Image enhancement of simplified ultrasonic CT using frequency analysis method

In this paper, a simplified ultrasonic CT system, which uses the information in three directions, that is, 90°, +45° and —45° about the inspection plane, is applied to the high strength steel, and the frequency analysis method for enhancing the C scan or CT image is developed. This frequency analysis method is based on the frequency response property of the material. By comparing the magnitudes in the frequency domain, the special frequency which shows a significant difference between the welded joint and base material was found and used to obtain a C scan or CT image. Experimental results for several kinds of specimens, having a welded joint by electron beam welding, a weld joint by arc welding, on a fatigue crack, showed that the obtained C scan or CT image has better resolution than the results of previous experiments using the maximum value of the received waveform.     

Reparability measurement of vision sensor in active stereo visual system

The active visual inspection has made giant strides in development. Due to the complexity of field conditions, the binocular stereo vision sensor in active stereo visual inspection system is difficult to acquire the ideal image pair under the poor illumination environment, or cannot work normally because one of two cameras is damaged. To solve the practical problem, a reparability method of the vision sensor in active stereo visual inspection system is proposed. Based on the traditional measurement platform with a structured stripe projector and two industrial cameras, a reparability mathematical model is established, which merges the measurement mode of the stereo vision and the structured light vision to inspect feature points based on the reparability measurement model. Meanwhile, a mathematical model and calibration method of the structured light vision are developed based on the homography between the image and light plane. The method greatly improved the stability and reliability of measurement data. It is proven by experiment that the method is valid, which can accomplish reparability tasks commendably and achieve uninterrupted inspection of feature points in the actual industrial applications.     

Solid particle erosion behaviour of glass fibre reinforced boric acid filled epoxy resin composites

The tests which involved angular aluminium (Al₂O₃) particles with two different sizes of approximately 200 and 400 μm were conducted at the operating conditions namely different impact velocities of approximately 23, 34 and 53 m/s, two different fibre directions [0° (0/90) and 45° (45/−45)] and three different impingement angles of 30°, 60° and 90°. New composites with addition of Boric Acid filler material at 15% of resin exhibited upper wear than the neat materials without filler material. This means the filler material has decreased the erosion wear resistance. SEM views showing worn out surfaces of the test specimens were scrutinised.     

聚氨酯夹芯板发泡缺陷电磁超声导波快速检测

聚氨酯夹芯板在生产中因发泡不均容易在聚氨酯泡沫层形成空洞型缺陷,直接影响其保温效果,为此提出了一种从金属板外侧实施的电磁超声SH导波检测的快速检测方法.通过理论分析、解析推导、仿真计算和试验验证,建立了聚氨酯夹芯板中的SH导波透反射比系数与激励参数之间的关系,结果表明,当磁铁间距为4.5 mm时,控制SH0导波入射角度...     

基于激光位移传感器的面角度测量技术研究

针对面角度现场测试需求,利用激光位移传感器的漫反射测量特性,搭建了面角度非接触测量装置,提出了一种结合三坐标测量机和位置敏感探测器对激光位移传感器进行空间坐标化标定的方法,从而构建出精确的面角度测量模型;采用蒙特卡洛法对面角度非接触测量装置的不确定度进行评定,在±25°测量范围内其结果为U=0.044°~0.046°(k=2);通过性能验证试验、重复性试验和稳定性试验对装置的性能指标进行考核,在±25°测量范围内其绝对测量示值误差不超过0.036°,重复性不超过0.004°,稳定性不超过0.021°;实验结果表明该基于激光位移传感器的面角度非接触测量装置准确可靠,具备开展面角度现场测试应用的前景。     

