基于KPCA的板坯表面缺陷识别方法

引入核方法分析研究了现有的板坯表面缺陷识别方法,提出了一种新的核函数,并将其应用到板坯表面缺陷特征提取中,用传统的支持向量机对图像进行分类,试验结果表明,新核函数提取的特征识别效果最好,识别率达到了91.55%。     

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引入核方法分析研究了现有的板坯表面缺陷识别方法,提出了一种新的核函数,并将其应用到板坯表面缺陷特征提取中,用传统的支持向量机对图像进行分类,试验结果表明,新核函数提取的特征识别效果最好,识别率达到了91.55%。     

基于特征融合与HPO-RVM的滚动轴承剩余寿命预测

为准确预测轴承的剩余使用寿命,提出基于特征融合与猎食者-猎物优化(HPO)算法优化相关向量机的轴承剩余寿命预测方法。提取时域、频域和时频域特征准确描述轴承的退化状态,利用综合评价指标对提取的特征进行筛选得到敏感特征集;采用核熵成分分析对敏感特征进行自适应融合,得到轴承的退化特征;构建混合核函数作为相关向量机的核函数以提高模型预测性能;最后,利用HPO算法得到混合核函数的参数,将寻优得到的参数用于寿命预测模型的训练。通过对轴承加速退化数据集进行实验,结果表明：所构建的寿命预测模型优于BP、ELM、SVM等模型,构造的混合核函数模型优于高斯核函数模型,采用的优化算法优于粒子群、遗传算法等。     

基于支持向量机的焊缝超声TOFD缺陷分类识别

为了实现对大型厚壁压力容器焊缝缺陷的准确识别,提高缺陷评定的准确性和检测效率,在基于标记的改进分水岭TOFD检测图像分割的基础上,结合典型缺陷图像的纹理特征,从图像空间域和频域特征,分别利用局部相位量化和局部二值模式获取缺陷区域的局部邻域特征参数,将二者特征参数进行归一化融合,再将融合特征向量用支持向量机进行分类识别。试验结果表明,检测图像4×4分块后提取的熔合特征识别率最优,分类识别正确率达到87.10%。     

基于卷积神经网络的CO_2焊接熔池图像状态识别方法

为了通过熔池图像对焊接状态进行判断,将卷积神经网络引入到CO_2焊接熔池图像状态识别中,提出了一种CO_2焊接熔池状态识别卷积神经网络CNN-M。该网络使用简单预处理的熔池图像作为输入向量,避免了人工提取图像特征的主观性对识别率的不良影响。同时,CNN-M采用了ReLU激活函数、随机Dropout及SVM分类器来降低样本集稀少可能导致的网络过拟合现象。试验结果表明,和人工提取熔池特征状态作为输入向量的BP神经网络相比,CNN-M在识别率及识别速度方面均体现出了更好的性能,其良好的泛化能力能够满足在线熔池状态监控的要求。     

基于改进的ORB算法的工件图像识别方法

针对传统的工件图像识别算法运行速度慢、匹配精度差等问题，提出一种改进的ORB（Oriented FAST and Rotated BRIEF）算法解决工件图像的实时与准确识别问题。该算法的流程是首先利用ORB算法提取工件图像的角点特征，随后为其添加SURF（Speed-Up Robust Features）描述符进行方向分配，得到具有旋转尺度不变性的图像角点，结合快速近似最近邻搜索算法进行特征点的匹配，实现工件图像的识别。实验结果表明：在图像存在旋转尺度变化的情况下，使用改进的ORB算法相比传统的ORB、SIFT（Scale Invariant Feature Transform）和SURF算法以及SIFT+SURF、SURF+FREAK组合算法在工件图像角点提取与目标匹配方面速度更快，识别精度更高，提高了工业机器人在搬运工件过程中对工件图像的识别效率和准确性     

区域生长算法的改进及其在异物检测中的应用

提出一种基于区域生长的图像分割算法,并达到异物识别的目的。该算法根据不同X射线图像直方图的特征,自动选取出所需要的种子点,并且通过对已进行过区域生长的部分进行概率统计,得出合适的阈值,进行种子区域生长。相对于一般的根据每幅图像手动选取种子点以及闽值的种子区域生长法（SRG）,该算法能够快速有效地进行图像分割,异物识别率高。     

