超声辅助磨料流加工的材料去除机理及参数研究

超声辅助磨料流加工是将超声加工与磨料流加工结合在一起的新型光整加工技术。为了进一步提高超声辅助磨料流的加工精度和加工效率,从材料去除机理的角度出发,建立了单磨粒的力学模型。通过Box-Behnken响应面实验对影响表面质量和加工效率的重要参数进行了研究。结果表明:与传统的磨料流加工相比,超声辅助磨料流获得了更好的表面质量和更快的加工速度;材料去除量和表面粗糙度变化率受超声频率扰动的影响最大;在一定范围内,随着超声频率的增大,表面精度先提高后降低,加工效率则不断提高。     

磨料流加工中夹具设计的研究

磨料流加工(AFM)是光整加工领域的一项新技术。磨料流加工由磨料流加工机床,夹具和流体磨料三部分组成。当用磨料流加工形状较复杂的零件时,夹具设计的好坏对表面加工质量和加工效率有重要的影响。本文分析了磨料通过工件孔道的特性。介绍了用于研究材料去除量与加工距离和形状关系的实验。材料去除量在通道两端比中间小是磨料流加工的一基本特性。本文讨论了如何避免因此而产生的工件变形以及如何利用这一特性来获取某种特殊效果。最后,给出了一个用于加工某不锈钢三通体的夹具。     

连杆大头孔磨料流加工的理论探讨及实验研究

针对H12V190Z柴油机连杆大头孔表面的磨料流加工方法进行了研究,利用CFD软件对其加工流场进行了模拟仿真,得到了流体磨料在流场中的压力和速度分布。结合工艺实验验证了经磨料流加工后连杆大头孔加工表面的粗糙度值有明显的减小,提高了连杆表面的质量,大大缩短了加工时间,提高了加工效率。     

磨料流加工工艺在汽车生产中的试验研究

一、磨料流加工概况 磨料流加工基本原理: 磨料流加工是一科新的机械光整加工方法,基本原理是:将流体磨料介质(由有一定弹性的高分子载体材料和磨粒混合而成的半流动磨料)填满工件与夹具之间,在一定压力作用下,使流体磨料介质在被加工零件表面上作往复移动,这种移动,就象一个软砂轮贴在金属     

粘弹性介质的磨料流加工

用含磨料的高分子树脂对难加工表面如盲孔、内部交错孔等进行磨料流加工,可顺利完成去毛刺、倒圆角、表面精饰等。文中给出了磨料粒度、介质等的选择。     

单向磨料流加工工艺特性研究

针对不能通过往复驱动流体磨料而采取单向磨料流加工工艺进行抛光的零件,首次揭示了沿着料流方向被加工孔道表面的粗糙度改善逐渐减弱的问题.分析确定从介观尺度研究单个磨粒的工作过程,采用CFD仿真,解析单向磨料流加工工艺的技术特性,包括速度、入口非稳定流动等随粘度变化的特性;使用Central Composite Design...     

粘弹性磨料流加工技术

磨料流加工，也称挤压研磨加工，是近几十年发展起来的一项新的机械加工技术。复杂孔内表面的加工，细孔、深孔、盲孔的精密研磨加工，异形曲面的高精度加工，用流动磨料加工法已取得了成功的经验，特别是在难加工材料方面，如不锈钢、镍铬钢、工具钢及其它合金钢、铜合金。铝合金，超硬合金等，更是得到广泛应用。磨料流加工如图1所示。工件夹持在上下对置的两个工作缸之间。工作时，填满在下缸体内的磨料介质在活塞的挤压下，被迫流过工件的通道而进入上缸体，然后由上缸体的活塞向下挤压，使磨料介质从工件的通道重新返回下缸体内。这样…     

淬硬工具钢内圆表面磁性研磨加工实践与研究

磁性磨料研磨是一种较新的光整加工的方法，它是在S、N两极之间加入磁性磨料，磁性磨料吸附在磁极和工件表面上，并沿磁力线方向排列成有一定柔性的“磨料刷”，工件一边旋转，一边做轴向振动，以达到去除表层金属的目的，使工件表面粗糙度大大下降。本文介绍了磁性磨料研磨的加工原理，对工件在磁场中的受力情况进行理论分析。对淬硬工具钢(T8A)工件内圆表面进行磁性磨料研磨的加工试验．得出了不同的磁感应强度，不同加工间隙，以及不同研磨时间对加工表面粗糙度和研磨量的影响；从而得出了优化的磁性磨料研磨的加工参数：磁感应强度B=1．0—1．2T；加工间隙△=1-3mm；研磨时间t=4—5min。     

