Integrated force measurement for on-line cutting geometryinspection

A novel on-line cutting geometry inspection technique based on the integrated force-sensing method has been developed. A piezoelectric force sensor, mounted at the back of a single crystal diamond tool, was used to measure the cutting forces encountered by the tool system as it plunge-cut parallel micro flow channels on copper foils about 125 μm in thickness. The force data were then converted by a software code which calculates the geometrical dimensions (depth and width) of the micro channels that had been cut. A series of experiments were conducted for four different feeds: 0.1, 0.3, 1.0, and 5.0 μm/rev., at a constant workpiece speed of 2,400 rpm. Error analysis showed that the maximum relative error of the measurement, as compared to the results from the theoretical analysis, is 9.8%. By incorporating this force sensing technique into the machine tool control system, a real-time control unit can be implemented which conducts on-line adjustment of the diamond cutting performance to improve manufacturing quality     

The drift of a number of idealized model icebergs

Dimensionless solutions for the equations of motion are introduced as an aid to understanding the movement of spherical and cubical semi-immersed objects during deceleration.Laboratory experiments show that such objects initially move under the action of a drag force that is proportional to the speed of the object, then enter a transition to a final stage where the drag force is proportional to the square of the speed of the object.Frictional and form drag coefficients are obtained by postulating that the product of the initial speed and the time constant for any one object is a constant.The approach and analysis presented in this study should provide insight regarding the probable behaviour of an iceberg under the action of various environmental forces.     

Analysis of Shadow Moire Technique With Phase Shifting Using Generalisation of Carre Method

Abstract: Experimental stress analysis can be conveniently investigated by classical shadow Moire technique. Moire is a non‐contact and non‐destructive technique, with a fast digitisation process. The phenomena of Moire fringes are the result of the projection of the fringes of a ruling on a certain object. It has measurement accuracy comparable with other systems and also low cost. The present study offers new algorithms for phase evaluation in measurements. Several phase‐shifting algorithms with an arbitrary but constant phase‐shift between captured intensity signs are proposed. The algorithms are similarly derived as the so‐called ‘Carre algorithm’. The idea is to develop a generalisation of Carre algorithm that is not restricted to four images. Errors and random noise in the images cannot be eliminated, but the uncertainty caused by their effects can be reduced by increasing the number of observations. An experimental analysis of the mistakes of the technique was made, as well as a detailed analysis of mistakes of the measurement. The advantages of the proposed algorithm are its precision in the measures taken, speed of processing and the immunity to noise in signs and images.     

采用力偶型径向柱塞马达的新型调速回路特性分析与试验

针对变量泵-定量马达容积调速回路调速范围有限,变量泵-变量马达调速回路结构复杂的问题,故提出采用力偶型径向柱塞马达的新型恒转矩调速回路。该马达输出轴的径向力平衡,通过力偶输出转矩,马达的一个壳体内可以形成内、外两个马达;在输入压力和流量不变的情况下,通过不同的配流方式可以输出三种转矩和转速,更能满足多种工况需求;三级恒转矩调速回路在三种工作方式下产生不同的动态特性,内马达单独工作时的动态特性较好。利用AMESim软件进行仿真分析并搭建实验台对力偶型径向柱塞马达新型调速回路进行试验分析,试验数据验证了新型调速回路可增加系统的转速转矩范围,丰富了力偶型径向马达的应用领域。     

MEASUREMENT OF VAN DER WAALS FORCE OF TONER ADHESION EMPLOYING A LINEARLY INCREASING ELECTRIC FIELD AND DETERMINING THE TONER JUMPING VOLTAGE

Both van der Waals and electrostatic forces of adhesion between toners and substrates play an important role in electrophotography processes employed in copying machines and laser printers. We report here a method of estimating van der Waals forces of adhesion between various substrates and toners of different particle sizes. The method involves the measurement of the detachment force and the resultant current caused by toner jumping between two closely-spaced conducting parallel plates. Conducting toners are first sprayed on the top surface of the bottom plate; the voltage across the two plates is then ramped at a constant rate. When the electrostatic force of detachment exceeds the forces of adhesion between the toners and substrate, there is a significant increase of current between the two parallel plates. The particles jump from the bottom plate and reach the upper electrode. Upon reaching the upper electrode, the initial induced charge is lost and the particles acquire electrostatic charge of the opposite polarity, then move toward the bottom plate. From the balance between the forces of detachment and adhesion (comprising of van der Waals, gravitational, and electrostatic image forces), the van der Waals force between the toner and test substrates can be determined.     

