功率谱密度函数评价方法探讨

高能量、高分辨力光学系统给传统的光学面形评价指标提出了新的要求。各项测试技术 ,信息理论的更新给我们的研究提供了可能。介绍采用 PSD功率谱密度函数来评价光学元件面形中频误差     

变截面涡旋齿三维形貌分析与功率谱密度表征

为了量化表征变截面涡旋齿形貌的变化规律并提取特征信息,以45#钢和硬铝7075材料进行了3段基圆渐开线变截面涡旋铣削加工实验,用Talysurf CLI 1000形貌仪测量了涡旋齿三维形貌和表面粗糙度,对形貌图像进行了分析和比较,运用一维和二维功率谱密度方法量化表征了涡旋齿形貌的频率?空间分布信息。形貌分析表明：45#钢试样涡旋齿形貌变化趋势接近走刀痕迹,呈现较强的规律性;45#钢涡旋齿试样表面形貌变化高度大于硬铝7075,且形貌的变化与型线位置无明显联系。二维功率谱密度分析表明,涡旋齿形貌呈各向异性特征,x方向空间频率0~0.02 μm-1是影响涡旋齿形貌的主导频率,涡旋齿主要缺陷存在于空间波长50 μm内。一维功率谱密度表征解析了涡旋齿试样粗糙度相近、但表面形貌和粗糙度差异性明显的现象。实现了涡旋齿形貌不同层次特征的定量表征和信息提取。     

摆线铣削表面特性的功率谱密度研究

为了研究摆线铣削加工方法下影响工件表面微观形貌的主要因素,采用不同切削参数进行了铣削加工实验,并结合功率谱密度法对获得的表面数据进行了更加全面的分析表征。实验结果表明:采用摆线铣削加工方式时,较大的径向切削深度有利于功率谱密度值降低,保证表面质量的同时,提高加工效率;每齿进给量和主轴转速分别和表面轮廓间距、加工振动联系紧密,影响表面凸起和缺陷;加工表面的主要频率分布能够反映加工工艺条件对加工表面形貌的影响。     

利用功率谱密度修改结构动力模型的方法

给出一种利用随机振动试验的功率谱密度测量结果进行结构动力模型修正的方法。质量，刚度和阻尼矩阵中的所有元素可可时也可以部分地被修正。修正结果在最小二乘意义下与功率谱密度测量值吻合，并利用参数辨识技术中的辅助变量法来消除或减少测量噪声产生的误差。算例表明本方法是正确和可靠的，并具有较高的修正精度。同时，修正模型还保持了有限元模型的带状稀疏特点。     

基于反射镜表面粗糙度计算极紫外望远镜分辨率

针对短波段成像系统中的散射问题,提出了一种基于反射镜表面粗糙度来计算极紫外太阳望远镜工作波段分辨率的方法.首先分析了两镜系统中散射光线的传播,讨论了反射镜表面粗糙度相对波长的比值与像面光强分布的关系.分频段测量了反射镜的表面粗糙度,利用k-相关模型拟合出全频段的一维功率谱密度(PSD).数值计算结果表明:在1/D到1/...     

高速铣削SiC_p/Al复合材料表面形貌功率谱密度研究

为了研究切削参数对高速铣削SiCp/Al复合材料表面微观形貌的影响,本文采用不同切削参数进行了高速铣削实验,利用Talyscan150型表面粗糙度测试仪对加工表面进行测量,对获得的表面数据进行功率谱密度(PSD)分析。结果表明:高速铣削SiC颗粒增强铝基复合材料时,进给量与铣削深度对功率谱密度影响不大,切削速度是主要影响因素,并且随着切削速度的增大,功率谱密度值降低,表面质量提高。加工表面的主要空间波长成分能够反映加工工艺条件对加工表面形貌的影响。     

用二维功率谱密度分析工程表面特征

工程表面的二维功率谱包含了丰富的有关表面特征的重要信息。本文阐述了二维快速付立叶变换（FFT）的基本原理，并用二维FFT和表面功率谱密度（APSD）的方法对磨削实验中的陶瓷加工表面进行了表面特性分析，介绍了从功率谱中提取信息的方法。     

三维表面粗糙度的表征和应用

表面粗糙度会直接影响零部件的耐磨性、密封性以及抗腐蚀性等,是评定机械加工和产品质量的重要指标。现代科技水平的不断提高对零件表面性能的要求也日益严苛。传统的二维表面粗糙度的测量和表征已经不再能够满足技术发展的要求,三维表面粗糙度由于能够更加全面、真实地反映工件表面的状态而受到人们的重视,成为研究热点。本文回顾了三维表面粗糙度的发展历史,系统地介绍了三维表面粗糙度参数及标准的发展现状,分析了表面形貌与功能特性的联系,概述了三维粗糙度参数在制造业、生物医疗、摩擦学与材料科学等领域的广泛应用,并进一步指出了三维表面粗糙度表征和应用的发展方向。未来随着相关研究(比如,三维测量的溯源性、重复性、参数表征体系等问题)的深入以及三维表面测量手段的发展,三维表面粗糙度参数也将不断完善和推广,并更多地与实际功能相结合来预测并指导生产,确保工件的表面质量。     

