基于图像拼接的砂轮表面三维形貌图重构

为了实现大面积砂轮表面形貌的计算机视觉检测,本文利用视频系统从两个不同视角采集钎焊金刚石砂轮表面形貌,通过特征配准法找出两幅图像的特征点和匹配点,然后对图像进行拼接融合,最终得到拼接后的目标图像,实现了砂轮表面三维形貌图的有效重构。     

超声相控阵矩阵阵列三维合成聚焦成像方法

掌握缺陷的三维形态信息,会更利于无损评估,因此将合成聚焦二维成像方法扩展,初步探索了三维合成聚焦成像方法,以直观得到缺陷的超声三维成像.将该方法在MATLAB平台编程实现,然后通过超声相控阵矩阵探头采集到的完备集数据后处理进行了验证.结果表明,通过三维合成聚焦处理后,得到探头下方空间的超声成像的三维图像数据,然后在此基础上使用等值面法将缺陷的三维图像分割出来.该图像能够清晰反映出反射体的真实位置及空间分布;在超声探头没有机械移动扫描的前提下能够得到缺陷三维图像.对于探头移动空间受限的检测位置获取缺陷三维图像有一定的理论意义及实用价值.     

cBN砂轮超声振动修整表面地貌实验研究

对cBN砂轮进行了超声振动辅助机械修整试验,研究了砂轮修整后表面地貌特征及砂轮表面静态有效磨粒数。实验结果表明,超声振动辅助修整的cBN砂轮表面的磨粒突出高度随振动频率增大而增大;砂轮表面静态有效磨粒数随着修整导程和修整深度的增加而减少。选择合理的修整参数,采用超声振动修整技术能够获得较理想的cBN砂轮表面。     

电镀cBN砂轮油石修整效果及评价研究

针对电镀砂轮制造过程中存在的磨粒等高性不好的问题,采用白刚玉油石对其进行修整。通过选择合理的修整参数,使得砂轮和油石的相互作用力控制在一定的范围内,实现突出高度较高,结合强度差的磨粒的去除;而对等高性较好,结合强度较高的磨粒影响不大,从而达到修整的目的。为了对修整效果进行评价,采用激光扫描方法得到修整前后砂轮的地貌,并根据地貌的不同特征分析和验证修整效果,重点关注磨粒出刃高度和等高性。     

基于线结构光的砂轮地貌测量技术研究

提出了一种新的基于线激光的视频测量系统来对砂轮地貌进行测量,以交比不变法则为基础,改进了线结构光测量中的定标方法,使得定标过程简化,且结果更易分析处理。对砂轮沿圆周方向的地貌进行了实测,采用区域分割和形态学滤波相结合的方法提取出一条单一连续的轮廓曲线,并以此得到了砂轮沿此曲线的相对坐标。结果表明,该方法简单有效,为砂轮自动化检测提供了一条新的思路。     

红外热波序列图像的图像分割与三维显示

研究了针对红外热波序列图像的图像分割和三维显示方法。红外热波无损检测只能得到被测工件表面温度变化的时间序列图像,无法直观到检测缺陷,利用三维显示技术可以产生深度三维立体图,方便技术人员更直观、精确地进行无损检测。三维显示效果的好坏直接取决于图像分割的效果。为此提出了基于局部极小值的区域生长分割算法,成功地提取出红外热波图像中缺陷成分的目标图像,并进行了三维显示,取得了较好的效果。     

基于二维位移传感器的砂轮表面形貌测量

砂轮表面的三维形貌对保证其磨削质量有重要意义。采用高精度二维位移传感器在线测量砂轮的表面形貌,再通过建立的砂轮三维形貌基准平面和数字滤波方法,用测量数据计算得到砂轮表面的三维形貌评价参数。结果表明:该评价参数与Zeta自动三维测量系统的测量结果基本相同,验证了该评价方法的有效性和实用性,可为砂轮修整及其磨削加工提供参考指标。      

基于数字化模型的砂轮表面地貌特性研究

单层电镀CBN砂轮通过电镀工艺将磨料固结在砂轮表面。通过严格的磨料粒径一致度控制,实现更高的砂轮品质是高端砂轮制造的关键技术。因此,建立磨料粒度及其分布与砂轮表面地貌特性之间的关系对砂轮设计及磨削质量控制将起到重要作用。针对单层电镀CBN砂轮提出了基于制造过程的数字化砂轮模型,可实现对砂轮生产制造过程中的每个步骤的仿真。通过对3种规格砂轮的建模与地貌测量,验证了模型的准确性和有效性。同时,通过该模型研究了磨粒直径标准差与砂轮微观地貌特征的关联机制,为砂轮数字化设计与质量控制提供了定量化依据。     

钎焊金刚石砂轮磨削石材中金刚石粒度对磨削力的影响研究

本文通过测量不同金刚石粒度的高频感应钎焊金刚石砂轮磨削花岗石过程中的磨削力，对砂轮所受的法向力和切向力进行了研究。对不同粒度条件下磨削深度、进给速度和砂轮线速度对磨削力的影响进行了分析。研究发现磨削力随砂轮线速度的增大而减小，随磨削深度和进给速度的增大而增大，磨削深度对磨削力的影响程度比进给速度大。小粒度金刚石磨削时，磨削三要素对磨削力的影响比大粒度金刚石磨削时大。     

