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用中心频率为15MHz的超声水浸聚焦法对45钢试样进行检测,对检测波形用不同的闸门宽度及闸门截取位置采样后进行FFT及IFFT,发现了不同闸门位置及闸门宽度对FFT及IFFT分析结果的影响规律。 相似文献
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针对滚动轴承故障信号强噪声背景和非线性等特点,为精确识别滚动轴承的故障特征频率并精准分类,提出了一种基于Hanning窗插值快速傅里叶变换并利用布谷鸟算法优化支持向量机的滚动轴承故障诊断新方法。采用Hanning窗对得到的频域信号进行加窗处理并求得样本特征的均方根特征值;经过布谷鸟算法优化后的支持向量机(CS-SVM)对样本数据进行故障诊断分类。通过凯斯西储大学的轴承故障振动信号数据进行的实验,验证了该混合智能诊断方法的有效性和优势,结果表明:所提出的方法可以对轴承故障准确进行分类。 相似文献
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针对非线性、强背景噪声下滚动轴承振动信号早期故障特征微弱,难以识别的问题,提出一种改进经验小波变换(EWT)降噪和快速谱相关相结合的滚动轴承早期微弱故障诊断方法。针对EWT频带划分方式受噪声影响较大,存在划分不合理的问题,提出极大值包络处理的划分方式;采用改进的EWT进行自适应信号分解,获得不同的固有模态分量,采用峭度准则筛选出有用模态分量,并进行重构得到降噪后的信号;为增强早期故障信号中的故障冲击周期成分,对降噪后的信号采用快速谱相关(Fast-SC)进行分析,获得平方增强包络谱;对平方包络谱中幅值突出的成分与故障频率进行对比分析,实现早期故障诊断。结果表明:与快速谱分析、改进EWT降噪结合快速谱峭度图相比,所提方法能有效增强早期故障特征频率,实现早期故障的准确诊断。 相似文献
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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。 相似文献
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Y. L. Cheng Z. Zhang F. H. Cao J. F. Li J. Q. Zhang J. M. Wang C. N. Cao 《工业材料与腐蚀》2003,54(8):601-608
Properties of the potential electrochemical noises (EN) generated during the corrosion process of aluminum alloys AA2024(T3), AA7075 (aged at 121°C/35 h + 160°C/20 h) and pure aluminum in 3wt% (mass fraction) NaCl solution were investigated in this study. During the initial stage of immersion, the EN amplitude of AA2024 is the largest while the EN amplitude of pure aluminum is negligible. The amplitude of the EN generated by these materials decreases with immersion time except the EN of AA2024 after extremely long immersion time (38 days in this study). Surface morphology corresponding to different stages of immersion and different types of EN were studied by scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) analysis. The result shows that the micro‐galvanic cells formed by the constituent particles and the alloy matrix play an important role on the corrosion process of the aluminum alloys and the EN behaviors of AA2024, AA7075 and pure aluminum is proved to be strongly related to the type and intensity of corrosion process. 相似文献
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7A60铝合金点蚀行为的电化学噪声和电化学阻抗谱表征 总被引:2,自引:0,他引:2
采用电化学阻抗谱(EIS)和电化学噪声(EN)方法研究回归再时效(RRA)热处理状态下7A60铝合金的点蚀行为,通过扫描电子显微镜(SEM)和能谱仪(EDS)观察和分析合金的组织和第二相颗粒成分。结果表明,7A60铝合金在3.5%Na Cl溶液中存在两个腐蚀阶段,并且可以用EIS出现两个电容时间常数的时间和由EN计算出的小波分形维数D的变化来表征。SEM和EDS分析结果表明,在7A60铝合金中,严重的点蚀主要是由阳极相Mg Zn2引起的,其次是Al2MgC u和Mg2Si相,Al7Cu2Fe相对7A60铝合金点蚀行为的影响不大。 相似文献
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研究纯镁在1.0%NaCl中性溶液中的腐蚀行为及其相应的电化学阻抗谱(EIS)和极化曲线,探讨不同时间段EIS的分形维数。结果表明,腐蚀过程及相应的EIS发展可分为3个阶段。初始阶段,EIS由2个重叠的容抗弧组成,相应的极化电阻及电荷转移电阻随着时间的延长而快速增加,而腐蚀速率则降低。而后,EIS图谱上出现2个容易辨认的容抗弧,电荷转移电阻及腐蚀速率基本保持稳定。长时间浸泡后,EIS图谱中低频部分出现感抗成分,电荷转移电阻降低,而腐蚀速率增加。EIS分形维数与材料表面形貌直接相关,将是分析腐蚀形貌极有用的工具。 相似文献
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Jin-Ju Park 《Corrosion Science》2003,45(5):995-1010
Pit formation and growth of alloy 600 has been investigated in aqueous 0.1 M Na2S2O3+0.1 M NaCl solution at elevated solution temperatures 298-573 K and at pressures 0.1-8 MPa in terms of fractal geometry using potentiodynamic polarisation experiment, potentiostatic current transient technique, scanning electron microscopy (SEM), image analysis method and ac-impedance spectroscopy. From SEM observation, it was realised that pit morphology changed from cylindrical shape developed at 60 °C to highly branched shape formed at 150 °C. Furthermore, corrosion pits formed and further grew without any morphological change during the whole pitting process below 200 °C. On the other hand, above 200 °C, the morphology of the pits changed from highly branched shape in the early stage of the pitting process to widely grooved shape in the later stage. After SEM observation of the pits, the fractal dimension of pits was determined as a function of solution temperature 60-150 °C using perimeter-area method. The value of the fractal dimension of the pits increased with increasing solution temperature. This is caused by the increase in the ratio of perimeter to area at higher solution temperature, indicating the formation of pits with highly branched shape. The appearance of specific shape and fractal dimension value of the pits at each solution temperature implies that the formation and growth of pits proceed with the typical fractal geometry throughout the whole pitting process irrespective of pit size. In addition, constant phase element (CPE) behaviour observed from the impedance spectra is discussed in terms of the fractal dimension of pits. 相似文献
