椭圆轨迹对超声波椭圆振动切削的影响

运用有限元仿真技术,从影响椭圆轨迹的参数入手,模拟了不同椭圆轨迹下TC4钛合金超声波椭圆振动切削过程,得到了不同椭圆轨迹下切削力和切削温度的变化曲线。经过对比分析,结果表明TC4钛合金超声波椭圆振动切削切削力、切削温度随相位差增大先减小后增大,切削力随切削方向、切屑流出方向振幅和振动频率的增大而减小,而切削温度随切削方向振幅增大而增大,随切屑流出方向振幅、振动频率增大而减小。     

超声波振动金刚石刀具对脆性材料临界切削深度的影响

通过脆性材料沟槽切削试验,研究了超声波直线振动金刚石刀具和超声波椭圆振动金刚石刀具对脆性材料临界切削深度的影响,与没加超声波振动的金刚石刀具相比,超声波振动金刚石刀具能增大对脆性材料塑性切削的临界切削深度。提出了超声波振动金刚石刀具切削脆性材料临界切削深度计算公式,分析了导致超声波振动金刚石刀具增大脆性材料塑性切削的临界切削深度的原因。     

实用化振动切削技术——椭圆振动车镗工艺及装备

椭圆振动车镗技术是一种主要应用在精密切削领域内的特种加工技术，特别是在提高工件的表面质量、刀具的使用寿命和薄壁零件的加工精度等方面效果显著。我们最新研制了椭圆超声波振动车镗系统，并对不同材料进行了切削试验，取得了很好的工艺结果，充分体现了超声波振动车镗技术在实际切削加工中的优势。     

超声椭圆振动切削硬质合金脆性-延性转变临界条件研究

为了实现硬质合金的高效延性加工,联系硬脆材料表面生成裂纹的临界载荷与超声椭圆振动切削硬质合金的主切削力,建立超声椭圆振动切削硬质合金脆性-延性转变的临界切削深度模型,研究切削速度、刀具圆弧半径、椭圆振动频率、振幅、硬质合金的硬度、断裂韧性与临界切削深度的关系;通过仿切削刻划试验,验证了切削速度与硬质合金的硬度、断裂韧性对临界切削深度的影响规律;对比普通切削,超声椭圆振动切削有利于提高硬质合金的临界切削深度,在改善加工表面质量及精度的前提下,提高了加工效率。     

高频超声椭圆振动精密切削

研制了一种新型的工作频率为147.5kHz的超声椭圆振动换能器,进行了高频椭圆车削硬铝(LY12)的试验。试验结果表明,在精密切削中,同普通切削相比较,高频椭圆超声振动切削对表面粗糙度具有负面影响,但具有降低切削力和提高加工精度的特点,而同低频(20.5kHz)椭圆振动切削相比较,在相同条件下,可采用较高的切削速度,从而提高了工作效率。     

功率型椭圆超声振动切削机构的研究

通过对椭圆超声振动切削机构切削性能的研究,设计一种能在标准四工位刀架上安装、切削性能优良的功率型椭圆超声振动切削机构。该机构通过两轴振动机构的调幅联动,很好地克服了谐振型超声振动切削机构的椭圆振动轨迹生成的限制,很容易生成特定微小区域内的任意椭圆轨迹。正交设计使该机构安装便捷、适用加工对象范围广,切削参数要求低,便于推广使用。实验证明,该椭圆超声振动切削机构明显改善试件表面纹理,切屑排出顺畅,工件表面的粗糙度明显降低。     

超声波振动切削中值得注意的问题

介绍了超声波振动切削的原理，并论述了振动切削中值得注意的问题。     

超声椭圆振动切削轨迹倾斜角度及速比对工件表面微观形貌的影响

超声椭圆振动改变了切削加工的微观过程,对改善工件表面加工质量具有明显优势。在分析超声椭圆振动切削微观过程的基础上,对不同倾斜角度和切削速比下的超声椭圆振动切削轨迹进行数值仿真。结果表明,倾斜角度从0°增至90°的过程中,工件表面振纹角度先增至45°,再逐渐减小;振纹高度从0.38μm增至1.33μm。随着切削速比的提高,相同切削时间内的切削次数减少,振纹高度迅速增加,且变化速率随倾斜角度的增大而加快。保持切削方向与椭圆轨迹长轴一致,同时采用较低的切削速比,对降低工件表面振纹高度效果显著。     

不分离型超声椭圆振动切削试验研究

超声椭圆振动切削在分离切削区能够有效地降低切削力、抑制加工过程颤振、提高零件表面加工质量和延长刀具的使用寿命,为此已成功地应用于精密和超精密加工领域.为更充分发挥超声椭圆振动切削技术的优势,拓宽其应用领域,在深入分析椭圆振动切削过程和表面微观形貌形成机理的基础上,通过具体的切削试验验证超声椭圆振动切削在不分离区仍然具有降低切削力、抑制加工颤振、降低已加工表面粗糙度等优势特性.同时,不分离型超声椭圆振动切削的加工效率是分离型椭圆振动切削的2～3倍,进一步提高超声椭圆振动切削的加工效率.但是,这些特性在不分离切削区随着速度系数的增加而逐渐减弱,当速度系数大于3以后,这些切削优势特性基本消失.     

