基于卷积神经网络X射线环焊缝缺陷检测

针对工业X射线焊缝图像对比度低、缺陷模糊且相对面积较小及难以识别的问题,设计了结合卷积神经网络的识别框架。根据缺陷图像特点,设计了对应的神经网络结构、卷积模板及池化模板的大小。在分析确定神经网络结构的基础上,卷积神经网络的灵敏度和训练算法也在文中一并给出。通过实例对神经网络结构进行了有效性的验证,缺陷检测准确率达97%,误报率仅为3%。同时,对适用于卷积神经网络进行识别的X射线焊缝图像进行了分析,发现灰度直方图有效信息跨度范围在50之上的卷积神经网络可以有效识别。文中所设计的神经络对X射线焊缝缺陷图像的识别可行、有效。创新点：(1)卷积神经网络结构设定为4级6层,卷积核大小尺寸为3×3,原始图像深度为1。经过第一次卷积操作后,有4个通道;经过3×3卷积核卷积后,有3个通道能够识别缺陷,则可以初步确认疑似缺陷区域。经过第二次卷积操作后,有16个通道;再次经过3×3卷积核卷积后,可以识别出缺陷图像。(2)通过对识别成功和识别失败图像灰度直方图进行分析,当灰度图跨度低于50时,图像检测目标与背景之间的对比度相对较低,卷积神经网络中卷积层难以提取目标特征,此时神经网络的识别失效,无法判定缺陷。当局部图像灰度直方图跨度高于50时,识别目标较背景突出,图像整体对比度较高,卷积层可以提取识别目标的特征,此时的卷积神经网络对焊缝图像有较好的识别效果。     

基于卷积记忆神经网络的数字表盘读数识别

针对巡检机器人在执行例检任务时,对数字表盘读数识别精确度低的问题,提出一种基于卷积记忆神经网络的数字表盘抄表算法。对高清摄像机获取的目标图像信息,经过图像轮廓提取算法定位到表盘字符区域,结合卷积神经网络(CNN)和长短期记忆网络(LSTM)模型的特点,提出了卷积记忆神经网络模型(CLSTM),与传统字符识别算法CNN和LSTM相比,此模型既不需要做字符分割,又能够优化特征提取。实验以电表进行测试,结果表明,相比于CNN和LSTM,此模型准确率更高。     

基于改进卷积神经网络的管焊缝X射线图像缺陷识别方法

针对卷积神经网络(CNN)应用于焊缝探伤图像识别时,目标区域占比小,局部信息冗余,激活函数小于零时出现硬饱和区导致模型对输入变化较敏感、网络参数难以训练的问题,采用超像素分割算法(SLIC)和改进的ELU激活函数构建CNN模型进行焊缝探伤图像缺陷识别. 首先,在CNN模型中使用ELU激活函数,在缓解梯度消失时对输入噪声产生更好的鲁棒性,同时,利用SLIC算法对图像像素进行像素块处理的特点,增大焊缝探伤图像中感兴趣区域的占比,降低局部冗余信息,提高模型在训练过程中的特征提取能力. 通过对焊缝探伤图像感兴趣区域提取并与所述CNN模型进行对比试验. 结果表明,该方法在焊缝探伤图像特征提取、训练耗时及识别准确率方面较传统卷积神经网络有更好的表现.     

基于3D卷积神经网络的装配动作识别

为了实现对工人装配动作的监测,提高装配质量和效率、降低成本,研究了基于深度学习的装配动作识别方法。采集9类常见装配动作的视频图像,建立了装配动作的数据集。并使用该数据集训练3D卷积神经网络模型,不断优化网络结构,构建了由6个3D卷积层、5个最大池化层、两个全连接层和一个输出层构成的3D神经网络模型。最后在装配动作数据集上进行了测试,结果表明构建的3D卷积神经网络模型可以很好的识别装配动作,识别准确率达到了88.5%。研究成果对大批量定制生产中装配动作的识别和装配质量监测具有一定的参考意义。     

