合金韧窝断口微观形貌的扫描白光干涉三维检测重构及Motif表征

针对30CrMnSiA合金韧窝断口复杂的表面特征,运用扫描白光干涉法检测微观形貌.系统采用Linnik结构,并通过空间频域分析算法重建断口表面三维形貌,试验中扫描行程达120μm,纵向检测精度优于5 nm,频域分析表现出很强的位相提取和噪声抑制能力.研究韧窝断口的三维Motif表征方法,提出包含深度、长度、宽度、面积、方向角和各向异性率等6参数的定义,以及基于面积和深度阈值的合并算法.考虑到韧窝三维形态的各向异性,对基于纵横比的表面微观粗糙度定义进行修正.采用3D-Motif法对试验获得的断口三维形貌进行表面纹理分割,提取韧窝个体特征参数和统计数据,其中测得断口表面微观粗糙度为0.15～0.70,从而为定量化研究材料的断裂机理提供客观依据.     

三维表面形貌的逾渗特性表征

为了建立表面形貌微观结构与其功能特性之间的关系,基于逾渗理论建立了表面形貌的逾渗模型,用逾渗概率、空体集团平均大小和空体集团分布系数对三维表面形貌的逾渗特性进行了量化表征。采用数字滤波技术生成具有给定自相关函数和纹理取向的数字化粗糙表面,分析了具有相同均方根粗糙度而结构不同的三维表面形貌的逾渗特性,给出了表面纹理方向参数和自相关长度对表面逾渗特性的影响,并借助部分三维形貌参数(ISO25178)建立了表面形貌与逾渗特性参数间的量化关系。结果表明:对于各向异性表面,沿横向搜索跨越空体集团,表面逾渗发生时的表面高度、逾渗阈值和逾渗体积均随着表面纹理方向参数的增大呈减小趋势,而空体集团分布系数呈增大趋势;沿纵向搜索时,其变化规律与横向相反。对于各向同性表面,逾渗发生时的表面高度和逾渗阈值随着表面自相关长度的增大呈先减小后小幅增大趋势,而逾渗体积和空体集团平均大小呈逐渐减小趋势。研究结果为面向功能的表面形貌设计提供了理论基础。     

基于多方向连续小波构造的粗糙表面建模

参数可控的表面形貌建模方法依赖于高效的数学建模工具,而传统的表面建模方法由于参数的非稀疏性和冗余性,难以将平稳纹理过程与非平稳随机分形过程相互有机结合。本文通过引入多方向小波建模并与多重分形建模方法相结合,构造了具有多尺度、多方向、多重分形性质的基于多方向小波的表面形貌建模方法。通过人工设定不同表面形貌参数,计算机可以对铣加工表面形貌的特征进行建模仿真,并生成对应的功率谱进行对比与分析。实验表明,通过多方向小波构造的粗糙表面相较于传统的各向异性分形表面建模或纹理建模,具有更优秀的纹理控制能力与多尺度建模能力,可以在任意方向与尺度上按需求建立准确的表面纹理形貌与多重分形特征,有效实现所需的表面形貌。     

表面微凹坑和纹理方向对界面摩擦的耦合影响

选取三种不同纹理的铝合金试样,并在试样上加工不同面积占有率的规则圆形微凹坑,利用自制的摩擦试验装置,在油润滑条件下以不同接触压力进行摩擦试验,试验过程中滑动方向与表面纹理方向的夹角分别为0°、45°、90°。利用非接触式三维轮廓仪测量试验前后试样的三维表面形貌,并选取Sa、Str、Vvv、Vvc等表面表征参数来分析滑动接触界面表面形貌的变化。结果表明：表面纹理方向的差异导致铝合金表面在滑动接触摩擦过程中表现出各向异性,而在其表面加工不同面积占有率的微凹坑,减弱了铝合金表面纹理方向性对界面摩擦的影响,反映出表面微凹坑和纹理对界面摩擦的耦合作用。同时界面摩擦对试件的表面形貌也有明显的影响,Str、Vvv、Vvc在试验后发生了规律性的变化。     