超声波振动珩磨的切削机理及特点

从切削运动、切削量、磨粒性能三个方面分析了超声波振动珩磨的切削机理，并归纳了超声波振动珩磨的特点。     

振动参数对超声椭圆振动切削的影响

基于超声振动切削原理和金属切削原理,利用有限元软件MSC/MARC建立了二维热力耦合正交切削有限元模型,对超声椭圆振动切削45钢的切削机理进行了研究,得到了切削温度及切削力的瞬时变化规律.     

“Multimode vibration cutting” – A new vibration cutting for highly-efficient and highly-flexible surface texturing

This paper proposes a new vibration cutting method named “multimode vibration cutting” for precision surface texturing. The proposed cutting method utilizes multiple unidirectional vibration modes mainly in the depth-of-cut direction. The vibrations at multiple frequencies induced to the tool tip can generate not only sinusoidal but also highly-flexible trajectories such as trapezoidal, triangular, and distorted triangular waves. Notably, only a sinusoidal vibration can be induced when a single resonant vibration is applied to the tool tip. Compared to conventional highly-flexible cutting methods for surface texturing, such as the utilization of fast tool servo and amplitude control of ultrasonic elliptical vibration cutting, the proposed method is highly-efficient because of its direct usage of high resonant frequencies. Compared to conventional highly-efficient cutting methods for surface texturing, such as linear and elliptical vibration cutting which mainly utilizes the vibration component in the depth-of-cut direction, the proposed method can generate highly-flexible trajectories for various micro texture profiles. In this study, an ultrasonic multimode vibration device is developed, and the mechanics of generating multimode vibrations are demonstrated. Turning experiments with several texture profiles are performed to confirm the validity of the proposed method for highly-efficient and highly-flexible micro/nano surface texturing.     

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。     

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.     

Suppression of forced vibration due to chip segmentation in ultrasonic elliptical vibration cutting of titanium alloy Ti–6Al–4V

Ultrasonic elliptical vibration cutting of titanium alloy Ti–6Al–4V is investigated in this research. Because products made of Ti–6Al–4V alloy are usually designed for possessing low-rigidity structures or good-quality cut surfaces, machining requirements such as low cutting forces and slow rate of tool wear need to be fulfilled for realization of their precision machining. Therefore, the ultrasonic elliptical vibration cutting is applied as a novel machining method for those products. Machinability of Ti–6Al–4V alloy by the ultrasonic elliptical vibration cutting with cemented carbide tools is examined to figure out suitable cutting conditions for precision machining of Ti–6Al–4V alloy. As experimental results, generated chips, cutting forces, and profiles of cut surfaces are indicated. A forced vibration problem occurred due to the segmented chip formation, which is also well-known in the ordinary non-vibration cutting. Therefore, characteristics of the forced vibration due to the chip segmentation are investigated in this research. Through the experiments, it is found that the frequency and magnitude of the forced vibration have relation with the average uncut chip thickness and cutting width. Especially, it is found that the averaging effect can suppress the forced vibration, i.e. the chip segmentation tends to occur randomly over the large cutting width, and hence the force fluctuations with random phases tend to cancel each other as the cutting width increases relatively against the average uncut chip thickness. Based on the investigations, a new practical strategy to suppress the forced vibration due to chip segmentation is proposed and verified. Using the proposed method significantly decreased cutting forces and good quality of surfaces are obtained when the forced vibration is suppressed compared to the ordinary non-vibration cutting results. Therefore, the results suggest that the precision machining can be realized without sacrificing the machining efficiency by increasing the width of cut and decreasing the average uncut chip thickness.     

飞机交点孔超声椭圆振动精密加工技术

针对常规方法加工30mm以上的飞机翼身交点孔存在动力不足、孔径精度差和表面质量不高等问题,采用超声椭圆振动镗削的方法,研制了超声椭圆振动镗削装置,并对30mm以上不同材料的翼身交点孔进行了镗削加工,取得了很好的工艺效果,充分体现了超声椭圆振动镗削技术在飞机交点孔加工中的优势。     

Analysis of regenerative chatter suppression with adding the ultrasonic elliptical vibration on the cutting tool

A method is proposed to suppress regenerative chatter in turning operation, in which the ultrasonic elliptical vibration is added on the cutting tool. It results in the fact that the cutting tool is separated periodically from the chip and the workpiece, and the direction of the frictional force between the rake face of the cutting tool and the chip is reversed in each cycle of the ultrasonic elliptical vibration. The experimental investigations show that the regenerative chatter occurring in ordinary turning operation can be suppressed effectively by applying the ultrasonic elliptical vibration on the cutting tool. In order to clearify the reason of the regenerative chatter suppression, theoretical analysis and computer simulation are performed on turning with ultrasonic vibration. There is a good agreement among the experimental investigations, theoretical analysis and the computer simulation.     

Characteristics of chip generation by ultrasonic vibration cutting with extremely low cutting velocity

Recently, mirror-surface machining of brittle materials such as ferrite, glass, and optical plastics has become more important, as these materials are used in optical communications and precision devices. Non-ferrous metals such as aluminium and copper were readily turned with diamond tools, but as the need for both infra-red and reflective optics escalated, the need to machine brittle materials arose. In this paper, ultrasonic vibration cutting at 20 kHz at extremely low cutting velocity for the precision machining of brittle plastics used for optical lenses is suggested and tested. The mechanism of chip generation, and characteristics of surfaces in the ductile mode, machined by ultrasonic vibration cutting are investigated. As a result, when micro cutting by ultrasonic vibration, it was confirmed that the chips generated by ductile mode cutting are obtained at 1/40 of the critical cutting velocity of the ultrasonic vibration cutting system, which is an extremely low cutting velocity.