Force propagation speed in a bed of particles due to an incident particle impact

The force propagation speed in granular matter is a very difficult property to be measured. A new technique has been developed to calculate the force propagation speed in granular matter based on measuring experimentally the contact time. The contact time for a particle hitting a bed of particles is estimated as the time taken for a particle to strike a bed of particles till the time of its ejection, and it is calculated using the discrete element method. The speed of force propagation in a bed of particles is estimated by plotting the dependence of the path length of the contact force on the contact time and finding the gradient of such dependence. Such approach leads to accurate results if the impact speed is below the yield velocity, i.e. no plastic deformations. It is found that the force propagation speed in spherical granular matter is proportional to the impact speed of the incident particle, which is different from force propagation in continuum matter. It is also found that the propagation speed is dependent on the material and diameters ratio of the interacting particles, but it is not dependent on the number of bed layers. The propagation speed in granular matter is normalized by dividing it by a reference propagation speed, i.e. the propagation speed at an impact speed of 1 m/s. It is found that the normalized propagation speed is independent of the material and diameter of the interacting particles, but it is logarithmically proportional to the impact speed. The proportionality constant is equal to 0.16, which can be taken as a universal constant for force propagation in spherical granular matter.     

A new detection system for extremely small vertically mounted cantilevers

Detection techniques currently used in scanning force microscopy impose limitations on the geometrical dimensions of the probes and, as a consequence, on their force sensitivity and temporal response. A new technique, based on scattered evanescent electromagnetic waves (SEW), is presented here that can detect the displacement of the extreme end of a vertically mounted cantilever. The resolution of this method is tested using different cantilever sizes and a theoretical model is developed to maximize the detection sensitivity. The applications presented here clearly show that the SEW detection system enables the use of force sensors with sub-micron size, opening new possibilities in the investigation of biomolecular systems and high speed imaging. Two types of cantilevers were successfully tested: a high force sensitivity lever with a spring constant of 0.17?pN?nm(-1) and a resonant frequency of 32?kHz; and a high speed lever with a spring constant of 50?pN?nm(-1) and a resonant frequency of 1.8?MHz. Both these force sensors were fabricated by modifying commercial microcantilevers in a focused ion beam system. It is important to emphasize that these modified cantilevers could not be detected by the conventional optical detection system used in commercial atomic force microscopes.     

A mathematical model of variable displacement swash plate compressor for automotive air conditioning system

A mathematical model of control mechanism used in the variable displacement swash plate compressor (VDSC) is developed firstly based on the force balance equation, mass and energy conservation equation. The model of moving components dynamics is developed then by analyzing the forces and force moments acting on the pistons and the swash plate. The compression process model is obtained by fitting the data from our experiments. And finally, the steady-state mathematical model of VDSC is developed by combining the three sub-models above. In order to verify the mathematical model, a test bench for control mechanism and the test system for VDSC have been established, and the simulated results agree well with the experimental data. The simulation results show that, like the variable displacement wobble plate compressor, there are four operation modes for the VDSC, i.e. constant rotary speed and constant piston stroke length (PSL), variable rotary speed and constant PSL, constant rotary speed and variable PSL, variable rotary speed and variable PSL, which have included almost all operation modes of the refrigeration compressor in common use. And there is a hysteresis zone and multiple-valued relationship between the compressor parameters when PSL changes.     

Aerodynamic forces and flow structures of an airfoil in some unsteady motions at small Reynolds number

Summary The aerodynamic forces and flow structures of a NACA 0012 airfoil in some unsteady motions at small Reynolds number (Re=100) are studied by numerically solving the Navier-Stokes equations. These motions include airfoil acceleration and deceleration from one translational speed to another and rapidly pitching up in constant freestream (equivalent to pitching up during translational motion at constant speed). It is shown that at small Reynolds number (Re=100), when the airfoil is performing fast acceleration or deceleration from one speed to another, a large aerodynamic force can be generated during and for a time period after the acceleration or deceleration; a large aerodynamic force can also be generated when the airfoil is performing a fast pitching motion in a constant freestream. In these fast unsteady motions, an airfoil in low Re flow can produce a large aerodynamic force as effective as in large Re flow, or the effect of unsteady motion dominates the Reynolds number effect. During the fast unsteady motion of the airfoil, new layers of strong vorticity are formed near the upper and lower surfaces of the airfoil under the previously existing thick vorticity layers, and it is the generation and motion of the new vorticity layers that is mainly responsible for the generation of the large aerodynamic force; the large-scale structure and movement of the newly produced vorticity layers are similar to that of high Re flow.     

The assessment of particle friction of a drug substance and a drug carrier substance

The centrifuge technique, which has been previously used in adhesion experiments, has been modified for use in single particle friction studies. Both flat compacted surfaces and large single particles were used as substrate surfaces to allow assessment of drug-drug, drug-drug carrier and drug carrier-drug carrier friction forces. Particle size, particle shape and surface roughness were identified as main factors influencing the change from a static into a dynamic friction process and the division between friction due to adhesion and ploughing. The forces of adhesion and friction were found to be proportional to the reversible energy of adhesion. The ratio between the force of adhesion and the press-on force applied and the ratio between the force of friction and the press-on force can be related to the yield stress and the reduced Young's modulus of the materials in contact.     

