Attenuated total refection spectroscopy under conditions weak absorption: New method for determination of integrated intensities

The basic principles of attenuated total reflection (ATR) spectroscopy are briefly described and its main areas of application are listed. It is shown using symbolic calculations that in the case of ATR spectra measured under conditions of weak absorbance, the area under the curve of absorbance of an isolated Lorentz absorption band is directly proportional to the integral band intensity. It is shown that the proportionality factor between these quantities contains a single a priori unknown parameter, i.e., the real part of dielectric constant of the studied medium in the maximum of the studied band. This fact offers a new scope for determining the integrated intensities of isotropic condensed media directly based on experimental ATR data.     

A systematic optimization approach for the calibration of parallel kinematics machine tools by a laser tracker

Parallel kinematics machine has attracted attention as machine tools because of the outstanding features of high dynamics and high stiffness. Although various calibration methods for parallel kinematics machine have been studied, the influence of inaccurate motion of joints is rarely considered in these studies. This paper presents a high-accuracy and high-effective approach for calibration of parallel kinematics machine. In the approach, a differential error model, an optimized model and a statistical method are combined, and the errors of parallel kinematics machine due to inaccurate motion of joints can be reduced by this approach. Specifically, the workspace is symmetrically divided into four subspaces, and a measurement method is suggested by a laser tracker to require the actual pose of the platform in these subspaces. An optimized model is proposed to solve the kinematic parameters in symmetrical subspaces, and then arithmetical mean method is proposed to calculate the final kinematic parameter. In order to achieve the global optimum quickly and precisely, the initial value of the optimal parameter is directly solved based on the differential error model. The proposed approach has been realized on the developed 5-DOF hexapod machine tool, and the experiment result proves that the presented method is very effective and accurate for the calibration of the hexapod machine tool.     

中凸变椭圆活塞加工系统动态特性研究

针对XJOC-2型中凸变椭圆活塞数控加工系统，通过理论分析建立了其动力学模型，通过激振实验研究了其动态特性及其对轮廓加工误差的影响，并提出了相应的改进措施及补偿策略，从而保证了系统良好的加工性能，最后针对曲型活塞进行了实际切削实验，取得了很好的结果。     

Structure factors and bonding in ΒNiAl

A combination of powder x-ray and critical voltage electron diffraction was used to determine the lattice parameter and low-angle structure factors of stoichiometric (ΒNiAI. A weighted least squares fit method was used to obtain an accurate lattice parameter from the x-ray line position data, and the integrated intensities were carefully analyzed to determine the Debye-Waller factors; the latter were found to be in good agreement with those obtained from the electron diffraction experiments. Highly accurate (errors ≅ 0.1%) low-angle structure factors were also obtained from the electron diffraction measurements, which were found to agree closely with first principles calculations in the local density approximation. This information reveals that bonding in NiAl is mostly ionic with some covalent contribution.     

一种新型的永磁同步电机电流预测控制方法

针对永磁同步电机控制系统中因参数误差引起系统性能下降的问题,提出一种基于参数辨识的永磁同步电机鲁棒电流预测控制法。通过引入鲁棒电流预测法来提高系统对电感参数的敏感度,但在电机实际运转中,电机电感参数误差主要影响直轴电流响应,而电机磁链参数误差主要影响交轴电流响应,同时电机磁链参数在恒加速过程中对电流稳态值影响较大,甚至会导致电流环的给定与反馈之间出现静差。在鲁棒电流预测控制基础上进一步提高电流控制系统的性能,采用递推最小二乘法,将电机模型中的电感、电阻和磁链3个参数拆分成两部分分别进行在线辨识,以减小辨识算法的复杂度以及对处理器性能的依赖。仿真和实验结果表明:该电流预测控制方法在保证系统稳定的前提下进一步提高电流控制系统的精度。     

Study of specific discharge energy in WEDM and its application

The relationship between machining parameters and machining characteristics of different materials in WEDM is difficult to obtain because a large number of experiments must be conducted repeatedly. A new concept attempting to solve this problem is presented in this paper. The specific discharge energy (SDE) defining as the real energy required to remove a unit volume of material is proposed. The SDE is constant for a specific material. Experimental results reveal that the relative relationship of SDE between different materials is invariant as long as all materials are machined under the same machining conditions. It is also found that the materials having close value of SDE demonstrate very similar machining characteristics such as machining speed, discharge frequency, groove width and surface finish of the machined surface under the same machining conditions. This result can be applied for the determination of the settings of machining parameters of different materials. Furthermore, by dimensional analysis of SDE, a quantitative relationship between machining characteristics such as the material removal rate and the efficiency of material removal and machining parameters is derived.     

