Automatic virtual metrology for wheel machining automation

Total inspection after wheel machining becomes essential for safety consideration and continuous improvement. However, conducting wheel-by-wheel actual metrology is very expensive and time-consuming. A novel idea is to use virtual metrology (VM) that predicts wheel quality based on process data collected from machine tool with a slight supplement of actual metrology data. The technology of automatic virtual metrology (AVM) has been proposed by the authors and successfully deployed in hi-tech industries, such as semiconductor, display and solar cell. The purpose of this study was to propose an approach to apply the AVM system factory-wide to wheel machining automation (WMA) for achieving total inspection of all the precision items of WMA under mass production environment.     

Automated sampling decision scheme for the AVM system

Reducing the sampling rate to as low as possible is a high priority for many factories to reduce production cost. Automatic virtual metrology based intelligent sampling decision (ISD) scheme had been previously developed for reducing the sampling rate and sustaining the virtual metrology (VM) accuracy. However, the desired sampling rate of the ISD scheme is fixed and set manually. Hence, whenever the VM accuracy gets worse, it cannot adaptively increase the default sampling rate in the ISD scheme. As a consequence, it would take more time to collect enough samples for improving the VM accuracy. Moreover, when the VM accuracy performs well all the time, it cannot automatically decrease the default sampling rate in ISD, which may result in unnecessary waste. Accordingly, this paper proposes an automated sampling decision (ASD) scheme to adaptively and automatically modify the sampling rate online and in real time for continuous improvement. The ASD scheme can monitor the VM accuracy online as well as update the VM models in real time for maintaining the VM accuracy when the VM accuracy becomes poor. Also, the ASD scheme can automatically reduce the sampling rate while the VM accuracy performs well.     

我国国防真空计量发展概况及成就

综述了近40多年来我国国防真空计量的发展概况及成就,内容包括真空(全压力)测量与校准、分压力测量与校准、气体微流量测量与校准.     

Advanced ART2 scheme for enhancing metrology-data-quality evaluation

The metrology-data-quality-index (DQI_y) algorithm was proposed to perform metrology-data-quality evaluation of the automatic virtual metrology system developed by the authors. The DQI_y algorithm is based on the adaptive-resonance-theory 2 (ART2). ART2 divides data into different patterns according to the similarity of process data, and then calculates the corresponding DQI_y value and its threshold, DQI_yT, for evaluation and judgment. However, in practical applications, the classical ART2 technique still could not cluster process data very precisely. Since some samples with dissimilar process parameters might be sorted into the same cluster, two or more groups could be found in the corresponding metrology-data cluster. This phenomenon may cause invalid DQI_y detection. To solve the problem above, the advanced ART2 scheme is proposed in this paper to enhance the accuracy of the DQI_y algorithm. A large industrial data-set showing both a shift in metrology measurements without a process shift and a process shift that was not captured by the metrology of the actual photo and color-filter production tools of a TFT-LCD factory were adopted as illustrative examples to verify the practicality of the proposed scheme. Experimental results show that the performance of the advanced ART2 is indeed better than that of the original ART2.     

Micromechanical modelling of elastic continuum with virtual multi‐dimensional internal bonds

A micromechanical model is developed for the elastic continua with virtual multi‐dimensional internal bonds. The basic idea of the presented model is that materials are discretized into mass particles and these mass particles are connected with randomized normal and shear bonds. Based on the Cauchy‐born rules and the hyperelastic theory, a constitutive relationship is derived. The constitutive relationship bridges the virtual bond stiffness and the macromaterial constants, i.e. Young's modulus and Poisson ratio. The presented model could represent the diversity of Poisson ratio. The motivation of the presented work is to provide a useful micromechanical model for the numerical simulation of material failure behaviours and improve the understanding of material failure mechanisms. To show the application of the presented model, a tensile failure example of brittle materials is analysed and numerically simulated. By comparison, a good agreement is found between the predicted and the experimental. The prospect of the presented model seems to be highly promising. Copyright © 2005 John Wiley & Sons, Ltd.     

总溶解固体含量(TDS)测量仪示值误差的不确定度评定

本文介绍了总溶解固体含量(TDS)测量仪的校准方法,并对其示值误差的不确定度进行评定。     

Numerical recipes for elastodynamic virtual element methods with explicit time integration

We present a general framework to solve elastodynamic problems by means of the virtual element method (VEM) with explicit time integration. In particular, the VEM is extended to analyze nearly incompressible solids using the B-bar method. We show that, to establish a B-bar formulation in the VEM setting, one simply needs to modify the stability term to stabilize only the deviatoric part of the stiffness matrix, which requires no additional computational effort. Convergence of the numerical solution is addressed in relation to stability, mass lumping scheme, element size, and distortion of arbitrary elements, either convex or nonconvex. For the estimation of the critical time step, two approaches are presented, ie, the maximum eigenvalue of a system of mass and stiffness matrices and an effective element length. Computational results demonstrate that small edges on convex polygonal elements do not significantly affect the critical time step, whereas convergence of the VEM solution is observed regardless of the stability term and the element shape in both two and three dimensions. This extensive investigation provides numerical recipes for elastodynamic VEMs with explicit time integration and related problems.     

