超精密加工技术研究现状及发展趋势

超精密加工是多种技术综合的一种加工技术,是获得高形状精度、表面精度和表面完整性的必要手段。根据当前国内外超精密加工技术的发展状况,对超精密切削、磨削、研磨以及超精密特种加工及复合加工技术进行综述,简单地对超精密加工的发展趋势进行预测。     

振动切削技术与零件加工表面完整性

论述了现代工业对零件加工表面完整性的要求 ,分析了零件加工表面完整性对零件使用性能的影响 ;讨论了振动切削的原理 ,指出振动切削是提高零件加工表面完整性的重要方法。     

光学脆性材料的金刚石切削加工

重点对脆性材料的超精密研磨、抛光加工技术及超精密磨削加工技术和超精密切削加工技术进行了分析研究。分析表明,硬脆材料光学元件主要应进行超精密研磨、抛光及超精密磨削加工;软脆材料光学元件主要应进行金刚石切削加工。对软脆材料金刚石切削进行了试验设计,指出了光学脆性材料的金刚石切削加工过程不同于金属加工过程,通过控制切削条件可以实现脆性材料塑性域加工,提高光学脆性材料的表面加工质量。     

光学玻璃的精密加工技术

光学玻璃作为一种典型的脆硬材料,采用普通的加工方法难以进行高效精密加工。本文介绍了光学玻璃的高效精密特种加工技术,对ELID法、激光加工、超声磨削以及精密铣削的最新研究进展进行了综述。采用ELID技术,通过控制加工工艺参数,使砂轮单个磨粒的最大切削深度小于脆性材料的临界切削厚度,实现了脆性材料的塑性加工,并得到精密光滑的表面;在加工非球曲面时,可使零件的精加工抛光量降到最低。最新激光加工技术通过增加预热激光束,极大降低已加工表面的热应力及拉伸应力,使得加工质量有了大幅提高。超声波磨削加工不仅改善了表面完整性,而且提高了加工效率,通过选用适当的刀具和工艺参数,使被加工工件表面粗糙度值比普通磨削降低了30%～40%。光学玻璃精密铣削技术通过优化刀具、加工方式及工艺参数,可提高加工质量和效率、降低加工成本。     

超精密加工现状综述

超精密加工是获得高形状精度、表面精度和表面完整性的必要手段.精密光学、机械、电子系统中所用的先进陶瓷或光学玻璃元件通常需要非常高的形状精度和表面精度(如0.1 nm级表面粗糙度)及较小的加工变质层.掌握超精密加工过程中材料去除规律和损伤层特性对提高加工的稳定性与经济性十分重要.对超精密加工中的超精密切削、超精密磨削和超精密研磨抛光技术进行综述,重点介绍各种典型加工方法及其材料去除机理.从加工精度和加工效率角度对上述几类超精密加工方法进行比较,介绍以实现高效精密加工为目的的半固着磨粒加工技术.对超精密加工的发展趋势进行预测.     

精密切削加工切削模型

本文从切削表面形成的机理出发,分析了精密切削过程中切削作用力的变化规律,建立了精密切削加工新的切削模型,得到了切削力与各主要参数的关系式及切削方程式,探明了精密切削加工机理。     

表面微观V形槽的超精密加工技术研究

表面微观V形槽是一种常见的微结构形式,应用广泛,加工精度要求高。对表面微观V形槽的超精密加工技术进行了研究,应用单点金刚石切削,分析刀具角度、切削参数、装夹方式、冷却润滑条件、进刀轨迹等影响加工质量的因素,并通过切削试验进行验证。通过试验,在平面和曲面上分别加工出了高精度表面微观V形槽,实现了微结构的超精密加工。     

超精密加工领域科学技术发展研究

超精密加工是获得高形状精度、表面精度和表面完整性的必要手段.随着对产品质量和多样化的要求日益提高,对超精密加工提出更多、更高的要求.超精密加工技术已成为包含当代最新科技成果的一个复杂系统工程.介绍各种超精密加工技术的内涵、应用范围、国内外研究现状、发展过程与趋势以及未来应研究开发的重要科学技术问题.从加工精度、加工质量和加工效率角度对先进的具有代表性的超精密加工机床、超精密切削、超精密磨削和超精密抛光技术进行重点评述和比较.分析我国在超精密加工领域中存在的主要问题以及与国外先进技术的差距,对超精密加工的技术发展趋势进行预测,提出我国本领域基础研究、技术及产业发展策略与对策.     

