基于RCSA的刀尖频响函数预测方法

为快速获取构建铣床稳定性叶瓣图所需的主轴—刀柄—刀具系统频响函数,提出一种有限元和响应耦合子结构分析法(RCSA)相结合的预测方法。以某型号主轴系统为研究对象,利用有限元法分别计算主轴、刀柄、刀具端点频响函数,再使用RCSA分别耦合主轴—刀柄结合面、刀柄—刀具结合面,最终得到主轴—刀柄—刀具系统刀尖频响函数。将得到的频响函数与理论算法以及完全有限元方法对比,在5000Hz以内,前7阶模态最大误差不超过15%。该方法可以在机床更换刀柄或刀具时只计算对应部分的频响函数,从而实现主轴—刀柄—刀具系统刀尖频响函数的快速预测。     

基于超声局部谐振的板结构缺陷定量检测方法

为提高板结构缺陷检测效能,提供一种基于宽带激励的超声局部谐振检测方法。利用最大类间方差法对宽带激励下的超声波场进行了分析处理,得到了缺陷的超声局部谐振频率,并将超声局部谐振频率下声场的空间分布用于板结构损伤检测成像;针对特定材料及厚度的各向同性板结构,通过均匀设计试验的方法,建立了缺陷尺寸与其超声局部谐振频率的关系模型。实验结果表明,所提超声局部谐振检测方法可以高效地实现各向同性及各向异性板结构损伤检测。利用回归分析模型还可实现缺陷几何参数的反演,且反演精度较高(半径反演误差最大为2 mm,厚度反演误差最大为0.6mm)。该方法为板结构缺陷检测及定量分析提供了可行的技术方案。     

等离子体射流产生前后变压器谐振点的变化研究

现在大量研究证明了等离子体射流产生后电极结构的介质电容和电阻等参数都会发生变化,而介质电容值的变化会引起高压变压器谐振点的变化。现在改进的针—环电极结构的基础上研究了等离子体射流产生前后变压器谐振点的变化,并分析了等离子体射流状态在谐振点附近的变化情况。实验结果表明,施加最小起始电压与电极结构上产生等离子体射流后,变压器的谐振点由原先的18 k Hz处前移至15.8 k Hz处;电源频率接近谐振点时,等离子体射流的长度增加,发光强度也明显增强。     

大负载纵弯谐振变幅器谐振特性的研究与试验

大负载功率超声纵弯谐振变幅器在旋转超声加工、超声清洗、金属疲劳检测等领域应用广泛,针对大负载工具的应用现状,对阶梯环盘负载与变幅杆组成的功率超声纵弯谐振变幅器进行了设计研究。基于Mindlin中厚板理论,建立了纵弯谐振变幅器的振动模型,推导了频率方程与变幅器振型解析表达式,设计了不同材料大负载功率超声纵弯谐振变幅器。通过阻抗分析试验和超声谐振试验对所设计的变幅器进行了谐振特性研究。对比试验结果证明:大负载功率超声纵弯谐振变幅器的谐振频率与设计频率相比最大误差为4.95%,理论计算与谐振试验得到的三环盘振幅曲线的整体形态一致,零振幅位置最大偏差为6.51%,变幅器作纵弯谐振,为超声谐振系统的设计与应用提供了技术参考。     

带轴锥齿轮超声研齿振动系统的设计与试验

为了满足带轴锥齿轮超声研磨加工的谐振频率要求,利用波动理论对不同结构的3种带轴锥齿轮的超声变幅系统进行谐振设计,建立了统一的谐振频率方程,并对位移放大系数和最大应力进行了比较。运用有限元方法,对由复合变幅杆和换能器组成的超声激励-变幅振动系统进行了模态分析和谐响应分析。最后对超声振动系统进行了阻抗分析和频率测试。试验结果表明：实际超声振动系统的谐振频率为23.269kHz,与设计频率误差约1.17%,试验结果与有限元分析和理论分析结果基本吻合,验证了理论设计的准确性。     