电阻点焊接头熔核面积的预测

以电阻点焊接头表面的数字图像作为信息源,探索了一种新的点焊接头质量无损检测方法。首先通过图像特征分析,将焊点表面图像划分为三个特征区域,提取三个同心圆的面积作为表征接头熔核面积的特征参量。其次,以提取的特征值作为输入向量,以接头横截面处的熔核面积作为评判标准,建立点焊接头熔核面积的SVM(支持向量机)等级分类模型。实验结果表明,该模型可以有效地对熔核面积进行预测分类,实现了对电阻点焊接头质量的无损评判,经验证其准确率可达96.667%。     

多核的LSSVM的轴承故障诊断算法研究

针对滚动轴承故障诊断中出现的多故障类型识别与诊断问题,在LSSVM和多核学习的基础上,提出了多核的LSSVM的轴承故障诊断算法。多核的LSSVM实现的关键是如何确定多核函数的每个基本核函数的权系数,采用核度量标准——核极化来解决此难题。首先,选择基本核函数及其核参数值;然后,用核极化求解基本核函数的权系数,组合多核函数;最后,创建多核的LSSVM算法模型,进行轴承故障诊断。美国西储大学的滚动轴承的实验结果表明,与5-fold SVM和LSSVM相比,多核的LSSVM算法具有更优的故障识别率,验证了所提算法的有效性。     

图像降维下的埋弧焊缺陷自动识别算法及框架

针对埋弧焊管焊缝的缺陷,应用X射线成像并检测,设计了自动化的缺陷识别框架与算法。首先对焊缝图像进行预处理,在中值滤波去除噪声后,选取sin函数变换为图像增强的工具,使得对象对比度得到了很大提升。然后采用OSTU算法进行ROI(Region of Interest)区域的提取,获得焊缝区域并且定位缺陷部位,如此实现焊缝缺陷自动化的获取。对建立的数据库里应用PCA进行像素矩阵降维,不仅去除噪声,减小数据量,同时还提取出像素矩阵的参数特征。对提取的焊缝缺陷进行识别,选取三种模式识别的方法进行比对,试验结果显示SVM的效果最好,两种缺陷正确识别率都达到了90%,而神经网络的方法则在80%左右。     

Effect of electrochemically reactive rust layers on the corrosion of steel in a Ca(OH)2 solution

Electrochemical and gravimetric measurements are used to study the effect of rust layers on the corrosion of rusted steel in a saturated Ca(OH)₂ solution imitating the liquid phase in concrete pores. The results indicate that the reduction of rust is the main cathodic reaction in the first phase of the corrosion process of rusted steel. Subsequently the oxygen reduction reaction becomes the cathodic predominant reaction, in which the rust seems to act as a porous electrode. In this research rust clearly favours the corrosion of rusted steel, and an approximately direct correlation is seen between the rust mass and the mass loss due to steel corrosion. In the electrochemical measurements, attention is paid to the overestimation of the corrosion rate deduced from the polarisation resistance in the case of specimens with the highest rust contents, a problem that is attributed to the inappropriateness of the conventional measuring procedure in the presence of high capacitance values and redox processes.     

A future application of pulse plating – silver recovery from hydrometallurgical bottom ash leachant

In the current study, electrodeposition-redox replacement was applied to a hydrometallurgical solution with the main elements of Ca (13.8?g L^?1), Al (4.7?g L^?1), Cu (2.5?g L^?1), Zn (1.2?g L^?1), Fe (1.2?g L^?1), S (1?g L^?1), Mg (0.8?g L^?1), P (0.5?g L^?1) and Ag (3.5?ppm). The solution originated from the leaching experiment of incinerator plant bottom ash, which was dissolved into 2 M HCl media at T?=?30?°C. The resulting deposit on the electrode surface was analysed with SEM-EDS and the observed Ag/(Cu?+?Zn) ratio (0.3) indicated remarkable enrichment of silver on the surface, when compared to the ratio of these elements (Ag/(Cu?+?Zn)) in the solution (6.8?×?10^?5). The enrichment of Ag vs. (Cu?+?Zn) could be demonstrated to increase ca. 4500 fold compared to the ratio of the elements in solution.     

