Development of a Dynamometer to Measure All Forces and Moments Applied on Tillage Tools

A new triaxial dynamometer was designed, constructed and tested to measure and locate the position of all forces and moments on tillage implements, up to a maximum force of 10 kN and a maximum moment of 10 kN × m. The design concept of the facility was based on four frames attached to each other by load cells and tillage tool were attached on the inner frame. Calibration of the system showed the reliable and precise performance of the dynamometer in tracking the forces and moments. Additionally, the designed setup operated desirably under field conditions. Draft measurement was compared to those predicted by ASABE Standard D497.7 and was found to be in standard range. By using the new facility, it would be possible to study the relationship between forces and moments at the varying practical cases and design of tines, toolbars and tillage equipments in regard to the soil type and available tractor power will be facilitated.     

Design, development and testing of a turning dynamometer for cutting force measurement

In this study, a turning dynamometer that can measure static and dynamic cutting forces by using strain gauge and piezo-electric accelerometer, respectively, has been designed and developed. The orientation of octagonal rings and strain gauge locations has been determined to maximize sensitivity and to minimize cross-sensitivity. The developed dynamometer is connected to a data acquisition system. Cutting force signals were captured and transformed into numerical form and processed using a data acquisition system consisting of necessary hardware and software running on MS-Windows based personal computer. The obtained results of machining tests performed at different cutting parameters showed that the dynamometer could be used reliably to measure cutting forces. Although the dynamometer was developed primarily for turning operations, it can be used to measure cutting forces during nearly all machining operations (milling, drilling, etc.).     

The influence of misalignment on the uncertainty of vertical torque calibration machine

Misalignment of torque calibration machines can cause parasitic bending loads inside the torque transducers in use. These parasitic loads may affect the machine uncertainty, specially for secondary torque calibration machines. Therefore, this study discusses the contribution of misalignment to the measurement uncertainty for a newly designed 3 kNm secondary vertical torque calibration machine. Radial axes shift up to 4 mm was applied which introduce small increased uncertainty.     

Load identification for a rolling disc: finite element discretization and virtual calibration

For many applications, direct measurement of forces in mechanical systems is difficult or even impossible, and indirect measurement involving inverse analysis must be adopted. One such application of major industrial relevance is the accurate measurement of contact forces acting on rolling bodies. In this paper, a newly proposed strategy for load identification is applied to an example problem of a rolling disc. Based on strain gauge measurements, the contact force is estimated using finite element analysis. A virtual calibration procedure is introduced in order to reduce the dependency of the results on the spatial discretization. In particular, the sensitivity of the results with respect to finite element discretization, sensor placement and noise is discussed. Numerical results based on synthetic data illustrate the behavior and accuracy of the proposed strategy.     

步行器精密测力系统中的人工神经网络标定新技术

设计了一种可用于步行器精密测力系统标定的3层反向传播人工神经网络模型,以测力系统12导联应变片电桥输出电压作为网络输入向量,6个负载分量力作为网络输出向量,并通过目标误差下的绝对误差和对比确定出模型隐含层的最优神经元数.有关误差校验结果表明,使用该神经网络技术标定后的系统最大单向力精度误差为7.78%,最大交叉干扰为7.49%,与传统的线性标定方法相比,能够有效提高步行器受载力的测量精度并大大降低干扰误差,未来有望为步行器助行康复训练效果的准确监控和评估提供帮助.     

一种立式磁致伸缩液位计校准装置的研制

作为一种高精度液位测量装置,磁致伸缩液位计应用日渐广泛。针对现有磁致伸缩液位计校准装置存在的操作复杂、设备占地面积大、精度相对较低等问题,设计了一种立式磁致伸缩液位计校准装置,采用高精密光栅尺作为测量标准,应用机械定位方法实现液位计的快速装调,采用竖直导轨系统自动实现浮子的上下定点移动,通过专用控制软件实现液位计的自动精确测量。对该装置进行测量不确定度评定,证明其具有很好的准确性与可靠性,可有效满足紧凑空间下测量范围为0~2 m的磁致伸缩液位计的校准需求,具有技术推广价值。     

Design and construction of a dynamometer to evaluate the influence of cutting tool rake angle on cutting forces

In this study, the influence of cutting tool rake angle on the cutting forces developed during turning operation was evaluated. For this purpose, a dynamometer was designed and constructed to measure cutting forces. In this dynamometer design, measurement of the cutting tool deflection under the cutting forces was aimed using two beam type load cells located suitably according to the cutting tool. In order to examine the influence of rake angle, turning tests were carried out on AISI 1040 steel workpiece using eight different rake angles. The turning tests at each rake angle were conducted at five different cutting speeds while depth of cut and feed rate were kept constant. The results showed that cutting forces decreased with increasing the rake angle.     

