Cu-W薄膜表面形貌各向异性与相结构

提出了一种基于离散小波变换和分形几何概念定量描述薄膜表面形貌各向异性的新方法，并据此研究了磁控溅射Cu—W薄膜表面结构特征随退火温度的演变．结果表明，薄膜表面聚合过程有两个不同阶段：孔洞处形核和颗粒生长；薄膜表面形貌分形维数可很好地描述表面粗化程度．研究发现，表面形貌各向异性变化趋势对相结构变化敏感．指出这种结合小波变换和分形几何概念表征薄膜表面形貌的方法，可以较灵敏地探测到Cu—W薄膜表面结构各向异性变化．     

切削刃数量对球墨铸铁铣削性能及表面形貌特征的影响

目的 提高球墨铸铁铣削表面质量和刀具寿命。方法 通过刀具轨迹计算和切削试验,研究球墨铸铁平面铣削过程中切削刃数量对切削性能、刀具磨损和表面形貌特征的影响,并用分形维数和表面粗糙度共同表征表面形貌。结果 刀具轨迹分析表明,由于铣削过程中,刀具切削方向和进给方向间的夹角不断变化,铣削表面不同位置和方向的表面形貌存在差异,进而导致表面粗糙度存在较明显的差异。通过铣削试验研究切削刃数量对铣削表面不同位置和方向的几何特征的影响规律发现,随着切削刃数量的成倍增加,切削力显著增加,同时刀具磨损量降低了36.5%,表面粗糙度值降低了39.2%,表面轮廓分形维数值增加了4.8%。结论 增加切削刃数量可以使每齿切削力和刀具磨损均显著减小,刀具寿命显著增加,同时表面粗糙度减小,分形维数增大,即切削刃数量的增加使表面质量更好,表面轮廓结构更复杂。     

电火花毛化表面形貌的分形机理与磨损性能

用分形几何理论表征电火花毛化表面微观形貌,通过常规的表面粗糙度指标,建立主要放电参数与毛化表面分形参数间的数学模型,利用分形参数研究电火花毛化加工参数对表面形貌的影响规律.在摩擦磨损分形预测模型的基础上,分析了表面形貌分形参数对磨损率的影响.确定主要的放电加工参数(脉冲峰值电流和脉冲宽度)所导致的加工表面形貌变化对最终...     

焊缝轮廓线激光检测系统开发及算法实现

目前焊缝表面检测主要依靠肉眼观察和简单测量实现,其科学性、精确性受到检验人员主观因素的影响。线激光扫描方法是工业应用中比较先进的非接触轮廓检测方法。通过线激光扫描,利用激光三角测量法可以得到物体轮廓,进而得到物体的形貌信息。基于上述技术,开发了一套焊缝轮廓线激光检测系统,系统由半导体线激光器、CMOS工业相机、LabVIEW虚拟仪器软件平台组成。基于LabVIEW编写了包括图像采集、图像处理与焊缝轮廓计算的系统,能够得到较为准确的焊缝表面轮廓信息。     

分度凸轮机构共轭接触域图象轮廓的分形表征及识别方法的研究

基于分形理论和计算机图象处理技术,研究分度凸轮机构共轭轮齿间的接触域图象的几何特征和分形表征方法,建立此类机构共轭轮齿上接触域图象轮廓识别的计算几何模型,用于分析和预测实际接触的共轭轮廓间磨损和接触应力分布状况,描述此类机构实际共轭接触域的复杂程度.同时可以分析和预测轮齿表面的摩擦磨损、接触应力、润滑条件等因素对机构运动精度的影响,以便合理地选择分度凸轮共轭曲面的形成方式.     

