基于TSP和塑料模具顶针板孔群加口工路径优化问题的研究

塑料工业的迅猛发展给塑料模具制造技术带来严峻挑战和剧烈的市场竞争.针对塑料模A脱模机构的重要部件一塑料模具顶针板的孔位加工所急需解决的效率问题,提出了一种塑料模具顶针拐孔群加工刀具轨迹优化技术,即利用图论中经典的"旅行商问题"--TSP数学模型,对塑料模具顶针板孔消加工进行了优化处理,以解决由于孔多、空行程现象严重而带来的加工时间浪费问题.实际应用效果较好提高了加工效率,取得了较好的经济效益.     

Limit loads for the plastic bending in plane strain of cantilevers containing rectangular holes under end shear

Slip-line field solutions and upper and lower bounds are given for the plane strain plastic yielding of a rectangular section cantilever containing a rectangular hole subjected to bending with shear, the hole taking varying positions along the longitudinal axis of the cantilever. Using mild steel specimens and an etching technique, both the loads and the modes of deformation at plastic collapse are shown to well authenticate the theoretical results.     

气缸磨损的修复

分析发动机气缸磨损变形的原因，提出气缸的修复方法。     

安全和容错的网格任务调度

为解决跨自治域的网络任务调度中的安全性和容错问题,提出了基于网格安全和容错的网格任务调度算法,并对用户任务的安全需求和资源的信任等级进行匹配,在系统安全等级较低且网络和主机可能失效的网格环境中进行容错任务调度。该算法根据网格系统的安全等级,自适应调整任务备份数,并对失败的任务重新调度。仿真结果表明,该算法可以有效提高不安全网格环境下的任务调度成功率,具有很好的容错性和可扩展性。     

机器人技术在航空维修中的应用探索

简要介绍了机器人技术在国内外航空领域的应用现状,分析总结了航空维修过程自身独有的特点,提出了机器人技术在航空维修应用中的偏重与限制。以国内某航空维修基地为例,分别从实际已实施典型案例和未来可应用方向这两个方面来阐述了机器人技术在航空维修领域的应用现状和探索方向。同时,基于航空维修自身特点,提炼了在航空维修领域应用机器人技术需要突破的4项关键技术。最后,对机器人在航空维修领域发展方向和趋势进行了展望。     

基于Freeform的逆向工程数据修复

介绍了基于力反馈技术的Freeform触觉式设计系统在逆向工程测量数据修复方面强大的功能。利用非接触式光栅扫描仪测量飞机模型的表面数据点云,通过Freeform的分割黏土、膨胀、镜像、平滑等功能,成功地恢复了飞机模型完整的表面数据。     

主轴定向故障检修

主轴定向装置是加工中心的一个重要装置，它直接影响到刀具能不能顺利交换。主轴不定向是指加工程序中有M19或手动输入M19后，主轴不能在指定方向停止，一直慢慢转动；或是停在不正确方向上，主轴无法更换刀具。     

自动化设备故障检测及维修方法的探讨

为了找出一套行之有效的设备故障检测及维修方法,从多年的工作经验出发,结合中医理论,总结出一套设备故障检测维修的望、闻、问、切的基本方法,并通过实际案例分析,阐述了如何应用此方法。按照此法,基本能顺利找出设备的故障原因,及时处理设备故障。这对自动化设备越来越普及的今天,有一定的意义。     

几种修复促进剂对TiO2/SiO2纳米添加剂减摩及修复效果的影响

在昆仑牌GL-5车辆齿轮油中研究了4种修复促进剂对TiO2／SiO2纳米添加剂减摩及修复效果的影响,并分析其作用机制。结果表明,修复促进剂的加入能有效降低TiO2／SiO2纳米添加剂的摩擦因数,提高表面修复量,其中最大减摩性能可提升28．2％,最大修复量可提高133．3％。磨痕表面SEM分析结果表明加入修复促进剂后修复层更光滑、平整。修复促进剂对减摩和修复的促进作用可能是由于修复促进剂在摩擦过程中释放出负离子自由基,从而降低TiO2／SiO2纳米粒子的反应活化能,使TiO2／SiO2纳米粒子更易同金属基体形成耐磨复合膜。     

微隙流动阻力与密封件尺寸参数的研究

分析了流动介质在微隙中的流动阻力,并根据流动阻力在微隙中的流动特性,分析和论证了确定非接触密封零件尺寸的方法,提出了设计中应注意的一些问题.     

岩心钻机双联齿轮的焊接修复

文中通过对双联齿轮的焊接修复性试验,总结修复该零件的工艺参数和编制相应的工艺规程,达到既修复该零件目的,同时又为类似零件的焊接修复性研究提供一定的参考价值.     

