用于强反射表面形貌测量的投影栅相位法

为了实现强反射表面三维形貌的光学非接触测量,提出一种改进的投影栅相位法。分析了强反射表面的反射光特点及其对相位解算的影响,指出了反射光亮度范围与相机动态范围的不一致是导致传统投影栅相位法测量失效的主要原因;提出了亮暗条纹投射、多曝光时间采集图像和图像合成等技术,使相机亮度测量范围与强反射表面的反射光亮度范围相一致,并分析了此方法的可行性和适应范围。最后,给出了改进投影栅相位法的条纹投射与图像采集步骤。实验结果表明,改进的投影栅相位法克服了强反射表面引起的条纹图像饱和或过暗问题,能够成功测量出99.6%以上的三维点云,有效解决了测量点云缺失问题,能够实现强反射表面三维形貌光学非接触测量。     

Enamel wear and surface roughness characterization using 3D profilometry

The aim of this work is to propose a characterization method of dental enamel topography through quantitative analysis by 3D profilometry, to allow relating changes in enamel texture with active wear mechanisms. Four extracted teeth, including an intact third molar tooth, were evaluated. The bearing area ratio curve was obtained and the functional and spatial parameters S_pk, S_k, S_vk and S_tr were extracted. Abrasive wear mechanism tended to increase the amplitude of irregularities until a certain point, when the material removal was capable of reaching the central zone of enamel, where the hydroxyapatite prisms are randomly oriented. The action of chemical agents was also observed, even when the abrasive wear was predominant. A relationship may exist between the variation of the irregularities’ directional pattern and the wear mode. The study presents micrographs of the analyzed surfaces to support the discussion.     

The surface failure of fluorapatite single crystals

Single crystals of various material are used for basic studies of friction and wear because of their simplicity. Single pass sliding enables one to sort out the effects influencing wear such as anisotropy and environment. A review of the literature is given for studies with metallic single crystals, diamond, magnesium oxide, and sapphire. Results are presented for studies on fluorapatite single crystals. Frictional anisotropy was found to be similar to that in MgO single crystals even though fluorapatite and MgO have different lattice structures. A new finding is the fact that repeated sliding at contact stress states above a threshold value causes catastrophic surface damage after the second pass even though very little damage appeared on the first pass. Most previous studies report the results of single passes. In practical sliding systems where repeated sliding is always occurring, wear of brittle materials must be dominated by the catastrophic mechanisms found on the second pass rather than by the events that occurred during the first pass.     

The surface failure and wear of graphite seals

Exfoliated graphite rings are now the most common form of die-formed seal for valve stems, and other stuffing box applications. However, there is very little fundamental knowledge of what determines their friction and wear. In earlier papers, it was shown that the mechanical properties of this material could be represented approximately by a geotechnical model designed for soils or rocks. In this paper, a simple test is described for measuring the friction and wear of seals against steel sliders in a controlled atmosphere. The results, which are rather surprising, can be explained by applying the geotechnical model referred to above, to the case of sliding.     

The role of wear in the failure of common tribosystems

The causes of failure of common tribosystems such as bearings, gears, brakes, seals and cams are reviewed in this paper and it is shown that wear, in particular sliding wear, is an important factor in those failures. It is further shown how surface analytical techniques can help in the diagnosis of failure through wear and in the search for possible remedies to prevent the onset of failure in tribosystems known to be susceptible to wear.     

电喷车起动故障的诊断与排除

起动故障一般表现为不能起动和起动困难,其中起动因难又分为冷起动困难和热起动困难。分析了各种不能起动的原因及起动困难的故障原因,并针对此提出了相应的解决措施。     

电动机控制系统的智能化故障诊断技术

电动机控制系统运行中的故障诊断问题可视为特殊的模式识别问题,而ANN是处理模式识别最有效的技术之一。对用于故障诊断器的BP网络应用了改进算法,并提供了常见故障样本,读者可进一步扩充完善。实际使用证明该方法完全能完成故障的在线诊断。     

Detection and diagnosis of surface wear failure in a spur geared system using EEMD based vibration signalanalysis

Gears are used for transmission of power, motion or both. Under increased power and higher speeds, tribological failures such as scuffing, pitting, mild wear and tooth breakage are of major concern. This paper presents the results of experimental investigations carried out to assess wear in spur gears of a back-to-back gear box under accelerated test conditions. The studies considered the estimation of specific lubricant film thickness and its effects on the fault growth on gear teeth surface. Ensemble empirical mode decomposition (EEMD) technique is used to extract the fault related features from the vibration signals acquired from the gearbox. The results highlight the advantage of EEMD technique for effective assessment of wear in spurgears.     