非下采样 Contourlet 变换在表面形貌评定中的应用

针对高斯滤波、小波滤波等方法在三维表面形貌分析中存在的不足,提出了一种基于非下采样Contourlet变换的三维表面形貌分析方法。该方法是先通过非下采样Contourlet分解变换,将三维表面形貌分解成不同尺度的子带;然后根据滤波截止波长,确定表面形貌不同成分所属的分解子带层数;最后通过非下采样Contourlet重构变换,重构表面形貌的不同成分。针对实际测量的三维表面形貌进行了分析,验证了该方法的有效性。     

回转体零件表面形状误差分析的小波变换方法

针对回转体零件实际加工形成的表面由多种频率成分构成的特点,为精确分解零件表面几何形状误差信号,在比较分析了传统数字滤波算法和小波算法的基础上,提出零件表面轮廓信号滤波的小波变换法。小波变换具有带通滤波的功能,它比传统的滤波方法更方便更有效。实验表明对实测信号进行小波变换滤波可以减少噪声信号的干扰,同时结合傅立叶变换可实现了表面形状误差、表面波度及表面粗糙度的综合提取,为三类误差的评定提供前题,满足了高精度测量的要求。     

钢管虚拟超声检测信号处理技术

针对表面粗糙的钢管进行超声波检测时存在的噪声高、信噪比低的问题,利用自行搭建的虚拟超声检测信号处理系统,对表面粗糙钢管的超声检测信号分别进行了基于传统傅里叶变换的频谱分析和FIR滤波以及基于小波变换的时频分析和小波去噪。通过对比试验发现,基于小波变换的信号处理技术可以对表面粗糙钢管的超声检测达到更好的去噪效果。     

基于小波变换的MAG快速成形焊缝截面建模

提出一种基于小波变换的焊缝截面形态建模方法。基于小波变换模极大原理提取了典型焊缝截面轮廓,分别采用三次样条、带约束的三次样条以及B样条曲线方法对提取的焊缝轮廓进行插值,并基于最小二乘法对插值后的焊缝边缘轮廓进行了数据拟合,得到了焊缝轮廓数学模型。结果表明,采用小波变换提取焊缝截面轮廓是可行的,带约束的三次样条曲线过渡平滑、无突变点,在该试验条件下得到的焊缝截面轮廓数学模型为正弦曲线。     

基于单片机测试系统对凿削磨损的动态测量和分析

介绍了单颗粒凿削磨损测试系统的原理、结构、测试方法以及在镁合金表面电弧喷涂锌铝合金的表面质量的检测中的应用.试验通过对试样划痕形貌尺寸数据的测量和对单片机力学信号的采集来进行计算,从而来绘制多条比能耗对应磨损体积的关系曲线,从对凿削磨损的开始到结束的整个磨损过程的动态分析,为磨损机理研究提供更多的细节,通过测试数据的处理,继而确定获得具有最佳耐磨性能的喷涂工艺参数.     

Analysis of 3D microtopography in machined KDP crystal surfaces based on fractal and wavelet methods

Potassium dihydrogen phosphate (KDP) crystal surfaces machined by precise milling and single point diamond turning (SPDT) methods are analyzed in this paper. The frequency information of 3D-machined KDP crystal surfaces are decomposed and analyzed by wavelet transform method, and 3D fractal properties of different KDP crystal surfaces are calculated and analyzed by fractal method. Through the integration of fractal and wavelet analysis, it can be found that the high-frequency information of machined surfaces is incorrelate with the machining process and it can reflect the anisotropic features of material structure. The anisotropy of the machined KDP surfaces is determined by the machining process. From analysis, the strong anisotropic surfaces are easier to form microscale waveness so as to impact the optical performance of KDP crystal components severely. The result of analysis reveals that the different machining method may produce unique feature in the machined surfaces and choosing reasonable machining method may improve the microtopographic structure of machined KDP crystal surface.     

Wavelet and fractal approach to surface roughness characterization after finish turning of different workpiece materials

In this paper, the surface profiles generated in longitudinal turning operations were characterized using continuous wavelet transform (CWT) and normalized fractal dimension D_n. In the comparative analysis, some characteristic roughness profiles after the turning of different workpiece materials, such as C45 medium carbon steel, nodular cast iron and hardened (55 HRC) high-strength alloy steel were selected. For wavelet characterization, both Morlet and ‘Mexican hat’ analyzing wavelets, which allow the assessment of extrema and frequency distribution, were utilized. The results of the CWT as a function of profile and momentary wavelet length are presented. It is concluded that CWT can be useful for the analysis of the roughness profiles generated by cutting processes. Moreover, the wavelet transform together with fractal dimension can be capable of the detection of local self-similarity in the surface profile.     