Effect of additives on the properties of plasma electrolytic oxidation coatings formed on AM50 magnesium alloy in electrolytes containing K2ZrF6

A plasma electrolytic oxidation (PEO) coating on AM50 magnesium alloy was obtained in a K₂ZrF₆–NH₄H₂PO₄–KF–C₆H₅O₇Na₃ electrolyte solution. The influence of the electrolytes on the properties of the PEO coating had been investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), roughness determination and electrochemical measurements. The experimental results show that 10 g L^? 1 K₂ZrF₆ and the presence of 8 g L^? 1 NH₄H₂PO₄ are beneficial for the passivation effect of the solution on AM50 Mg alloy as well as the compactness of the PEO coating. Many pores with large dimension on the surface of the coating are filled with coating compounds (mainly MgF₂), and the characteristics of these pores are influenced by the concentration of KF. The addition of KF and C₆H₅O₇Na₃ enhances the growth rate of the coating. The coating shows high corrosion resistance in the presence of 10 g L^? 1 K₂ZrF₆ combined with 8 g L^? 1 NH₄H₂PO₄, 3 g L^? 1 KF and 5 g L^? 1 C₆H₅O₇Na₃.     

Mangrove (Rhizophora apiculata) tannins: an eco-friendly rust converter

Abstract

Rust converters are chemical formulations that can be applied to corroded surfaces to convert residual rust on iron/steel surfaces into harmless and adherent chemical compounds. The known hazardous effects of most synthetic rust converters have led to a search for safer, more environmentally friendly natural products. Tannins, a class of natural, non-toxic and biodegradable polyphenolic compounds, extracted from plant sources have been proposed as an alternative. The transformation of rust in the presence of 5 g L^?1 tannins extracted from mangrove (Rhizophora apiculata) barks was studied. Three different methods of pre-rusted sample preparations were tested. The rust composition of the steel was dependent of sample preparation. The pre-rusted samples prepared formed predominantly lepidocrocite and magnetite. Transformation of rust components to ferric-tannates, particularly lepidocrocite, in the presence of mangrove tannins that could be observed via Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy analysis indicated their potential as rust converters.     

Multilayer planar rectangular coils for eddy current testing: Design considerations

Planar rectangular coils provide some interesting features different from those of pancake coils, such as good performance in conductivity measurement at high frequencies, high sensitivity to scratches and other shallow imperfections and the possibility of inspecting complex surfaces. The impedance of these coils has been modeled by different authors. A brief discussion of some analytical approaches in the literature is presented and calculations using the second-order vector potential approximation are introduced, aimed at the study of the influence of coil shape and size on the sensitivity to electrical conductivity of the substrate. Three cases were modeled, (A) coil in free space—inductance L₀ as a function of number of turns (n) and width of the spiral conductive lanes (c) for different coil inner shape factor (rr_i); (B) coil on a conductive substrate (Zircaloy-4)—impedance change, ΔZ, as a function of f·σ, the product of the test frequency (f) and the substrate electrical conductivity (σ) for different rr_i and (C) coil sensitivity to small changes in σ(Δσ).L₀=L₀(c, n) increased as expected with n and/or coil area and decreased with shape factor. Normalized ΔZ depends strongly on inner rr_i, the curves (or surfaces) for smaller values of rr_i enclosing those for larger values. Another shape factor, the outer shape factor (rr_o), was introduced. Strong dependence of the sensitivity to Δσ on n was observed, as well as the existence of an optimal theoretical frequency. Because the sensitivity to surface conditions also increases with coil size, it could be established that for conductivity assessment it is better to use coils with the smallest n and c, compatible with the particular application, and that the resolving power for this type of measurements is not greatly affected by the shape factor.     