基于深度学习优化SSD算法的硅片隐裂检测识别

针对传统的通过机器视觉和机器学习算法检测识别硅片隐裂所存在的精度低、识别率差、检测耗时长的问题,提出一种新的检测方法,即采用优化的单个深度神经网络来检测图像中的目标的方法 (Single Shot MultiBox Detector,SSD),对SSD的特征提取网络融合了密集连接卷积网络(Densely Connected Convolutional Networks,Dense Net),解决了原网络对低于0. 1 mm的裂痕提取困难的缺点。通过实验,优化后的SSD检测算法对低于0. 01 mm裂纹检测精度比传统的通过纹理滤波和SVM分类检测算法提高了22%,比没有优化的SSD算法检测准确率提高了6%。证明了本文作者所提方法的有效性。     

基于二元函数拟合的X射线焊缝图像缺陷分割方法

由于存在焊缝图像噪声强、不清晰、对比度低的问题,导致图像分割效果差,文中提出一种基于二元函数拟合的X射线焊缝图像缺陷分割方法。通过正弦变换函数对原始焊缝图像增强处理,使用B样条曲线拟合图像内的灰度曲线,计算高斯曲率与平均曲率得到焊缝表面图像边缘特征,通过二元函数得到不同类型的焊缝边缘数据,结合焊缝图像的表决图,完成对焊缝图像缺陷完美分割。试验结果表明,该方法分割精度高,且在缺陷类别识别和检测效果图上都要高于卷积神经网络算法、目标检测算法、多视觉成像算法的,证明所提方法分割效果好,有实际的应用价值。     

基于卷积神经网络的工件识别算法

针对传统工件识别算法特征提取困难、通用性差、工件的平移、旋转和光照变化对识别效果影响较大、识别准确率不高等问题,提出了一种基于卷积神经网络的工件识别算法。卷积神经网络由4层网络构成,包括2层卷积层和2层全连接层。实验任意选取了10种工件进行识别。在神经网络训练阶段对这10种工件共采集1万张图片,其中9000张图片作为训练集,剩下1000张图片作为验证集。训练时采用在卷积层加入批归一化层和在全连接层使用随机失活的方法,使网络能够得到更好的训练效果。当迭代次数达到10万次时基本得到理想的训练效果。测试时通过摄像机采集图像,对采集到的图像进行预处理,然后将预处理后的图像送入网络进行识别。在光源稳定室内环境下进行实验,实验结果表明基于卷积神经网络的工件识别平均所需时间为0.169s,平均识别准确率为98.3%,准确率高于传统基于特征提取和模板匹配的工件识别。     

基于Faster R-CNN算法的列车轴承表面缺陷检测研究

将深度学习Faster R-CNN应用于列车轴承图像的表面缺陷检测。建立人工数据库BSD,通过对图像增广弥补数据不足的缺陷;采用Faster R-CNN算法进行目标检测和识别,卷积神经网络采用ZF Net模型,对BSD数据集训练,得到检测结果;并与传统检测方法Canny算法的检测结果进行比较。试验结果表明:和传统Canny算法比较,基于Faster R-CNN算法的轴承缺陷的检测精度为93.03%、检测时间为0.29 s,相比传统Canny算法检测精度提升21.73%、检测时间减少2.21 s,同时准确率大幅度提高,能够实现轴承表面缺陷的精确检测和识别,满足铁路部门对轴承检修的需求。     

基于工件纹理和卷积神经网络的刀具磨损检测

文章在现有刀具磨损检测算法的研究基础上,针对铣削刀具磨损检测提出了一种基于卷积神经网络的刀具磨损检测算法。对原始的AlexNet卷积神经网络参数以及训练算法进行了优化,同时搭建了实验平台,进行了机床切削实验并采集了大量的工件纹理图片,使用这些图片样本对所改进的方法进行验证并与其他算法进行了对比研究。结果表明,改进后的AlexNet卷积神经网络算法能够更好地对刀具磨损程度进行判断。     

基于改进卷积神经网络轴承故障诊断

卷积神经网络(Convolution Neural Network,CNN)是一种常用的智能故障诊断方法.针对卷积神经网络结构中参数较多,训练时间长,并且sigmoid和ReLU激活函数运用带来梯度消失和均值偏移.基于以上问题提出了一种改进非线性映射函数的卷积神经网络模型.把振动信号转换成二维振动图像表示其故障纹理,在...     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。