The role of surface roughness in the friction of sliding contacts

Results are presented of studies to assess the role of surface roughness in the friction of sliding contacts. A model of the surface roughness uses conical steel needles. A theoretical model based on the mechanics of interaction is included. Experimental and calculated results are discussed in relation to real engineering surfaces and the models compared     

Fourier transform profilometry employing novel orthogonal elliptic band-pass filtering for accurate 3-D surface reconstruction

The article proposes a novel orthogonal elliptic band-pass filtering methodology in Fourier Transform Profilometry (FTP) for significant improvement of accurate 3-D measurement surface reconstruction with arbitrary object colors. Compared with phase shifting profilometry (PSP), FTP using fringe projection can achieve a general 3-D surface profilometry more efficiently by employing one-shot imaging. However, a challenging problem commonly encountered by FTP using fringe projection is its unreliable extraction of precise spectral information from the spectral domain especially when the spectral domain is complicated to process. Various filtering methods previously proposed in FTP have been proved unsuccessful or nonrobust. Thus, a new band-pass filter is developed from an adaptive orthogonal elliptic region to achieve higher accuracy of 3-D surface reconstruction. A comprehensive theoretical analysis is performed to investigate the physical measurement limits of the proposed method. The experimental results obtained confirm that the measurement accuracy of dimension and sphericity can be greatly enhanced when compared with that achieved by the traditional circular band-pass filter. The proposed method is proved to outperform all the other existing FTP band-pass filtering approaches. The maximum dimensional error measured can be controlled within 1.25% of the overall measuring height with various surface colors. However, it is also verified that the traditional three-step PSP can achieve slightly better measuring repeatability than the proposed method.     

The role of spatial frequency analysis in correlating atomic force microscopy and optical profilometry with self‐etch adhesive enamel bond fatigue durability

The purpose of this study was to: (a) evaluate the role of enamel surface roughness on bond fatigue durability and (b) evaluate statistical differences in roughness values based on measurement technique, including the use of spatial filtering for optical profilometry (OP). OptiBond XTR (Kerr Corp), Prime & Bond elect (DENTSPLY Caulk), Scotchbond Universal (3 M Oral Care), and XTR pre‐etched with Ultra‐Etch phosphoric acid (35%) (Ultradent) self‐etch adhesives were used to treat enamel. A flat ground enamel surface was included as a control. Atomic force microscopy (AFM) and OP were used to measure the surface topography of each enamel surface following the application of adhesives. AFM, OP, and filtered OP (FOP) roughness values, where FOP was designed to only include the lateral spatial resolution consistent with AFM roughness values, were collected. Spatial resolution filtering with OriginPro was used to compare line scans from the two imaging techniques and generate the FOP group. These micro‐ versus nanoscale lateral roughness values were correlated with shear bond and shear fatigue strengths of the adhesives bonded to enamel. Roughness values showed differences based on measurement technique and strong correlations with bond and fatigue strength. The filtered OP group demonstrated the importance of careful usage and reporting of atomic force microscopy and OP metrics in adhesive dentistry. Best practices for surface roughness analysis were also discussed.     

模具失效形式判定依据与技术应用性研究

阐述模具一般表面失效形式和失效机理,并且依据失效形式总结了模具失效判据以及给出描述性失效判据,为进一步研究模具失效提供了基本思考路线.     

The role of the surface amorphous layer of articular cartilage in joint lubrication