微磨料水射流加工脆性玻璃的冲蚀机理研究

微磨料水射流加工技术正成为制造微细结构零件重要的经济高效的微细加工技术。作者在玻璃上进行微磨料水射流微细槽加工的实验基础上,对微磨料水射流加工的表面形貌、材料冲蚀去除机理及加工工艺性能进行了研究。结果表明,玻璃加工表面沿着槽道的方向形成了波纹状形貌,呈非对称或对称的波形,波纹表面很光滑,波纹图案沿着射流冲击区的径向方向发展。由于黏性流体的阻滞作用,脆性玻璃在微磨料水射流加工过程中,在黏性流区域没有发现任何裂纹,材料的冲蚀去除主要是以塑性断裂的方式为主,形成了光滑的加工表面。适当地控制加工工艺参数,在低压下,微磨料水射流加工是一种用于脆性材料上微细通道的加工切实可行的方法,并可获得良好的加工表面质量。     

钛合金磨料流光整加工表面完整性研究

目的 研究磨料流光整加工钛合金格栅表面完整性。方法 用电火花加工制备钛合金试样,通过磨料粒径、加工压力、加工次数的单因素试验,来研究其对试样表面粗糙度和表面形貌的影响规律,选用三种初始粗糙度不同的钛合金试样来进行磨料流光整加工效果试验,对比分析磨料流光整加工对试样表面残余应力的影响,进行加工次数的单因素试验研究磨料流加工过程中其对工件表面显微硬度的影响。结果 对于钛合金试样来说,磨料粒径和加工压力越大,表面抛光效果越明显,表面粗糙度就越低。当磨料粒径从38 μm增加到420 μm时,相对应的表面粗糙度值Ra从5.815 μm降低到0.824 μm;当加工压力从8 MPa增加到24 MPa时,相对应的表面粗糙度值Ra从4.314 μm降低到1.398 μm。而随着加工次数的增加,表面粗糙度值Ra从整体上呈现下降趋势,最后趋于稳定,当加工次数从10增加到80时,相对应的表面粗糙度值Ra从5.925 μm降低到0.307 μm,并且最后稳定在0.300 μm附近。钛合金试样经磨料流光整加工之后,表面残余应力由原来的拉应力变成了压应力。随着加工次数的增加,钛合金试样表面显微硬度整体上呈现先减小后增大的趋势,当加工次数从10增加到50时,显微硬度值从532.83HV降到357.73HV,当加工次数从50增加到90时,显微硬度值从357.73HV上升到393.48HV,试样表面显微硬度的均匀性也显著增加。结论 增大磨料粒径和加工压力或者增加加工次数,都能降低工件表面粗糙度,钛合金工件经过磨料流光整加工之后,表面完整性有较大改善。     

Modeling of material removal and surface roughness in abrasive flow machining process

Abrasive flow machining process provides a high level of surface finish and close tolerances with an economically acceptable rate of surface generation for a wide range of industrial components. This paper deals with the theoretical investigations into the mechanism of abrasive flow machining (AFM) process. A finite element model is developed for the flow of media during AFM and the same is used to evaluate the stresses and forces developed during the process. Theoretical analysis to estimate the material removal and surface roughness obtained during AFM is also proposed. The theoretical results are compared with the experimental data available in the literature, and they are found to agree well.     

Modelling the abrasive flow machining process on advanced ceramic materials

Abrasive flow machining (AFM) is a unique machining method used to achieve high surface quality on inner, difficult-to-access and on outside contours. Using AFM, it is possible to realise predefined edge rounding on any brittle or hard material. AFM is easy to integrate in an automated manufacturing environment. The abrasive medium applied during AFM is a fluid consisting of a polymer which carries silicon carbide or super-abrasive grains. With a specified pressure and temperature, this fluid flows in alternating directions along the contours of the workpiece resulting in an abrasive effect. AFM is also well suited to process advanced ceramic materials. Especially advanced ceramics are playing increasingly a significant role as a substitute for metals. However the high costs for the inevitable finishing process on ceramics prevent a more frequent use. This paper represents the technological results of a research-project discovering the fundamental principles of AFM on advanced ceramic materials such as a correlation between flow processes, surface formation and edge rounding. Furthermore an insight into a process model is given, which was developed using modern simulation techniques. The overall objective of this approach is to anticipate work results like surface quality and edge rounding on any user-defined geometry.     

Development of magneto abrasive flow machining process

Abrasive flow machining (AFM) is a relatively new process among non-conventional machining processes. Low material removal rate happens to be one serious limitation of almost all such processes. Limited efforts have hitherto been directed towards improving the efficiency of these processes so as to achieve higher material removal rates by applying different techniques. This paper discusses the possible improvement in surface roughness and material removal rate by applying a magnetic field around the workpiece in AFM. A set-up has been developed for a composite process termed magneto abrasive flow machining (MAFM), and the effect of key parameters on the performance of the process has been studied. Relationships are developed between the material removal rate and the percentage improvement in surface roughness of brass components when finish-machined by this process. Analysis of variance has been applied to identify significant parameters and to test the adequacy of the models. Experimental results indicate significantly improved performance of MAFM over AFM.     

