利用功率谱密度函数表征光学薄膜基底表面粗糙度

光学表面的表面粗糙度通常利用两个传统参数方根粗糙度σ和相关长度l来进行表征。主要就如何引入功率谱密度函数(PSD)表征表面微观形貌进行了初步研究。说明了一维和二维功率谱密度(PSD)函数的数学计算方法、PSD函数的物理意义,同时给出了PSD函数与传统的表面评价指标σ和l之间的关系。利用不同仪器对多种样品进行测试,在分析比较测试结果的基础上,总结了利用PSD函数评价光学表面粗糙度的优点。功率谱密度函数作为一个全面的光学表面评价参数,正得到越来越广泛的重视和应用。     

The effect of fluoride therapies on the morphology of bleached human dental enamel

The aim of this in vitro study was to evaluate qualitatively the surface morphology of enamel bleached with 35% hydrogen peroxide (HP) followed by application of fluoridated agents. Forty intact pre molars were randomly distributed into four groups (n = 10), treated as follows: Group I (control group) remained stored in artificial saliva at 37 °C, Group II - 35% HP; Group III - 35% HP + acidulated fluoride (1.23%) and Group IV - 35% HP + neutral fluoride (2%). The experimental groups received three applications of bleaching gel and after the last application all specimens were polished. This procedure was repeated after 7 and 14 days, and during the intervals of applications, the specimens were stored in artificial saliva at 37°C. Scanning electron microscopy (SEM) analysis showed superficial irregularities and porosities to varying degrees in bleached enamel compared to control group. Sample evaluation was made by attributing scores, and data were statistically analyzed using Kruskal-Wallis and Dunn tests (P < 0.05). SEM qualitative investigation demonstrated that 35% hydrogen peroxide affected human dental enamel morphology, producing porosities, depressions, and superficial irregularities at various degrees. These morphological changes were higher after the application of 1.23% acidulated fluoride gel.     

Analysis of surface finish in milling by power spectral density measurement

The power spectral densities (psd) of surface profiles of milled steel samples have been determined by analogue measurement techniques, ie by a spectral analyser. The recorded psd curves indicate the presence in the surface profiles of some periodic components. Increase of cutting speed during milling causes the spectral density values to decrease. By psd measurement it was possible: to distinguish between surface profiles with the same R_a value, but milled under different cutting conditions; and to detect axial run-out of the milling cutter, which results in waviness of machined surfaces.     

Effect of in‐office bleaching agents on the surface roughness and morphology of different dental composites: An AFM study

The aim of this study was to evaluate, using atomic force microscopy, the effect of two different bleaching agents on the modification of dental composites materials. This modification will be judged by analyzing the variation of surface roughness and surface morphology of two different composites: one containing nanoparticles and other consisting of microhybrid resin. The bleaching was performed by using two different concentrations of hydrogen peroxide: HP Blue (20% hydrogen peroxide) and Whiteness HP Maxx (35% hydrogen peroxide). Disks of Esthet X and Filtek? Z350 composites were used. Atomic force microscopy was used for analyses of the same place of the sample before and after treatment. A total of 12 analyses were performed per group (n = 12). The samples were analyzed qualitatively by evaluating morphological changes in the images and quantitatively by using roughness parameters (Ra). Data were analyzed statistically using Kruskal–Wallis, Mann–Whitney, and Friedman tests (P < 0.05). Changes were observed both qualitatively and quantitatively only in the groups where Esthet X resin was used. The use of hydrogen peroxide bleaching agents caused changes only in the surface of microhybrid composites, with no changes being observed in the composite containing nanoparticles. Despite being even significant, these alterations are clinically slight and can be eliminated by polishing them. Microsc. Res. Tech. 76:481–485, 2013. © 2013 Wiley Periodicals, Inc.     

