新型六筋式应变切削测力仪研究报告

本文分析了传统应变测力仪无法有效提高静刚度的原因,给出了以剪切与拉压应变相结合方式为特点的六筋式应变切削测力仪设计方案及结构原理。标定实验证明,新型通用测力仪在静刚度和固有频率上可以远远超过压电式测力仪,刀杆式车削测力仪灵敏度达到测量克服切削力的水平。     

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。     

整体式压电三向车削测力仪的研制北大核心CSCD

针对三维动态车削力的测量需求及刀杆式、平台式压电测力仪的不足,研制了一种带有双弹性环结构的整体式压电三向车削测力仪。设计了测力仪的2种结构方案,并对比了2种方案的优劣,阐述了测力仪和压电测试系统的测量原理,对测力仪进行了静态标定实验和动态冲击实验,实验结果表明:测力仪具有优良的静、动态性能,满足了动态车削力的测量需求。     

新型压电式车削测力仪

新型压电式车削测力仪采用对称的双弹性环结构,该结构的"推挽"特性提高了测力仪灵敏度和实现了传感器XY切型晶组温度自动补偿功能,降低了切削热对测力仪的干扰.同时利用有限元分析软件ANSYS,对测力仪弹性环结构进行了优化设计.静、动态标定的技术指标完全达到了实际工程应用的要求.     

《新型高灵敏度压电式钻削测力仪》

压电晶体双向动态钻削测力仪是钻削及其它孔加工机理研究以及实现钻削加工过程自动监控必不可少的手段,亦可在其它各个方向用来测量轴向力及扭力矩。本文对传感器及测力仪的结构设计、计算给以全面论述,为使测力仪获得高性能,结构上采用优化后的弹性薄壁螺纹筒夹进行予载。得到高刚性、高灵敏度,则是在这一领域中的一个创新。     

高频响测力仪固有频率的理论分析与试验

针对现有测力仪固有频率较低而无法准确测量高转速下铣削力的难题,基于附加弹性测力原理设计了高频响测力仪,测力系统的固有频率达到9kHz以上,运用邓克莱法建立了测力仪的简化模型,推导出固有频率的解析式;进行了有限元仿真与模态试验,获得了测力仪固有频率的仿真值、实测值以及振型;最后进行了高转速铣削力验证试验。研究结果表明,该测力仪固有频率的解析值和仿真值略大于实测值,但三者较为接近,测力仪关键结构尺寸与其固有频率密切相关,利用简化模型和有限元法进行高频响测力仪的结构优化设计合理可行,为同类测力仪的结构优化设计提供了参考依据。     

SAW智能测力仪

从声表面波（SAW）的原理出发介绍我们新研制的全数字式智能测力位──SAW智能测力仪。     

新型压电式测力仪多功能静态标定平台的研制

为了解决压电测力仪的静态标定,文中介绍了自行研制的高精度、高刚性静态标定平台原理与结构。该标定台垂直力、水平力均采用螺旋加载方式,力值大小由三级标准测力环直接读取;而扭矩的加载采用"力×力臂"法,通过平移两个水平加载机构形成力臂,同时产生大小相等、方向相反的两个力来实现。对该标定台进行精度和刚度实测,结果表明相关指标均达到了CIRP-STCC标准。无疑,利用该标定平台可完成单向、双向力传感器、三向压电式测力仪以及钻削测力仪的静态灵敏度、线性、重复性、滞后以及横向干扰标定。     

一种分离式自解耦型精密测力仪

介绍一种分离式自解耦型精密测力仪，对其一些主要性能进行了较深入的实验研究。结果表明，测力仪具有较高的性能和实用性。     

一种多功能测力仪标定加载器

介绍一种用于测力仪加载及标定设备 ,它通过手动操作可对多种测力仪进行多方向加载、标定。其结构简单可靠 ,操作方便 ,有一定实用价值。     

基于有限元分析的微孔钻削测力仪研究

通过分析应变式测力仪传统理论模型,设计了一种用于微小孔钻削测力仪的灵敏元件等效模型.利用有限元分析工具对测力仪灵敏元件进行了动力学和静力学分析,对测力仪的结构尺寸进行了优化设计,使测力仪的固有频率和灵敏度达到较为理想的状态.在此基础上研制了一套高灵敏度应变式微小孔钻削测力系统,通过试验验证,取得了比较理想的微小孔钻削过程力信号曲线,测力仪的测力范围、灵敏度、固有频率都达到了设计要求,可以满足实际工程应用和测试研究的需要.     