Non-isothermal annealing of a cold rolled commercial twin roll cast 3003 aluminum alloy

It is shown that the recrystallization behavior of a cold rolled twin roll cast, commercial 3003 aluminum alloy under non-isothermal conditions, can be satisfactorily modeled by combining the approaches developed by Semiatin et al. and Puchi et al. The first approach allows the determination of the apparent activation energy for recrystallization without any ambiguity, information that can then be used in the second approach to define clearly the search range for the value of the apparent activation energy for recrystallization and to determine simultaneously the Avrami constants, from experiments conducted at a single heating rate. It is also shown that the apparent activation energy for recrystallization in this alloy varies between approximately 34 and 79 kJ/mol, with the trend being to find smaller values of this parameter as the strain applied to the material increases. Such low values of this energy were corroborated by isothermal experiments conducted in samples of the same material. The microstructural evolution of the samples annealed under non-isothermal conditions indicates that the rate of growth of the recrystallized grains in the rolling direction is significantly higher that in the short transverse direction, due to the pinning effect of the second phase particles aligned along the rolling direction, which leads to recrystallized structures with an aspect ratio significantly higher than 1. The effect of the strain applied to the material on the recrystallization kinetics is quantified by expressing the time required to achieve a given recrystallized fraction as a function of the effective strain, by a simple parametric relationship that involves three numerical constants. Recrystallization experiments conducted under non-isothermal conditions are found to be more suitable for the evaluation of the effect of the strain applied on the recrystallization kinetics in comparison with isothermal tests, since larger strains can be applied to material before the annealing treatment.     

Effect of film thickness on microstructure parameters and optical constants of CdTe thin films

Different thickness of cadmium telluride (CdTe) thin films was deposited onto glass substrates by the thermal evaporation technique. Their structural characteristics were studied by X-ray diffraction (XRD). The XRD experiments showed that the films are polycrystalline and have a zinc-blende (cubic) structure. The microstructure parameters, crystallite size and microstrain were calculated. It is observed that the crystallite size increases and microstrain decreases with the increase in the film thickness. The fundamental optical parameters like band gap and extinction coefficient are calculated in the strong absorption region of transmittance and reflectance spectrum. The possible optical transition in these films is found to be allowed direct transition with energy gap increase from 1.481 to 1.533 eV with the increase in the film thickness. It was found that the optical band gap increases with the increase in thickness. The refractive indices have been evaluated in transparent region in terms of envelope method, which has been suggested by Swanepoul in the transparent region. The refractive index can be extrapolated by Cauchy dispersion relationship over the whole spectral range, which extended from 400 to 2500 nm. It is observed that the refractive index, n increases on increasing the film thickness up to 671 nm and then the variation of n with higher thickness lie within the experimental errors.     

基于复合直梁型柔性铰链的导轨直线度测量研究

刚度是影响柔性铰链机械性能的重要参数指标,建立复合型柔性铰链拉伸刚度模型,在不同参数、不同尺寸条件下计算其解析解,通过ANSYS Workbench对其进行静力学仿真,分析各个结构参数对其刚度的影响,同时得出该种复合柔性铰链在同等尺寸及力的作用下比传统双边平行铰链有较大的输出位移。在解析解与仿真结果误差较小的情况下,设计出一种参数最优化的复合柔性铰链并搭建了测量平台,对滚珠丝杆驱动的导轨进行了直线度误差测量,将其结果和激光干涉仪测量结果对比,验证了基于该柔性铰链搭建的测量平台满足直线度的测量需求。     

带极堆焊带极电流磁控技术的试验研究

利用模拟带极堆焊状态下带极电流对控制磁场存在与否及强度、位置变化的反应,应用电工学原理分析带极堆焊磁控技术。结果表明,在相同的电流、电压参数条件下,磁控装置的磁极所处位置、磁场强度会直接影响带极电流的分布,造成电流在带极宽度方向上的改变。由此推断堆焊时电磁控制是磁场对电流分布状态的控制,进而控制电弧在带极宽度方向上的均匀性和稳定性,保证宽带极的稳定堆焊。     