Systemically alendronate was incorporated into dental tissues but did not cause morphological or mechanical changes in rats teeth

This study evaluated the effect of the systemic use of sodium alendronate in rats in vivo. Forty‐five Wistar rats aged 36 to 42 days and weighing 200 to 230 g were randomly assigned to a control group (n = 20), which received distilled water, and an experimental group (n = 25), which received 2 weekly doses of 1 mg/kg of chemically pure sodium alendronate. The animals were killed after 60 days of treatment. The tibias were removed for analysis of bone mineral density by dual‐energy X‐ray absorptiometry (DXA). Then, the maxillary incisors were extracted for analysis of the mineralized dental tissues using fluorescence spectroscopy (FS), scanning electron microscopy (SEM), bright field microscopy (BFM), and cross‐sectional microhardness (CSMH) testing. DXA and CSMH data were subjected to statistical analysis by Kruskal‐Wallis test (5% significance level). The experimental group presented higher bone mineral density than the control group by DXA. FS analysis revealed presence of alendronate in the mineralized dental tissues of the specimens of the experimental group. Significant morphological differences were not found by SEM and BFM. Enamel and dentin (100 and 300 μm from the dentinoenamel junction) CSMH data did not show significant difference between the control and experimental groups. Based on the obtained results, we conclude that while alendronate increased the bone mineral density and was incorporated into the mineralized dental tissues it did not cause significant alterations in the morphology and microhardness of rat incisor enamel and dentin. Microsc. Res. Tech. 75:1265–1271, 2012. © 2012 Wiley Periodicals, Inc.     

Two‐ and three‐dimensional profilometer assessments to determine titanium roughness

In this study, a comparative topography analysis of titanium (Ti) surfaces was performed using two‐ (2D) and three‐dimensional (3D) profilometers. Ti samples were either only sandblasted (SB) using Al₂O₃ particles or were SB and received an additional chemical treatment using a solution of 4% HF (SLA). Samples with no treatment were used as a control group (C). Therefore, three different surfaces were evaluated: SB, SLA and C. The Ti surface topographies were evaluated by scanning electron microscopy. An Ra roughness measurement was performed on each Ti sample by 2D and 3D profilometers. Surface roughness was also characterized using amplitude, spatial and hybrid 3D parameters. 2D and 3D profilometer analyses produced very close results. Mean Ra values range from 0.19 to 0.25 (C, p<0.05), 0.84 to 0.99 (SLA, p<0.05) and 0.98 to 1 µm (SB, p>0.05). The statistically different Ra values depending on the surface studied may be explained by methodological and technical differences. Also, 3D profilometer seems to be the more appropriate analytical method for measuring the roughness of Ti surfaces because it also describes surface organization. SCANNING 31: 174–179, 2009. © 2009 Wiley Periodicals, Inc.     

磨损表面的稳健高斯滤波评定方法研究

磨损表面形貌的评定方法,对于磨损表面状态评定、摩擦特性的分析有着重要的作用,而表面形貌数据的滤波方法,是评定方法中的关键组成之一。采用Tukey、Hampel、IGGI和QC 4种典型稳健权函数分别与高斯滤波结合组成的稳健高斯滤波方法,对由实验得到的黏着磨损和磨料磨损盘表面采集的数据进行稳健滤波分离;通过由稳健高斯滤波与标准高斯滤波得到的三维磨损表面低频基准面的对比分析,以及从磨损表面滤波分离出的高频评定参数的影响分析,研究稳健高斯滤波的滤波稳健性和滤波效率;从滤波后的高频功率谱密度分布特性方面,进一步探讨滤波的稳健性;讨论磨损表面形貌数据中特异值与磨损特征的关系。研究表明：Tukey和Hampel稳健高斯滤波具有良好的滤波稳健性,能有效地分离磨损表面的低频评定基准和包含磨损特征的高频信息;而磨损特征主要分布在高频信息的低频段区间,其功率谱密度函数与表面磨损状态及其摩擦学特性相关。     

Shear bond strength and ultrastructural interface analysis of different adhesive systems to bleached dentin

Background: It remains unclear as to whether or not dental bleaching affects the bond strength of dentin/resin restoration. Purpose: To evaluated the bond strength of adhesive systems to dentin submitted to bleaching with 38% hydrogen peroxide (HP) activated by LED‐laser and to assess the adhesive/dentin interfaces by means of SEM. Study design: Sixty fragments of dentin (25 mm²) were included and divided into two groups: bleached and unbleached. HP was applied for 20 s and photoactivated for 45 s. Groups were subdivided according to the adhesive systems (n = 10): (1) two‐steps conventional system (Adper Single Bond), (2) two‐steps self‐etching system (Clearfil standard error (SE) Bond), and (3) one‐step self‐etching system (Prompt L‐Pop). The specimens received the Z250 resin and, after 24 h, were submitted to the bond strength test. Additional 30 dentin fragments (n = 5) received the same surface treatments and were prepared for SEM. Data were analyzed by ANOVA and Tukey's test (α = 0.05). Results: There was significant strength reduction in bleached group when compared to unbleached group (P < 0.05). Higher bond strength was observed for Prompt. Single Bond and Clearfil presented the smallest values when used in bleached dentin. SEM analysis of the unbleached specimens revealed long tags and uniform hybrid layer for all adhesives. In bleached dentin, Single Bond provided open tubules and with few tags, Clearfil determined the absence of tags and hybrid layer, and Prompt promoted a regular hybrid layer with some tags. Conclusions: Prompt promoted higher shear bond strength, regardless of the bleaching treatment and allowed the formation of a regular and fine hybrid layer with less deep tags, when compared to Single Bond and Clearfil. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.     