机载设备安装姿态视觉校准中的靶板标定

基于飞机机载设备安装姿态视觉校准系统Archer-M的研发,提出针对系统中姿态测量辅助靶板的标定方法。首先,利用摄像机从不同方位拍摄靶板图像,在相差一个尺度因子的情况下确定靶点位置关系。然后,利用单个发光二极管（LED）靶点的多次精确移动和图像叠加的方法恢复绝对尺度,求解靶点的相对关系。最后,通过精确控制靶板的位姿运动,利用运动前后各坐标系之间的相对关系,求解出“靶/座"相对位姿,并进一步针对只用于物体姿态测量的靶板,提出了分别沿两个垂直方向运动的简化“靶/座"标定方法,从而大大降低了标定过程中对标定设备的要求。实验结果表明：距离为3~12 m时,姿态角度的测量标准差为0.004~0.017°,姿态测量精度与激光跟踪仪相当。     

基于偏振分像的制冷器件晶粒双面等光程共焦成像缺陷检测装置

针对待测晶粒大的情况,为解决晶粒双面检测时双面之间产生光程差导致的的成像清晰度问题,提出了一种基于偏振分光成像法的半导体制冷器件晶粒相邻双面同时成像缺陷检测的装置。利用偏振分光器与直角转像棱镜对采用偏振分束器与偏振相机的晶粒天面和侧面同时等光程共焦成像检测装置进行了光学设计,完成了晶粒相邻双面同时等光程偏振成像缺陷检测的实验验证。结果表明,该偏振分光成像检测技术可以实现晶粒相邻面的同时缺陷检测,并能很好地满足相邻面等光程成像缺陷检测的性能要求。当晶粒相邻面等光程共焦时,检测分辨率可达到110 lp/mm以上,而当晶粒相邻面离焦（准共焦）仅±0.20 mm时,分辨率则降至45 lp/mm以下。本检测装置具有双面成像清晰度好、成像光路共焦调整方便、检测装置结构简单可靠,以及提高的缺陷检测性能等优点。     

Rogowski coil current transducer compensation method for harmonic active power error

In the harmonic active power measurement, the highest uncertainties are generally introduced by the current and voltage transducers. In a previous paper, the authors showed that the current transformer (CT) can introduce significant errors in such measurement, especially if the phase shift between voltage and current is close to ±90°. In such condition the errors on harmonic power measurement are mainly due to the CT phase displacement. This paper shows that better results can be achieved with more linear transducers, such as the Rogowski coil current transducers (RCCTs), whose metrological performance in distorted condition can be improved, by means of a proper compensation method. The proposed method for RCCTs compensation is based on the frequency response and it allows to reduce the errors on harmonic power measurement, also for phase shift close to ±90°. The study is supported by several experimental tests.     

A 360° single-axis tilt stage for the high-voltage electron microscope

A new type of specimen stage that permits more than 180° of tilting about the axis of a side-entry rod has been developed for a high-voltage electron microscope (HVEM). Roughly cylindrical specimens, with radial dimensions of less than a few micrometres, that can be mounted on the tip of a microneedle or micropipette are applicable. For glass micropipettes, the energy of the 1-MeV beam of the HVEM is sufficient to image specimens through both walls. The stage employs a spindle mechanism that holds these needles or micropipettes coaxial with the tilt axis, allowing the specimen to be rotated without restriction. This arrangement, along with the cylindrical form of the specimen, is an important development for single-axis tomography, because it permits a complete 180° set of projections to be recorded. The angular accuracy of the stage was demonstrated to be within ±0.20°, with a cumulative error of less than 1.0° over a 180° span. The new stage was tested using puffball spores mounted on a micropipette. A 180° tilt series was recorded and processed to yield a tomographic three-dimensional reconstruction which was displayed both as a cross-sectional view perpendicular to the tilt axis, and as a shaded surface viewed from different directions. The same computations were repeated using subsets of the tilt series to assess the effect of various amounts of missing information. Visual inspection of a selected cross-section from these reconstructions indicated that limiting the angular range to 160° produced results nearly as good as the full data set. Limiting the range to 140°, however, produced a noticeable geometric distortion, which became increasingly severe with ranges of 120° and 100°.     

