航空钛合金薄壁件加工工艺

正航空薄壁件的加工既有薄壁件加工的特点又有难加工材料的加工特点,在本文中以我公司加工的钛合金圆筒零件为例说明航空薄壁件的加工。1.零件工艺性分析我公司在加工圆筒零件(见图1)时,零件材料为钛合金TC4,外圆φ198mm,内孔φ195mm,长度200mm,表面粗糙度值Ra=1.6μm。     

现代特种加工技术的发展

20世纪以来,航空科学技术迅速发展。为保证在高温、高压、高速、重载和强腐蚀等苛刻条件下的工作可靠性,在飞机、发动机和机载设备上大量采用了新结构、新材料和复杂形状的精密零件。鉴于对有特殊要求的零件用传统机械加工方法很难完成,难于达到经济性要求,各种异于传统切削加工方法的新型特种加工方法应运而生。目前,特种加工技术已成为航空产品制造技术群中不可缺少的分支,在难切削材料、复杂型面、精细表面、低刚度零件及模具加工等领域中已成为重要的工艺方法。     

飞机结构零件数控加工技术研讨

随着我国航空制造技术的发展，对飞机结构零件的加工要求越来越高，尤其是对于零件的表面质量、深腔和薄壁形状以及零件的加工精度都提出了更高的要求。目前欧美许多发达国家按照高精度、高效率、高柔性的制造发展方向，已开始普遍使用高速铣削机床，并针对飞机结构零件的特点进行了大量的工艺技术研究。另外通过对难加工材料的加工工艺方法进行研究，大大提高了以钛合金为代表的难加工材料的加工效率，使飞机结构零件的数控加工不再成为制约整个飞机研制和生产的“瓶颈”。     

航空难加工材料典型零件切削技术研究

航空发动机典型零部件大多采用钛合金、高温合金等难加工材料,不但强度、硬度高,且韧性和延伸率大,导热性差,加工表面的加工硬化大,切削性能差。航空零部件是在高温、高压、高转速的恶劣环境下工作,每一种新产品的开发都意味着零件功能、结构、材料的重大变更,也是对切削加工提出的开发任务。航空典型零件中的盘类零件趋向薄壁。为保证盘类件在高转速下平衡,主要表面的尺寸精度、位置精度、形状误差、表面粗糙度等     

航空壁板类零件转角高速加工的应用技术

高速加工具有生产效率高、加工精度高、表面质量好和生产成本低等优点。在现代航空产品中,高速加工已广泛应用于飞机的梁、框和大型壁板等承力构件。由于航空制造业中主承力结构件多数为整体坯料"掏空"的整体结构件,因此,在材料去除率大、加工质量要求高、加工周期长的整体结构件的加工中更能体现其独特的优势。但是,其转角的加工还延用传统加工方式。本文通过实例,对高速切削零件转角加工技术提出了全新的加工方案,为航空壁板类及墙类零件的高速加工提供了实践基础。     

特种加工技术在航空产品中的应用

在现代航空发动机设计中，为满足高性能航空发动机的要求，必须大量采用新材料、新结构，于是产品的可制造性就对制造技术提出了新的挑战，如难加工材料、复杂型面、精密表面的加工及特殊要求的零件加工等问题。特种加工技术的采用，可使航空发动机零件数量减少，结构设计简化，从而在性能、适用性、可靠性、维修性等方面均得到提高。     

基于复合加工特征的航空结构件频响快速预测

航空结构件作为飞机中占比最大的零件，具有大尺寸、多槽腔、弱刚性和高材料去除率等特点，如何在保证加工过程稳定的前提下高效去除结构件材料是航空结构件加工的一大瓶颈问题，零件频响的快速预测是选择高效切削参数的前提。通过对典型航空结构件加工特征的分类和提取，构建了“槽腔-筋”复合加工特征，建立了其参数化的频响特性分析模型，并计算了复合加工特征若干刚度薄弱点的频响特性。将其与复合加工特征零件、整体零件相应位置的频响函数进行对比，结果表明模型预测精度满足要求，验证了使用复合加工特征模型频响特性代替整体零件模型频响特性的可行性。同时，复合加工特征有限元模型的自由度数量远小于整体零件有限元模型自由度数量，充分体现了所提出的方法预测结构件频响的快速性。     