三维超声辅助平面磨削力研究

三维超声辅助磨削力的研究一直是超声加工领域的空白,本研究首先以三维超声辅助平面磨削力为研究对象,从宏观力学角度进行分析,建立了三维超声辅助平面磨削力的数学模型,并分析在不同磨削参数下磨削力的变化情况,最后进行了试验验证。研究结果表明:在一定条件下,三维超声辅助平面磨削下的磨削力小于二维超声辅助平面磨削力,约下降20%;随砂轮转速的增大,磨削力下降,且当砂轮转速大于3000 r/min时,磨削力下降明显;随着进给速度与磨削深度的增加,磨削力增加明显;实验验证同模型分析一致。      

3D laser investigation on micron-scale grain protrusion topography of truncated diamond grinding wheel for precision grinding performance

A grain tip (GT) truncation is proposed to truncate grain protrusion tips of #270 diamond grinding wheel in plunge grinding of hard and brittle material. In this study, a 3D laser microscopy was employed to measure the wheel working surface and parameterize its 3D grain protrusion topography. The objective is to investigate how micron-scale grain protrusion parameters influence grinding performance such as grinding force and surface roughness. First, the GT truncation was performed after dressing of diamond grinding wheel in grinding experiment of quartz glass; then its 3D grain protrusion topography was constructed by smoothing 3D measured noise, matching measured point cloud, transferring protrusion frame and extracting 3D diamond grains; finally, the grain protrusion parameters such as grain protrusion number, grain protrusion height, grain protrusion volume, grain rake angle, grain clearance angle, etc. were investigated in connection with ground surface and grinding force. It is shown that GT truncation averagely decreases grain protrusion number, grain protrusion height, grain protrusion volume, grain rake angle and grain clearance angle by about 44%, 74%, 75%, 24% and 70% on whole wheel surface, respectively. However, it greatly increases active grain number by about 32 times and active grain volume by about 181 times in actual grinding with the depth of cut in 1 μm, thus leading to a decrease (about 80%) in surface roughness and an increase (about 40 times) in grinding force. It is also found that truncated diamond grain tips are mostly shaped with nanometer-scale tip wedges along grain cutting direction, leading to about 75% very large negative grain rake angles and about 75% large grain clearance angles, thus contributing to ductile-mode grinding. It is confirmed that the active grain number and active grain volume for the actual depth of cut may be regarded as main grain protrusion parameters to evaluate and predict the precision grinding performance of a coarser diamond grinding wheel.     

砂轮表面形貌仿真方法研究

砂轮表面形貌对磨削加工过程和已加工表面质量有着极大影响,但由于砂轮表面磨粒分布的随机性,描述砂轮表面形貌非常困难。通过对砂轮表面进行采样和数据处理,运用统计学理论和Johnson变换方法获得了非正态分布砂轮表面形貌的数学描述方程,在此基础上对砂轮表面形貌进行仿真。选用伯明翰14参数集的部分参数作为评价标准,对测量的砂轮表面形貌和仿真形貌进行比较,结果显示:二者具有很好的一致性,6个参数的平均相对误差仅为2.97%。结果充分证明了该仿真方法的正确性。      

砂轮表面形貌检测方法的研究进展

砂轮表面形貌特征是砂轮磨削性能的主要决定因素。准确地检测砂轮表面形貌不仅有助于进一步认识磨削机理,更是砂轮表面形貌建模和磨削仿真不可或缺的先决条件。本文中总结了典型的砂轮表面形貌检测方法,概述了各检测方法的基本原理,并分析了它们的优势和不足。最后,分析了国内外砂轮表面形貌检测方法的发展现状,指出了现阶段存在的问题,展望了砂轮表面形貌检测方法的发展前景。      

Analysis and simulation of the grinding process. Part I: Generation of the grinding wheel surface

This paper is in three parts describing the analysis and simulation of the grinding process. This first part is concerned with the generation of the wheel surface by single point diamond dressing. In grinding, the grinding wheel has to be dressed periodically to restore wheel form and cutting efficiency. Understanding the process of generating the grinding wheel surface is important for the control of the grinding process. Generation of the wheel surface is simulated as a single diamond dressing process on a computer generated wheel. The wheel is simulated by grains randomly spaced in the wheel volume. The topography of the wheel cutting surface is generated by simulating the action of an ideal dressing tool as it dresses the wheel. The simulation of the wheel topography takes account of the motion of the dressing tool, grain size, grain spacing, grain fracture and grain break-out. The simulated cutting surface is used for further simulations of grinding. The simulation of grinding using the simulated grinding wheel surface is described in Sections 2 and 3 where a comparison is made of results predicted from simulation with results obtained from experiments. By matching simulated and experimental results, it is possible to explain the relative importance of dressing and grinding parameters.     