一种新的预测铣刀刀尖频响函数的方法

为准确快速地预测铣刀刀尖点频响函数,提出一种基于逆响应耦合子结构分析（IRCSA）法辨识刀柄-刀具结合面参数的刀尖点频响函数预测方法。该方法通过建立计算刀柄末端频响函数矩阵和刀尖点频响函数矩阵的数学模型,利用逆响应耦合子结构分析法求取随频率变化的刀柄-刀具结合面参数。通过Cuckoo search算法及有限元分析确定刀尖点频响函数中对刀柄-刀具结合面复刚度矩阵变化最为敏感的固有频率,取该频率对应的结合面参数为刀柄-刀具结合面复刚度矩阵的辨识结果,由此计算出刀尖点频响函数。通过硬质合金圆柱棒、2刃铣刀和4刃铣刀进行验证,对比了所提预测方法、Cuckoo search优化算法预测的刀尖点频响函数与实测值三者之间的差异,实验结果表明该预测方法预测的刀尖点频响函数的固有频率和实测固有频率的误差在5%以内,所用时间约为Cuckoo search优化算法的1%,达到了较高的预测精度,并且更加省时、简便。     

高速数控工具系统RFID自动识别技术综述

介绍了RFID自动识别技术、刀具管理系统工作原理和RFID在刀具管理中应用现状,指出了目前数控加工刀具与刀柄的管理中应用的RFID技术存在的问题,展望了RFID在刀具管理中应用前景和方向.     

基于变步长谐振频率跟踪的超声驱动电源

用于超声清洗的超声驱动电源,压电换能器工作在水中的深度不同会导致其固有串联谐振频率产生偏移,进而使得电源输出处于失谐状态,降低了电源的输出效率.针对该问题,采用了一种基于变步长谐振频率跟踪方法,通过测量逆变桥输出电流有效值与直流电源输出电流平均值,并变步长调节电源的输出频率,使得两者的电流比值达到最小,能够使电源输出恢...     

功率超声铆焊变幅杆的设计与分析

功率超声塑料铆焊变幅杆的设计中,纵波谐振频率和振幅是设计的关键。某工程实践中以阶梯形铆焊变幅杆为设计对象,有限元模态分析中,其纵波固有频率为19 982 Hz,谐波扫频响应共振频率为20 082 Hz,阻抗测试频率为19 813 Hz,三者误差率较小,且在材料阻尼率为0.004时,变幅杆端头有仿真最大振幅59.16μm,与激光测振仪测量的振幅49.8μm同样误差较小,实践加工验证,铆焊效果较好。结果表明有限元固有模态、谐波响应、阻抗分析、振幅测试分析可为超声变幅杆的工程设计提供高效的设计、分析、测试方法。     

RFID平台的数控工具系统管理软件开发

构建了RFID硬件系统,以Labview为平台开发了高速数控刀柄及刀具的管理系统,通过串口控制读写设备读写标签内数据,利用数据库管理模块完成刀具记录的添加、查询、修改、删除,实现了刀具的自动识别与管理。     

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.     

一种轻小型四极杆质谱仪射频电源的研制

四极杆结构是四极杆质谱仪的核心结构，由射频电源分别施加两组高压高频信号进行驱动，利用电场的变化和输入离子的质荷比差异对离子进行筛选。针对四极杆质谱仪小型化的研制需求，以信号调制模块、放大模块、反馈电路和直流模块为基本构型，设计了一种应用于轻小型四极杆质谱仪的射频驱动电源。经实际测试，该电源可以在谐振频率1.33 MHz、扫描频率10 Hz的输入条件下，输出峰 峰值电压最高可达3.33 kV的调幅射频高压信号并驱动四极杆结构，扫描切换时间不高于1 ms。射频电源输出信号稳定、波动小、交直比的波动为0.1%。该射频电源相较于常规的四极杆射频电源具有更高的扫描范围，体积小巧，功耗仅30 W，接口简单，有较高的实用价值。     

Dynamic model of shock-vibrating machining of welded joints by ultrasonic tools with an intermediate striker

