超声振动铣削加工参数对切削力的影响

为了改善传统铣削钛合金的加工条件,研究了进给方向超声振动辅助铣削对切削力的影响。定值计算了不同振动频率、振幅、铣削速度时的净切削时间比,建立了对工件施加超声振动的铣削加工三维有限元模型,根据仿真结果讨论了加工参数对进给方向切削力瞬时值的影响,并结合净切削时间比分析了加工参数对三个方向切削力平均值的影响。研究表明:施加超声振动后切削力明显减小;振动频率小于40kHz和振幅小于30μm时切削力平均值同净切削时间比变化趋势一致,当频率或振幅超过上述值时,刀具、工件间的摩擦力对切削力平均值的影响显著。     

振动切削机理研究

振动切削是一种脉冲切削，是在传统切削过程中给刀具(或工件)施以某种可控的有规律的振动，使刀具以一定的振幅或频率振动的加工方法。通过动态理论及金属学原理分析振动切削加工方法，阐明振动切削提高系统剐度、降低切削力及促进切削液渗透的作用。     

陶瓷的重叠振动切削

一、陶瓷精密切削法分析陶瓷的精密切削法是通过刀具的尖端将陶瓷有规则,一点一点地不断产生崩裂的切削方法,具体如下: 1.利用脉冲切削波形精密切削陶瓷利用作用时间短的脉冲状切削力波形,使陶瓷在刀具的刀尖附近产生崩裂。其金刚石车刀以频率f、振幅a在切削方向进行超声波振动,通过振动切削来作用于陶瓷。由于脉冲切削力波形的作用,使得在车床主轴卡盘上所夹持的陶瓷工件吃刀分力方向的弹簧常数K提高T/tc倍,从而可取得刚性化效果。 2.用间断脉冲波形切削力精密切削陶瓷根据振动切削,使间断脉冲切削力波形产生作用进行重叠振动切削。这种间断的脉     

超声振动车削TC4钛合金的切削性能研究

为了探究超声振动车削过程中切削力和切削温度的变化规律,使用Third Wave Advant Edge切削仿真软件,基于POWER-LOW本构模型和ALE网格划分方法建立TC4钛合金车削加工的有限元模型,获得传统车削与超声振动车削的切削力和最高切削温度变化情况。结合超声振动车削中刀具切削速度和位移变化规律,对传统车削与超声振动车削的切削力和最高切削温度变化规律展开对比分析;探究超声振动车削中的工件进给速度、刀具振频和振幅对切削力的影响规律,实现各加工参数的最优组合,为实际加工提供参考。     

陶瓷材料的振动切削

图1(a)所示的切削力波形是用于通常精密切削的,图1(b)所示的脉动切削力波形是利用振动切削技术进行精密切削的。日本宇都宫大学根据这种振动切削,把连续的脉冲切削力波形改造成了如图1(c)所示的间断式波形,亦即开发了断续脉冲切削力波形的新型的重叠振动切削。这种重叠振动切削是一种让切削刀具沿切削方向以频率f、振幅a超声波振动,再使之以频率F、振幅A的低频振动,使切削速度v<2πAF进行振动切削的     

基于射流支撑薄壁件镜像加工尺寸误差补偿设计

低刚度薄壁件在切削加工过程中因切削力而容易产生切削变形和切削振动等尺寸误差,对薄壁件产生尺寸误差的影响因素进行分析,并针对薄壁件在切削过程中因受切削力作用而产生尺寸误差,设计了一种应用水射流镜像加工薄壁件的新型加工工艺方法,以此减小薄壁件的尺寸误差。最后,通过实验验证了水射流镜像加工技术可有效的提高薄壁件的加工精度。     

超声椭圆振动切削装置应用现状及发展综述

椭圆振动切削装置可很好地解决高性能材料的硬脆性加工难的问题。椭圆振动切削装置通过给刀具施加超声振动使刀具与工件分离,这种方式可降低切削力,提高工件表面的加工质量。该文首先介绍了该装置的切削原理,其次对其结构特点和研究现状做了分析,最后对该装置的性能特性进行了总结。目的是通过对这类装置的介绍和性能分析,使超精密加工领域的相关科研工作者和技术人员较好地掌握类似装置的性能特性,为后续加工装置的优化设计提供理论参考。     

高速切削加工稳定性研究

振动是金属加工过程中的一个复杂问题,其形成的颤振不仅限制了机床加工效率的提高,还对机床和切削刀具造成很大的危害。对数控加工特别是高速加工过程中颤振的研究和控制技术是先进制造技术的重要研究课题,本文介绍了切削动力学建模的两个环节:切削力建模和刀具—工件动力学建模;根据切削力建模方式的不同,将其归纳为基于试验的经验公式建模法、解析建模法和基于人工智能及软件技术切削力建模法;根据铣削加工过程中稳定区域的不同预测方式,切削稳定性分析方法分为时域分析方法、频域分析方法、试验分析方法,并对三种方法的优势和不足进行对比分析;对切削颤振的抑制措施进行了总结介绍;展望了高速切削加工稳定性研究的关键技术,为切削加工振动的理论研究与工业应用提供借鉴和参考。     

