螺旋槽丝锥切削模型建立及切削过程模拟

建立了螺旋槽丝锥模型并利用DEFORM-3D有限元软件模拟丝锥的攻丝过程,将模拟得到的切削力与试验测量的切削力进行对比,证明该丝锥模型可以用来模拟丝锥攻丝过程的受力状况。用该丝锥模型研究了切削速度对切削力的影响,结果表明:随着丝锥转速的提高,切削扭矩先减小后增大,在转速为200r/min时扭矩最小。     

机械式低频振动攻丝切削力实验研究

本文根据振动攻丝基本原理,研制出具有振动攻丝功能的振动攻丝卡头,并利用该卡头对振动攻丝切削力变化特点进行了大量的实验研究。结果表明采用振动攻丝切削力呈现出理想的波形化效果,切削力峰值略低于普通攻丝,切削力平均值为普通攻丝的１／５～１／２。     

刀具磨损过程中切削力动态分量信号分形维数的变化规律研究

研究了刀具磨损过程中切削力动态分量信号分形维数的变化规律 ,发现分形维数在刀具初期磨损和剧烈磨损阶段较正常磨损阶段高。由于切削力信号动态分量的分形维数随刀具磨损状态的变化而变化 ,使得它可以作为切削过程中判断刀具工作状态的一个参数     

基于VB的切削力系统设计

通过对切削用量选择的分析可知,精确计算切削力有重要的意义,因此使用VB开发了切削力分析系统.该系统实现了快速计算切削力、切削功率、切削扭矩,并能动态显示切削力变化曲线,减少了手工处理时的繁琐分析和计算,在实际生产中为选择切削用量提供了理论依据.     

基于刀具磨损和切屑形成对切削Ti6Al4V的切削力特性研究

为了研究钛合金Ti6Al4V切削过程中的切削力特性,采用硬质合金涂层和无涂层刀具进行了外圆干车削试验,提取切削力信号,通过研究切削力的静动态特性,揭示了切削力与切削速度、刀具材料、刀具磨损以及切屑形成的关系.结果表明:钛合金切削过程中,切削力的静态分量中径向力Fp最大,直接导致刀具后刀面磨损;随着切削速度的变化,切削力的变化是由刀具磨损、材料本身的特性等多方面因素综合作用的结果,切削力动态分量分形维数可用于刀具状态监控;锯齿形切屑的产生与切削力的高频变化有直接的关系,锯齿生成频率可以作为切削力动态分量频率的一个表征,选取适当的切削参数可以降低由于锯齿屑产生引起的切削力振动.     

难加工材料攻丝摩擦扭矩的试验研究

分析了攻丝过程及退回过程两阶段丝锥的力学特征,在此基础上分别建立了切削扭矩和摩擦扭矩力学模型。针对难加工材料GH4169和TC4,采用M6标准丝锥进行攻丝试验。结果表明:摩擦扭矩占攻丝扭矩的比率分别为45%和55%;针对45钢,摩擦扭矩则很小。可见,摩擦扭矩大是GH4169和TC4攻丝困难的主要原因。     

硬孔攻丝用高性能先端丝锥的设计及应用

热后硬孔攻丝螺纹变形量小、尺寸稳定、强度高。该工艺方法对刀具强度要求较高,使用普通高速钢丝锥和螺纹铣刀加工时,普通高速钢丝锥无法承受热后硬孔攻丝所产生的大扭矩而频繁折断,报废率较高,同时螺纹铣刀成本高,不适合大批量生产。针对热后硬孔攻丝工艺复杂、成本高的问题,专门设计了硬孔攻丝用高性能先端丝锥,解决硬孔攻丝难题,并与其他种类丝锥进行了切削力对比。     

振动切削在螺纹加工中的应用

针对应用日益广泛的难加工材料的攻丝难题,根据振动切削基本原理,研制出具有振动攻丝功能的激振装置,并对其进行理论研究和实验分析,结果表明:振动攻丝切削力呈现出明显波形,攻丝扭矩的均值大大低于普通攻丝.     