铌基合金切削加工过程中刀具优化研究

通过研究硬质合金和CBN刀具切削加工铌基合金材料过程中的加工性能,优化出适合铌基合金材料零部件超精密切削加工的刀具材料。通过硬质合金刀具在铌基合金材料切削加工过程中切削三要素(切削速度、进给量和切削深度)的正交切削加工试验,研究了其对切削加工表面粗糙度的影响,建立了硬质合金刀具切削加工铌基合金材料表面粗糙度预测模型,并利用AdvantEdge金属切削有限元仿真软件开展了切削工艺参数对切削加工过程的影响。     

单点金刚石切削加工表面粗糙度的影响因素分析

本文研究了单点金刚石切削加工表面微观形貌形成机理,建立了圆弧刃金刚石刀具超精密加工表面微观形貌的理论模型,重点分析了主轴转速、进给量、刀尖圆弧半径和振动等因素对超精密加工表面粗糙度的影响。     

Chip perforation and ‘burnishing–like’ finishing of Al alloy in precision machining

In precision machining, a high quality machined surface cannot be achieved without using a diamond tool, due to the deterioration of workpiece surface integrity. Burnishing process is often used to improve the surface integrity by minimizing the roughness of the machined surface. For any given cutting tool-workpiece combination, the surface roughness depends on a parameter known as relative tool sharpness (RTS), which is quantified as the ratio of undeformed chip thickness (a) to tool edge radius (r). To achieve burnishing-like surface quality from precision machining, it is necessary to understand the material deformation behaviour in machining. Moreover, the quality of the machined surface is also directly related to the formation of μ-chip and its geometry. Thus, in this study, an attempt has been undertaken to develop the behavioural chip formation mechanics for the transition from unstable to the stable regime. Orthogonal microcutting experiments have been conducted with Al alloy (Al 6082) workpiece to investigate the micro-mechanics of chip perforation and to develop the chip stability mapping. Furthermore, the quantitative assessment criterion has been adopted to determine the material flow stress, which augmented the investigation of the burnishing-like deformation behaviour. By appraising the factors like machined surface integrity, compressive flow stress and improvement of surface roughness (R_a) profile, a ‘burnishing-like’ finishing zone has been identified. Additionally, SEM and EDX analyses have been performed to study the elemental composition of μ-chips, which allowed to validate the transition phenomena of chip perforation from incomplete (unstable) to complete (stable) chip formation. The applicability of this novel study lies in its ability to produce superior quality machined surface without requiring a secondary finishing operation and thus, improving the performance of precision machining.     

Effect of cutting speed on surface integrity and chip morphology in high-speed machining of PM nickel-based superalloy FGH95

High-speed machining is being recognized as one of the key manufacturing technologies for getting higher productivity and better surface integrity. FGH95 powder metallurgy superalloy is a kind of nickel-based superalloy which is produced by near-net-shape technology. With increasing demands for high precision and high performance of FGH95 components in aerospace industry, it is essential to recognize that the machined surface integrity may determine machined part service performance and reliability. Then, little is known about the machined surface integrity of this superalloy. Thus, the surface integrity in high-speed machining of FGH95 is investigated in this paper. Experiments are conducted on a CNC milling center with coated carbide tools under dry cutting conditions. The surface integrity is evaluated in terms of surface roughness, microhardness, and white layer. The influence of cutting speed on chip morphology is also investigated. Experiment results show that surface integrity and chip morphology of FGH95 are very sensitive to the cutting speed. When cutting speeds are below 2,400?m/min, the values of surface roughness have little variation, while when cutting speeds are in the range of 2,800–3,600?m/min, the values of surface roughness are higher than that of other cutting speeds. Severe work hardening is observed resulting from high-speed machining of FGH95 superalloy. The higher the cutting speed, the higher the surface hardness. When cutting speeds are in the range of 2,800–3,600?m/min, the white layer thickness is slightly higher than that of other cutting speeds. In high-speed machining of FGH95, the chip is segmented and has a typical sawtooth shape. The degree of serrated chip increases with the cutting speed. When the cutting speeds exceed 2,400?m/min, serrated chips change into fragment chips.     

超精密加工技术与直线电动机在超精密加工装备中的应用

超精密加工是多种技术综合的一种加工技术,通过超精密加工能够使被加工零件的形状精度、表面粗糙度和表面完整性达到空前的水平。直线电动机以其独特的优势,在超精密装备中得到更广泛的应用。本文主要针对超精密加工技术与直线电动机在超精密装备中的应用,以及在国内外的发展状况进行了阐述,重点提出了超精密加工技术与直线电动机在加工制造业中应用的明显优势,同时也说明了它们的一些缺点及可行的解决方法。     

高速切削温度动态变化规律的数值模拟

切削温度与刀具磨损、工件加工表面完整性及加工精度密切相关,其变化规律反映出高速切削过程本质的重要方面。本文应用数值模拟,对高速切削加工过程中切屑、工件和刀具三方面的温度随切削速度、进给量、切削深度的动态变化进行了研究,探讨了其变化规律,其结论有助于优化高速切削工艺及建立高速切削数据库。     

超声振动精密深孔镗削试验研究

通过超声振动深孔镗削试验,研究了超声振动镗削时切削速度、进给量和背吃刀量对加工精度和表面粗糙度的影响规律,分析了精密深孔超声振动镗削时的切削机制.     