Sensitivity analysis for justification of utilising special purpose machine tools in the presence of uncertain parameters

Decision-makers in manufacturing area frequently face machine tool selection problem under uncertainty due to competitive market changes. Special purpose machines (SPMs), a relatively new class of reconfigurable machine tools, are used to react quickly to changes. Justification of utilising these machines vs. other machine tools requires a technique to investigate the sources of uncertainties. In this work, sensitivity analysis is utilised to investigate the sources of these uncertainties and errors which may reveal new insights for evaluating a machine tool. An illustrative example is provided to show the sensitivity of parameters on the economic performance of SPMs compared to the other alternatives. The results show that this analysis provides additional information and moves the decision closer to the optimum alternative.     

Application of Methods of Spectroscopy of Attenuated Total Internal Reflection for Analysis of Biological Objects

The potential for the study and determination of the optical constants of strongly scattering biological objects using spectroscopic analysis of repeated attenuated total internal reflection (ATR) is considered. The optical circuits of repeated attenuated total internal reflection adapters intended for joint operation with infrared-range spectrophotometers are presented.     

Integrated analysis of the performance of TQM tools and techniques: a case study in the Taiwanese motor industry

Most studies of total quality management (TQM) have focused on the managerial aspects and associated success factors of TQM programmes, whereas relatively few studies have examined the appropriateness and performance of the large number of available tools and techniques that actually implement TQM practices. To assist in determining the best strategy for improving the performance of TQM tools and techniques, the present study integrates a modified importance–performance matrix with elements of failure mode and effects analysis (FMEA) to provide a comprehensive methodology for assessing and improving the performance of TQM tools and techniques in the Taiwanese motor industry. The methodology presented here can be applied in a variety of industries, including the Taiwanese motor industry, to enable efficient utilisation of TQM tools and techniques and thus improve quality, reduce costs and shorten cycle times.     

精密磨擦材料氧化铝/聚酰亚胺磨片的制备

采用一次成膜和程序升温法,制备了以聚酰亚胺为基底的氧化铝新型磨片(Al2O3/PI),可用于硬脆性机件表面的精加工和抛光.扫描电镜(SEM)显示,Al2O3/PI磨片为双层膜型,磨料层厚度约50μm,基底厚度约150 μm.差热分析(DSC/TGA)、拉伸强度和断裂伸长率测试表明显示,Al2O3/PI磨片的热分解温度大于500℃,并具有PI膜的高强度和良好的柔韧性.对磨片制备过程的主要影响因素及铜片的抛光效果进行了讨论.     

衍射光栅刻划机精密工作台定位特征识别试验研究

针对机械式衍射光栅刻划机精密定位工作台定位过程中产生的振动信号特性与光学性能指标（杂散光强度和波前质量）之间的关系,提出利用改进的Hilbert-Huang变换(HHT)获得的时频谱和边际谱对超精密工作台精定位特性进行研究。首先,给出了基于固有模态函数（IMF）筛选和瞬时频率差分求解的HHT信号处理算法。然后,设计了光学测量实验获得工作台50nm定位信号。最后,完成精密定位信号的特征提取和振动测试验证。结果表明:利用改进的HHT可以精确地完成精密定位信号的特征提取,从而为在衍射光栅的制造工艺中从根源上降低衍射光栅的杂散光强度和提高波前质量提供依据。     

金属外壳水三相点容器

水三相点是ITS-90国际温标中最重要的定义固定点,其复现不确定度是传递到整个温标的.目前,通常采用不同的冻制方法在硼硅玻璃或石英水三相点容器内冻制均匀的冰套来复现水三相点.冻制过程中,由于在水三相点容器内生成冰桥,会造成容器的破裂.为了解决此难题,研制了金属外壳水三相点容器,利用高纯水自发相变原理,在液体槽内自动冻制...     