微织构刀具超声振动辅助加工切削性能仿真研究

对微织构刀具在超声振动辅助加工时的切削性能进行仿真研究。在研究中,在CAXA软件中建立刀具参数相同的二维刀具和微织构刀具,导入AdvantEdge软件,分别进行二维普通刀具切削、二维微织构刀具切削、二维普通刀具超声振动切削、二维微织构刀具超声振动切削,对比分析四种切削的仿真结果。通过仿真研究发现,微织构结构可以有效降低刀具温度,高温区域明显减小,同时可以减小刀具应力,减小高应力区域,对切削力的影响则不大。超声振动辅助加工可以有效减小切削力,降小刀具应力,对刀具温度的影响则不大。微织构结构和超声振动辅助加工同时作用,刀具温度最低,切削力和应力最小,并且可以延长刀具寿命。     

基于机器学习与群智能算法的精车大螺距螺杆切削优化研究

大螺距螺杆在精加工的过程中,其径向切深大,参与切削的切削刃长,进给速度大,使其切削力数十倍增加,造成刀具振动剧烈,热力耦合场不稳定,加剧了刀具的磨损,刀具的振动和磨损是造成工件表面质量劣化的主要原因。通过进行切削优化的研究,可以解决工件表面质量差的问题。首先,比较机器学习与回归方式的拟合误差,选用精确性更高的机器学习方法建立了切削力和切削温度的预测模型。其次,采用不同的群智能算法对优化目标进行求解,比较不同算法的求解性能,选择人工蜂群算法的优化结果为最优参数组合。最后,对不同切削方案得到的工件表面粗糙度进行测量,结果表明:采用优化后的参数加工,得到的工件表面粗糙度下降了20%,改善了工件表面质量,达到了切削优化的目的。     

Dynamic contour error compensation in micro/nano machining of hardened steel by applying elliptical vibration sculpturing method

In this study, a novel dynamic contour error compensation technique has been proposed for the elliptical vibration cutting process achieved through the ultra-precision amplitude control. The influence of the contour error, triggered due to the inertial vibrations of the friction-less feed drive system, on the machining accuracy deterioration has been experimentally investigated. In order to reduce the contour error, a compensation method utilizing a real-time amplitude control in the elliptical vibration cutting process has been applied. In the proposed method, the dynamic motion error along the depth of cut direction is detected by utilizing the precise linear encoders installed on the feed drive system. The motion error in real-time is subsequently converted into cancelling amplitude command for the vibration control system of the ultrasonic vibrator, thus, guaranteeing that the envelope of the vibration amplitudes auto-tracks the dynamic reference position of the motion axis in the depth of cut direction. Due to this, a constant nominal depth of cut can be obtained even though the inertial vibrations disturb the feed drive control during machining. A series of experimental investigations have been conducted in order to analyze the machining performance by employing the proposed method. The maximum machining error is observed to significantly decrease from 0.6 to 0.04 μm by applying the proposed compensation method. Finally, the micro dimple array with a structural height from about 200 to 600 nm could be accurately fabricated with a maximum machining error of 36.8 nm, which verified the feasibility of the proposed amplitude control compensation method.     

Ultra-precision nano-structure fabrication by amplitude control sculpturing method in elliptical vibration cutting

This paper studies the nano-structure fabrication on hardened steel by means of elliptical vibration cutting equipped with the ultra-precision amplitude control sculpturing method. Machining performance of the amplitude control sculpturing method is investigated, and the limitation in nano-scale machining is explored. In this proposed method, machinable part geometry is essentially restricted by vibration conditions and tool geometry. In addition, a considerable error between the amplitude command and the envelope of the tool trajectory is generated when the slope of the machining part geometry becomes steep. To overcome this error, a compensation method for the amplitude control command is proposed. In order to clarify the machining performance of the proposed technology, a series of analytical and experimental investigations are conducted. Furthermore, by applying the proposed command compensation method, nano-structures with a large ratio of structure height to wave length are machined accurately. The proposed sculpturing method is subsequently applied to the machining of nano-textured grooves and a three-dimensional grid surface, which verifies the feasibility of the proposed amplitude control sculpturing method.     

超声椭圆振动车削的切削特性

为了深入研究超声椭圆振动切削特性及其应用前景,通过建立超声椭圆振动切削模型,根据运动学方程,分析和推导出了切削占空比、振纹高度、振动频率、振幅之间的关系,揭示了超声椭圆振动车削表面粗糙度、加工精度、加工效率之间的相互关系。通过切削力和表面粗糙度试验对推导出来的结果进行了验证,试验结果表明有效减小切削力是超声椭圆振动切削加工应用的主要优势。     

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。     

虚拟加工中的加工误差分析与预测

分析了影响虚拟环境下复杂曲面产品数字化端铣加工误差产生的主要因素,综合考虑刀具和工件的柔度,同时考虑加工表面的变形敏感度,讨论面向虚拟制造的加工尺寸误差预测模型总体框架,提出了一个端铣加工过程表面加工尺寸误差预测模型。所给出的表面误差预测模型较全面地考虑了端铣加工过程,适于多种加工条件,能够反映端铣加工过程由切削力导致的系统变形对加工误差所造成的影响。最后给出了一个仿真实例。     