On the corrosion behaviour of novel high carbon rail steels in simulated cyclic wet-dry salt fog conditions

Eutectoid rail steels are prone to excessive corrosion in the coastal locations in India. In order to minimise this problem, four new rail steels with microalloying elements, Cu, Cr, Ni and Si were designed. The corrosion behaviour of these four rail steels were compared with the behaviour of three rail steels already in commercial application. Quantitative evaluation done by weight loss measurements after simulated wet-dry salt fog exposure test showed similar weight loss values for all rail steels. The FTIR spectra of rust samples revealed the presence of Fe_3−xO₄ as the major phase in both inner and outer layers of rusts on all the rail steels. Relative amounts of the different rust phases have been compared. SEM micrographs of the rusted samples revealed that the rust on Cr-Cu-Ni and Cr-Cu-Ni-Si rail steel was more compact than other rail steels. Impedance spectroscopy showed that the rust formed on Cr-Cu-Ni and Cr-Cu-Ni-Si rail steels resulted in the higher impedance in the high frequency region, compared to other rail steels.     

Enhancement the Adhesion between Epoxy Coating and Rusted Structural Steel by Tannic Acid Treatment

An eco-friendly rust converter treatment based on tannic acid was optimized by orthogonal experiment, and the adhesion of the epoxy top-coating system was evaluated. The results showed that the adhesion between the epoxy coating and the rusted steel after treatment was enhanced from 1.93 to 5.97 MPa. This adhesion improvement was attributed to the formation of the micro-cracked tannic conversion layer and the increase of the compactness of the rust layer. The failure analysis suggested that the remainder rust was still the key issue for the further adhesion improvement of the coating system.     

Effect of rust converting treatments on corrosion rate and sulphate nest development in prerusted steel

Abstract

Three types of anticorrosive treatment were applied to carbon steel specimens prerusted in a condensation chamber in the presence of sulphur dioxide. These were: impregnation with prehydrolysed methyltriethoxysilane in ethyl alcohol; impregnation with the same solution containing suspended zinc stearate; and coating with an inorganic zinc phosphate primer. The specimens were then corroded for 135 days in clean air at 4°C and 100% relative humidity. The extent of corrosion was estimated from mass loss on descaling; three layers in the rust were separated and characterised by scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. The roughness of the descaled surface was also estimated. The results show that each of the treatments approximately halved the rate of corrosion of already rusted steel, not simply by forming a barrier, but by modifying the distribution of sulphate in the rust.     

Tribological Behavior of Plasma-Sprayed Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-20 wt.%TiO<Subscript>2</Subscript> Coating

Al₂O₃-20 wt.% TiO₂ ceramic coatings were deposited on the surface of Grade D steel by plasma spraying of commercially available powders. The phases and the microstructures of the coatings were investigated by x-ray diffraction and scanning electron microscopy, respectively. The Al₂O₃-20 wt.% TiO₂ composite coating exhibited a typical inter-lamellar structure consisting of the γ-Al₂O₃ and the Al₂TiO₅ phases. The dry sliding wear behavior of the coating was examined at 20 °C using a ball-on-disk wear tester. The plasma-sprayed coating showed a low wear rate (~4.5 × 10^?6 mm³ N^?1 m^?1), which was <2% of that of the matrix (~283.3 × 10^?6 mm³ N^?1 m^?1), under a load of 15 N. In addition, the tribological behavior of the plasma-sprayed coating was analyzed by examining the microstructure after the wear tests. It was found that delamination of the Al₂TiO₅ phase was the main cause of the wear during the sliding wear tests. A suitable model was used to simulate the wear mechanism of the coating.     

低碳钢在模拟酸雨大气条件下的锈蚀演化

利用干湿循环加速腐蚀实验和电化学极化曲线法研究了低碳钢在模拟工业酸雨大气条件下的锈蚀演化过程.结果表明:实验初期锈蚀速度随干湿循环次数的增加而增大,随后转为随干湿循环次数的增加而降低;带锈低碳钢的干湿循环下的腐蚀产物促进阴极过程抑制阳极过程;在干湿循环加速腐蚀进程中低碳钢表面铁锈的化学组成、结构变化表现为在锈蚀初期α-FeOOH含量较低,锈层疏松,锈蚀速度随干湿循环次数增加呈上升趋势;后期随α-FeOOH含量的增加和锈层变得更加致密,腐蚀速度转变为随干湿循环次数增加而下降.