砂轮约束磨粒喷射精密光整加工表面功率谱分析和摩擦磨损特性研究

对砂轮约束磨粒喷射精密光整加工微观形貌进行功率谱分析和摩擦磨损特性研究。利用平面磨床M7120对精磨后45#钢工件材料进行喷射精密光整加工;用TALYSURF5轮廓仪测量加工后的微观几何参数值;用扫描电镜观察表面微观形貌变化;用功率谱密度函数评价磨削加工和光整加工表面的微观形貌特征;利用MG-2000型销-盘式高速高温摩擦磨损试验机研究表面形貌对摩擦磨损的影响。结果表明,磨粒喷射精密光整加工均化和改善了工件表面的波纹度,降低了工件表面粗糙度值,提高了工件表面的形状精度;光整加工表面摩擦因数和磨损量与磨削加工表面相比明显降低,表面质量明显改善,从而提高了零件的使用寿命和精度保持性,摩擦磨损实验结果和功率谱密度分析相吻合。     

工程零件粗糙表面建模方法研究

随着科技的发展,零件比表面积增加,零件表面几何形貌对设备性能的要求日益显著.由于需要借助有限单元法模拟零件表面上发生的物理、化学现象,因此对零件表面计算机建模的研究具有较强的理论和实际意义.介绍目前粗糙表面的主要建模方法,并指出各种方法的优点及其局限性.     

Assessing conformal thin film growth under nonstochastic deposition conditions: application of a phenomenological model of roughness replication to synthetic topographic images

In this work, a simple method to follow the evolution of the surface of thin films during growth on substrates characterised by high roughness is detailed. To account for real cases as much as possible, the approach presented is based on the hypothesis that deposition takes place under nonstochastic conditions, such as those typical of many thin film processes in industry and technology. In this context, previous models for roughness replication, which are mainly based on idealised deposition conditions, cannot be applied and thus ad hoc approaches are required for achieving quantitative predictions. Here it is suggested that under nonstochastic conditions a phenomenological relation can be proposed, mainly based on local roughening of surface, to monitor the statistical similarity between the film and the substrate during growth or, in other words, to detect changes of the bare substrate morphological profile occurring during the film growth on top. Such approximation is based on surface representation in terms of power spectral density of surface heights, derived from topographic images; in this work, such method will be tested on two separate batches of synthetic images which simulate thin films growth onto a real rough substrate. In particular, two growth models will be implemented: the first reproduces the surface profile obtained during an atomic force microscopy measurement by using a simple geometrical envelope of surface, regardless the thin film growth mechanism; the second reproduces the columnar growth expected under nonstochastic deposition conditions. It will be shown that the approach introduced is capable to highlight differences between the two batches and, in the second case, to quantitatively account for the replication of the substrate roughness during growth. The results obtained here are potentially interesting in that they account essentially for the geometrical features of the surfaces, and as such they can be applied to synthetic depositions that reproduce different thin film depositions and experimental contexts.     

Effects of viscosity and surface roughness on gear contact tribological layers

The increasing dependence on more robust additive chemistry to improve gear pitting resistance requires the additive technology development to rely less on a trial‐and‐error approach and more on a better basic understanding of the influence of additive chemistry on tribological contact layers' physical and chemical changes. The use of secondary neutral mass spectrometry (SNMS) and nanoindenter to analyse tribological contact layers had been carried out by Inacker and co‐workers at NMI. They found that the alkyl structure of zinc dithiophosphate (ZDTP) and the type of cation have a profound effect on the thickness and nanohardness of the tribological layer. An extension to that study has been carried out in this investigation, which involves a design experiment of two variables (oil viscosity and surface roughness) while keeping the additive chemistry constant to determine their impact on the tribological layer. The methods used to analyse the tribological layers include SNMS, nanoindenter and SEM coupled with focused ion beam imaging of the rectangular well‐shaped cross section. The results in general are in agreement with the findings of Inacker and his co‐workers, namely greater micropitting reduces the thickness of the tribological layer and brings closer the depth of nanohardness maximum to the surface. Copyright © 2006 John Wiley & Sons, Ltd.     