Dynamic characterization of multi-axis dynamometers

In this paper, we present a comprehensive technique for accurate determination of three-dimensional (3D) dynamic force measurement characteristics of multi-axis dynamometers within a broad range of frequencies. Many research and development efforts in machining science and technology rely upon being able to make precise measurements of machining forces. In micromachining and high-speed machining, cutting forces include components at frequencies significantly higher than the bandwidth of force dynamometers. Further, the machining forces are three-dimensional in nature. This paper presents a new experimental technique to determine the three-dimensional force-measurement characteristics of multi-axis dynamometers. A custom-designed artifact is used to facilitate applying impulsive forces to the dynamometer at different positions in three dimensions. Repeatable and high-quality impulse excitations are provided from a novel impact excitation system with a bandwidth above 25 kHz. The force measurement characteristics are presented within 25 kHz bandwidth using 3 × 3 force-to-force frequency response functions (F2F-FRFs), which capture both direct and dynamic cross-talk components to enable fully three-dimensional characterization. The presented approach is used to characterize the dynamic behavior of a three-axis miniature dynamometer. The effects of force-application position, artifact geometry, and dynamometer-fixturing conditions are explored. Moreover, the relationship between the force-measurement characteristics and structural dynamics of the dynamometer assembly is analyzed. It is concluded that the presented technique is effective in determining the force-measurement characteristics of multi-axis dynamometers. The changes in dynamometer assembly that affect its structural dynamics, including artifact (workpiece) geometry and especially the fixturing conditions, were seen to have a significant effect on force-measurement characteristics. Furthermore, the force-measurement characteristics were seen to change substantially with the force-application position. The presented technique provides a foundation for future compensation efforts to enable measuring forces within a broad range of frequencies.     

Development and evaluation of tool dynamometer for measuring high frequency cutting forces in micro milling

A tool dynamometer is developed for measuring the high frequency cutting forces, and evaluated in micro milling of aluminum 6061-T6 using a tungsten carbide (WC) micro end mill. To improve the accuracy and productivity of the machining process, it is essential to monitor and control the machining process by measuring cutting forces. In order to improve the precision and quality of machined parts, high-speed machining with smaller micro tools is required, causing higher frequency cutting forces. The first natural frequency of tool dynamometers is high enough to precisely measure the high cutting forces. We investigate dynamic characteristics of the tool dynamometer theoretically and experimentally. The measurable frequency range of the developed tool dynamometer was higher than the commercial tool dynamometer, and the measured cutting force signals were not distorted at high-speed of above 60,000 rpm. The results showed that the developed dynamometer is able to measure the static and dynamic force components in high-speed micro milling.     

基于工业摄像技术的动态轴功率测量

基于工业摄像技术提出一种非接触测量传动轴动态轴功率的方法。首先设计了轴功率测量系统,提出了测量轴转速和轴转矩的方法。通过数字散斑的相关搜索和亚像素计算等手段,测得轴转速和转矩值,最终计算得出轴功率。为验证本文方法的测量精度,搭建了车载试验系统,并在底盘测功机上对其进行了实际测量试验。试验结果表明:提出的轴功率测量方法得到的结果与底盘测功机测量结果变化趋势一致,其相对误差平均值为9.37%。其中轴转速的测量范围可以覆盖整个过程,测量值波动较小,与底盘测功机测量结果基本一致,其相对误差平均值为0.73%,抗噪能力强;轴转矩的测量范围可覆盖部分高转矩,测量值波动较大,两者测量结果趋势一致,其相对误差平均值为15.15%,抗噪能力较弱。本文方法克服了一些传统测量方法的不足,为解决轴功率动态测量提供了一种新思路。     

Accurate measurement of micromachining forces through dynamic compensation of dynamometers

In this paper, we present a comprehensive approach for accurate measurement of high-bandwidth three-dimensional (3D) micromachining forces through dynamic compensation of dynamometers. Accurate measurement of micromachining forces is paramount to gaining fundamental understanding on process mechanics and dynamics of micromachining. Multi-axis dynamometers are used to measure 3D machining forces. However, specified bandwidth of these devices is below the frequencies arising during micromachining while using ultra-high-speed (UHS) spindles. This limitation arises from the effects of the dynamometer's structural dynamics on the measured forces. Therefore, accurate measurement of micromachining forces entails high frequency correction of the signals acquired by the dynamometer by removing the influence of those effects. The presented approach involves: (1) accurate identification of 3D force measurement characteristics of the dynamometer within a 25 kHz bandwidth to capture the effects of the dynamometer dynamics; (2) design of a pseudo-inverse filter-based compensation technique to remove the influence of the dynamic response in 3D; and (3) validation of the compensation technique through custom-devised experiments. Subsequently, the compensation method is applied to the micromilling process to obtain accurate broadband 3D micromachining forces using a miniature multi-axis dynamometer. It is concluded that the presented approach enables accurate determination of 3D micromachining forces. The presented compensation technique is also readily applicable for expanding the bandwidth of large dynamometers.     

