共查询到19条相似文献,搜索用时 93 毫秒
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摩擦力和摩擦振动的分形行为研究 总被引:6,自引:1,他引:6
在不同的摩擦磨损试验机上提取了摩擦磨损过程中摩擦力和摩擦振动的时间序列信号,采用关联维数方法研究了摩擦力和摩擦振动的分形行为.结果表明:摩擦力和摩擦振动信号具有分形特征;随着摩擦磨损过程的进行,信号分形维数的变化出现规律性的递增或递减;对于“收敛”或磨合磨损过程,不同阶段摩擦信号的分形维数趋于增大;对于“发散”的摩擦磨损过程,不同阶段的摩擦信号的关联维数趋于减小.摩擦力和摩擦振动的分形维数的变化规律同摩擦磨损过程中表面形貌分形维数的变化规律相似。 相似文献
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磨合过程摩擦力单重分形和多重分形的研究 总被引:8,自引:2,他引:8
分别在CD40润滑油和加入添加剂的CD40润滑油润滑条件下,通过销-盘摩擦磨损试验机对船用柴油机活塞环和缸套进行磨合磨损试验,提取摩擦力的时间序列信号,应用分形维数和多重分形谱研究了摩擦力的分形行为.结果表明:摩擦力信号具有分形特征;随着磨合磨损过程的进行,信号的分形维数和多重分形谱出现规律性的变化;不同阶段信号的分形维数趋于减小,与磨损表面粗糙度的变化规律一致;不同阶段信号的多重分形谱呈现出递增或递减趋势,反映了磨损表面的动态变化过程.因此,摩擦力信号的分形维数和多重分形谱可以对磨合磨损过程进行定量分析. 相似文献
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摩擦信号分形维数与载荷和速度的关系研究 总被引:3,自引:2,他引:3
在立式万能摩擦磨损试验机上对GCr15/45#钢摩擦副进行不同接触载荷和滑动速度下的摩擦磨损试验,对初始滑动距离1 000 m内的摩擦系数信号进行数据采集,运用结构函数测度方法对摩擦系数信号进行分形表征,计算不同载荷和速度下的分形维数,研究摩擦信号的分形维数随载荷和速度的变化规律.结果表明,摩擦系数信号具有显著的分形特征,其分形维数随载荷和速度而变化.在相同载荷下,分形维数随滑动速度增加而增大;在相同速度下,分形维数随着接触载荷增加而增大.磨损率与摩擦系数信号的分形维数正相关. 相似文献
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在环端面接触磨损试验机上,采用45^#钢—铜配副进行磨损试验,收集不同磨损阶段的磨屑,用光学显微镜进行统计,分析磨粒积聚与磨损表面之间的分形维数关联性.结果表明,磨粒积聚数与其粒径之间存在显著的分段分形特征,第二分形维数同试验时间具有反抛物线函数关系.对磨损表面轮廓的分形测量表明,磨损表面的分形维数变化也具有相似的反抛物线函数关系.此外,磨损表面分形维数同磨粒积聚分形维数具有很好的相关性,但二者之间在磨合前后的对应关系稍有差别;磨粒积聚第二分形维数同磨损率变化成反比. 相似文献
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表面轮廓分形维数计算方法的研究 总被引:42,自引:5,他引:42
阐述了表面轮廓分形和分形曲线的基本概念,对目前常用于表面轮廓分形维数的4种计算方法的基本思路作了评介,指出这些方法的计算结果都存在一定的偏差,对选择不同计算尺度得到的分形维数表现出较大的不稳定性,致使分形维数难以准确地反映表面轮廓的真实复杂特征.根据表面轮廓的均方差与区间尺度成比例的性质,提出了表面轮廓分形维数计算的协方差加权法.通过与Weierstrass-Mandelbrot分形函数曲线的分形维数计算的比较,协方差加权法所得表面轮廓分形维数的稳定性良好,计算结果的准确性也明显提高,可以简化表面形貌的识别过程,为摩擦学研究中更准确地描述粗糙表面的复杂特征提供了一种简便适用的新方法. 相似文献
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采用低功率直流磁控溅射法制备了GeSb2Te4薄膜,利用扫描电子显微镜、X射线衍射仪和原子力显微镜(AFM)分析了薄膜的微观结构和相组成,研究了薄膜表面的分形特征.结果表明:沉积态GeSb2Te4薄膜为无规则、无择优取向的非晶材料;薄膜表面形貌AFM图像具有分形特征,基于自行编制的采用盒计数法求解随机分形维数的C语言程序,计算得到沉积态GeSb2Te4薄膜的分形维数为1.93;针对一维和二维随机分形多重分形谱的计算表明,沉积态GeSb2Te4薄膜满足分形的标度不变性;通过对沉积态和退火态薄膜进行多维分形谱计算,发现经过230 ℃退火处理的薄膜样品的多维分形谱较窄且晶化分布均匀. 相似文献
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Planar images of Rayleigh scattering and laser-induced predissociative OH-fluorescence (OH-LIPF) have been obtained simultaneously
in turbulent premixed jet flames on a single-shot basis. The geometric structure of temperature and OH isocontours were extracted
for fractal analysis. A power-law fractal behavior can be identified in the ensemble-averaged flame length measure. It was
found that the inner and outer cut-off scales of OH contours are larger than those of the iso-temperature contours; while
the OH images show comparatively smaller fractal dimensions. The joint-pdf ’s between flame temperature and OH LIPF signals
at different heights are also derived to evaluate the flame stretch effect on local flame structure. Comparison of image pairs
near the extinction limit suggests that Rayleigh thermometry is more adequate to characterize the fine-scale flame front wrinkling
in highly stretched turbulent premixed flames.