Articular cartilage is a complex soft tissue that performs multiple functions in the joint. In particular, the amorphous layer that covers the surface of articular cartilage is thought to play some role in lubrication. This study aimed to characterize the surface amorphous layer (SAL) using a variety of techniques, including environmental scanning electron microscopy, transmission electron microscopy, white light interferometry, and biochemical analysis of its composition. Friction tests were conducted to investigate the role of the SAL in lubrication. A protocol to remove successfully the SAL without damaging the underlying cartilage was developed and the material removed from healthy cartilage was found to contain approximately equal quantities of glycosaminoglycan (GAG), protein, and lipid. Cartilage-on-cartilage friction tests were conducted on fresh, healthy cartilage with and without the SAL, under both dynamic and static operating conditions. Removal of the SAL was not found to change the friction coefficient. However, subsequent staining of specimens indicated that the SAL had replenished during the test following loading. The replenished SAL was characterized and found to contain lipids and sulphated GAGs with undetectable protein. This study revealed experimental evidence of surface layer replenishment in articular cartilage. It was postulated that the surface layer regeneration mechanism was purely mechanical and associated with movement of GAGs and lipids through the cartilage matrix during deformation, since the experimental set-up did not contain any means of biochemical activation.     

The role of stepover ratio in prediction of surface roughness in flat end milling

Surface roughness prediction studies in end milling operations are usually based on three main parameters composed of cutting speed, feed rate and depth of cut. The stepover ratio is usually neglected without investigating it. The aim of this study is to discover the role of the stepover ratio in surface roughness prediction studies in flat end milling operations. In realising this, machining experiments are performed under various cutting conditions by using sample specimens. The surface roughnesses of these specimens are measured. Two ANN structures were constructed. First of them was arranged with considering, and the second without considering the stepover ratio. ANN structures were trained and tested by using the measured data for predicting the surface roughness. Average RMS error of the ANN model considering stepover ratio is 0.04 and without considering stepover ratio is 0.26. The first model proved capable of prediction of average surface roughness (Ra) with a good accuracy and the second model revealed remarkable deviations from the experimental values.     

现场控制仪表的故障诊断与补偿容错控制系统

本文针对过程控制系统的实际问题,首先建立符合工业实际的多种传感器故障和执行器故障的合理描述模型,然后利用神经网络建模、自适应阈值方法研究了故障鲁棒检测与诊断问题,并设计了一种有效的工厂级主动补偿容错控制策略.     

PNN在塔式起重机故障诊断中的应用

PNN是基于Parzen窗函数和Bayes分类规则的前向型自监督神经网络模型,具有强大的非线性处理能力,快速的收敛速度和准确的分类效果。以塔式起重机的典型故障样本为例,给出了利用该模型进行诊断和预报的详细过程。理论分析和仿真实验结果表明,利用PNN对塔式起重机进行故障诊断的方法可行、有效,有很高的实用价值。     

有限元分析在真空泵故障诊断中的应用

针对真空泵在产品试制过程中产生异常振动的问题,首先,排除了制造和装配的原因,然后从设计的角度分析了其原因。将真空泵支架的二维工程图转化为实体模型,导入ANSYS Workbench进行了有限元模态分析,发现其固有频率在真空泵的旋转频率范围内,存在共振现象;即而对其进行了方案修改,以及有限元模态分析,发现其固有频率避开真空泵的旋转频率范围。对按修改后方案制造的真空泵支架进行了装配后试车,发现原来异常振动的现象已经排除。研究结果表明,有限元也可在故障诊断中发挥重要作用,是故障诊断的一种方法。有限元分析是针对实体模型的一种数值分析方法,其计算结果精度较高。     

油液分析故障诊断中的信息融合问题

总结了故障诊断油液分析结果的种类多、表征各异、离散与随机性、定量与定性交叉、信息量大、信息冗余和不一致性等7类特点。提出了信息综合和信息融合的概念和区别,对信息融合和应深化问题作了展望。     

带式输送机减速器常见故障诊断

对带式输送机减速器因外部工作环境和内部因素的影响，出现漏油、齿轮损坏、轴承损坏的现象进行分析和研究，并运用频谱分析法对减速器振动信号进行监测与诊断，以此判断早期减速器零部件故障，为修复减速器、寻找故障原因提供理论依据。     

基于故障行为的模型诊断方法

提出一种利用故障行为求解所有极小诊断的新方法,并结合带有终止节点的集合枚举树形式化地表达计算过程,逐步生成所有的极小诊断.该方法不用求解冲突集及冲突集的碰集,一次直接求出所有的极小诊断,避免了由于调用基于假设的真值维护系统时的组合爆炸而引起的NP-完全问题.在集合枚举树中添加了终止节点,从而避免了非极小诊断的产生,且不会因剪枝而丢失正确的解.实验结果表明,该算法程序容易编制,且效率较好,可以满足复杂的被诊断对象的实时性要求.