Robust segmentation of CMM data based on NURBS

Segmentation is a crucial step towards the interpretation of discrete three-dimensional measurement data. This paper presents a robust method for compound free-form surface segmentation and reconstruction. In the proposed method, a cloud of measurement data are collected through a coordinate measuring machine (CMM). The set of measurement data is then sliced along, at most, three orthogonal directions. On each slicing plane, measurement data is fitted by a 2D NURBS spline. Now, maximum curvature points on each NURBS spline can be calculated. These points represent the boundary of the digitised object. With the proposed method, three-dimensional segmentation is simplified to a two-dimensional problem. The effectiveness of the proposed segmentation method will be illustrated with examples of a hair drier and a telephone receiver.     

The effects of elbow joint angle on the mechanical properties of the common extensor tendon of the humeral epicondyle

The purpose of this study was to determine the effects of elbow joint angle on mechanical properties, as represented by ultimate load, failure strain and elastic modulus, of bone-tendon specimens of common extensor tendon of the humeral epicondyle. Eight pairs of specimens were equally divided into two groups of 8 each, which selected arbitrarily from left or right side of each pair, positioned at 45° and 90° of elbow flexion and subjected to tension to failure in the physiological direction of the common extensor tendon. For comparison of the differences in the failure and elastic modulus between tendon and the bone-junction, data for both were evaluated individually. Significant reduction in ultimate load of bone-tendon specimens was shown to occur at 45°. The values obtained from the bone-tendon junctions with regard to the failure strain were significant higher than those from tendon in both loading directions, but the largest failure strain at the bone-tendon junction was found at 45°. The elastic modulus was found to decrease significantly at the bone-tendon junction when the loading direction switched from 90° to 45°. Histological observation, after mechanical tensile tests, in both loading directions showed that failure occurred at the interface between tendon and uncalcified fibrocartilage in the thinnest fibrocartilage zone of the bone-tendon junction. We concluded that differences in measured mechanical properties are a consequence of varying the loading direction of the tendon across the bone-tendon specimen.     

AUTOMATIC INSPECTION SYSTEM FOR DEFECTS OF PRINTED ART TILE BASED ON TEXTURE FEATURE ANALYSIS

An automatic inspection system of printed art tile defects is reported in this artucke. After calculating eight defect features of art tile using the gray level co-occurrence matrix and the average R, G, B values of a defective area, the results were input into a backward propagation neural network for training the defect classifier. During inspection, the proposed system compared the inspected image with a standard image and removed noise by an erosion operation in order to preliminarily determine whether the art tile had defects. For the defective art tile images, the proposed classifier successfully identified four types of common printing defects. The proposed algorithm had an average recognition rate of 90%, suggesting that the recognition accuracy is good, and only requires 1–2 s to inspect an art tile with the size of 15 × 15 cm². The inspection speed is faster than the conventional manual inspection, and recognition results are more stable. The proposed system can reduce the risk of error caused by the long duration of manual inspection, and thus, can reduce manufacturing costs.     

The development of automated solder bump inspection using machine vision techniques

Visual inspection is an important task in the manufacturing processes for integrated circuit boards. In this paper, we focus on the solder bump inspection problem, and an automated visual inspection method using machine vision techniques is proposed. The solder bump inspection method consists of image grabbing, image preprocessing, feature extraction, and defect detection and classification. Five defect types of solder bumps to be inspected are bridging solder, excess solder, incomplete solder, non-wetting, and missing solder. The solder area, the number of edge pixels, the deviation from center, and the deformation ratio are used as the features for solder bump defect detection and classification. The proposed method is a hybrid algorithm, and it consists of two stages: the training stage and the inspection stage. The experimental results show that the proposed method is effective in detecting defects of solder bumps.     

60°二维扫描镜轴系误差测量方法研究

绕固定Q轴和动短轴Z轴摆动的60°二维扫描镜,在相同的扫描视场内,比45°镜摆动角度小、像旋也小。但是其特殊的结构也使得它的轴系误差分析比45°镜复杂,采用传统的测量方式无法满足测量的需要。通过对国外相关测量技术的调研,结合60°二维扫描镜自身的特点,提出了一种新的测量方式,并给出了这种测量方式的理论模型,实验证明这种测量方式能够较好地适用于分析60°二维扫描镜轴系误差的情况。     