Movement patterns of ellipsoidal particle in abrasive flow machining

Abrasive particle movement pattern is an important factor in estimating the wear rate of materials, especially, as it is closely related to the burring, buffing and polishing efficiency of the abrasive flow machining (AFM) process. There are generally two kinds of particle movement patterns in the AFM process, i.e. sliding–rubbing and rolling. In mechanism, AFM particle–workpiece interaction is taking place in any one or a combination of the possible modes: elastic/plastic deformation by grooving particle movement; elastic/plastic deformation by rolling particle movement; chip formation (micro-cutting) by grooving particle movement, ridge formation by grooving and rolling particle movement, and low-cycle fatigue wear. Grooving particle movement pattern has a greater contribution to wear mass loss of workpiece than rolling mode. Considering the machining efficiency of a machine part is predominantly dependent upon its wear mass loss speed, it can be concluded that particle movement patterns are key parameters to machining efficiency in AFM. In this paper, ellipsoidal particles are investigated to understand particle movement patterns. An analytical model of ellipsoidal geometry to determine particle movement patterns in AFM is proposed with given particle ellipticity, normal load, particle size and material hardness. From the analytical model and particle movement pattern criterion proposed by the present authors, a statistic prediction of particle movement patterns is completed by computer programmed by C++ language. It is found that a seat position of ellipsoid is an easy grooving position for a particle and a large ellipticity value predominantly increases grooving particle numbers. Smaller workpiece hardness, larger particle radius and higher normal load promote grooving of the particles. Sharper particles are much more easy to groove; moreover, grooving pattern will be predominant if particle ellipticity is below 0.8. Increasing workpiece hardness tends to decrease grooving regime while other parameters are fixed in AFM process. In three-body abrasion, hard material paired with soft material will result in more rolling particles. Abrasive contour and material hardness in many variables are two predominant parameters to give distinct influence on particle movement pattern.     

Atomic force microscopy study of biaxially oriented polypropylene films

Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true surface features of the sample, rather than contamination on the AFM tip.     

Performance evaluation and rheological characterization of newly developed butyl rubber based media for abrasive flow machining process

The precision manufacturing technology always demands a good surface finish at low cost. This scenario drives both industries and research community to develop novel finishing processes. Presently, there are many techniques and one among them is abrasive flow machining (AFM) process. The media developed by optimum process variables mainly governs the performance of AFM. In the present experimental endeavor, an attempt is made in the direction of developing new media based on viscoelastic carrier and its characterization for fine finishing through AFM process. The newly developed media was again characterized through rheological properties. It is found that temperature, shear rate, creeping time and frequency have impact on rheological properties and the percentage ingredients of media govern trends of their relations.     

Experimental investigation into cutting forces and active grain density during abrasive flow machining

It is important to know cutting force components and active grain density during abrasive flow machining (AFM) as this information could be used to evaluate the mechanism involved in AFM. The results show that cutting force components and active grain density govern the surface roughness produced during AFM process. In this paper, an attempt has been made to study the influence of these two parameters, namely cutting force and active grain density, on the surface roughness. This study will help in developing a more realistic theoretical model.The present paper highlights a suitable two-component disc dynamometer for measuring axial and radial force components during AFM. The influence of three controllable variables (extrusion pressure, abrasive concentration and grain size) on the responses (material removal, reduction in surface roughness (R_a value), cutting forces and active grain density) are studied. The preliminary experiments are conducted to select the ranges of variables by using single-factor experimental technique. Five levels for abrasive concentration and six levels for extrusion pressure and abrasive grain size were used. A statistical 2³ full factorial experimental technique is used to find out the main effect, interaction effect and contribution of each variable to the machined workpiece surface roughness. The machined surface textures are studied using a scanning electron microscope.     

原子力显微镜在马氏体相变浮突研究中的应用

用原子力显微镜在大气环境中对Ｆｅ－Ｎｉ－Ｃ合金中的马氏体浮突进行了观察和定量测量。结果表明，原子力显微镜既可清楚地观察浮突形貌，又可定量测量其高度和形状变化，从而提出了一种研究相变浮突的新方法。     

In situ AFM study of the surface morphology of polypyrrole film

In this paper we focus on the surface morphology of polypyrrole film by using in situ atomic force microscopy (AFM). The formation process of polypyrrole film and the transformation process of the film from the oxidized to reduced state were clearly observed.