磁悬浮车辆随机振动响应分析及其平稳性研究

以德国Transrapid磁悬浮系统为原型，建立了磁悬浮车辆/线路相互作用模型，高速磁悬浮线路随机不平顺则引入了分段功率谱表述模型。运用数值积分法和时频转换法对磁悬浮车/线、车/桥系统随机响应进行了仿真分析，并以先进地面交通车辆走行品质UTACV规范和铁道车辆Sperling平稳性指标对磁悬浮车辆运行平稳性进行评价。     

飞机舱门地面风载响应特性研究

为了保证舱门机构具有高的静态结构刚度、优良的动态结构性能,研究了自然界中脉动风的风谱及其数值模拟方式,介绍了采用风速功率谱密度方法进行随机风载分析的过程,建立了一个舱门打开状态的完整计算模型,分析了舱门在静态风载和动态风载下的位移响应。结果表明动态风载响应约为静态风载响应的４０．８％,研究结果为该型飞机舱门的设计提供了一定的理论依据。     

路面功率谱密度换算及不平度建模理论研究

为了明晰路面不平度空间域统计量的计算,以及几种重要功率谱密度(power spectral density,简称PSD)之间的关系,以帕塞瓦尔定理和维纳-辛钦定理为依据,在推导空间域自相关函数和PSD计算公式的基础上,导出了不平度空间域位移、速度与加速度PSD以及空间频率与角频率PSD之间的换算关系。另外,为了完善傅里叶逆变换法路面建模中PSD离散化的理论基础,以傅里叶级数与变换、离散傅里叶变换和频域卷积定理为依据,从离散化的原因、目的和结果验证出发论证了PSD离散化的正确性。就模拟路面验证问题,指出直接法谱估计的不合理之处,论证了平均周期图法谱估计时,空间与时间采样频率分别对应着空间域和时间域PSD输出。结果表明,上述换算关系和论证是正确的,可应用于路面不平度建模和汽车平顺性分析。     

Prediction of surface roughness during abrasive flow machining

An analytical model is proposed to simulate and predict the surface roughness for different machining conditions in abrasive flow machining (AFM). The kinematic analysis is used to model the interaction between grain and workpiece. Fundamental AFM parameters, such as the grain size, grain concentration, active grain density, grain spacing, forces on the grain, initial topography, and initial surface finish (R _a value) of the workpiece are used to describe the grain-workpiece interaction. The AFM process is studied under a systematic variation of grain size, grain concentration and extrusion pressure with initial surface finish of the workpiece. Simulation results show that the proposed model gives results that are consistent with experimental results.     

Effects of surface forces and surface roughness on squeeze thin film of elastohydrodynamic lubricated spherical conjunction

The pure squeeze thin film elastohydrodynamic lubrication motion of circular contacts with effects of surface forces and surface roughness taken into account is explored under constant load conditions. The coupled transient stochastic Reynolds, elasticity deformation, the load balance, surface forces (hydrodynamic, solvation and van der Waals pressure) and lubricant rheology equations were solved simultaneously by using the finite difference method and the Gauss–Seidel iteration method. The simulation results reveal that the differences between radial type roughness and circular type roughness problems are apparent as the film thickness is thinner than 5 nm. The oscillation phenomena in pressure and film thickness come mainly from the action of solvation forces. The effects of surface forces become significant as the film thickness becomes thinner. The film thickness with circular type roughness is thicker than that with radial type roughness. Copyright © 2012 John Wiley & Sons, Ltd.     

特定频域特性的风模型研究

为了保证风力机设计过程中所需要载荷计算的准确性,以确保风力机各零部件的动力学分析和寿命计算,需要在实验室中得到与自然风具有相同数学特性的风速序列。对Kaimal功率谱密度函数进行逆傅里叶变换得到离散时间序列,通过对该序列的频谱特性与某风场实测风速序列的频谱特性进行对比分析,结果表明,该方法能够得到具有特定功率谱密度和随机特性的风速时间序列。