振幅对超声振动钻削力的影响研究

超声复合机械加工机理与普通切削加工有本质的区别。主要表现在超声加工是一种脉冲式切削加工,对延长刀具寿命、提高表面加工质量、改善刀具切削性能有很大意义。其本身的优良性能已经被国内外专家学者所认可。但是超声振动振幅的大小对孔的钻削质量和刀具寿命的影响非常重要。文中自行设计了一套超声复合钻削装置,且对超声钻削加工装置设计中存在的问题和关键工艺进行了分析,并对不同振幅对钻削力与扭矩的影响进行了对比研究。实验结果对超声加工有一定的指导作用。     

Development of metal cutting process accompanied by a localized compressive hydrostatic stress field formation: Examination by molecular dynamics simulation

Improving machined surface integrity is important for precision machining. The aim of this work is to develop a cutting tool, which enables to generate a localized compressive hydrostatic stress field in the vicinity of cutting point to suppress unnecessary plastic flow and to improve the surface integrity of workpiece. In this paper, as the first step a simple cutting tool attached with a laminar jig equipped with a small rectangular hole for cutting chip elimination was proposed, and a molecular dynamics simulation of nano-cutting of monocrystalline aluminum was performed in order to verify and reveal the effectiveness and issues, respectively, of proposed method for improving machined surface integrity. The obtained simulation results were also compared to those using a normal cutting tool in order to clarify the cutting mechanism. As a result, it was clarified that a high compressive hydrostatic stress field was successfully introduced in the vicinity of cutting point. Consequently, the burr formation and elimination of cutting chip were remarkably suppressed and smoothened, respectively by using proposed cutting tool.     

The role of viscous deformation in the machining of polymers

This study aims to evaluate the machinability of typical thermoplastic and thermosetting polymers and understand the effect of their viscous properties on surface integrity, chip formation and machining forces. The interaction between the strain rate and temperature during machining was particularly addressed. It was found that the viscous deformation of a polymer plays a decisive role in determining the quality of a machined surface. To minimize the surface roughness, for instance, the machining conditions must be selected in such a way that the material removal deformation falls in the regime without visco-plastic scaling/tearing and brittle cracking. The optimal machining condition must be based on the polymer properties, such as the glass transition temperature, fracture toughness and molecular mobility. The shear stress in the shear plane of chipping is a good measure of the coupled effect of strain rate and temperature rise. In addition, the study discovered two new types of chips whose deformation and curling were in close relation to the surface integrity of the machined components.     

软体磨具新技术

零件曲表面的磨光,抛光技术是精密加工技术领域的难题,传统的磨具难以直接对不规则的曲面进行加工。作者研究的软磨具,是一种体内均匀含磨料的新型高分子复合材料、磨料和抛光粉为加工要素,聚氨酯基网链状高分子材料为连接剂并为抛光要素。新型软磨具为三维柔软的弹性体,能适应任意曲率的零件（金属或非金属）表面的磨光和抛光要求。本文包括新型软磨具的生成理论,制造技术和曲面零件抛光的工艺性能试验研究。     

预应力切削镍基高温合金的试验研究

针对镍基高温合金在切削后加工表面分布严重的残余拉应力等问题,提出采用预应力切削方法,以实现在加工过程中主动控制加工表面残余应力分布状态;通过研制轴类零件的车床专用预拉伸装置,在0 MPa、150 MPa和300 MPa三种预应力条件下对高温合金轴件进行预拉伸处理;通过硬质合金刀具预应力切削镍基高温合金的对比试验,对三种预应力条件下的切削力、切屑形态以及表面完整性包括已加工表面残余应力、加工表面粗糙度、表面形貌和显微硬度等指标进行对比。结果表明：在一定范围内,采用预应力切削方法可省去加工后续的残余应力调整工序,并能在加工表面获得合适的残余压应力;残余压应力的值可通过调整施加的预应力大小来进行主动控制;与普通切削相比,预应力切削可得到均匀的锯齿形切屑,切削力没有显著增加;预应力切削可获得良好的表面完整性,且不会引来额外的加工硬化。