Development and validation of a technique to measure and compare the opening characteristics of tamper‐evident bottle closures

Large sections of the population encounter difficulty in opening consumer packaging of many kinds. Screw‐caps in particular can cause problems for a range of people with a variety of impairments. This paper describes the development and initial testing of a novel multi‐axial force and torque transducer, designed for the study of loading conditions when tamper‐evident bottle closures are opened manually. The transducer, which comprises seven beams that are sensitive to direct forces and torques in each of three axes, can provide comprehensive information on the loading conditions that occur when an instrumented bottle is opened. Importantly, the transducer has been designed to fit inside a typical 500 ml capacity plastic soft drinks bottle so that it does not interfere with the way in which the subject grips the bottle and cap, or applies forces and torques, in order to open the bottle. The method to obtain load data from the calibration matrix, along with initial opening force and torque test data from two user groups, elderly and young, is described. It is clear from the results of these tests that the elderly and young groups exhibit significantly different torque and force profiles to open bottles. It is anticipated that the transducer will be a valuable tool in future studies of opening strategies. Copyright © 2006 John Wiley & Sons, Ltd.     

测力刀柄系统标定技术研究

测力刀柄系统可实时监测切削过程的轴向力和扭矩的变化,为测试自主设计的测力刀柄系统的使用性能,设计并研制了一套标定辅助工装,搭建了标定实验平台,完成了静、动态标定实验。采用逐级加、卸载法,确定了测力刀柄系统的线性度、重复性和滞后性等静态特性指标;通过脉冲激励法获得了测力刀柄系统的固有频率、阻尼比和最大工作频率等动态特性指标。最后,针对测力刀柄系统进行了钻、铣削对比切削实验,结果表明,该系统与Kistler测力仪相比,在轴向和扭矩方向上的测量偏差均小于2%,能够准确反映动态切削过程中轴向力和扭矩的变化。     

A dynamometer design and its construction for milling operation

In this study, a strain gauge based dynamometer capable of measuring three-force components during metal cutting has been designed and constructed. In order to read and save the cutting force data automatically on a computer during metal cutting, a data acquisition system with the necessary hardware and software was also devised and connected to the developed dynamometer. Cutting force signals were captured and processed using a personal computer through operational amplifiers and analog-to-digital converter. Although the dynamometer was developed primarily for milling operations, it can be used to measure cutting forces during nearly all machining operations (turning, grinding, drilling, etc.). Machining tests were performed at different cutting parameters and the results showed that the dynamometer could be used reliably to measure cutting forces.     

扑翼飞行器测力平台设计与振动特性仿真分析

扑翼飞行器是基于鸟类仿生学理论衍生出的新型无人飞行器,主要通过机翼周期性上下扑动来提供飞行器所需的升力和推力,在军用和民用飞行器领域均有广阔的应用前景。扑翼飞行器气动力测量作为样机气动性测试的重要手段,多维气动力的准确测量可为新型扑翼飞行器设计优化和飞控品质的提高提供试验数据支持。本文介绍了一种新型组合式多维小量程测力平台,可实现扑翼飞行器六维气动力和气动力矩的测量。考虑到扑翼飞行器机翼上下扑动过程动态测力需求,应用Ansys Workbench有限元分析软件对测力平台进行了模态分析和频响分析,获得在工作频率下的频率响应,仿真结果表明测力平台的振动特性满足设计要求。     

Application of Bragg grating sensors in the characterization of scaled marine vehicle models

Experiments using two different fiber-optic Bragg grating strain sensor systems to measure dynamic loads, slamming forces, and bending moments on a scaled catamaran model are reported. The system designed to measure slamming forces is based on dynamic locking of the laser diode wavelength to the peak wavelength of a Bragg grating mounted in a force cell. The sensor system has a dynamic range of 27 dB (1-550 N) and a bandwidth in excess of 1 kHz. For the measurement of bending moments, a time-domain multiplexing system, which used a unique pulsed rf modulation technique, of two Bragg grating sensors mounted on a steel beam was designed. The dynamic range of this system was also 27 dB [17 Nm (Newton meter) with a 0.03-Nm resolution]. The bandwidth was limited to approximately 50 Hz.     

The design of a multi-purpose multi-component strain gauge dynamometer

The design, construction and calibration of a multi-purpose multi-component strain gauge dynamometer is described. The dynamometer was constructed for use with a free surface water channel, which can also be used as a water tunnel or a cavitation tunnel. In this experimental facility, the large speed range available (0·03 to 6·1 m/s) and the variety of projects encountered require the measurement of a wide range of loads in several different configurations. The dynamometer system has been based on a unit block concept so that the blocks can be assembled into a suitable configuration and complexity of components to suit each particular problem.
The basic design concept is described together with the calibration results and the magnitude of the interactions. It is concluded that the overall accuracy of the dynamometer blocks and the absence of interaction coupled with the versatility of the system confirm the choice of the original design.     