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。     

研磨表面微观形貌的三维检测及Areal表征

介绍了三维表面微观形貌的检测方法,分析了采用高斯滤波提取基准中面的原理,针对研磨表面形貌的表征选取了一组Areal表征参数。运用原子力显微镜(AFM)扫描研磨工件的表面,采用高斯滤波提取基准中面进而分离出表面微观形貌的三维信息,在此基础上计算出表征参数值。试验表明研磨表面微观形貌呈现高斯分布规律,采用高斯滤波方法及所选的Areal表征参数能够有效地表征研磨表面的三维微观形貌。     

基于SFS技术的纹理力触觉再现方法研究

虚拟现实技术中,纹理的力触觉表达通常需要提取纹理表面的高度轮廓特征,从而再现纹理的凹凸感,而图像纹理则反映的是纹理表面的二维灰度特征.提出了一种根据图像灰度信息恢复表面三维轮廓(shape from shading,SFS),并用于纹理的力触觉表达的方法.采用Tsai & Shah算法从二维纹理图像中恢复出表面三维微观形状,并用力触觉模型渲染.该方法无需专门仪器测量物体表面的微观轮廓,无需设计专用的纹理力触觉表达装置.实验表明该方法是可行的,并通过对实验结果的分析给出了改进方向.     

汽车用薄板表面的空间特征的研究

提出了三个空间参数来表征汽车用薄板表面的频率分量的构成、纹理方向性和峰密度等空间特征。利用触针表面形貌仪和数据采集系统对不同类型薄板的三维形貌进行了测量,计算了各个薄板的空间参数值,对各薄板表面形貌的空间特征进行了分析。     

单晶硅磨削表面脆塑转变表征方法

为了对单晶硅磨削表面脆塑转变特征进行有效的表征,研究了单晶硅脆塑性磨削模式下的表面形貌。首先,基于工件旋转法磨削原理,对单晶硅进行了磨削试验。然后,利用三维形貌轮廓仪和扫描电子显微镜对不同磨削速度下的单晶硅表面形貌进行了测量和分析。最后,利用表面脆性破碎面积百分比Sbf、表面破碎率Sc、分形维数DL、表面纹理纵横比Str等参数对单晶硅磨削表面脆塑转变特征进行了研究。通过不同表征方法的对比分析,得出了基于参数Str的单晶硅磨削表面脆塑转变特征的有效表征方法。     

磨削加工表面纹理的特征分析

表面形貌与加工表面摩擦、磨损、润滑性能密切相关.采用平面磨削的方法在机械零件常用材料45钢试件表面制作一些有规则的纹理(如横纹理、30°斜纹理、45°斜纹理),采用表面形貌统计参数中的轮廓高度算术平均值R<,a>、微观不平度十点高度R<,a>、轮廓微观不平度的平均间距S<,m>对表面形貌进行评价,分析了表面形貌表征参数与磨削表面纹理的相关关系.结果表明磨削表面形貌不仅与加工过程中的工艺参数密切相关,而且其纹理特征在很大程度上影响了表面形貌参数.     

Some issues of traceability in the field of surface topography measurement

This paper highlights some of the reasons that surface topography measurements can have an ill-defined traceability route. Whereas the most common instruments on the shop floor are two-dimensional (2D) or profiling systems, there is a clear industrial trend towards three-dimensional (3D) surface topography instruments. Currently, there is no clear traceability route for three-dimensional measurements, and recent comparisons show alarming discrepancies between the various commercial instruments. This paper reviews these instrumental problems and highlights the need for unambiguous mathematical definitions for surface texture parameters and rigorous uncertainty evaluations. This paper also reviews some of the metrology issues that will be encountered when using three-dimensional surface texture measuring instruments to measure complex features on microsystems.     