Study on axial-feed mirror finish grinding of hard and brittle materials in relation to micron-scale grain protrusion parameters

An axial-feed mirror finish grinding of hard and brittle materials is proposed by controlling grain protrusion parameters. In this grinding, the grinding wheel feed is along the wheel axial direction rather than in the traditional wheel cutting direction. The objective is to understand how micron-scale grain protrusion parameters influence ductile-mode grinding and ultimately to realize efficient mirror finish grinding using a coarse diamond grinding wheel. In this study, the grain tip truncation (GT-truncation) was performed after dressing to improve grain protrusion topography. First, a formation model of axial-feed ground surface was constructed to analyze the effect of grain protrusion parameters and grinding parameters on the critical cutting depth transferred from brittle-mode removal to ductile-mode removal; then GC dressing and GT-truncation of #180 diamond grinding wheel were experimentally performed to investigate surface roughness and ductile-mode grinding behavior with reference to grinding parameters and grain protrusion parameters; finally, a truncated coarser #60 diamond grinding wheel was employed for mirror finish grinding to observe active grain number and grain protrusion angle. Theoretical analysis shows that this ductile-mode grinding is dominated by active grain number, active grain protrusion angle, wheel rotating speed and axial-feed speed, but it does not depend on the depth of cut assumed to be less than the grain protrusion height. Experimental results indicate that the GT-truncation may increase active grain number and grain protrusion angle for ductile-mode grinding when the axial-feed speed decreases to some extent. Moreover, the micro tip radius of diamond grain also influences the ground surface. It is confirmed that by increasing active grain number and grain protrusion angle synchronously, a truncated #60 diamond grinding wheel can be applied for efficient mirror finish grinding of the SiC ceramic plate at the axial-feed speed of 50 mm/min and the tool path interval of 0.1 mm.     

用磨粒叶序排布砂轮磨削外圆生成的凹坑表面仿真

结构化凹坑表面能够有效降低零件表面的流体拖曳摩擦阻力,从而改善零件在流体中的运动性能。从生物学的叶序排布理论出发,设计了磨粒叶序排布的超硬材料砂轮,并应用该砂轮磨削外圆生成结构化的凹坑表面。利用Matlab软件对磨粒叶序排布砂轮的磨削过程进行运动学仿真,获得了磨粒叶序排布参数及磨削参数对磨削区域内结构化凹坑表面形貌的影响规律。仿真及实验结果表明:转速比影响凹坑的周向排布和凹坑尺寸,转速比越高,凹坑周向排布越密集,凹坑尺寸越小;叶序系数影响凹坑的轴向排布,叶序系数越小,凹坑轴向排布越密集;磨削深度影响凹坑尺寸,磨削深度越深,凹坑宽度和深度越大,毛刺隆起高度越高,约为磨削深度的一半。      

In-process measurement of topography change of grinding wheel by using hydrodynamic pressure

This paper deals with an in-process measurement method for topography change of a grinding wheel, which can apply to wet grinding. A pressure sensor is set beside a grinding wheel with a small gap. When grinding fluid is dragged into the gap, hydrodynamic pressure, which corresponds to the gap length and the topography, can be measured. This method is applied to a cylindrical grinding machine. No electromagnetic properties of a workpiece and a grinding wheel affect measured results. The pressure is decreased with the increase of the gap length when the grinding fluid is supplied in the tangential direction of the grinding wheel. Spectra of the pressure are measured with an FFT analyzer. Higher frequency components are increased with the progress of grinding because of turbulent flow. Loading and dulling of a grinding wheel can be detected by the proposed method as well as its wear.     

Simulation of precision grinding process, part 1: generation of the grinding wheel surface

This paper is in two parts describing the kinematic simulation of the grinding process. The first part is concerned with the generation of the grinding wheel surface. A numerical procedure for effectively generating the grinding wheel topography is suggested. The procedure is based on the transformation of a random field. The sufficient condition for the transformation is discussed, and two transformations satisfying the condition are introduced. Numerical examples are used to illustrate the viability of the approach. It will be shown that the generated and measured grinding wheel topography share the same probabilistic characteristics.     

Influence of surface topography evolution of grinding wheel on the optimal material removal rate in grinding process of cemented carbide

Most of the reported studies on the optimization of grinding parameters do not consider the evolution of the surface topography of grinding wheels, and the established empirical models will no longer apply when the surface conditions of the grinding wheel changes. In this paper, an integrated model based on the surface topography of grinding wheel is established. The grinding process of cemented carbide is simulated using the established model, and the simulation results are analyzed to obtain the surface roughness model and the specific grinding energy model based on the undeformed chip thickness distribution. Subsequently, the grinding constraint models are defined according to the two grinding constraints—surface roughness and specific grinding energy. Through inversion analysis, the maximum material removal rate of the given grinding wheel surface conditions satisfying the defined grinding constraints are obtained, and the influence rules of the grinding wheel surface conditions on the maximum material removal rate are analyzed. Then the grinding wheel surface conditions are adjusted by changing the radial dressed height of the grinding wheel and the arrangement distance of the grains in wheel circumferential direction to improve the maximum material removal rate of the grinding wheel. Finally, the optimization results are verified through grinding tests of cemented carbide.