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研究了快速傅立叶变换、不变矩的原理及特点,并应用于热轧中厚板表面缺陷图像特征提取。从现场在线采集热轧中厚板的表面缺陷图像,将每幅图像划分成64×64(像素)大小的子图像。对子图像进行快速傅立叶变换,得到子图像的幅值谱,再对幅值谱求七个不变矩,然后把求得的七个不变矩作为特征向量输入BP神经网络分类器进行识别。实验表明该方法具有较好的特征提取能力,能够很好的识别热轧中厚板表面缺陷。 相似文献
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为借助Greenwood-Williamson(GW)接触模型开展粗糙表面接触分析,基于微凸体识别的参数定义法和基于随机过程理论的谱矩法都被广泛用于微凸体分布参数计算。为厘清应用不同计算方法产生的接触求解差异,针对粗糙曲面接触,利用快速傅里叶变换重构获得不同统计分布下的粗糙表面随机样本,由三点定义法和谱矩法分别计算仿真样本的微凸体峰点分布参数,对样本开展GW接触分析,得到两种计算方法下接触预测结果,对结果进行了对比讨论,分析了样本表面统计分布参数、高通滤波常数、曲率半径和载荷的影响。最后,通过试验数据对谱矩法的计算偏差进行了检验,对微凸体分布参数计算给出了建议。 相似文献
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根据旋转机械循环平稳特征,介绍循环频率估计的二阶循环矩估计方法,通过对调幅模型的仿真分析,进一步提出了倒二阶循环矩幅值谱和倒二阶循环矩平方谱故障诊断方法,并对其在齿轮调制类故障诊断中的有效性进行了仿真及实例分析。 相似文献
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针对因轮毂轴承摩擦所带来的能耗问题,分析了轮毂轴承摩擦的影响因素,研究了滚道预载荷、密封过盈量、密封润滑脂、密封接触表面粗糙度等因子对摩擦力矩的影响。通过对轮毂轴承寿命校核载荷谱与耐久性试验载荷谱的分析,给出了较为科学的摩擦试验方法;基于此试验方法,开展了滚道预载荷、密封过盈量、密封润滑脂、密封接触表面粗糙度等因子的摩擦试验。研究结果表明:外密封唇口过盈量对摩擦力矩的影响不显著,但在密封处采用更低粘度润滑脂,使得摩擦力矩下降了14%;同时,控制密封接触面粗糙度在Ra 0.4以下时,对降低摩擦力矩也有较好的效果;该结果对于低摩擦轮毂轴承的开发具有一定的指导意义。 相似文献
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表面特性对灵敏轴承摩擦力矩的影响分析 总被引:2,自引:2,他引:0
影响轴承摩擦力矩的因素很多,其中轴承工作表面特性对摩擦力矩的影响最为显著。分析了表面粗糙度、可润湿性、表面硬度、沟道圆度和表面缺陷等因素对轴承摩擦力矩的影响。附图2幅,参考文献3篇。 相似文献
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针对某导弹支撑座在环境激励下易引发连接螺栓松动这一具体问题,在支撑座模型结构的宽带随机振动实验的基础上,探讨了实验中的问题,根据支撑座连接螺栓在不同预紧力情况下的结构稳态响应信号,分析了信号功率谱特征的差异,提出了相应的谱矩松动故障特征的提取方法。分析结果表明,谱矩因子的降低作为该结构连接螺栓松动的诊断特征是可行的。 相似文献
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带座外球面球轴承调心力矩的计算分析 总被引:1,自引:0,他引:1
对带座外球面球轴承中轴承与轴承座之间的接触表面进行了受力分析,推导出了轴承座和外圈间的表面接触应力,进而给出了调心力矩的计算式,并结合配合表面的表面粗糙度值对调心力矩计算式进行了修正,最后给出了UC200系列带座外球面球轴承不同座孔偏差下调心力矩的实例计算。 相似文献
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The peak identification scheme based method(three-point definition) and the spectral moments based method(spectral moment approach) are both widely used for asperity peak modeling in tribology. To discover the differences between the two methods, a great number of rough surface profile samples with various statistical distributions are first randomly generated using FFT. Then the distribution parameters of asperity peaks are calculated for the generated samples with both methods. The obtained results are compared and verified by experiment. The variation rules of the differences between the two methods with statistical characteristics of rough surfaces are investigated. To explain for the discovered differences, the assumptions by spectral moment approach that the joint distribution of surface height, slope and curvature is normal and that the height distribution of asperities is Gaussian, are examined. The results show that it is unreasonable to assume a joint normal distribution without inspecting the correlation pattern of [z], [z′] and [z′′], and that the height distribution of asperities is not exactly Gaussian before correlation length of rough surface increases to a certain extent, 20 for instance. 相似文献
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基于频谱合成的自然地形生成方法 总被引:2,自引:0,他引:2
逼真模拟自然场景中的地形 ,是计算机图形学研究的一个重要课题。近年来 ,利用分形技术生成视觉效果良好的地形成为研究的热点。但是 ,目前存在的分形方法 ,生成的分形地形均是各向同性的。而真实自然地形往往是各向异性的。为此 ,本文基于频谱合成法 ,提出并实现了一种生成各向异性分形地形的新方法 ,该方法通过指定分形曲面谱密度来实现分形的各向异性。最后 ,利用统计方法计算出分形曲面在不同方向上的分形维数 ,实验结果表明 ,曲面是各向异性的 ,算法是正确且有效的 相似文献
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A new method for the evalution of the quality of electropolished suraces is presented. A theoretical analysis was carried out and the results were confirmed by experiment. The relevance of the slope of the surface profile to the evaluation of surface quality was determined. Electropolishing processes affect to a much greater extent the reduction of the standard deviation of the slope than the reduction of the standard deviation ordinates. 相似文献