Received: 12 September 1997/Accepted: 19 May 1998 相似文献
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滑坡分维特征及其预测意义 总被引:2,自引:0,他引:2
本文依据分形理论,采用盒维数法计算了西藏樟木地区滑坡及其水系的空间分维。分析了分维的变化特征。发现滑坡高潮期前存在不同幅度的降维现象,滑坡区滑坡活动程度不同,其水系分维在不同观察尺度下变化幅度有显着的差别。探讨了分维的预测意义。 相似文献
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关联表面分形特性的润滑模型 总被引:1,自引:0,他引:1
在分配有面粗糙度与材料表面分形特性关系的基础上,将分形特性引入润滑方程,提出了关联表面分形特性的润滑模型,并分析了润滑模型中压力流量因子和剪切流量因子与表面分形维数之间关系。计算结果表明:在相同分形维数(D)下,随着微突体纵横比v的增大,压力流量因子和剪切流量因子相应增大,且其随分形维数D的变化同随油膜粗糙度比H的变化相比呈现出更强的不规则特性,出现局部最大和最小值,并且分辨率较高。 相似文献
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On star product fractal surfaces and their dimensions 总被引:3,自引:0,他引:3
Generallyspeaking,fracturesurfacesofmaterialsarerough,irregularandrandom.Thefractureandweaknessinrock,concrete,ceramicsandmetalsignificantlyaffectthedeformation,strength,andconductivityofthesematerials.Manypaper(suchas[1~3])focusedonthefracturesurfa… 相似文献
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Fractures play an important role in reservoir engineering as they dominate the fluid flow in the reservoir. All evidence suggests
that rarely can one model flow and transport in a fractured rock consistently by treating it as a uniform or mildly nonuniform
isotropic continuum. Instead, one must generally account for the highly erratic heterogeneity, directional dependence, dual
or multicomponent nature and multiscale behavior of fractured rocks. As experimental methods are expensive and time consuming
most of the time numerical methods are used to study flow and transport in a fractured rock. In this work, we present results
of the numerical computations for single phase flow simulations through two-dimensional synthetically created fracture apertures.
These synthetic rock fractures are created using different fractal dimensions, anisotropy factors, and mismatch lengths. Lattice
Boltzmann method (LBM), which is a new computational approach suitable to simulate fluid flow especially in complex geometries,
was then used to determine the permeability for different fractures. Regions of high velocity and low velocity flow were identified.
The resulting permeability values were less than the ones obtained with the cubic law estimates. It has been found that as
the mean aperture–fractal dimension ratio increased permeability increased. Moreover as the anisotropy factor increased permeability
decreased. Neural network simulations were used to generalize the results. 相似文献
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锡基巴氏合金磨损表面的分形与磨损率 总被引:6,自引:1,他引:6
利用结构函数分析法研究了滑动摩擦学系统中金属磨损表面轮廓线的分形特性。结果表明:磨损表面轮廓线在小于Sm的尺度上具有分形结构。采用结构函数法可以方便地确定粗糙表面轮廓线的分形参数,即垂直于滑动方向上磨损表面轮廓线的分维D可作为磨损表面分维的特征值,它与金属磨损率的变化有着密切的关系,最佳分维Dopt值对应于材料的最低磨损率。 相似文献
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断面分形研究中的几个问题 总被引:6,自引:0,他引:6
本文讨论了分形几何应用于断裂研究的几个基本问题.主要内容包括断面的分形特征及分维测量,分维与宏观力学性能(如断裂韧性等)的关系,分形断裂模型及分形断裂的物理机理. 相似文献
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Fractal analysis of turbulent premixed flame surface 总被引:3,自引:0,他引:3
The fractal-like character of the laminar flamelet surface in turbulent premixed combustion of lean methane/air mixtures was studied by using the laser tomography technique to visualize the instantaneous flame surface in the two-dimensional section cut by the laser sheet. The fractal analysis of the surface revealed that the surface actually exhibits a self-similarity behavior in a narrow range of scale, and the value of fractal dimension can be defined. The inner cutoff scale was the laminar flame thickness, while the outer cutoff scale was the flame size. The fractal dimension was found to depend on the orientation of the section, and to increase towards downstream. It is suggested that the observed fractal-like character is not directly connected to approach flow turbulence, but should represent certain aspects of the flamelet itself. 相似文献