非合作旋转目标闭环检测与位姿优化

若要实现空间失效卫星、空间碎片等非合作目标,尤其是具有自旋运动特性的目标的在轨服务或者离轨清除,需要精确测量追踪航天器与目标之间的相对姿态。当目标旋转一周后,对重访区域的闭环检测与位姿优化是减小累积误差,提高测量精度的重要保证。首先,本文介绍了视觉词袋库的建立和基于视觉词袋的非合作目标闭环检测策略。然后,基于相似性变换,对图像序列关键帧集和当前帧进行了联合位姿图优化,实现了对刚体变换矩阵的校正。最后对不同运动角速度下的不同目标,采用不同相机进行地面模拟测试实验,验证了方法的有效性和可靠性。实验结果表明:对于以12(°)/s角速度运动的非合作目标,当测量稳定后,绝对角度误差约为1(°),相对角度误差约为1%,平均角速度误差约为0.12(°)/s。可以满足非合作目标相对姿态测量的任务需求。     

Are the core structures of dislocations and grain boundaries resolvable by HREM?

Linear or planar defect structures have been recently studied by high resolution electron microscopy (HREM). Defects are generally difficult to solve for several reasons: they are non-periodic and their images are limited to a very few projections along low index axes. For edge dislocations in materials having a high lattice friction, image analysis is possible and relatively fine details are now available about core radii and location of the atom pairs. The accuracy, however, of the proposed structures is within ± 0·025 nm if a priori information is known. This is not always sufficient to distinguish between several models. For a high angle tilt grain boundary the situation is comparable. A discussion of the errors introduced by several factors (object orientation, optical axis alignment) and measurement of experimental parameters is presented. At present all the information content of an image is not used: intensity profiles and quantitative comparison of simulated and experimental images should provide better ways for solving an unknown structure. However, the improvement of the point resolution is the key factor for further progress in defect analysis.     

FDM 3D打印聚醚醚酮零件摩擦磨损特性研究

为研究3D打印各向异性对摩擦性能的影响,通过熔融沉积成型(FDM)制备了0°、45°、90°3种打印角度的聚醚醚酮(PEEK)试样,研究3种不同打印角度及载荷变化对PEEK试样摩擦学性能及磨损机制的影响。利用MFT-5000摩擦磨损试验机对PEEK材料进行室温水润滑下的往复滑动摩擦试验,用超景深显微镜观察磨损后表面形貌。试验结果表明：不同载荷下3种打印角度试样的摩擦因数由大到小依次为0°试样、90°试样、45°试样,磨损率由大到小依次为90°试样、45°试样、0°试样;随着载荷的增大,3种不同打印角度试样的摩擦因数均呈现下降趋势,磨损率则呈现上升趋势;PEEK磨损机制是黏着磨损以及疲劳磨损引起的表层脱落。     

Calibrated Thermal Microscopy of the Tool–Chip Interface in Machining

This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool–chip interface during the steady‐state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 µm. The system is based on an InSb 128 × 128 focal plane array with an all‐reflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond‐turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control–volume approach; and 2) a simplified finite‐difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.     

Pressure and Temperature Field Measurements of a Lightly Loaded Circumferential Groove Journal Bearing

The current study presents the experimental determination of the lubricant film pressure and temperature distributions on one land of a symmetrical two-land circumferential groove journal bearing (CGJB) operating under low-load steady-state conditions. Film pressure and temperature measurements are done both in axial and circumferential directions. Five axial planes, with three equally spaced pressure tappings per plane, construct the base pressure measurements grid. The pressure tappings circumferential location is shifted 20° from one plane to the neighboring plane. Similarly, the base temperature measurements grid consists of four axial planes, with three equally spaced thermocouples per plane. Hence, by rotating the bearing sequentially, with an angular step of 10°, it is possible to create fine measurement grids. This method of measurement is valid, because the circumferential groove journal bearing's operation is independent on the angle of loading. Two supply pressures were considered for the tests. The higher supply pressure leads to a smoother bearing operation. In the diverging zone, subatmospheric regions were measured. Superposing pressure and temperature fields reveals that the maximum temperatures are encountered in the sharp pressure drop region.