车削精度主动控制系统与动态模型的研究

本文分析了以压电陶瓷作为驱动元件的振动切削刀具的振动特性和实现刀具谐振切削的电路匹配,分析了主轴误差补偿方法的特点,提出以振动切削和误差补偿为基础的提高车削加工精度的主动控制系统,并建立了该系统的动态模型,推导其频率响应函数,实验证实了该方法能全面地提高工件的加工质量。     

超声振动切削技术与误差补偿技术的综合应用

分析了误差补偿技术和超声振动切削技术的特点，设计出能同时实现误差补偿和振动切削的执行机构，将振动切削技术引入误差补偿系统中，以提高加工表面质量和精度。     

深孔超声圆周振动钻削

超声振动深孔加工是在钻孔时使工件或刀具沿轴向或圆周方向产生一定频率和振幅的振动，从而改变了刀具与工件材料的相互作用条件，改变了切削机理，改善了切屑形成的条件，可大大提高加工质量。超声振动钻孔时，可在轴向或圆周方向施加振动。轴向振动对于钻头外缘附近的切削刃来说相当于径向的外圆振动切削，由于高频振动的影响会加速外缘切削刃后刀面的磨损。周向扭转振动可使刀具外缘切削刃的振动方向与主运动方向一致，有利于提高刀具耐用度，加工效果要好得多。为了探讨通过简单改装、调整现有机床，设计安装一套简单而又通用的圆周振动…     

超声振动精密切削振幅对工件尺寸误差的影响

精密超声振动切削是将一定振幅的高频振动添加到刀具的运动过程中的一种加工方式,具有切削力小,加工精度高,加工表面质量好等特点。采用动力学分析方法利用二自由度的振动切削工件-刀具系统模型,并借鉴普通切削中对切削力的分析方法,首次从理论上实现了对振动切削中刀具振幅对工件变形影响的研究,并采用数值模拟的方法给出它的变化规律:在精密振动切削使用的振幅范围内,刀具振幅的变大会使工件的净位移减小、进而使工件的尺寸误差减小。同时,给出了不同刀具前角、切削速度和切削深度条件下,工件尺寸误差随振幅变化的规律。     

振动频率对超声辅助切削的影响

对超声辅助切削而言,刀具振动频率是一项至关重要的影响因子。本文从理论上分析了刀具振动频率对超声切削的影响,并利用有限元软件MSC.Marc建立了超声切削的二维正交热力耦合模型,通过有限元仿真研究了刀具振动频率对切削应力和切削温度的影响规律。     

新型超声振动切削系统研究

定量研究了完成振动切削所需的刀具超声振动功率，据此提出了采用高效的压电换能器以及直接驱动刀具的新型超声振动切削系统，并对系统特性进行了测试。     

星载复杂结构钛合金薄壁件超声振动切削研究

为了实现轻量化设计,航天器常采用复杂结构钛合金薄壁件作为承载、连接和定位元件,但是这类零件在切削过程中容易产生刀具磨损和变形,导致加工精度低,难以满足工作要求.基于钛合金薄壁件切削特性研究,采用超声振动金刚石车削方式控制切削力、装夹力引起的加工变形和残余应力,通过在线补偿修正刀具磨损误差;对壁厚(3～5)mm的典型星载钛合金薄壁件进行椭圆形超声振动切削,尺寸精度达到5μm,圆度误差为2.83μm,满足加工精度和稳定性要求.     

自由轮廓曲面铣削加工的表面尺寸误差补偿

针对自由轮廓曲面铣削加工,提出了一种补偿加工中由于刀具变形引起的表面尺寸误差的方法。通过对铣削过程分析,推断出在稳态铣削过程中,当刀具变形发生时,在垂直于刀轴的平面内,实际的切削载荷对刀具的作用力和刀具对挠曲变形的抗力处于瞬时平衡状态。理想的加工情形是刀具的实际切削位置严格遵循名义刀具轨迹,因此表面尺寸误差补偿的过程可以转化为:以名义刀具轨迹界定刀具的实际径向切深,进而是切削载荷和刀具变形量,在实际刀具轨迹规划中补偿该刀具变形量。加工试验表明该误差补偿方法能有效地降低自由轮廓曲面铣削加工的让刀误差。与现有的误差补偿方法相比,该方法能综合考虑刀具系统的柔性,在实施过程中也无需耗时的迭代计算。     

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。     

超声振动钻削钛合金的刀具温度和磨损分析

针对超声振动钻削钛合会过程中刀具温度较高,但刀具磨损较低的问题,对普通钻削和超声振动钻削AISI - Al2024、AISI-1045、Ti6Al4V进行了有限元仿真和试验,分析了刀具温度、磨损、切屑形态等切削过程变量,解释并研究了其加工机理.结果表明:虽然超声振动叠加的能量提高了刀具温度,但在切削区由于超声减摩作用,...     