The role of knife sharpness in the slitting of plastic films

An experimental apparatus has been built that provides information on forces associated with slitting plastic films. The apparatus uses commercially available scissors as an analogue to the counter-rotating knife blades used in industry. Cutting forces were measured using sharp and worn blades at a range of slitting speeds from 0.05–2.5 m s^–1. Two important film-base materials were studied; the first was polyethylene terephthalate (PET) and the second, acetal butylate. The influences of speed and knife-edge radius were measured for each base material. For the PET-based film, the forces increased as the blade became dull and decreased with cutting speed. At low speeds, the force required to cut the acetal butylate film was independent of speed, but a sharp decrease in force was observed at a speed that depended upon the blade sharpness. An empirical model for the slitting process has been developed that can estimate the forces measured.     

Precision experiments to search for the fifth force

Among the four known fundamental forces in nature, electromagnetism and gravity give rise to effects which extend over macroscopic distances, whereas the strong and weak forces act only over subatomic distances. It is natural to ask whether there can exist additional forces, particularly ones capable of acting over macroscopic distances in analogy to electromagnetism and gravity. This question is the object of intense investigation both experimentally and theoretically, in the wake of suggestions of a possible fifth force. The theoretical motivation for such a force is reviewed, along with the experimental situation in 1989     

采用数字同步技术的轴类零件尺寸光电检测

根据线阵CCD对二维图像进行扫描检测的特点,提出一种基于数字同步技术的轴类零件尺寸检测方法。它用数字方法保证扫描位移量(或者位移速度)与CCD行扫描次数(或者行扫描速度)严格对应,CCD的行扫描由扫描位移量控制,有效消除了被测物体运动速度变化对检测分辨力和精度的影响,提高了检测精度;采用数字同步技术,使检测在扫描位移的加速、恒速和减速过程中均能进行,提高了检测速度;采用图像边缘自动跟踪方法,自动获取边缘参数,实现被测物体的二维多尺寸自动定位检测。检测实验表明,该方法的检测误差≤0.02mm;当被测物体轴向尺寸为100mm时,检测时间<5s。     

Kalman filter-based force estimation in a clamped plate using reduced order model and noisy measurements

Deterministic techniques are available for force estimation in dynamic systems in time, frequency, and modal domain. But, these techniques are susceptible to measurement noise and require an accurate model of the system, hence, are not suitable for precise force estimation. Some combined deterministic-stochastic approaches are available in the literature for unknown input force estimations, where force estimations are performed by considering the model uncertainty and measurement noise. In the present work, one such technique is extended by incorporating reduced-order model to estimate forces in of plate structures. Kalman filter and a recursive least-squares (KF-RLSE)-based technique which uses displacement and/or velocity measurements for force estimation is used in the present work with a reduced-order model. Time-varying unknown forces acting at single/multiple locations are reconstructed using the measured responses from the plate. Numerical simulation followed by experimental verification is presented. The effect of error in model parameters on the force estimation is presented, and robustness of the input estimation technique is tested for different levels of measurement noise.     

Aerodynamic properties of a wing performing unsteady rotational motions at low Reynolds number

Summary The aerodynamic forces and flow structures of a wing of relatively small aspect ratio in some unsteady rotational motions at low Reynolds number (Re=100) are studied by numerically solving the Navier-Stokes equations. These motions include a wing in constant-speed rotation after a fast start, wing accelerating and decelerating from one rotational speed to another, and wing rapidly pitching-up in constant speed rotation. When a wing performs a constant-speed rotation at small Reynolds number after started from rest at large angle of attack (=35°), a large lift coefficient can be maintained. The mechanism for the large lift coefficient is that for a rotating wing: the variation of the relative velocity along the wing-span causes a pressure gradient and hence a spanwise flow which can prevent the dynamic stall vortex from shedding. When a wing is rapidly accelerating or decelerating from one rotational speed to another, or rapidly pitching-up during constant speed rotation, even if the aspect ratio of the wing is small and the flow Reynolds number is low, a large aerodynamic force can be obtained. During these rapid unsteady motions, new layers of strong vorticity are formed near the wing surfaces in very short time, resulting in a large time rate of change of the fluid impulse which is responsible for the generation of the large aerodynamic force.     