发动机缸体结合面孔位置度测量方法的研究

发动机缸体结合面倒角孔加工和测量时,其基准为底面及其上的2个定位销孔.由于倒角孔及其基准不在同一平面上,混合使用多个线阵及面阵CCD(charge-coupled device)对倒角孔和定位销孔分别成像,提出了用于孔位置度测量的高精度空间坐标转换算法.最终系统测量数据与作为基准的CMM(coordinate measuring machine)测量数据比对,孔位置最大偏差值为0.030 mm,测量相对误差优于0.03％,测量数据标准差误差小于0.015 mm,在95％置信水平下,系统测量不确定度小于±0.035 mm,系统测量时间小于3 min.在工业现场的大量实验结果表明,提出的倒角孔位置度测量方法能够满足生产线上发动机缸体结合面孔组位置度测量的需要.     

On the effects of friction on free volume holes in PTFE

Since the macroscopic properties of materials are relevant to their micro structure, the detection of microscopic defects or their changes in size and concentration is an interesting topic in materials science. The positron annihilation lifetime (PAL) method used here is established as a unique technique that can provide information about the size and concentration of free volume holes directly without significantly intervening in the bulk properties of the specimens. To our knowledge, this is the first time that PAL techniques have been used to study the wear mechanism of macromolecular tribomaterials. Here we present the results of a study in which the correlation between the fretting wear behaviour of polytetrafluorethylene (PTFE) and the changes in its free volume size and concentration in amorphous-crystal interface regions was found to be δω =A.δτ₃, where δω is the wear loss of PTFE under fretting wear conditions, A is a constant, and δτ₃ represents the relative change in the third lifetime components after the friction test. The results indicate that fretting mainly influences the characteristics of atomic-scale free volume holes in the amorphous-crystal region in PTFE, and under high-load fretting wear conditions the ductile polymer PTFE possesses a self-curing function for its defect-free micro volume holes.     

Effect of slot edge defects on the head/tape spacing

The effect of slot edge defects on the performance of the head/tape interface is studied for single and double module heads. A number of typical edge defects was created artificially on a glass replica of an actual head, and three-wavelength interferometry was used to study spacing changes caused by these defects. The results show that head edge defects have a small influence on the flying behavior of tape with the effects being localized to the immediate defect area.     

柴油机"飞车"故障分析与排除

通过对柴油机发生的"飞车"故障的有关部件喷油泵的速度特性和调速器工作原理的介绍,提高对"飞车"故障发生原因的认识.当柴油机发生"飞车"时,及时分析判断,速查故障原因,采取紧急措施,排除故障.     

螺旋桨修理中的静平衡检验方法研究

在总结生产实践的基础上,对固定螺距螺旋桨的卧式静平衡检测方法,以及可调螺距螺旋桨的采用球面液压支承的静平衡检测方法,进行了详细阐述,并比较了两者之间的优缺点,得出结论是:采用球面液压支承的静平衡检测装置,能满足大型螺旋桨特别是调距桨修理与验收的要求。     

Effect of inclusions and holes on the stiffness and strength of honeycombs

A finite element study has been performed on the effects of holes and rigid inclusions on the elastic modulus and yield strength of regular honeycombs under biaxial loading. The focus is on honeycombs that have already been weakened by a small degree of geometrical imperfection, such as a random distribution of fractured cell walls, as these imperfect honeycombs resemble commercially available metallic foams. Hashin–Shtrikman lower and upper bounds and self-consistent estimates of elastic moduli are derived to provide reference solutions to the finite element calculations. It is found that the strength of an imperfect honeycomb is relatively insensitive to the presence of holes and inclusions, consistent with recent experimental observations on commercial aluminium alloy foams.     

Oral biofilm formation on the titanium and zirconia substrates

OBJECTIVE: The aim of this randomized crossover investigation was to assess the biofilm formation on two titanium and one zirconia substrates in relation to the topography and surface roughness of the materials. METHODS: Twenty‐four discs specimens for each evaluated material (Machined pure titanium, Cast pure titanium, or Zirconia) were evaluated after oral cavity exposure in six healthy subjects. The study was conducted in 3 phases according to the material evaluated. Each subject was asked to use a removable splint containing 4 disks of the same tested substrate, 2 located in the anterior, and 2 in the posterior region. Participants were asked to use the intraoral splint during 24 h. The total biofilm covering on the discs was evaluated by 1% of neutral red staining. EMV and surface roughness was carried out to correlate with the biofilm found between different substrates. RESULTS: Data showed higher mean roughness values for zirconia (Zc) when compared with titanium specimens (MPT and CPT; P < 0.001). MPT and CPT presented no differences between them (P > 0.05). The mean percentage (%) of covering biofilm on substrates was 84.14 for MPT, 86.22 for CPT and 90.90 for Zc. CONCLUSION: There were no significant differences in the total area of formed biofilm among the tested groups. No correlation was found between surface roughness and the total amount of formed biofilm in the groups. Microsc. Res. Tech., 2013. © 2012 Wiley Periodicals, Inc.