表面统计粗糙度理论与评定方法

本文对表面粗糙度研究的现状和存在的问题进行了分析,提出了表面统计粗糙度SSR的新概念,给出了它的评定参数和相应的评定方法。由SSR的基本评定参数FEP(表面轮廓模型参数α)可确定任何一种评定参数及其关系。本文还建立了表面轮廓和分离表面轮廓测量干扰及仪器误差的数学模型。通过一系列的试验和计算机上的计算,证明本文所提出的理论和方法是正确的。     

一种自调整的空间面轮廓度误差的评定方法

基于最小二乘法并结合二维样条插值函数和优化技术 ,提出一种用于空间面轮郭度误差评定的数据处理方法 ,其优点是在轮郭度误差评定过程中、能自动地实现被测轮廓与理论轮廓之间的适应性调整 ,从而能够分离并消除被测轮廓与其测量基准之间的位置误差对轮廓误差评定结果的影响。文中以汽轮机叶片轮廓的轮廓度误差评定为例 ,证实了这种评定方法的优越性。     

粗糙表面轮廓的分形维数计算

本文介绍了粗糙表面轮廓盒维数的计算方法，并指出分形轮廓曲线的盒维数在１和２之间，而且其数值与取样长度、采样点数及测量仪器的分辨率均有关系．     

驱动速度对表面粗糙度参数测量准确度的影响

该文针对轮廓法M制触针式表面粗糙度测量仪器由于其驱动速度变化可能引起表面粗糙度评定参数测量准确度受损的问题，从参数的定义、轮廓的滤波特性、轮廓的畸变等方面作出了较为详细的分析和讨论，同时也提出了改善驱动机构速度特性和仪器信号处理方法的一些思路和建议。     

基于面域功率谱密度的金刚石车削相对振动辨识

在金刚石车削中,刀具与工件之间的相对振动会在加工表面上生成具有某种规律性的特征,并恶化表面质量.本文仿真了振动影响下的金刚石端面车削表面的成型,并研究了刀具与工件之间的相对振动对表面形貌的影响.传统的二维轮廓方法并不适用于整个表面特征的分析,只能采用径向、周向和进给螺旋方向的轮廓进行联合分析.采用由二维快速傅里叶变换推导得到的面域功率谱密度函数可以一次性描述加工表面的形貌,并依此形成了一种根据表面数据分析辨识刀具与工件之间相对振动的系统方法,拓展了面域方法在加工表面分析上的应用.最后,通过金刚石实际车削表面的分析验证了该方法的有效性.     

分数布朗运动环境下亚式期权定价的新方法

本文考虑分数布朗运动环境下几何平均型亚式期权定价问题,给出了一种基于可靠性数学思想的期权定价的新方法.首先,通过It5公式推导出亚式期权所满足的概率密度转移函数.其次,类比可靠性数学中求平均寿命的方法,用无套利定价方法给出了分数布朗运动环境下几何平均型亚式看涨期权定价公式.结果表明该方法同样适用于其它类型欧式期权.     

基于Stewart的表面粗糙度随形测量技术研究

在生产加工、测量控制过程中,许多问题的解决需要建立在对机械零件表面的几何特性和构造的准确认识的基础上。传统的分析主要是对单个轮廓的表面几何特性进行描述,而实际的零件却是三维立体的,通过对单个轮廓的分析来推断工件表面的三维几何特性,存在很大的不确定因素。因此,把检测范围从二维扩展     

计算几何评定国度的方法研究

和传统方法相比，计算几何方法评定圆度误差几何直观性强、结果准确，而又能解决同时存在多个最小径向间距MRS(Minimum Radial Separation)圆心的问题。按照被测轮廓的表示，该方法可分为两类：一类是用被测工件表面上取的样本点来近似地表示该轮廓；另一类是用这些样本点产生一个简单多边形来表示该轮廓。这两种方法确定的内接圆是不同的。文章对比分析了它们的适用性、精度和计算效率以及存在的问题。     

分数布朗运动环境中最值期权定价

假定股票价格遵循由分数布朗运动驱动的随机微分方程,建立了分数布朗运动环境下金融市场数学模型,利用分数布朗运动随机分析理论与未定权益定价方法,获得欧式未定权益一般定价公式,并得到欧式最值期权价格的解析表达式以及平价关系.     

二维表面粗糙度最小二乘评定基准线的改进

现行国家标准中二维表面粗糙度评定的最小二乘基准线为折线,并且存在间断现象.对现行最小二基准线进行了改进,用最小二乘直线在整个评定长度内进行滑动和平均,将获得的光滑曲线作为表面粗糙度的评定基准线.通过算例和仿真分析,改进的最小二乘方法能够描述缓变、连续曲线.该基准线与国际标准推荐的高斯基准线具有较好的一致性,并且粗糙度的评定结果相同.改进的最小二乘基准线对现行标准的最小二乘基准改动小,继承了现行最小二乘基准计算简便和实用的特点,评定过程中不损失轮廓数据,评定基准线光滑、连续,消除了现行最小二乘基准线间断的现象.     

An Examination of Wire Electrical Discharge Machining (WEDM) of Al2O3 Particulate Reinforced Aluminum Based Composites

The material removal mechanism in wire electrical discharge machining of an alumina particulate reinforced aluminum based composite and the related machined surface morphologies were investigated. Under the two cutting conditions of this study, fine and coarse cuttings, the surface roughness measurements on the machined surfaces of the composite material did not show a significant difference, but their corresponding surface topographies were found to be intrinsically different. Besides, surface bandings were observed on the machined surfaces of some fine cut specimens and was believed to be caused by shifting of the wire. Based on these observations and the measured profiles, a material removal scheme for the two cutting conditions was proposed.     

