Weight minimization of a speed reducer by heuristic and decomposition techniques

Discrete combinatorial optimization techniques (heuristics)[1–5] have been extended for optimum synthesis of medium-and-large-scale mechanical systems [6,7]. Decomposition techniques based on the kinematic structure of mechanisms have been developed. Other decompisition methods have been previously outlined[7]. The decompositon techniques were then combined with a heuristic search to obtain efficient optimization method for large-scale mechanical systems. The optimization scheme has been applied for weight minimization of a speed reducer. The results obtained by the techniques, which have been developed, indicate that these methods are more efficient than various schemes, such as adaptive optimization approach, random-gradient technique, and Monte-Carlo method. all previously employed for weight minimization of a speed reducer.     

Time delay effects on performance and stability of a low cost electrostatic suspension system

To expand the potential industrial applications of electrostatic suspension systems, a low cost suspension system with high-voltage supplies instead of high-voltage amplifiers has already been implemented. In that system, the performance and stability are strongly affected by the time delay inherent in the system. It is therefore important to understand the sensitivity of stability and performance in relation to the time delay. In this paper a low cost electrostatic suspension system based on a delay controller is presented. The effect of time delay on the characteristics of the suspension system will be investigated. The critical time delay of the suspension system, defined as the maximum time delay that can be accepted by the system in order to ensure the system stability, will be derived in terms of bias voltage. The recoverable set whose domain depends on time delay will be found as well. The simulation and experimental results will show the effectiveness of the proposed method. In the experiments, a 3.5-inch aluminium disk was suspended without any mechanical contact at a reference gap length of about 300 μm in both atmospheric and vacuum environments.     

Forming limit diagram of aluminum/copper bi-layered tubes by bulge test

Chemo-mechanical-grinding (CMG) is a hybrid process which integrates chemical reaction and mechanical grinding between abrasives and workpiece into one process. It has been successfully applied into manufacturing process of silicon wafers where both geometric accuracy and surface quality are required. This paper aims to study the potential of CMG process in manufacturing process of single crystal sapphire wafers. The basic material removal mechanism in terms of chemical effect and mechanical effect in CMG process has been analysed based on experiment results of two different kinds of CMG wheels. The experiment results suggest that chromium oxide (Cr₂O₃) performs better than silica (SiO₂) in both material removal rate (MRR) and surface quality. It also reveals that, no matter under dry condition or wet condition, CMG is with potential to achieve excellent surface quality and impressive geometric accuracy of sapphire wafer. Meanwhile, test result by Raman spectrum shows that, by using Cr₂O₃ as abrasive, the sub-surface damage of sapphire wafer is hardly to be detected. Transmission electron microscopy (TEM) tells that the sub-surface damage, about less than 50 nm, might remain on the top surface if chemical effect is not sufficient enough to meet the balance with mechanical effect in CMG process.     

Simultaneous minimization of total tardiness and waiting time variance on a single machine by genetic algorithms

This paper considers a single machine scheduling problem, with the objective of minimizing a linear combination of total tardiness and waiting time variance in which the idle time is not allowed. Minimizing total tardiness is always regarded as one of the most significant performance criteria in practical systems to avoid penalty costs of tardiness, and waiting time variance is an important criterion in establishing quality of service (QoS) in many systems. Each of these criteria is known to be non-deterministic polynomial-time hard (NP-hard); therefore, the linear combination of them is NP-hard too. For this problem, we developed a genetic algorithm (GA) by applying its general structure that further improves the initial population, utilizing some of heuristic algorithms. The GA is shown experimentally to perform well by testing on various instances.     

Determination of the forming limit diagrams by using the fem and experimental method

This paper presents the implementation of forming limit diagrams (FLDs) by the FEM and experimental method for sheet metals, which are vastly used in automobile industry. Several different methods were employed to measure the strains of the deformed sheet metals in experimental method. The uncertainty of each method was determined and the most efficient and economic way was introduced. Because of complexity and expensiveness of the experimental method, simulating of the deep drawing test to obtain the FLD has also been implemented by FEM. The FEM results show excellent agreement with experimental data in present work. Hence, the FEM can be a suitable and reliable method to obtain a FLD.     

材料屈服极限对工程车辆驾驶室翻车保护结构有限元仿真结果的影响

以非线性有限元技术为理论基础,根据国际试验标准中力的加载方式,建立含有翻车保护结构(ROPS)的非线性有限元模型.通过Nastran的非线性分析对模型进行了最小侧向承载能力、垂直承载能力和纵向承载能力分析,比较了ROPS材料屈服极限对最小侧向承载能力变形和应力结果的影响,为后期的有限元模型修正提供了较可靠的依据.     