Realistic simulation of surface defects in five-axis milling using the measured geometry of the tool

Managing macro- and micro-geometry of surfaces during manufacturing processes is a key factor for their following uses. Indeed, micro-geometry and surface topography are directly linked to the performances of functions (contact, friction, lubrication, etc.) by texture parameters to ensure the desired local geometry. Common models for simulation of surface topography are based on ideal geometry of the machining tool and cannot represent surface defects. The actual prediction and simulation of defects are one step forward in a competitive context. In this paper, the realistic model proposed aims to simulate and predict as finely as possible local defects of machined surfaces taking into account the actual edge geometry of the cutting tool. The combined use of the machining kinematics and of the measured geometry of the cutting edges leads to the representation of the geometrical envelope of the surface using a Zbuffer technique. Simulation assessment is carried out by the analysis of 3D surface topography parameters such as surface complexity and relative area and by a comparison of simulation results to an experimental case of study.     

Surface topography analysis in high speed finish milling inclined hardened steel

The surface texture of a milled surface is an inherently important process response in finish milling. It is one of the most commonly used criteria to determine the machinability of a particular workpiece material. However, literature survey on the study of the surface topography analysis relating to the cutter path orientations when high speed finish inclined milling is scant. Previous works were either involved in conventional milling of easy-to-cut workpiece materials or machining at different workpiece inclination angles. Furthermore, none of the previous work has detailed the true surface topography of the machined surface with regards to the cutter condition. Instead, the works provided quantitative values in terms of the Ra value. This article is concerned with evaluating cutter path orientations on an inclined workpiece angle of 75° to simulate finish milling of free form moulds and dies. Surface topography effects are assessed with regards to different cutter path orientations on its surface. The aims of this study are to provide an in-depth understanding on the surface texture produced by various cutter path orientations when high speed finish inclined milling hardened steel at a workpiece inclination angle of 75° using surface topography analysis and determine the best cutter path orientation with respect to the best surface texture achieved. 3D topography maps together with 2D surface profiles are used to assess the experimental results. The conclusion is that milling in a single direction vertical upward orientation gave the best workpiece surface texture.     

Development and machining performance of a textured diamond cutting tool fabricated with a focused ion beam and heat treatment

This paper presents the fabrication method and machining performance of a textured diamond cutting tool. To improve the machining performance, a texture was fabricated on the rake face of the diamond tool with a depth of 43 nm and width of 1.8 μm by utilizing a focused ion beam (FIB) followed by heat treatment. In addition, a FIB-induced non-diamond phase that adversely affects the machining performance was removed. A machining experiment using aluminum alloy and nickel phosphorus was conducted to evaluate the proposed method. A significant decrease in friction was observed at the tool–chip interface after texturing. This corresponds to a reduced cutting force, which indicates that the machining performance of the tool was improved by texturing. The magnitude of the effect depends on the shape and direction of the texture. The textured tool was able to machine a surface topography similar to that with a non-textured tool, which indicates that the texture effect can be obtained while maintaining the quality of the machined surface by fabricating the texture far from the cutting edge.     

Model for the prediction of 3D surface topography in 5-axis milling

The paper deals with the prediction of the 3D surface topography obtained in 5-axis milling in function of the machining conditions. For this purpose, a simulation model for the prediction of machined surface patterns is developed based on the well-known N-buffer method. As in sculptured surface machining the feed rates locally vary, the proposed model can be coupled to a feed-rate prediction model. Thanks to the simulation model of 3D surface topography, the influence of the machining strategy on resulting 3D surface patterns is analyzed through an experimental design. Results enhance the major influence of the tool inclination on 3D topography. Surface parameters used in the study are strongly affected by the variation of the yaw angle. The effect of the feed rate is also significant on amplitude parameters. Finally, the analysis brings out the interest of using surface parameters to characterize 3D surface topography obtained in 5-axis milling.     