Design, calibration and error analysis of a piezoelectric thrust dynamometer for small thrust liquid pulsed rocket engines

Small thrust liquid pulsed rocket engines operating in pulsed mode have gained a good reputation in attitude control applications for their potential reliability and efficiency. However, the pulsed characteristic creates a difficult measurement problem. In this paper, a novel thrust dynamometer with high natural frequency is developed for accurately measuring the pulsed thrust. It consists of two shear mode piezoelectric quartz crystal sensors and an integral shell. The sensors are inserted into unique double-elastic-half-ring grooves with an interference fit. Stiffness equations of the shell which are used to estimate the amount of interference are derived. The thrust dynamometer is calibrated both statically and dynamically. Static calibration uncertainty is evaluated. A trapezoidal impulse force is used to simulate the pulsed thrust for further characterizing the dynamic measurement performance of the thrust dynamometer. An evaluation algorithm of dynamic error is presented and used to evaluate the results of the dynamic simulation. The results show the thrust dynamometer has high sensitivity and natural frequency, good linearity and repeatability, and excellent dynamic performance. It can accurately trace trapezoidal thrust signal of 50 Hz without waveform distortion.     

Measurement of transient cutting force by means of a Fourier analyser

Measurements of transient cutting force are often required for analysing transient phenomena in cutting or detecting tool chipping. With most existing tool dynamometers which detect cutting force through strain, however, accurate measurements of transient cutting force cannot be expected because of inadequate frequency characteristics or large time lag. This paper proposes a method of measuring the transient cutting force. In this method, cutting force is calculated by means of a digital Fourier analyser from the output of a tool dynamometer and the transfer function, which has been identified in advance under the same set-up as used for the cutting test. The assessment tests have revealed that the cutting force calculated in this way is extremely close to the real value, regardless of the dynamic rigidity of the tool dynamometer. This method is also applicable for accurate detection of acceleration of a simple system.     

Design,development and testing of a four-component milling dynamometer for the measurement of cutting force and torque

The cutting forces generated in metal cutting have a direct influence on generation heat, tool wear or failure, quality of machined surface and accuracy of the work piece. In this study, a milling dynamometer that can measure static and dynamic cutting forces, and torque by using strain gauge and piezo-electric accelerometer has been designed and constructed. The orientation of octagonal rings and strain gauge locations has been determined to maximise sensitivity and to minimise cross-sensitivity. The force and torque signals were captured and processed using proper data acquisition system. The dynamometer has been subjected to a series of tests to determine its static and dynamic characteristics. The results obtained showed that the dynamometer could be used reliably to measure static and dynamic cutting forces and torque.     

Design,development, and calibration of a force-moment measurement system for wheel–rail contact mechanics in roller rigs

A force measurement system, referred to as “dynamometer”, for accurately acquiring the contact forces and moment in a single-wheel roller rig using piezo-electric load cells is designed and developed. Accurate determination of the wheel–rail contact forces and moments is an essential requirement for studying the wheel–rail contact mechanics. The dynamometer is placed in the load-path between the wheel–rail interface and the ground, enabling it to measure the forces and moments at the interface. A series of tests are performed to determine the quasi-static and dynamic characteristics of the dynamometer. Additionally, finite element analysis and multi-body dynamic modeling are used to establish flexural modes and dynamic interface between the components. The simulation and test results indicate that the dynamometer is able to accurately and reliably measure the contact forces and moments at the wheel–rail interface.     

高灵敏度深小孔压电钻削测力仪的研制

研制了用于测量深小孔钻削加工的高灵敏度压电式动态测力仪。通过分析深小孔钻削加工的特点,明确了该条件下测力仪应具备的高灵敏度等性能。为了使测力仪具有高灵敏度的性能,从传感器测力原理及测力仪的结构等方面进行了详细论述。讨论了两种扭矩测量方法,分别设计了最简捷的测力仪结构形式,进行了相应的实验,对结果进行了比较和分析。静、动态标定结果证明,双传感器分布结构的测力仪灵敏度高,动态性能、精度等均达到规定标准。在此基础上,分别进行了测力仪灵敏度一致性实验和实际钻削加工验证测试,测量结果表明,在测力仪的测试区域内均可准确、可靠地测量出深小孔钻削力。