Surpassing the lateral resolution limit by a factor of two using structured illumination microscopy

Lateral resolution that exceeds the classical diffraction limit by a factor of two is achieved by using spatially structured illumination in a wide-field fluorescence microscope. The sample is illuminated with a series of excitation light patterns, which cause normally inaccessible high-resolution information to be encoded into the observed image. The recorded images are linearly processed to extract the new information and produce a reconstruction with twice the normal resolution. Unlike confocal microscopy, the resolution improvement is achieved with no need to discard any of the emission light. The method produces images of strikingly increased clarity compared to both conventional and confocal microscopes.     

基于系统稳定性的可靠性分析研究

从控制理论的角度出发，认为“可靠性”本质上是产品功能的稳定性问题，同时给出了基于稳定性的产品可靠性分析的定量方法与定性方法。进一步结合机械可靠性设计理论作了具体分析。     

Prediction of limit strain in sheet metal-forming processes by 3D analysis of localized necking

Theoretical prediction of forming limit strain of sheet metal is developed in the framework of the three-dimensional general bifurcation theory. The onset of the three-dimensional discontinuous velocity field in the biaxially stretched uniform sheet is predicted. Three fundamental mode vectors, i.e. shear horizontal, shear vertical and normal modes are introduced and it is demonstrated that any bifurcation mode is represented by the linear combination of them. The onset of the bifurcation is numerically analyzed in terms of the modes by the use of the linear comparison solid originally introduced by Hill in 1959. In this study, a linear constitutive relation is adopted for the linear comparison solid, which is developed based on the constitutive theory proposed by Goya and Ito and is capable of incorporating the directional dependence of the plastic strain rate on the stress rate. The numerical results show that forming limit strains predicted by the three-dimensional mode theory is much higher in general than that given by Stören and Rice in 1975. Then, it is revealed from the three-dimensional mode analysis that the bifurcation mode that arises can be changed from one type to another according to the sign of stress ratio. It is also shown that the strain limit predicted by the three-dimensional mode analysis gives upper limit lines for the bifurcation lines proposed in the past for any linear strain-path directions.     

Reduction of the scanning time by total variation minimization reconstruction for X‐ray tomography in a SEM

Total variation minimization is applied to the particular case of X‐ray tomography in a scanning electron microscope. To prove the efficiency of this reconstruction method, noise‐free and noisy data based on the Shepp & Logan phantom have been simulated. These simulations confirm that Total variation minimization‐reconstruction algorithm better manages data containing low number of projections with respect to simultaneous iterative reconstruction technique or filtered backprojection, even in the presence of noise. The algorithm has been applied to real data sets, with a low angular sampling and a high level of noise. Two samples containing micro‐interconnections have been analyzed and 3D reconstructions show that Total variation minimization‐based algorithm performs well even with 60 projections in order to properly recover a 500 nm diameter void inside a copper interconnection.     

调制激光器激励法的热电偶时间常数测试

提出一种利用大功率高频调制CO2激光作为激励源,对表面温度传感器进行时间常数测试的新方法。建立了时间常数测试系统,对温度范围不同、时间常数各异的热电偶进行了时间常数测试,给出了测试曲线。实验证明该系统可以测试亚毫秒至秒量级表面温度传感器的时间常数,其激励源所提供的温度阶跃可覆盖常温至高温范围。     

Residual stress behaviors induced by laser peening along the edge of curved models

Laser peening (LP) induces high-magnitude compressive residual stresses in a small region of a component. The compressive residual stresses cause plastic deformation that is resistant to fatigue fracture. Fatigue cracks are generally nucleated at critical areas, and LP is applied for those regions so as to delay the crack initiation. Many critical regions are located on the edge of the curved portion of structures because of stress concentration effects. Several investigations that are available for straight components may not give meaningful guidelines for peening curved components. Therefore, in this paper, we investigate residual stress behaviors induced by LP along the edge of curved models. Three curved models that have different curvatures are investigated for peening performance. Two types of peening configurations, which are simultaneous corner shot and sequential corner shots, are considered in order to obtain compressive residual stresses along an edge. LP simulations of multiple shots are performed to identify overlapping effects on the edge portion of a curved model. In addition, the uncertainty calculation of residual stress induced by LP considering laser pulse duration is performed.     