A low cost 3D shape measurement method based on a strip shifting pattern

We present a simple, low cost but fast 3D shape measurement method. There is no limitation on the object's material and texture. We use a projector to project a strip shifting pattern on the object, and a digital camera to record videos of the scene. The distortion of the strip shadow on the object is used to get the object's 3D information. A novel space-time edge finding method is introduced to position the shadow edge accurately. This edge finding method overcomes the effect of inter-reflection and high light. Using this space-time information, we can calculate the pixels' 3D coordinates. To get the 3D shape of an object with black texture, we improve the black strip pattern to a 3-color strip pattern. The bad data are filtered by a post-processing 3D filter, which makes full use of the neighborhoods' geometric constraints and the view point constraint. Meanwhile, our measurement method is fast, regardless of the complexity of the shape.     

Investigating the effect of WEDM process parameters on 3D micron-scale surface topography related to fractal dimension

The wire electric discharge machining (WEDM) process is a violent thermal process in which a certain volume of metal is eroded by thousands of electrical discharges in a fraction of 1 s. The process is widely used in tooling, especially in the cutlery and mold industry. However, the poor properties of surfaces such as high tensile residual stresses, high surface roughness, white layers, and microcracks are generated in the process. These properties vary with different levels of process parameters. In this paper, a new graphical evaluation of micron-scale surface topography on WEDM process is proposed by the fractal method. The objective is to quantify 3D micron-scale surface topography effect of process parameters such as pulse-on time, pulse-off time, cutting feed rate, wire tension, wire speed, and water pressure on working surface in dressing. Firstly, adaptive measuring was conducted on the basis of 3D micron-scale surface topography by the ?₁₈(2¹×3⁵) Taguchi standard orthogonal experiments; secondly, the fractal dimension was conducted to identify 3D micron-scale surface topography; and finally, the effect of WEDM process parameters was investigated with reference to the fractal dimension (FD) of 3D micron-scale surface. The results have shown that the pulse-on time is the most dominant factor in affecting the surface texture. Moreover, the interaction effect between process parameters is analyzed. It has also been observed that the optimized combination of pulse-on time of 3 μs, pulse-off time of 20 μs, cutting feed rate of 4 mm/min, wire tension of 6 kgf, wire speed of 6 m/min, and water pressure of 5 kgf is suitable for 3D micron-scale surface, and the FD of 3D micron-scale surface is increased by 11 %.     

Modeling and controlling of surface micro-topography feature in micro-ball-end milling

The machined surface micro-topography has a great influence on the surface quality and the surface function. A simulation algorithm of machined surface topography is present in this paper, in which the influence of the tool vibration is considered. From the overall surface texture formation, surface texture interval, surface texture height, and surface texture direction, the geometric characteristics of surface micro-topography in micro-milling was defined and investigated. The influence of process parameters, especially the initial phase angle of cutter and the tool vibration, on the geometric characteristics of surface micro-topography is investigated, and the method to control the process parameter is proposed. Especially, this paper presents a novel method, through the planning of noncutting tool path, to control the initial phase angle of cutter which has significant effect on surface topography. The experiments shows that the control deviation of the surface texture direction is less than 2°, and the machined surface topography consistent with the simulation result, which means that the modeling and controlling of surface topography is feasible and effective.     

Modeling and predicting for surface topography considering tool wear in milling process

This paper presents a model for the prediction of surface topography considering tool wear during the milling process. First, the cutting edge path equation, which can be transformed into equivalent polynomial equations and solved for discrete positions along the feed direction, is established including the effect of tool wear. Then, cutting edge is divided into a series of cutting points and an algorithm is proposed to determine the range of divided position angle. Finally, surface topography model is established based on the established cutting path equation, the range of position angle, the calculated cutting time, and spiral lag angle. By using this model, surface topography generation is simplified with respect to other models in literature and the modeling method of surface topography does not need to mesh the workpiece and the model can easily be extended to include other factors on surface generation. Based on the established surface topography model, an algorithm is proposed to simulate generation of surface profile in milling operation. Experimental work and validation of the established model is performed on a five-axis milling center by using stainless steel 1Cr18Ni9Ti and cemented carbides milling cutter. Cutting test results about the topography generation of the plane and cylindrical surface show good agreement with model predictions.