SAFBM of Softer Materials: An Investigation into the Micro-Cutting Mechanisms and the Evolution of Roughness Profile

Swirling Fluidized Bed Machining (SAFBM) is a nontraditional machining process and novel variant of Fluidized Bed Machining (FBM) in which the former has overcome certain drawbacks of the latter such as roughness variation and shading effect. SAFBM generates significant material removal and surface finish on the workpiece surface during the machining process with consistency and flexibility. The present detailed study emphasizes on the machining of softer materials such as brass and aluminum using abrasive particles such as silicon carbide in order to analyze the effect of various micro-cutting mechanisms on the generation of surface texture. This study examines the evolution of surface roughness profile after progressive machining with abrasives ranging from coarse, medium and fine grades of SiC with the help of optical microscopic images of the machined surface. The research concludes that using SAFBM, flat and uniform surface finishing with modification ratio in terms of roughness parameters ranging from 5 to 7 is possible within 7–8 hours of processing.     

Numerical simulation bistatic scattering from three-dimensional conducting rough surface with forward?backward method-based vector basic functions

To more really simulate distribution of vector-induced currents along a three-dimensional (3-D) conducting rough surface, it is better for vector basic functions to be used to describe the vector-induced currents. The forward-backward method (FBM) has been further developed to be combined with the vector basic functions to numerically calculate 3-D conducting rough surface scattering problem in this paper, meanwhile, the FBM is first well explained through some matrix forms. The FBM has been used to numerically simulate the bistatic scattering from 3-D conducting rough surface. Some numerical results have been discussed in the paper.     

Investigation into Influence of Feed Speed on Surface Roughness in Wire Sawing

Aimed at obtaining the minimum machined surface roughness at an appropriate feed speed during the wire-sawing process, the theoretical mathematical model of material removal rate of the non-rigid cutting tool-wire saw is presented, which is based on the Preston equation. According to this theoretical model, this diamond wire-sawing experiment is designed to study the effects of feed speed on machined surface roughness. The experimental results indicate that the minimum machined surface roughness can be acquired by setting the process parameters as the setting curve of spindle speed and feed speed. The investigation provides the theoretical basis and research methods for study of this kind of wire-sawing machine and optimizing process parameters, in order to obtain a low-roughness machined surface.     

Influence of material swelling on surface roughness in diamond turning of single crystals

Abstract

The effect of material swelling on the surface roughness in ultraprecision diamond turning has been investigated. Experimental results from the power spectrum analysis indicate that the profile of the tool marks is distorted by the effect of swelling of the materials being cut. A good correlation exists between the surface roughness and the amount of swelling that has occurred in the machined layer. Radically different surface roughness profiles were obtained when machining aluminium and copper single crystals with the same cutting plane and tool shape. The difference in the machining behaviour could not be accounted for by elastic recovery alone but could be explained by considering the plastic deformation induced in the machined layer.     

无氧铜超精加工表面微观形貌的分形维数表征

单点金刚石超精密加工能够获得纳米级的低粗糙度表面。进一步的实验表明,采用该工艺进行退火态无氧铜切削,已加工表面在刀痕基础上还会出现清晰的晶界浮凸现象。传统的粗糙度概念无法有效表征与区分含有晶界浮凸信息的超精加工表面微观形貌。引入分形维数概念,采用该理论中尺码法对无氧铜超精加工表面的微观形貌进行分形维数计算;为降低切削刀痕信号干扰、突出晶界浮凸信息,设计表面信号带阻滤波方法。计算结果表明,超精加工后的表面分形维数包含了加工刀痕与晶界浮凸信息,由于两者尺度相近,传统的粗糙度测量无法区分其差异;采用带阻滤波与尺码法耦合方式,能够有效识别晶界浮凸特点,定量地反映微观尺度下超精加工表面的形貌特征信息。     

基于分形和小波的几何型面加工误差综合分析

对几何型面加工误差提出并建立了基于分形和小波的综合分析方法，可以精细分析几何型面加工误差的微细成分，并重构出型面轮廓加工误差曲线，以便进行公差与性能关系分析以及加工过程质量监控等相关工作。应用实例表明，该方法是非常有效的。     

复合材料的切削加工表面结构与表面粗糙度

普通金属材料的切削加工理论表面粗糙度可以用公式计算。复合材料经切削加工后其表面留有各种凹凸缺陷,这些谷峰轮廓并非由刀刃直接切出,故不宜用现有普通材料的公式计算其理论表面粗糙度。纤维增强复合材料的切削加工表面结构和粗糙度与切削方向密切相关。颗粒增强复合材料无方向性,其已加工表面结构和粗糙度主要受增强颗粒硬度和粒度以及含量控制。增强体与基体的界面强度及切削刀具和工艺条件对复合材料加工表面粗糙度有很大影响。      

Wire electrical discharge machining of Al2O3 particle and short fibre reinforced aluminium based composites

Abstract

The wire electrical discharge machining behaviour of alumina particle and short fibre reinforced aluminium based composites was studied. Under the two cutting conditions of this study, namely coarse and fine cutting, the average surface roughness R_a of the particle reinforced composite was found always to be higher than that of the corresponding machined matrix surfaces, however, the opposite was found to be true for the fibre reinforced composite. Comparing the surface quality of the two composites, in terms of roughness measurements, the fibre reinforced composite was superior to the particle reinforced composite. Although cutting conditions have little effect on the overall R_a of the two composites, their corresponding surface topographies were found to be intrinsically different. Surface banding was observed on the fine cut surfaces of the particle reinforced specimens, which was believed to be caused by shifting of the wire. Based on the machined surface morphology and the measured surface profiles, the material removal mechanism for the two reinforced composites is discussed.

MST/3412