Investigation of assumptions and approximations in the virtual fields method for a viscoplastic material model

The Virtual Fields Method (VFM) is an inverse technique used for parameter estimation and calibration of constitutive models. Many assumptions and approximations—such as plane stress, incompressible plasticity, and spatial and temporal derivative calculations—are required to use VFM with full‐field deformation data, for example, from Digital Image Correlation (DIC). This work presents a comprehensive discussion of the effects of these assumptions and approximations on parameters identified by VFM for a viscoplastic material model for 304L stainless steel. We generated synthetic data from a Finite‐Element Analysis (FEA) in order to have a reference solution with a known material model and known model parameters, and we investigated four cases in which successively more assumptions and approximations were included in the data. We found that VFM is tolerant to small deviations from the plane stress condition in a small region of the sample, and that the incompressible plasticity assumption can be used to estimate thickness changes with little error. A local polynomial fit to the displacement data was successfully employed to compute the spatial displacement gradients. The choice of temporal derivative approximation (i.e., backwards difference versus central difference) was found to have a significant influence on the computed rate of deformation and on the VFM results for the rate‐dependent model used in this work. Finally, the noise introduced into the displacement data from a stereo‐DIC simulator was found to have negligible influence on the VFM results. Evaluating the effects of assumptions and approximations using synthetic data is a critical first step for verifying and validating VFM for specific applications. The results of this work provide the foundation for confidently using VFM for experimental data.     

Application of Stereovision to the Mechanical Characterisation of Ceramic Refractories Reinforced with Metallic Fibres

Abstract:  Optical methods that yield displacement or strain fields are now emerging significantly in the mechanical sciences. At the Research Center on Tools, Materials and Forming Processes (CROMeP) at École des Mines d'Albi, a binocular stereovision system has been developed that can be used to measure: (a) the three-dimensional (3D) shape of a static object, or (b) the surface strains of an object undergoing some 3D mechanical or thermal stress. In this paper, the application of the stereovision technique to investigate the behaviour of ceramic refractories reinforced with metallic fibres is presented: (i) after the rupture of the sample for assessing the 3D orientation of the fibres in order to correlate a micro-mechanical model of fibre pullout with the macro-mechanical results of tensile tests, and (ii) during a tensile test for measuring the 3D displacement/strain field around a notch.     

Assessment of influence of systematic errors on the precision with which the normalized frequency of a sinusoidal signal is determined by means of a discrete fourier transformation with interpolation

The influence of systematic errors caused by the infleunce of the imaginary part in the spectrum of a sinusoidal signal on the estimator of its normalized frequency is analyzed by means of a discrete Fourier transformation with interpolation and a window with maximal rate of descent of the side lobes. An expression for the absolute error of the normalized frequency is presented and a condition for the minimal integral number of cycles of the sine curve is found; note that computation of the actual integral number of cycles enables us to assure that this error will be less than some specific value. The reliability of the expressions that are obtained is confirmed by a computer simulation. Translated from Izmeritel’naya Tekhnika, No. 2, pp. 26–30, February, 2009.     

Controlled stepwise growth of siloxane chains using bivalent building units with different functionalities

Organic/inorganic hybrids of silicon and their subsequent chemical modification are of interest for tailoring and structuring surfaces on the nanoscale. The formation of organic (sub)monolayers on hydroxylated silicon surfaces was employed to synthesize molecular siloxane chains by stepwise wet-chemical condensation reactions. Functionalizations with small alkyl-monochlorosilanes, yielding dimethylsilyl, diisopropylsilyl, di-tert-butylsilyl terminations, and with an aryl-monochlorosilane, providing diphenylsilyl groups, were studied. The SiH moiety of these end groups could be selectively oxidized to the corresponding silanol. The reactivity of this group opened the possibility of bonding additional species step by step in bottom-up growth reactions. In particular, dimethylsiloxane units were studied as possible molecular building blocks. By repeating the oxidation and condensation reactions the stepwise growth of one-dimensional siloxane chains was demonstrated. The ongoing chain growth was characterized by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry (NIR-UV), and contact-angle experiments.     

Multivariate analysis of anionic, cationic and nonionic textile surfactant degradation with the H(2)O(2)/UV-C process by using the capabilities of response surface methodology

Anionic, cationic and nonionic surfactants being frequently employed in the textile preparation process were subjected to H(2)O(2)/UV-C treatment. As a consequence of the considerable number of parameters affecting the H(2)O(2)/UV-C process, an experimental design methodology was used to mathematically describe and optimize the single and combined influences of the critical process variables treatment time, initial H(2)O(2)concentration and chemical oxygen demand (COD) on parent pollutant (surfactant) as well as organic carbon (COD and total organic carbon (TOC)) removal efficiencies. Multivariate analysis was based on two different photochemical treatment targets; (i) full oxidation/complete treatment of the surfactants or, alternatively, (ii) partial oxidation/pretreatment of the surfactants to comply with the legislative discharge requirements. According to the established polynomial regression models, the process independent variables "treatment time" (exerting a positive effect) and "initial COD content" (exerting a negative effect) played more significant roles in surfactant photodegradation than the process variable "initial H(2)O(2) concentration" under the studied experimental conditions.