基于SQL SERVER的高速加工数据库

高速加工目前已广泛应用于航空、汽车、模具制造等领域,用于加工复杂结构工件,但其工艺参数的选择和使用已成为困扰零件加工的一个大问题,迫切需要针对特定材料建立加工数据库。笔者利用SQL SERVER作为平台,构建出高速加工数据库框架,并用Visual Basic语言和SQL语句实现了2A12铝合金材料的高速加工数据库的初步运行。     

难加工材料的加工技术

工程机械的一些零件由难加工材料制成。充分认识难加工材料的种类、切削加工的特点及其应当使用的刀具材料,研制先进的刀具及其材料,采用新的加工技术,是解决难加工材料加工问题的有效途径。     

飞机整体框类结构件铣削加工的模拟研究

针对航空整体结构件铣削加工变形的复杂制造问题，建立了三维铣削加工有限元模型。深入研究了材料模型、残余应力施加、动态切削载荷、材料去除等铣削加工模拟所涉及的关键技术．并详细论述了铣削加工模拟过程。应用该模型对某框类结构件进行了不同铣削顺序的加工模拟，通过零件变形模拟值与实验加工所得零件变形值的比较，证明该有限元模型可以实现对零件铣削加工变形规律的预测。     

薄壁件切削加工变形及补偿技术研究现状

薄壁件在航空航天领域有着广泛应用,由于薄壁件刚度较低,加工余量大,工艺性差,容易发生切削变形,因此被认为是机械加工中的难题。本文介绍了薄壁件的结构特点,分析了薄壁件切削变形的影响因素,表明材料与结构、装夹工艺以及残余应力的释放与重分布等是造成薄壁件变形的主要原因,并总结了目前国内外研究薄壁件变形补偿技术发展状况。     

Influence of anisotropy of nickel-based single crystal superalloy in atomic and close-to-atomic scale cutting

Nickel-based single crystal superalloy is widely used in the field of aerospace and nuclear reaction equipment due to its good properties. Ultra-precision machining technology is an important means to ensure the surface quality of parts. However, the anisotropy of materials has great influence on the evolution of surface and subsurface defects and the removal of materials in the process of machining. In this paper, The MD (molecular dynamics) modeling and simulation verification of cutting anisotropic nickel-based single crystal superalloy workpiece with silicon nitride tool is carried out by using the mixed potential function simulation. Through cutting simulation and visualization, the types, number, deformation area and dislocation evolution of the machined surface defects and inside of the workpiece defect of nickel-based single crystal superalloy with different crystal orientations are analyzed. The evolutionary mechanism of the machined surface defects and the law of material removal are discussed. The research content provides a theoretical basis for parameter optimization and improvement of machining quality in the atomic and close-to-atomic scale (ACS) cutting process, and technical support for efficient and precise machining process of the nickel-based superalloy.     

Experimental and numerical investigation of cutting forces in micro-milling of polycarbonate glass

Abstract

Polycarbonates have found important applications in various types of industries including optical, automotive, aerospace, biomedical, and defense manufacturing industries. Conventional mechanical machining has the capability to create complex multi-scale parts and components for various materials including polymeric materials. This study investigates the cutting forces generated during the machining of polycarbonate glass using the micro-milling process. The goal of this research is to machine high quality micro-channels in polycarbonates for microfluidic applications. Both experimental investigation and numerical simulations using the Finite Element Method (FEM) have been carried out to assess the cutting forces generated in three directions during machining of polycarbonate. The effectiveness of tool coating on the reduction of cutting forces has been investigated. It was found that with the careful combination of depth of cut and feed rate, the ductile mode machining of polycarbonate can be achieved, which produces lower cutting forces, that could result in improved surface finish and low tool wear. Both lower and higher of depths of cut were found to generate higher cutting forces due to dragging action and higher tool-workpiece contact area respectively. The Finite Element Method (FEM) was found to be effective in simulating the cutting forces with acceptable range of errors, and thus, could be used to predict cutting forces at the parametric combinations beyond the capacity of the machine or without carrying out further expensive experimentation, for which the chances of tool failure are higher.     