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The real area of contact between a rough and an ideally flat surface is evaluated from the spectral moments of the profile of the rough surface. A stochastic criterion for plastic deformation of the asperities is developed and applied to determine the percentage of plastic and elastic deformation in the total area of contact at a given separation. An illustration is given to delineate the theory through experimental profile data obtained from a ground surface. 相似文献
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为了提高接触表面的建模精度,利用小波的多尺度分析能力,对表面轮廓进行多尺度小波分解,提出了计算机械加工表面轮廓分形维数的对数小波谱法以及有效分解尺度概念,并认为轮廓只在有效分解尺度上具有分形特征;通过M-B函数模拟生成不同分形维数、不同采样区间的分形轮廓;应用对数小波谱法计算了模拟轮廓的分形维数,进而与功率谱密度法(PSD法)等5种方法的计算结果进行了分析比较,结果表明:对数小波谱法能很好地处理分形的多尺度特征,并且选用sym4小波时计算精度最高,误差在0.15%以内;最后应用对数小波谱法对一实际机械加工表面轮廓分形维数进行了计算,说明了其实用性。 相似文献
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The purpose of this paper is to analyze the turning machinability of a martensitic steel, according to the cutting speed, and through signal analyses of the morphology of the machined surface. We initially carried out the classification of a large number of parameters of roughness, on the basis of their relevance with regard to cutting speed. The originality of the proposed method lies in the combination of the classical technique of analysis of variance with the statistical technique of resampling of data, called Bootstrap. Another characteristic of the study consists in the addition to the traditional categories of roughness parameters (Amplitude, Frequency, Morphological and Hybrid parameters) to analyze multiscale aspect of surface topography through fractal analysis. According to the analysis carried out, the fractal dimension and the slope of the signal (dz/dx) of the topographical signal of the studied surface appear much more relevant than all the other Euclidian parameters. The fractal dimension and the slope of profile allow us to estimate a critical transition speed between the cutting states by generalized strain hardening and those by localized strain hardening. This parameter is also more relevant than the others, because it allows a good analysis of the influence of cutting speed, within each of the two machining modes. The obtained result is relevant because it provides a practical and inexpensive method for the quality control of the machined surface, to manufacturers and engineering companies, without removing some mechanical part, but only through a direct analysis of the slopes of the profile, with, in particular, the help of a portable instrument. We establish later that the transition between disorder and order of the aspect of the observed profiles is essentially due to an instability, which we analyze by the chaos theory. For that purpose, we propose an original construction of an attractor that presents a fixed point for low cutting speeds. This attractor characterizes, beyond the critical cutting speed, an instability described by a phenomenon of successions of states on the attractor between work hardening by localized shear plastic deformation and softening due to the rise in temperature. 相似文献
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机械加工表面形貌分形特征的计算方法 总被引:10,自引:1,他引:10
提出应用小波变换计算表面形貌分形特征参数,基于Weierstrass-Mandelbrot函数(W-M函数)和Majumdar-Bhushan函数(M-B函数)这2种常用于表征和模拟机械加工表面轮廓曲线的标准分形函数,验证了小波变换计算分形维数具有很高的精度。与其它计算表面形貌分形维数的方法进行了比较,结果表明小波变换方法的稳定性和准确性好。应用小波变换计算了不锈钢和铜2种材料的机械加工表面的分形维数。 相似文献