高速铣削中切削力动态分量信号分形特征的研究

本文研究了高速铣削调质 45钢时切削力动态分量信号的分形特征 ,通过试验研究了不同刀具材料和不同切削速度对切削力动态分量信号分形维数的影响 ,并对这些影响进行了机理的分析。研究表明 :分形维数可以表征切削力动态分量的随机性和切削状态的平稳性     

球头铣刀切削力计算机预报模型的数值仿真

借助建立的铣刀切削力、扭矩和切削功率的计算机预报模型 ,对平前刀面球头铣刀的切削性能进行了数值仿真研究 ;通过分析各种切削参数对切削性能的影响规律 ,获得了不同切削条件下球头铣刀切削力和扭矩的特征和变化趋势     

新型扭矩—轴向力传感器标定研究

扭矩—轴向力传感器是研究复合振动攻丝过程的重要装置。在振动攻丝机上安装扭矩和轴向力传感器,可以实现扭矩和轴向力的在线测量,对研究在振动攻丝过程中扭矩和轴向力的关系具有重要意义。为了研究新设计的扭矩—轴向力传感器的基本特性,选择了标定设备和标定方法对传感器进行静态标定和动态标定,得出传感器的静态特性和动态特性指标,为进一步设计和改造传感器结构提供理论依据。     

Dynamic analysis of tapping mode atomic force microscope (AFM) for critical dimension measurement

Transient dynamics of tapping mode atomic force microscope (AFM) for critical dimension measurement are analyzed. A simplified nonlinear model of AFM is presented to describe the forced vibration of the micro cantilever-tip system with consideration of both contact and non-contact transient behavior for critical dimension measurement. The governing motion equations of the AFM cantilever system are derived from the developed model. Based on the established dynamic model, motion state of the AFM cantilever system is calculated utilizing the method of averaging with the form of slow flow equations. Further analytical solutions are obtained to reveal the effects of critical parameters on the system dynamic performance. In addition, features of dynamic response of tapping mode AFM in critical dimension measurement are studied, where the effects of equivalent contact stiffness, quality factor and resonance frequency of cantilever on the system dynamic behavior are investigated. Contact behavior between the tip and sample is also analyzed and the frequency drift in contact phase is further explored. Influence of the interaction between the tip and sample on the subsequent non-contact phase is studied with regard to different parameters. The dependence of the minimum amplitude of tip displacement and maximum phase difference on the equivalent contact stiffness, quality factor and resonance frequency are investigated. This study brings further insights into the dynamic characteristics of tapping mode AFM for critical dimension measurement, and thus provides guidelines for the high fidelity tapping mode AFM scanning.     

Analysis of dynamic cantilever behavior in tapping mode atomic force microscopy

Tapping mode atomic force microscopy (AFM) provides phase images in addition to height and amplitude images. Although the behavior of tapping mode AFM has been investigated using mathematical modeling, comprehensive understanding of the behavior of tapping mode AFM still poses a significant challenge to the AFM community, involving issues such as the correct interpretation of the phase images. In this paper, the cantilever's dynamic behavior in tapping mode AFM is studied through a three dimensional finite element method. The cantilever's dynamic displacement responses are firstly obtained via simulation under different tip‐sample separations, and for different tip‐sample interaction forces, such as elastic force, adhesion force, viscosity force, and the van der Waals force, which correspond to the cantilever's action upon various different representative computer‐generated test samples. Simulated results show that the dynamic cantilever displacement response can be divided into three zones: a free vibration zone, a transition zone, and a contact vibration zone. Phase trajectory, phase shift, transition time, pseudo stable amplitude, and frequency changes are then analyzed from the dynamic displacement responses that are obtained. Finally, experiments are carried out on a real AFM system to support the findings of the simulations. Microsc. Res. Tech. 78:935–946, 2015. © 2015 Wiley Periodicals, Inc.     

