The experiment results show that the proposed method is fast and accurate, and it satisfies the requirement of online, flexible, fast, and high-precision measurement of weld studs’ pose parameters in automobile and other manufacturing industries.     

One-pot synthesis of PdBi/reduced graphene oxide catalyst under microwave irradiation used for formic acid electrooxidation

The Pd and PdBi nanoparticles dispersed on the reduced graphene oxide (Pd/rGO and PdBi/rGO) have been synthesized through one-pot reaction under the irradiation of microwave and the obtained composites have been characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and their electrocatalytic activities have also been evaluated. It is found that the PdBi_0.05/rGO catalyst exhibits higher activity and better stability toward formic acid electrooxidation compared with Pd/C and Pd/rGO. The excellent electrocatalytic performance indicates that the addition of appropriate amount of Bi can greatly enhance the activity and stability of Pd catalysts for the formic acid oxidation.     

Progress in terahertz nondestructive testing: A review

Terahertz (THz) waves, whose frequencies range between microwave and infrared, are part of the electromagnetic spectrum. A gap exists in THz literature because investigating THz waves is difficult due to the weak characteristics of the waves and the lack of suitable THz sources and detectors. Recently, THz nondestructive testing (NDT) technology has become an interesting topic. This review outlines several typical THz devices and systems and engineering applications of THz NDT techniques in composite materials, thermal barrier coatings, car paint films, marine protective coatings, and pharmaceutical tablet coatings. THz imaging has higher resolution but lower penetration than ultrasound imaging. This review presents the significance and advantages provided by the emerging THz NDT technique.     

基于机器视觉技术的水表在线检定系统研究

设计了一套基于机器视觉技术的水表在线检定系统。使用模板匹配技术定位梅花针,分别对基准表和各待检表梅花针转过的齿数同时计数,当基准表计数到达设定值时同时停止计数,计算待检表误差,判断是否合格。现场试验表明,该方法比现有的激光反射计数法检定精度更高,解决了激光反射计数法无法检定梅花针上有气泡的湿式水表的问题。     

Rise of cyborg microrobot: different story for different configuration

By integrating organic parts achieved through evolution and inorganic parts developed by human civilisation, the cyborg microrobot is rising by taking advantage of the high flexibility, outstanding energy efficiency, extremely exquisite structure in the natural components and the fine upgradability, nice controllability in the artefact parts. Compared to the purely synthetic microrobots, the cyborg microrobots, due to the exceptional biocompatibility and biodegradability, have already been utilised in in situ diagnosis, precise therapy and other biomedical applications. In this review, through a thorough summary of recent advances of cyborg microrobots, the authors categorise the cyborg microrobots into four major classes according to the configuration between biomaterials and artefact materials, i.e. microrobots integrated inside living cell, microrobots modified with biological debris, microrobots integrated with single cell and microrobots incorporated with multiple cells. Cyborg microrobots with the four types of configurations are introduced and summarised with the combination approaches, actuation mechanisms, applications and challenges one by one. Moreover, they conduct a comparison among the four different cyborg microrobots to guide the actuation force promotion, locomotion control refinement and future applications. Finally, conclusions and future outlook of the development and potential applications of the cyborg microrobots are discussed.Inspec keywords: medical robotics, cellular biophysics, mobile robots, molecular biophysics, polymers, microrobotsOther keywords: locomotion control refinement, actuation force promotion, combination approaches, biological debris, living cell, artefact materials, biomaterials, biomedical applications, biodegradability, exceptional biocompatibility, natural components, energy efficiency, human civilisation, purely synthetic microrobots, cyborg microrobot     

QPQ技术中渗氮时间对合金铸铁组织及摩擦性能的影响

采用OM、SEM、硬度测试、摩擦磨损试验等方法研究了QPQ技术中渗氮时间对合金铸铁组织与摩擦性能的影响。结果表明,QPQ处理后,合金铸铁表面形成的渗层物相主要由Fe_2-3N、Fe₂O₃和FeO组成。渗层厚度的平方与渗氮时间存在线性关系,在580 ℃渗氮盐浴条件下,氮元素在合金铸铁中的扩散激活能为70.07 kJ/mol。在90~150 min渗氮时间内,随着渗氮时间延长,渗层的表面硬度值由522 HV0.05降低至441 HV0.05,当渗氮时间延长至180 min,表面硬度值回升至455 HV0.05。与未处理试样相比,QPQ处理的试样具有更小的摩擦因数,并且QPQ处理后试样表面的犁沟显著变浅,表面的金属剥落也得到明显改善,且随着渗氮时间的增加,渗层厚度增加且稳定材料。经180 min渗氮处理的QPQ试样具有最优综合性能,表面硬度值为455 HV0.05,摩擦因数为0.32。     

多孔储液介质自润滑机理研究进展

多孔储液介质是启发自关节软骨的仿生摩擦材料,因具有良好的自润滑性能,在工业生产中发挥着重要作用。早期多孔储液介质多是针对不同基体材料及骨架结构进行优化设计,或是根据单因素理想边界建立润滑数值模型,对多孔储液介质的润滑机理缺乏系统的理论描述,限制了其大规模的工业应用。根据不同的结构形式和润滑机理,将多孔储液介质分为有限直孔储液介质和随机多孔储液介质,总结了有限直孔储液介质中空化现象、流体运动、惯性效应、气-液耦合对润滑性能的影响,论述了基于渗流力学、流-固耦合作用的随机多孔储液介质自润滑理论的发展,以及多孔储液介质的应用现状。分析和讨论了多孔储液介质自润滑机理研究的难点问题,对推动多孔储液介质润滑机理的研究和工程实践应用具有重要的参考意义。     

A Constrained Block Iterative Algorithm for Multiple-Access Interference Suppression

Doherty, J. F., and Hsieh, Y.-T., A Constrained Block Iterative Algorithm for Multiple-Access Interference Suppression, Digital Signal Processing12 (2002) 12–20An interference suppression scheme using a block iterative, row-action projection (RAP) algorithm for direct-sequence spread-spectrum (DS/SS) code-division multiple-access (CDMA) systems is presented. The performance results for the near–far multiple-access interference scenario using the RAP algorithm are compared with a normalized least mean square (NLMS) algorithm. It is shown that the CDMA receiver employing the RAP algorithm has a faster convergence rate and a lower steady-state bit error rate compared to the receiver employing the NLMS algorithm.