极紫外多层膜基底表面粗糙度综合表征技术

研究用不同清洗方法对硅基底表面粗糙度的影响,首先使用原子力显微镜(AFM)直接测量硅片表面粗糙度;然后,利用直流磁控溅射方法,在相同制备工艺条件下镀制M o/S i多层膜,使用X射线衍射仪(XRD)对多层膜二级衍射峰进行摇摆曲线扫描;最后,利用同步辐射测量多层膜的反射率,间接表征基底的粗糙度。结果表明,超声清洗后镀制的多层膜反射率最高,结论与AFM,XRD等表征方法一致。     

LabVIEW在货运车箱振动自功率谱密度函数分析中的应用

在实验室内对车载物资和装备进行随机振动试验具有很大的经济意义,目前国际上普遍采用的一种试验方法是在频域内再现功率谱密度和随机波形,而功率谱密度通常是由实测振动数据经过自功率谱密度函数分析后得到.LabVIEW可以很好的完成自功率谱密度函数分析.首先介绍了LabVIEW中有关自功率谱密度函数的基本理论和算法,对待处理原始数据进行了简要介绍,然后详细叙述了自功率谱密度函数的计算步骤,最后开发出集数据输入、计算以及显示保存结果等功能于一体的虚拟仪器.经实践检验证明该虚拟仪器实用且效率高.     

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.     

Evaluation of discrete displacement transducer by spectral analysis of surface roughness

A discrete displacement transducer using an optical technique and attached to a commonly used stylus instrument is described. The proposed transducer plays an important role in generating a digital output of surface profile from the viewpoint of sampling error. The working accuracy is discussed with reference to the spectral analysis of surface roughness.     

减小SiO2光波导表面粗糙度的ICP干法刻蚀工艺研究

波导表面粗糙度引起的散射损耗是SiO2光波导传输损耗的主要来源,通过降低表面粗糙度可以获得低损耗SiO2光波导。通过优化ICP干法刻蚀工艺的各参数(如温度、压强、气体流量、感应/偏置功率等)获得了低粗糙度的SiO2光波导,并采用SEM和AFM对刻蚀表面粗糙度进行了定量测试。采用优化刻蚀工艺可将表面粗糙度从35.4nm降低到3.6nm,波导传输损耗约为0.1dB/cm。     

In-proces sensors for surface roughness and their applications

Potential non-contact optical methods for in-process surface roughness measurement are described, including reflected light position detection, focu     

A new optical technique for roughness measurement on moving surface

A new optical technique which allows the roughness of moving surfaces to be determined was developed. The new technique which is called the dark/bright ratio (DBR) method utilizes the combined effects of speckle and scattering phenomena. The roughness of surfaces is inferred from the dimensions of the recorded dark or bright area in the speckle pattern. Although it is a relative method, it has great potential to be used for in-process measurement and automation owing to the simplicity of both its principle and required optical set-up. The new technique has also been proved to have large measuring range and with high precision. The principle of this technique and the set-up of the measuring system are described. Experimental results for both static and dynamic conditions, which were compared to those obtained using the traditional stylus technique, were found to be in good agreement. The reliability of the new technique in obtaining roughness data of surfaces under various speed conditions (from 0 to 0.017 m/s) was validated.     

功率谱密度约束下多频激励的非线性失真研究

多频激励信号通过放大器后产生的非线性失真对测量准确性具有较大影响。本文对功率谱密度约束下的多频激励信号产生的非线性失真进行了定量和定性的研究,给出了不同谱线间隔、非线性阶数、谐波相位和频率分布下的数值计算结果,并从三个方面进一步阐释了非线性失真的作用机制。首先,通过仿真发现,二阶非线性时,由具有 Schroeder 相位的多频激励信号产生的二类失真分量的相位为随机分布,而不是和一类失真分量反相。其次,通过计算一类失真分量、二类失真分量以及总失真的变化,解释了通过对多个具有随机相位的多频激励信号产生的非线性失真求平均来减小二类失真分量影响的测量方法。最后,发现了具有 Schroeder 相位的多频激励信号所产生非线性失真的特殊分布机制。本文的研究对准确评估和深入理解非线性失真具有重要意义。     

Extraction the unbalance features of spindle system using wavelet transform and power spectral density

Identification of the spindle unbalance is very important for the ultra-precision machining tools. In the first part, the frequency information for the spindle system is computed by two methods. In the second part, the results between the modal information of the spindle and the error frequency of the measured workpiece surface which processed by wavelet transform and power spectral density is compared, the signal feature in the waviness which is consistent with the spindle unbalance frequency is extracted. In the last part, the identified result is compared, it proves the extraction and identification method for the spindle unbalance of the machine tool is correctness and validity.     

Influence of surface roughness features on mixed‐film lubrication

An optical technique (three‐dimensional spacer layer imaging) has been developed to map accurately lubricant film thickness in thin‐film elastohydrodynamic (EHD) contacts. This experimental technique has been used to study the influence of surface roughness features, asperity height, and slope on EHD film thickness and pressure. Single ridges transverse to the entrainment direction were used to represent asperities. It was found that the ridges with lower slopes generate films of greater minimum thickness. Below a certain entrainment speed, the minimum film thickness declined at a rate dependent on the ridge slope. At low speeds, the ridges with higher slopes entrapped a larger volume of lubricant ahead of the ridge and along the entrainment direction. For all speeds, the highest ridges entrapped the most lubricant. Both ridge slope and ridge height had a negligible effect on mean film thickness in the contact. Asperity pressure increased with higher ridge slope, but was not influenced by entrainment speed. An increase in pressure was found where lubricant is entrapped upstream of a ridge.