Low Force Measurement Based on Impedance of a Piezo-resonator

Piezoelectric transducers have effectively been used for force measurement due to their inherently large stiffness. The primary transduction parameter of piezoelectric transducer is voltage which is used mostly for dynamic and sometimes for quasi-static force measurement. Other parameters of piezoelectric transducers such as resonant frequency, electrical impedance, etc. have also been used for force measurement. In the present work, precision measurement of conductance of a radial mode piezo-resonator has been carried out under different static loading and the resultant change in resonant conductance of the resonator have been evaluated as a function of loading force. This method based on resonant conductance measurement can prove to be effective in measuring forces between two interfaces which is an important requirement in many scientific and technical problems.     

自适应变阻力特征加油稳定伞设计及气动特性研究

该文基于骨架弹簧片原理,提出了一种新型自适应变阻力特征加油稳定伞设计方法,以实现稳定伞的阻力特征面积随飞行速度变化自适应发生改变,在一定速度范围内保持阻力值基本恒定,使得加油稳定伞与加油机的相对位置基本固定。为了验证该设计方法的正确性,充分了解弹簧片弹性模量和厚度参数对稳定伞气动特性的影响规律,该文通过风洞测力试验和变形测量技术研究了四套弹簧片自适应变阻稳定伞的气动特性,并对数据结果的拓展应用进行了分析,提炼出了工程估算模型。结果表明:该文所提出的自适应变阻力特征稳定伞设计方法正确合理,风速变化时骨架弹簧片发生自适应弹性变形,使得阻力特征面积能够自适应调整,起到稳定阻力大小的作用;弹簧片抗弯刚度越小,变形越大,在试验风速范围内,1.0 mm钢弹簧片稳定伞的自适应特性最优;与传统恒定阻力特征加油稳定伞相比,自适应变阻稳定伞的稳定性能更好,气动载荷动态测量结果波动更小;所获得的研究结果以及工程估算模型能为工程适用的自适应变阻稳定伞设计提供重要的数据支撑。     

输电塔气动力系数和气动导纳风洞试验研究

输电塔结构的非定常抖振力与来流风速之间存在复杂的非线性关系,基于风洞试验得到的某1 000 k V格构式直线输电塔弹性模型的基底力以及参考高度处同步采集的风速时程,采用线性和高斯两种近似假定计算了非定常气动力系数并与试验值进行了比较;提出了包含结构气动阻尼效应在内的总气动导纳的概念,通过基底脉动力谱和来流脉动风速谱的比值对总气动导纳函数进行识别,并用基于频域相干函数对导纳函数的线性部分进行了估计。结果发现,风偏角线性近似所计算静气动力系数的偏差较高斯近似小;由于气动抖振力非定常性质明显,不考虑总气动导纳函数将高估输电塔模型的抖振响应;脉动风力与脉动风速间有较强的非线性关系,用线性导纳函数计算的抖振力谱将低估脉动风分量的影响。     

LSM control of Maglev vehicle ride quality

The ride quality of a high speed repulsion type magnetically levitated vehicle using linear synchronous motor (LSM) propulsion has been studied. Vehicle motion is dependent upon the active LSM forces, the passive magnetic lift and drag forces, the aerodynamic drag force, and the technique employed for control. Derivations of the passive lift and drag forces and of the active heave and propulsion control forces are presented. For a balanced three phase LSM, it is shown that harmonic force pulsations disappear, except for the sixth harmonic and its multiples. A control technique which stabilizes the surge motion and provides needed damping in heave to guarantee acceptable ride quality has been simulated. Transient responses, for a vehicle traveling at 120 m/s show stable well damped motion. At this velocity, sixth harmonic effects are completely negligible. Stochastic results show that the heave motion power spectral density response to a moderately rough guideway, i.e., A = 1.34 × 10^-5m, more than satisfies the UMTA ride quality specification.     

Accurate analytical measurements in the atomic force microscope: a microfabricated spring constant standard potentially traceable to the SI

Calibration of atomic force microscope?(AFM) cantilevers is necessary for the measurement of nanonewton and piconewton forces, which are critical to analytical applications of AFM in the analysis of polymer surfaces, biological structures and organic molecules at nanoscale lateral resolution. We have developed a compact and easy-to-use reference artefact for this calibration, using a method that allows traceability to the SI (Système International). Traceability is crucial to ensure that force measurements by AFM are comparable to those made by optical tweezers and other methods. The new non-contact calibration method measures the spring constant of these artefacts, by a combination of electrical measurements and Doppler velocimetry. The device was fabricated by silicon surface micromachining. The device allows AFM cantilevers to be calibrated quite easily by the 'cantilever-on-reference' method, with our reference device having a spring constant uncertainty of around ± 5% at one standard deviation. A simple substitution of the analogue velocimeter used in this work with a digital model should reduce this uncertainty to around ± 2%. Both are significant improvements on current practice, and allow traceability to the SI for the first time at these nanonewton levels.