工艺参数对透明光学制品残余应力的影响

通过光弹实验测量残余应力的分布形态,并通过应力-光学定律计算出相应的残余应力值,将该数值与模拟值做了分析比较。结果表明,对于同一工艺参数,残余应力的数值从浇口附近至流动末端逐渐减小;对于不同工艺参数,对残余应力的影响程度从大到小的顺序为熔体温度、模具温度、注射压力、冷却时间。     

Integrated machining error compensation method using OMM data and modified PNN algorithm

This paper presents an integrated machining error compensation method based on polynomial neural network (PNN) approach and inspection database of on-machine-measurement (OMM) system. To improve the accuracy of the OMM system, geometric errors of the CNC machining center and probing errors are compensated. Machining error distributions of a specimen workpiece are measured to obtain error compensation parameters. To efficiently analyze the machining errors, two machining error parameters, W_err and D_err, are defined. Subsequently, these parameters can be modeled using the PNN approach, which is used to determine machining errors for the considered cutting conditions. Consequently, by using an iterative algorithm, tool path can be corrected to effectively reduce machining errors in the end-milling process. Required programs are developed using Ch language, and modified termination method are applied to reduce computation times. Experiments are carried out to validate the approaches proposed in this paper. The proposed integrated machining error compensation method can be effectively implemented in a real machining situation, producing much fewer errors.     

Femtosecond exciton dynamics in DOO-PPV films

We studied the ultrafast exciton dynamics in DOO-PPV films using the technique of femtosecond photoinduced absorption decay. We found that the exciton dynamics contains an ultrafast decay component of about 2 ps that remains unchanged at intensities up to five times the threshold excitation intensity for the phenomenon of emission spectral narrowing. We argue that amplified spontaneous emission of waveguided or leaky modes, depending on film thickness and excitation geometry, is the dominant mechanism for both spectral narrowing and ultrafast decay component. In very thin films we found that the process of amplification of leaky waves may be responsible for the amplification of the 0-0 emission band rather than the 0-1 band, that has been usually observed at high excitation intensities in thicker films.     

Texture Evolution,Formability and Ridging Resistance of a Sn-bearing Ferritic Stainless Steel Under Different Hot Band Annealing Temperatures

The microstructure, texture evolution and spatial orientation distribution during cold rolling and the subsequent annealing as well as formability and ridging of a Sn-bearing ferritic stainless steel under different hot band annealing temperatures were investigated. The four hot bands with annealing temperatures of 900, 950, 1000 and 1050 °C were all cold-rolled to 80% reductions and then were annealed at the same temperature of 900 °C. The results show that optimizing hot band annealing process is benefi cial to reduce the amount of {001} 110 grains and weaken the texture intensity, and thus, to reduce ridging and improve formability. In the present study, the fi nal sheets with hot band annealing temperature of 900 °C possess small and inhomogeneous grains with a large amount of {001} 110 orientations, which deteriorates the formability and increases the ridging. In comparison, the fi nal sheets with hot band annealing temperature of 950 °C are comprised of uniform and equiaxed 111//ND(ND: normal direction) recrystallized grains with a high texture intensity favorable for the improvement in r value and surface quality. However, when hot band annealing temperature further increases to 1000 and 1050 °C, it shows a sharp decrease in r value and a remarkable increase in ridging as a result of a reduction in γ-fi ber texture intensity and an increase in grain size in the fi nal sheets. Suitable controlling and optimizing hot band annealing process is essential to improve the formability and reduce the ridging.     

Evaluating the stress intensity factor using white light photoelastic experiment

In this study, a method is proposed to evaluate the stress intensity factor using isochromatics multiplied and extracted from original isochromatic images obtained from a white light photoelastic experiment. This method utilizes R, G and B isochromatics which are captured using a color CCD camera and an image processor in dark- and light-field circular polariscopes. First, for each color, the dark-field intensities are subtracted from the light-field intensities so that each point of the resultant image has a positive, zero or negative value. The isochromatics are then obtained as a series of points whose value is zero, which are extracted using image processing. The fringe orders are assigned to the extracted isochromatics using calibration curves. The stress intensity factor is determined using the Irwin method. This method is applied to an epoxy resin plate with a crack formed at one side under 3-point bending. The result shows that the stress intensity factor is accurately evaluated using R, G and B isochromatics near the crack tip. This article based on a presentation made in the symposium “The 4th International Conference on Fracture and Strength of Solid”, held at POSTECH, Pohang, Korea, August 16–18 under the auspices of Far East and Ocean Fracture Society (FEOPS),et al.     