用太赫兹时域光谱技术对防虫防蛀剂进行质量检测

太赫兹时域光谱技术可以分辨化合物结构上的微小差异并应用于物质检测与分析,为有机化工产品的鉴别及更宽有效光谱区的测试提供了新的实验方法。本文运用太赫兹时域光谱技术研究了樟脑、对二氯苯和萘三种防虫防蛀剂在太赫兹波段的光学特性。在室温氮气环境中,得到了樟脑、对二氟笨和萘在0．2-2．5THz波段的折射率和吸收谱,样品在此波段的折射率和吸收谱存在显著差异。对二氟苯和萘都有毒性。实验表明,用太赫兹时域光谱技术可以清楚地分辨出三种防虫防蛀剂以及其混合物的折射率和吸收谱的差异,通过判断特征谱线的差异从而判断此种防虫防蛀剂的毒性,此法简单,快速,准确。     

Motion stability analysis of non-sinusoidal oscillation of mold driven by servomotor

The investments of the electro-hydraulic servo system of the mold non-sinusoidal oscillator are great, the modification ratio of the mechanical type is unable to be adjusted online, and some continuous casters suffer from server resonance during the casting. A mold non-sinusoidal oscillation mechanism driven by servomotor is proposed and the prototype is produced in the lab, the investment is low and the modification ratio is can be adjusted online, and the stability problem is studied. At first the dynamics model of the servomotor non-sinusoidal oscillation is established, and the kinematics differential function is deduced. Furthermore, based on the harmonic balance method, the eigenvalues of the system are solved; the criterion of the stability of the system is put forward. In addition, the eigenvalues and harmonic with different oscillating parameters are analyzed. Analytical results show that the real parts of the eigenvalues are positive, the system will be unstable, and the resonance will occur when the positive real parts of the eigenvalues are extremum. A foundation is established for solving the running smooth problem and next application of this mechanism.     

加强维护保证整流机组运行的稳定性

对比新老设备的特点,谈谈整流机组的维护办法,以及新引进设备对整机的运行效率的改变,给维护工作带来的方便。     

Mechanism of reduction of fretting fatigue limit caused by hydrogen gas in SUS304 austenitic stainless steel

The fretting fatigue strength of pre-strained SUS304 is reduced in hydrogen gas. The mechanism of the reduction is discussed. In hydrogen gas, local adhesion between contacting surfaces occurred and many small cracks were formed at the adhered spots. The major crack propagated from one of the small cracks. The roles of the adhesion in relation to the initiation and propagation of the small cracks were examined by a two-step environment test. When adhesion was prevented by an oxidized film, no failure of the specimen occurred. It can be presumed that the stress conditions were more severe in hydrogen gas than that in air due to local adhesion.     

咪唑类物质的气溶胶飞行时间质谱研究

使用气溶胶激光飞行时间质谱（AL-TOF MS）和基于同步辐射光源的热解吸/可调谐真空紫外飞行时间光电离气溶胶质谱（TD-VUV-TOF-PIA MS）对7种咪唑类物质（咪唑、咪唑-2-甲醛、2-甲基咪唑、4-甲基咪唑、1-乙基咪唑、2-乙基咪唑、1-正丁基咪唑）进行分析,获得了每种样品在2种不同电离方式下的指纹图谱。前者主要获得这些样品物质的碎片峰信息,后者则主要获得含有完整母体峰的质谱信息。用上述标准样品的指纹图谱对乙二醛-硫酸铵溶液喷雾产生二次有机气溶胶（SOA）的质谱进行识别。通过咪唑样品的AL-TOF MS特征峰组合,可以解析出乙二醛与硫酸铵经水相反应生成咪唑类物质。由TD-VUV-TOF-PIA MS获得的咪唑样品在不同光子能量下的质谱特征,可以确认上述水相反应生成的咪唑类物质中含有咪唑与咪唑-2-甲醛。这两种方法互为补充,可为准确评估SOA水相形成贡献,以及完善气溶胶模式模拟提供数据支持。     

A Time-to-Code Converter with a Selection of Time Intervals by Duration

A time-to-code converter with preliminary selection of measured time intervals by duration is described. The intervals are selected with the use of Analog Devices programmable delay generators. The selection time of the measured time intervals is 50 ns, the conversion range is from 0 to 100 ns, and the resolution is 0.1 ns.