Direct measurement of tapping force with a cantilever deflection force sensor

An experimental set up dedicated to the measurement of atomic force microscope tapping force was developed. In the set-up, a standard TappingMode™ probe cantilever was used to tap another cantilever equipped with its own low noise and high sensitivity deflection detection system for force measurement. The amplitude and phase change of the tapping lever as well as the deflection of the sensing lever were simultaneously recorded as a function of tip/surface separation. Since the deflection of the sensing cantilever reflects the average force over one interaction cycle, we measured the total average force quantitatively after calibrating the spring constant and deflection sensitivity of the sensing lever. Considerable effort was made to achieve the same force curve in the tapping force measurement as occur during imaging of conventional samples such that the detected tapping force reflects the same interaction of the imaging process.     

Complex dynamics of carbon nanotube probe tips

Carbon nanotube (CNT) tips in tapping mode atomic force microscopy (AFM) enable very high-resolution imaging, measurements, and manipulation at the nanoscale. We present recent results based on experimental analysis that yield new insights into the dynamics of CNT probe tips in tapping mode AFM. Experimental measurements are presented of the frequency response and dynamic amplitude-distance data of a high-aspect-ratio multi-walled (MW) CNT tip. Higher harmonics of the microcantilever are measured in frequency ranges corresponding to attractive regime and the repulsive regime where the CNT buckles dynamically. Surface scanning is performed using a MWCNT tip on a SiO(2) grating to verify the imaging instabilities associated with MWCNT buckling when used with normal control schemes in the tapping mode. Lastly, the choice of optimal setpoints for tapping mode control using CNT tip are discussed using the experimental results.     

振动攻丝机的控制系统

振动攻丝是一种新型的加工方法。本系统用步进电机作为动力源实现丝锥的扭转振动,简化了机械结构。本文介绍了各子系统的功用及控制方法。步进电机及其驱动系统将脉冲信号放大去控制步进电机的运行。微型计算机控制系统控制脉冲序列的发送,实现振动攻丝中转速、振幅和频率的无级调整。切削过程控制系统利用测力传感器取得信号,经过A/D转换和数据处理,再将数字信号反馈给计算机去控制攻丝参数的改变。     

Energy dissipation and frequency shift of a damped dynamic force microscopy

The closed-form solution of the transient response of damped dynamic force microscopy subjected to the nonlinear interatomic force is derived. The frequency shift and the decay rate of a V-typed probe can be determined easily and precisely by the proposed method. If the taper ratio is zero, a uniform cantilever is obtained. Moreover, the transient response of a non-uniform cantilever can be determined also in the same way. The complex Young's modulus is used to describe the viscoelastic material property. In the modulus, the loss factor is introduced. The relation between the Q-factor and the loss factor is discussed. Moreover, the relation between the energy dissipation and the frequency shift is revealed. Finally, the effects of several parameters on the Q-factor, the frequency shift and the decay rate are investigated. The proposed method can be easily applied to investigate the tapping mode of AFM.     

采用振动攻丝提高工艺系统刚度的机理研究

对振动攻丝可提高工艺系统刚度的动力学机理进行了理论分析和试验验证 ,指出减小净切削时间比(Tc/T)可提高攻丝系统刚度 ,从而达到改善丝锥耐用度和螺纹加工质量的目的     

应变式切削测力系统动态特性的研究

本文对应变式切削测力仪的动态性能进行了研究,比较测力仪弹性无件在粘贴应变片前后固有频率和阻尼比的变化。结论是：应变片的粘贴不会造成测力仪固有频率的损失;测力系统的通过频率取决于系统中固有频率最差的环节－动态应变仪。最后,用实验的方法验证了测力系统对动态力的测量结果。     

振动攻丝加工中丝锥的刚性化

分析了振动攻丝的实现方式及其运动原理。基于振动攻丝的动态角位移方程得出丝锥最大偏转角和攻丝扭矩的关系式,并给出了净切削时间比和振动圆频率对丝锥最大偏转角的影响规律,丰富了振动攻丝丝锥刚性化机理。