Dry Sliding Friction Experiments at Elevated Velocities

Abstract: An enhancement of an existing tribometer device developed by Philippon et al. (2004, Wear 257 , 777–784) is presented in this work. This experimental device is made up of a dynamometer ring and a specific load sensor allowing to apply an apparent normal force on specimens and to measure frictional forces respectively. Problems such as static calibration of both distinct parts supported by conducted numerical simulations is given and described in detail. Further discussion, again supported by numerical analysis, validates the placing of the strain gauges and explains the problems of sensitivity of loading surface and cross‐sensitivity. The entire experimental setup is then discussed explaining the mounting of the strain gauges located on the tribometer device, showing the configuration of the Wheatstone quarter‐bridges, presenting the signal conditioning amplifier system and the digital oscilloscopes which all together create one uniform data acquisition system. The set up is adapted on a gas gun to carry the Steel 1080 on Steel VascoMax 300 experiments. The main set of experiments with sliding velocities varying from 10 to 60 m s^?1 are performed in the same tested setup. The recordings of normal and tangential forces leading to the friction coefficient determination are discussed. The values of dry friction coefficient μ according to the experimental parameters are in good agreement with those observed in the literature. Using this new configuration, the effects of the sliding velocity on the surface roughness changes and on the dry fiction coefficient are also investigated. Moreover, very interesting relations between wear and sliding velocity are observed.     

Numerical simulation of the interaction forces between turbine meter and particles in a standpipe

A numerical study of the dynamic behaviour of a turbine meter measuring solid flowrate was carried out by use of the discrete element method. The simulation was conducted with a cylindrical standpipe of 30d in diameter and 40d high, filled with 30000 mono-sized spheres of diameter d, and with a turbine fixed at the centre of the standpipe at a height of 20d. The variations of the torque and rotational speed of the turbine and the porosity of particles around the turbine with time were first investigated. It was observed that these variables fluctuate significantly at the initial stage and gradually reach a macroscopically steady stage. The dependence of the resultant rotational speed on solid flowrate was then measured and shown to be qualitatively comparable to the experimental observation. The force structure of particles around the turbine and the statistical distributions of the forces and torques acting on the turbine originated from its interaction with neighbouring particles were finally analysed. The results indicate that the torque originated from the particle-blade interactions on the blade top surface acts as a driving torque to make the turbine rotate, while the torques due to the particle-blade interactions on the blade bottom and side surfaces balance this driving torque, leading to a macroscopically constant rotational speed.KeywordsDiscrete element simulation, granular dynamics, flow measurement, turbine meter     

Diaphragm gauge for measuring explosive impulse

The measurement of shock and stress waves under the action of explosion and impact loading has long been a concern of scientists and engineers. A number of methods have been developed over the years for measuring the physical parameters that are involved in the material dynamics resulting from an explosion. This work describes the development, calibration and validation of a passive copper diaphragm gauge aimed at measuring the impulse acting on it, resulting from an explosion in air. It is found that the diaphragm deformation (central deflection) can be used to measure the impulse, given the calibration curve. Once the gauge is calibrated, it can be used to measure the impulse acting on it in other media (water, soil, etc.). Such gauges are useful in measuring explosion induced impulses acting on structures. This usefulness is the result of the gauge simplicity and reproducibility. It can be used as a passive gauge or, when instrumented with strain gauges, as a passive and active (electronic) gauge.     

A MILLING CUTTER DYNAMOMETER

A unique milling cutter dynamometer has been designed and developed which enables radial and tangential forces acting on a cutter tooth to be recorded throughout its cutting action. The research value of this instrument has been demonstrated in a series of comparative experiments involving up-cut and down-cut milling.     

基于标准表法的精密数字测温仪校准方法

参考流量与电学计量领域利用标准表对仪器进行校准的方法,提出一种采用高精度的测温电桥与高稳定性的直流电阻箱组合作为标准装置,校准精密数字测温仪的方法.用此方法对精密数字测温仪进行校准并进行测量不确定度分析,结果表明在-195 ～660℃氛围内,温度示值误差的合成标准不确定度为0.5 ～0.7 mK.此方法采用的标准器准确...     

无源光网络中突发光功率计校准方法的研究

介绍了一种利用连续光功率计和示波器进行突发光功率计校准的方法,设计制作了稳定度为±0.01dB/15 min的脉冲光源,通过将脉冲功率的直接测量转换为平均功率的间接测量,实现了突发光功率量值的有效溯源。给出了不确定度评定方法,在0.1 dB分辨力条件下测量不确定度达到0.2dB(k=2)。该方法和装置被广泛用于无源光网络突发光功率计的校准,保证了实际工程中突发光功率测量的准确性。