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.     

钛合金高速旋转超声椭圆振动侧铣削切屑特征和刀具磨损研究

难加工材料钛合金在采用传统铣削方式时,随着切削速度的增加,切削力和切削温度都迅速增加,使得切削条件恶化并加速刀具磨损,从而导致刀具过早失效。将超声椭圆振动加工技术引入到高速铣削中,进行了钛合金高速旋转超声椭圆振动侧铣削试验。从切屑特征以及刀具后刀面磨损两个方面研究了高速超声椭圆振动铣削参数匹配对钛合金加工的影响。首先基于高速超声椭圆振动铣削过程中刀具-工件的运动学特点推导出高速超声椭圆振动铣削加工参数与振动参数间的匹配关系,然后利用本实验室自行研制的超声椭圆振动铣削装置进行了不同参数匹配关系下的验证性切削试验。试验结果表明：合理的参数匹配使得超声椭圆振动铣削在高速条件下依然能够实现分离型断续切削加工。相比普通铣削加工,分离型的高速超声椭圆振动铣削能够获得更加微细的切屑,切削热能够被及时地带走;良好的切削条件使得刀具的后刀面磨损均匀而缓慢,从而延长刀具的使用寿命;高速超声椭圆振动铣削能够有效地提高生产效率。     

超声研齿不灵敏性振动切削机理与实验

提出了超声研磨螺旋锥齿轮的理论与方法。分析了超声研齿不灵敏性振动切削机理。超声振动使研磨切削抗力减小,动态啮合精度提高,因此,使研磨效率与齿面质量得到相应提高。进行了普通与超声研齿对比试验表明,超声研齿材料去除率可达到普通研磨的三倍,齿面微切削与塑性流动纹理明显,点蚀深度、划痕长短均匀,齿面质量明显优于普通研磨齿面,即粗糙度低至0.2μm,轮廓支承长度率Rmr(c)=100%,水平截距c=1.2μm。     

超声振动螺线磨削表面微观形貌建模与仿真研究

为了实现高效率、高质量、低损伤的硬脆材料加工,对工件或砂轮同时施加砂轮轴向和径向的超声振动,该方法的显著特点是磨粒切削轨迹呈三维空间螺旋线型,将其定义为超声振动螺线磨削方法。在磨削工艺和二维超声振动的多参数共同作用下,材料去除机理产生复杂变化,表面微观形貌创出过程变得极其复杂。为此,提出一种超声振动螺线磨削加工表面数值仿真方法。基于超声振动螺线磨削几何映射关系,建立磨粒相对工件的空间螺旋线切削运动模型,进而给出超声振动螺线磨削加工表面生成模型,模拟出普通磨削和超声振动磨削的三维表面微观形貌,对比分析了超声振动对表面形成过程的影响规律。最后将仿真表面与磨削试验表面对比,发现两者微观形貌特征规律基本一致,验证了仿真方法的正确性和有效性。     

齿轮超声加工技术的研究综述与展望

齿轮超声加工相对于齿轮传统加工可以提高生产效率、延长刀具寿命、改善齿轮表面质量和齿形精度。结合功率超声振动加工特性和应用现状,阐明了齿轮超声加工研究与应用的必要性。详细论述了超声振动滚齿、研齿、齿轮电化学加工、珩齿的加工机理,实验研究与工艺效果。对齿轮超声加工机理材料去除模型研究、振动系统设计、新型刀具设计、生产应用等方面做出了展望。     

Cusp error reduction under high speed micro/meso- scale milling with ultrasonic vibration assistance

In the conventional use of vibration assisted machining, vibratory motion is mostly applied to the continuous machining processes such as turning where the cutting speed is much lower than the vibration speed. Even the recent articles on vibration assisted milling processes are also quite limited to low spindle speed less than 3k RPM. This study investigates vibration assistance that is applied to the workpiece in a high speed micro/meso-scale intermittent milling system where the cutting speed is much higher than the vibration speed. In addition to this, the vibration effect is analyzed considering feed and cross-feed directional application separately, which gives an idea of a right vibration assistance direction for surface quality improvement. To validate this, a one-directional ultrasonic vibration assisted milling system with ultrasonic frequency at 40 kHz and with amplitudes of a few microns is designed and its effect on the machined surface quality is investigated at high spindle RPMs over 15k. As a result, cusp heights are found to be reduced with ultrasonic vibratory motion of cutting edge in high cutting speed. Furthermore, the machined surface quality clearly tells that feed directional vibration assistance is able to generate better surface quality with reduced wavy burrs than cross-feed directional vibration assistance.     

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.