Using the methods of the theory of shock-vibrating machining systems, machining by ultrasonic tools with a loose striker is considered in the form of forced oscillations of a two-weight system with two impact joints. The amplitude-frequency and phase-frequency characteristics of an ultrasonic shock-vibrating system under machining load are computed. The stability of shock-vibrating oscillations as a function of the tool design parameters and machining conditions is investigated. The independence of the ultrasonic converter resonant frequency from the clamping pressure up to the stability threshold is established. The parameters (clamping, excitation frequency) of the most effective mode of shock-vibrating machining, in which a maximum transfer of acoustic energy to the medium being machined is achieved, are determined. It is shown that the resonant frequency of the converter under load does not coincide with the maximum of the amplitude-frequency characteristic of the striker; therefore, the traditional automatic frequency control system adjustment to the converter resonance is not capable of ensuring oscillation excitation of the shock-vibrating system at the frequency of the most productive mode of machining.     

STUDY ON MECHANISM OF ARC-EXCITED ULTRASONIC

A mechanism of excited arc to be an controlled "ultrasonic emission source" is described. An developed electrical source with an certain frequency bandwidth for the purpose of the arc-excited is connected with an conventional welding power supply through coupling the cables for the experiment. Some resonant frequency bands for the arc-excited ultrasonic are discovered in the welding process, and its frequency, amplitude and phase'shift are recorded. This principle demonstrates that arc can be used not only for a thermal source, but also for an ultrasonic emission source, which may be extent to the industrial application in some new ways, such as for automatic welding process control and quality inspection.     

Design and dynamic modeling of a 2-DOF decoupled flexure-based mechanism

Flexure mechanisms with decoupled characteristics have been widely utilized in precision positioning applications.However,these mechanisms suffer from either slow response or low load capability.Furthermore,asymmetric design always leads to thermal error.In order to solve these issues,a novel 2-DOF decoupled mechanism is developed by monolithically manufacturing sets of statically indeterminate symmetric(SIS) flexure structures in parallel.Symmetric design helps to eliminate the thermal error and Finite Element Analysis(FEA) results show that the maximum coupling ratio between X and Y axes is below 0.25% when a maximum pretension force of 200 N is applied.By ignoring the mass effect,all the SIS flexure structures are simplified to "spring-damper" components,from which the static and dynamics model are derived.The relation between the first resonant frequency of the mechanism and the load is investigated by incorporating the load mass into the proposed dynamics model.Analytical results show that even with a load of 0.5 kg,the first resonant frequency is still higher than 300 Hz,indicating a high load capability.The mechanism’s static and dynamic performances are experimentally examined.The linear stiffnesses of the mechanism at the working platform and at the driving point are measured to be 3.563 0 N·μm-1 and 3.362 1 N·μm-1,respectively.The corresponding estimation values from analytical models are 3.405 7 N·μm-1 and 3.381 7 N·μm-1,which correspond to estimation errors of-4.41% and 0.6%,respectively.With an additional load of 0.16 kg,the measured and estimated first resonant frequencies are 362 Hz and 365 Hz,respectively.The estimation error is only 0.55%.The analytical and experimental results show that the developed mechanism has good performances in both decoupling ability and load capability;its static and dynamic performance can be precisely estimated from corresponding analytical models.The proposed mechanism has wide potentials in precision positioning applications.     

一种改进的基于响应耦合子结构法的刀尖点频响函数预测方法

针对现有的基于响应耦合子结构法(RCSA)的刀尖点频响函数预测方法需要辨识主轴-刀柄、刀柄-刀具结合面参数以及需要自制刀柄模型等引起的预测误差和预测过程复杂等问题,提出一种改进的基于RCSA的铣刀刀尖点频响函数预测方法。该方法首先改进已有的子结构划分方法,将机床-主轴-刀柄-刀具系统划分为机床-主轴-刀柄-部分刀杆、剩余刀杆和刀齿三个子结构;然后改进主轴-刀柄处转动频响函数的计算方法,通过铣刀的模态锤击实验采用反向RCSA和有限差分法计算机床-主轴-刀柄-部分刀杆结构的转动频响函数,并基于Euler梁模型计算出剩余刀杆、刀齿子结构的频响函数;最后将三个子结构的频响函数耦合确定刀尖点的预测频响函数。以一立式加工中心为研究对象,应用所提出的方法对铣刀刀尖点的频响函数进行了预测,并与其实测频响函数进行对比。对比结果表明：刀尖点的预测频响函数与实测频响函数符合程度较高,其预测、实测前三阶固有频率之间的误差在6.9%以内,所提出的方法可行有效、简单方便,且可直接基于铣刀的模态实验计算主轴-刀柄的频响函数,避免了相关结合面参数的辨识和刀柄模型的制作。     