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采用电化学方法研究N,N′-双(2-亚甲基吡啶)-1,2-亚氨基乙烷(BPIE)Schiff碱在0.010 mol/L HCl溶液中对AZ91D镁合金的腐蚀抑制作用。动电位极化曲线表明,BPIE Schiff碱是一种混合型缓蚀剂。电化学阻抗谱(EIS)测量证实了BPIE的腐蚀抑制作用。随着缓蚀剂浓度的增加,由于有更多的缓蚀剂吸附在AZ91D镁合金表面,电荷转移阻力减小,双电层电容减小。电化学噪声(EN)分析获得的数据在时间和频率域与EIS和极化曲线所得结果表现出良好的一致性。采用扫描电子显微镜(SEM)、X射线衍射(XRD)和能量色散X射线(EDX),研究BPIE的缓蚀作用。SEM照片显示,在存在BPIE的情况下,AZ91D合金表面的腐蚀损伤得到减轻。XRD分析显示,在存在BPIE的情况下,对应于富镁α相的谱峰强度增大,表明合金样品的腐蚀程度低。EDX分析也证实了BPIE的缓蚀作用。此Schiff碱化合物通过物理吸附在合金表面,吸附行为遵循Langmuir等温吸附模型。 相似文献
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采用扫描电子显微镜,X射线能谱,Tafel极化曲线和电化学阻抗谱法研究了铈镧转化膜对AZ63镁合金耐蚀性能的影响。结果表明,铈和镧的复合转化膜比单一稀土膜的表面更加均匀致密,对镁合金的耐蚀性有明显改善。双稀土转化膜的缓蚀效果随着浸泡成膜时间的增长而增加。延长时效时间有助于铈和镧的进一步氧化,耐蚀性能先增后减,时效48 h膜层的耐蚀效果最好。 相似文献
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Dense alumina ceramic coatings of 7 μm thickness were fabricated on 2024 aluminium alloy by microarc oxidation (MAO). The corrosion behaviour of the MAO coated alloys was evaluated using potentiodynamic polarisation and EIS measurements. The results show that the corrosion process of the coated alloy can be divided into three stages: (1) the initial stage (the first 2-6 h of immersion): penetration of corrosion medium into the aluminium alloy was inhibited by coating; (2) the second stage (after 24 h of immersion), corrosion medium penetrated to attack the interface between the substrate and the coating; (3) the final stage (after about 96 h): corrosion process was controlled by the diffusion of corrosion products. 相似文献
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CORROSION MONITORING OF LY12 IN SODIUM CHLORIDE SOLUTION WITH ELECTROCHEMICAL NOISE TECHNIQUE 总被引:2,自引:0,他引:2
1. IntroductionThe study of spontaneous current or potential fluctuations, which has been designatedas electrochemical noise (EN), for the characterization of corrosion processes has receivedconsiderable attention since 196811--4]. The study of such fluctuations for the characterization of a corroding interface hajs an importal advantage over all the other electrochemicaltechniques since it is completely non-perturbative[4--7]. So far, the study of corrosion potential fluctuations was applied… 相似文献
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AZ91D镁合金在NaCl溶液中腐蚀过程的电化学噪声分析 总被引:1,自引:0,他引:1
通过电化学噪声技术(EN)、小波变换(WT)、噪声电阻(Rn)和功率谱密度(PSD)等方法研究了AZ91D镁合金在碱性含氯溶液中的腐蚀行为.结果表明,AZ91D镁合金在碱性含氯溶液中的腐蚀过程可以分为三个不同的腐蚀阶段:伴随氢气泡产生、吸附和脱附的阳极溶解阶段,点蚀发展阶段和最后形成MgH2保护膜的腐蚀抑制阶段. 相似文献
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Fakiha El-Taib Heakal Madiha A. Shoeib Maanoum A. Maanoum 《Protection of Metals and Physical Chemistry of Surfaces》2017,53(1):177-187
Magnesium alloys are materials difficult to plate due to their high reactivity. The surface passive layer formed in air or water must be first removed prior the plating process. Generally, it was shown that electroless Ni–P coatings on AZ91D alloy are directly related to its surface pretreatment parameters and the various plating conditions. Micro-image morphology and chemical composition of the different coats were characterized by SEM, EDX, XRF and XRD techniques. Electrochemical polarization, porosity and adhesion tests were also performed to study the corrosion resistance of the samples. The plating step was accomplished either after a zincating treatment or directly after the fluoride activation treatment using basic nickel plating bath. Successful direct EN coatings obtained are good corrosion barriers for AZ91D alloy in aggressive environments. 相似文献