超声振动改善深孔镗削加工质量

深孔加工在航空发动机制造过程中广泛存在,由于其刚性弱,静态让刀量大,导致加工颤振和刀具磨损严重,使得其加工质量难以得到保证。超声振动切削作为一种特种切削加工手段,具有降低切削力,提高系统刚性和抑制加工颤振等优势。将超声振动应用于深孔镗削,进行了断屑条件验证,孔径误差测量,已加工表面粗糙度测量以及表面形貌观测等试验。试验结果表明,超声振动镗削能够有效缓解深孔镗削过程中的堵屑问题,减小孔径误差和表面粗糙度,抑制切削颤振,从而改善深孔镗削加工质量。     

振动钻削的变速减振特性分析

钻削加工中的切削颤振是十分有害的 ,它严重地影响加工精度和生产率的提高 ,降低机床和刀具的寿命。振动钻削方法具有消减切削颤振的特殊功能 ,能够取得良好的加工效果。根据振动钻削所具有的变速切削特性 ,提出了振动钻削的变速减振新概念。在深入研究了机床加工系统的振动响应规律和振动变速切削减振的能量化原理的基础上 ,揭示了振动变速切削的瞬态不充分响应的减振本质。     

Micro/nano sculpturing of hardened steel by controlling vibration amplitude in elliptical vibration cutting

A new ultra-precision sculpturing method in micro/nano scale for difficult-to-cut materials is proposed in the present research. Elliptical vibration cutting technology is well-known for its excellent performance in achieving ultra-precision machining of steel materials with single crystal diamond tools. Elliptical vibration locus is generally controlled and held to a constant in practice. On the contrary, the proposed method utilizes the variations of the elliptical vibration locus in a positive manner. Depth of cut can be actively controlled in elliptical vibration cutting by controlling vibration amplitude in the thrust direction. By utilizing this as a fast tool servo function in elliptical vibration cutting, high performance micro/nano sculpturing can be attained without using conventional fast tool servo technology. A high-speed amplitude control system is developed for elliptical vibration, with a bandwidth of more than 300 Hz, where the vibration amplitude can be controlled within 4 μm_p-p. The developed control system is applied to sculpturing ultra-precision nano textured grooves on hardened steel with single crystal diamond tools. It is confirmed that the textured grooves have the desired shapes, and their profiles agree well with the vibration amplitude commands input to the control system. Further, a high performance micro/nano sculpturing system for plane surfaces is developed, where the vibration amplitude is controlled in synchronization with the planing motion of an ultra-precision machine tool. Nano sculpturing experiments on hardened steel, carried out by the developed system, are reported, as well as consequent picture images and a variety of dimple patterns that were formed successfully on the hardened steel as nano-scale sculptures.     

Finite element modeling of ultrasonic-assisted turning: cutting force and heat generation

Abstract

Adding ultrasonic vibrations to conventional turning can improve the process in terms of cutting force, surface finish and so on. One of the most important factors in machining is the heat generation during the cutting process. In ultrasonic-assisted turning (UAT) the tool tip also vibrates at very high frequency and this sinusoidal motion causes complexity in heat modeling of the cutting system. Modeling and simulation of cutting processes can help to understand the nature of process and provides information to select optimum conditions and machining parameters. In this article, a finite element model has been developed for predicting tool tip temperature in UAT. The effect of machining parameters including cutting speed, feed rate and amplitude of vibration on the tool tip temperature has been investigated. In order to simplify the machining process, the cutting experiment has been carried out in dry condition. The results showed that by applying ultrasonic vibration to the cutting tool, the tool tip flash temperature increases but in some condition its average value could be less than the conventional machining.     

Design of ultrasonic elliptical vibration cutting system for tungsten heavy alloy

Nanoscale surface roughness of tungsten heavy alloy components is required in the nuclear industry and precision instruments. In this study, a high-performance ultrasonic elliptical vibration cutting (UEVC) system is developed to solve the precision machining problem of tungsten heavy alloy. A new design method of stepped bending vibration horn based on Timoshenko’s theory is first proposed, and its design process is greatly simplified. The arrangement and working principle of piezoelectric transducers on the ultrasonic vibrator using the fifth resonant mode of bending are analyzed to realize the dual-bending vibration modes. A cutting tool is installed at the end of the ultrasonic vibration unit to output the ultrasonic elliptical vibration locus, which is verified by finite element method. The vibration unit can display different three-degree-of-freedom (3-DOF) UEVC characteristics by adjusting the corresponding position of the unit and workpiece. A dual-channel ultrasonic power supply is developed to excite the ultrasonic vibration unit, which makes the UEVC system present the resonant frequency of 41 kHz and the maximum amplitude of 14.2 μm. Different microtopography and surface roughness are obtained by the cutting experiments of tungsten heavy alloy hemispherical workpiece with the UEVC system, which validates the proposed design’s technical capability and provides optimization basis for further improving the machining quality of the curved surface components of tungsten heavy alloy.