Conditions for the achievement of the stage of stationary radiation swelling

Conditions for the realization of the stage of stationary radiation swelling are analyzed. A model is suggested that describes the coalescence of pores during their growth. It is shown that after a definite relationship between the parameters of the pore-size distribution is achieved, the integrated area of the pore surface stops changing, which ensures the constancy of the rate of radiation swelling. Experimental data have been obtained on the variation of the porosity characteristics in steel of grade ChS-68 upon high-fluence neutron irradiation. It has been established that with increasing porosity the integrated area of the pore surface first increases and then saturates as the porosity reaches a value of 8–11%.     

DETERMINATION OF THE PARAMETERS OF SUPERPLASTIC FORMING FOR LONG RECTANGULAR THIN SHEET TITANIUM ALLOY Ti-6A1-4V

1.IntroductionSuperplasticmaterialsareknowntobepolycrystallinematerialshavingultrafine-grainedmicrostructureandexhibitingexceptionalductilitywhensubjectedtotensionunderelevatedtemperaturesandrelativelysmallstrainrates.Themechanicalbehaviourofsuperplasticmaterialsisnow11suallyinvestigatedduringstandarduniaxialtensiletests,see,e.g.,[lt2].Superplasticflowischaracterizedbyrelativelylowflowstress,whichishighlystrainratedependentinvalue.Thefollowingphenomenologicalrelationshipisusuallyusedtodescribe…     

铣削加工颤振稳定域影响参数研究及优化

建立圆柱形铣刀铣削加工动态切削数学模型,采用一种解析法计算并绘制稳定域图,获取加工稳定性随工艺参数变化的规律。分析系统参数对铣削加工颤振稳定特性的影响,提高固有频率、增大系统刚度和阻尼有助于提高系统加工稳定性。基于动态变化的稳定域图及共振功率半频带频率,提出一种铣削稳定性约束下铣削参数优化模型,获取最大加工效率下的主轴转速、径向进给量及轴向进给量参数的最优值。开发铣削稳定性分析仿真软件,实现铣削颤振稳定域分析、共振区域分析、铣削参数优化等功能。将复杂设计分析过程工程实用化,具有工程应用价值。该方法同样可推广到磨削、车削的颤振分析。     

Effects of illumination on capacitance characteristics of Au/3C-SiC/p-Si/Al diode

Au/3C-SiC/p-Si/Al Schottky barrier diode was prepared using atmospheric pressure chemical vapor deposition technique. The device parameters such as barrier height, ideality factor, and series resistance were calculated using current-voltage characteristics, and were found to be 0.44 eV, 1.55, and 1.02 × 10⁴ Ω, respectively. The photocapacitive properties of the diode were studied under various illumination intensities. The transient photocapacitance measurements indicate that the capacitance of the Au/3C-SiC/p-Si/Al Schottky diode is very sensitive to illumination. The photocapacitance of the diode increases with increase in illumination intensity. The increase in photocapacitance with increase in illumination intensity suggests that these devices could be utilized as a photocapacitive sensor for optical sensors.     

Investigation on characteristic of J integral parameter in welded joints

The J integral parameter and its application feasibility in welded joints with different weldmatchings in yield strength (overmatching weld and undermatching weld), different material constitutive laws (material with a Ludes yield plateau and power hardening) and under different fracture types (ligament yielding fracture and general yielding fracture) are investigated. First the condition of J integral path independent has been studied based upon finite element analysis by using ADINA procedure on welded joints. It was shown that the J integral is path dependent for the cases studied in this paper. Then experiments were carried out to study availability of J integral as a plastic singularity parameter at the tip of the notch in welded joints. The results show that J dominance in most cases studied is not validated in v and u displacement fields. From both considerations mentioned above it can be concluded that J-integral as controlling parameter used to estimate the safety of welded structures is not alw