Rotary ultrasonic machining: effects of tool natural frequency on ultrasonic vibration amplitude

Rotary ultrasonic machining (RUM) is a hybrid machining process that combines the material removal mechanisms of grinding and ultrasonic machining. RUM has been applied to hole-making for a wide range of materials. It is known that ultrasonic vibration amplitude has significant effects on cutting force, torque, and surface finish in RUM. One experimental observation that has been reported in the literature multiple times states that different tools show different vibration amplitudes on the same ultrasonic power level. However, no analyses can be found in the literature to explain this observation. The existence of this knowledge gap makes it difficult to explain some experimentally obtained trends or to conduct more realistic physics-based modeling work. The objectives of this research are to understand the effects of tool natural frequency on ultrasonic vibration amplitude in RUM, to provide an explanation to the observation and verification of measurement methods, and also to guide tool design and selection in RUM. Ultrasonic vibration amplitudes of tools are measured by three methods and compared. It is found that tool natural frequency significantly affects ultrasonic vibration amplitude. The tool with its natural frequency closest to that of the ultrasonic power supply (20?kHz) generates the highest ultrasonic vibration amplitude on every ultrasonic power level tested.     

An identification method for spindle rotation error of a diamond turning machine based on the wavelet transform

This paper presents an identification method for the spindle rotation error from the flatness error in the workpiece surface. The spindle rotation error is identified by the wavelet transform, Weierstrass function, and power spectral density (PSD). The flatness error comprises various errors of the machine tool, such as spindle rotation error, guideway error, motor error, and ball screw error, therefore, wavelet transform is used to process the measured result of the workpiece and the signal is decomposed into high-frequency and low-frequency signal. Weierstrass function is used to fit the spindle rotation error. According to the PSD analysis of the processed signal in the frequency domain, the spindle rotation error is identified from the measured flatness error, this method provides a basis for the identification of machine tool errors.     

基于谐振式MEMS传感器的仪表开发关键技术

针对基于谐振式MEMS传感器开发数字智能仪器仪表的高精度、快响应频率测量技术展开研究。以一谐振式MEMS气压传感器为开发样件,其差分输出是两路40～70 kHz之间的正弦频率信号。对传统的频率测量方法进行阐述分析,提出一种新的结合传统测频方法各自优点的频率检测方法。设计实现相关软、硬件,搭建测试系统,实验结果表明该测频方案针对40～70 kHz的频率信号误差小于±0.02 Hz,响应时间为1 s以内。     

Design and fabrication of a novel vibrational system for ultrasonic assisted oblique turning process

We designed and fabricated suitable vibrational equipment for ultrasonic assisted oblique turning process to enable researchers to perform experimental tests with the operating conditions closest to common assumptions of cutting mechanics theories. Applying ultrasonic vibrations to the tool cutting edge along tangential direction and in the presence of inclination and tool cutting edge angles necessitates a novel design and fabrication of vibrational horn with special oblique geometry. In this vibrational horn, the natural frequency of longitudinal vibration mode is forced to be in a certain frequency range of the ultrasonic power supply. The novel tool-workpiece assembly was designed using modal analysis to provide the most conformity of cutting geometry and process parameters between theory and practice. Three-dimensional cutting forces were measured experimentally in vibrational oblique turning process carried out by the mentioned horn. The most suitable conditions to profit from ultrasonic vibrations in oblique turning process were determined, and these experimental results were in agreement with modal analysis results.