超声加工技术的应用现状及其发展趋势

根据近年来超声加工技术的发展状况,综述了超声加工技术的应用现状及其发展趋势。超声加工技术具有其极强的切削能力、极小的切削抗力、极细微的光整能力以及极高的强化能力。国内外学者对超声振动系统中的超声换能器和变幅杆进行研究,目的在于增加系统的功率与变幅杆的振幅,以及适用于特定的加工环境。超声加工技术以其工艺优势在难加工材料加工、深小孔加工、薄壁件加工、超声表面光整强化、超声焊接和磨粒冲击等加工领域获得越来越广泛的应用,并且其应用涉及半导体工业、高速列车、汽车制造、航空航天、光学元器件、医疗工业等产业领域。随着超声加工技术应用的日益普遍,超声复合加工、微细超声加工、旋转超声加工以及超声骨切削技术也将得到进一步的发展和运用。     

电解加工在航空航天领域的应用研究

论述了电解加工技术的原理和特点,从高硬度材料加工、薄壁零件加工、整体复杂构件加工和微小孔加工等方面分析了航空航天领域中应用电解加工技术对比传统机械加工技术的优势,同时介绍了电解加工技术在航空航天领域的应用现状。     

Efficient optimisation of machining processes based on technical specifications for surface roughness: application to magnesium pieces in the aerospace industry

Magnesium is one of the lightest metallic materials and is well known and widely used in the aeronautic and aerospace industries. The pieces machined in these industrial fields must satisfy stringent surface roughness requirements to achieve a product quality that conforms to the design specifications. The aim of this investigation is to optimise efficiently the dry turning of magnesium pieces to achieve a surface roughness within technical requirements. A cost-effective and flexible statistical optimisation procedure, which is based on the technical specifications of surface roughness as well as on a robust experimental design, identified different optimal cutting conditions that provide a surface finish which meets the roughness specifications in magnesium parts. Furthermore, as a consequence of such optimisation procedure, the machining time was reduced, and the aerospace companies could select among the optimal operating conditions by also considering productivity, safety and environment criteria to control production of the surfaces finish.     

C/E复合材料螺旋铣削制孔方法抑制缺陷产生的机理

传统钻削加工碳纤维/环氧树脂(Carbon/epoxy,C/E)复合材料时容易产生加工缺陷,而螺旋铣削作为一种新的制孔方法在航空材料的加工中逐渐受到关注。为分析螺旋铣削制孔方法抑制缺陷产生的机理,以传统钻削加工为参照,分别利用螺旋铣削及传统钻削两种方法对C/E复合材料进行制孔试验,并对螺旋铣削与传统钻削刀具的运动轨迹进行分析。在具有相同的加工效率及刀具切削速度的基础上,对两种加工方法的加工参数进行优化。进行制孔对比试验,并对制孔过程中的切削温度、切削力及加工质量进行检测与分析。结果表明,切削温度是影响C/E复合材料制孔质量的重要因素,且由于螺旋铣削制孔时的切削温度显著低于传统钻削制孔温度,因此螺旋铣削制孔质量明显优于传统钻削制孔质量。螺旋铣削制孔时的切削温度较传统钻削时降低69℃以上,降幅大于36%,因此有效避免了制孔出口处的撕裂及分层现象。     

Experimental investigation of top burr formation in high-speed micro-end milling of titanium alloy

ABSTRACT

Superalloys with burr-free parts are most preferably used in biomedical, aerospace, marine and automotive applications. In order to reduce the global pollution content, industries strive to execute stringent green manufacturing technologies. There is a need to investigate the different available tools in high-speed micro-milling process to achieve desired burr free with good surface finish on super alloys without using traditional coolants. In machining of titanium and its alloys, because of low thermal conductivity and reactivity with tool materials instigate the burr formation on work material and lowers the tool performance. The main objective of this article is to investigate the top burr formation in high-speed micro-end milling of alpha + beta-titanium alloy-grade 23 ELI (Ti-6Al-4V) under dry cutting conditions using Uncoated and physical vapor deposition coated AlTiN, TiAlN tungsten carbide end mills. Machining performance of the three cutting tools was compared. From the comparison of cutting tools for machining titanium alloy-grade 23, it is found that coated TiAlN tools produce less burr formation than coated AlTiN and uncoated tungsten carbide tools.     

现代高速切削与工具技术

高速加工和高效加工是目前获得高效机械加工生产率的重要手段，它在航空和航天产品的零件制造、模具制造以及汽车零部件制造等领域有较大的需求。机床采用高速传动技术、高速进给技术、高速切削刀具，配以大功率或大扭矩主轴系统以及复合加工技术，可实现高速加工与高效加工。近几年我国在机床高速化技术方面的研究开发取得了长足进步，并开发出相应的主机产品，为我国数控机床向高速、高效和精密方向发展奠定了基础。