On the use of fractal methods for the tool flank wear characterization

Fractal theory is widely used to analyze the topography of machined surfaces, but the relationship between fractal dimensions and tool flank wear has hardly been reported. In this paper, the fractal dimensions of tool flank wear are described based on the surface roughness R_a rather than the conventional worn width VB to evaluate tool wear, thus providing better fractal identification in evaluating tool performance.     

Fractal characteristic analysis of electrochemical noise with wavelet transform

In the study, the fractal parameters were introduced to describe the irregular characteristic of electrochemical noise, which were calculated with wavelet transform to overcome some defects of other methods. Compared with other fractal parameters, wavelet standard deviation (STD) exponent (Hws) had smaller deviation and could describe the fractal characteristics of electrochemical noises in a wide range, therefore Hws was chosen to evaluate general and local irregularity of potential signals generated from 7075-T76 aluminum alloy in 3.5% NaCl solution without and with different inhibitors respectively. The results showed that the smaller general Hws value, the more frequently potential fluctuated on the electrode surface, and the less effect of inhibitor in the solution. The difference between general Hws and 1 reflected the condition of surface passivity. Local Hws could effectively extract the local feature of electrochemical noise and quantitatively describe the change of its fractal characteristic with time, which was a promising index to analyze electrochemical noise in practice.     

Investigation on abrasion-corrosion properties of WC-based composite with fractal theory

Morphology analysis of a worn surface is one of the significant methods to study wear mechanism. To surmount the weakness of conventional surface characterization system and investigate the abrasion-corrosion properties of WC-based matrix, the fractal geometry combined with three-dimension cloud point has been adopted in this study. Tests were conducted in various saline slurry with a modified abrasion test rig capable of monitoring the in-situ electrochemical behavior. The microstructures and compositions of the worn surface were characterized by scanning electron microscopy (SEM) and Raman spectrometer respectively. Results indicate that the increased sodium chloride in the slurry can enhance the variation of the worn surface morphology, leading to a higher value of fractal dimension (FD). Specifically, a raise from 2.444 to 2.515 can be witnessed with the saline gradually increasing to saturation. Furthermore, the corrosion products on the worn surface were identified as a mixture of oxides and hydroxychloride, and the multi-oxide films were much more common. Interpretation for the change of FD combined with abrasion-corrosion mechanism has also been detailed in this paper.     

ELECTROCHEMICAL NOISE ANALYSIS OF PURE ALUMINUM IN SODIUM CHLORIDE SOLUTION WITH WAVELET TRANSFORM TECHNIQUE

1．I口毗rodOCtlOOThe characterlzatlon and monltoringofcorroslon process usingelectrochemlcal noisetechnology has received considerable attention since 1968[1－41．One of*theion most imper－tant advantages offered by this electrochemlcal technique Is its l     

基于分块迭代函数系统的缸套表面织构的分形表征EI北大核心CSCD

表面织构的物理特征是影响活塞组件-缸套系统摩擦学特性和织构减摩效应的关键因素。为了准确有效地描述活塞组件-缸套系统减摩织构的物理特征,提出一种基于曲波变换和分块迭代函数系统(Partitioned iterated function system,PIFS)的减摩织构物理特征的定量表征方法。从活塞组件-缸套系统减摩织构表面的灰度图像出发,运用离散曲波变换方法对减摩织构表面的灰度图像在各个方向上进行多尺度分离。研究与减摩织构物理特征相关的灰度图像信息的分块迭代函数系统分形描述方法,通过计算减摩织构物理特征的分形维数,并与差分盒维数(differential box-counting,DBC)方法计算得到的分形维数进行对比,验证PIFS方法的有效性。结果表明,与差分盒维数方法计算得到的分形维数相比,针对不同网纹织构和不同形状组合、截面尺寸以及深度的凹坑织构,PIFS方法计算得到的分形维数能够更为敏感和有效地反映减摩织构物理特征的变化。