作用力作功、反作用力也作功

本文是"新功能理论"一文的第一部分,对保守力作功、保守反作用力也作功、非保守力作功、非保守反作用力也作功的分析,得出了"作用力作功、反作用力也作功"的结论.特别是对非保守力作功的研究,得到了非保守力作耗散功的同时、非保守反作用力也伴随着作耗散功,非保守力作功一般同时具有非保守性非耗散力作功、耗散力作功双重效果的结论.     

压电薄膜力传感器及其牙咬力的测量应用研究

本文介绍一种用于测量牙咬力的传感器-压电簿膜力传感器.它应用压电薄膜受到机械应力产生电极化,从而产生电荷的原理来测量牙咬力.这种压电薄膜厚度仅25μm,用它来作为传感器测量牙咬力时无咬合间隙,测量的值能反映出牙齿真实的咬力.     

原子力显微镜的力曲线分析与转化

原子力显微镜测定的力曲线需转化为力位移曲线来应用.力位移曲线是以任意点为零点的,当研究粘附或者分子模型对比时,需要知道针尖样品间的作用力或确切的零点位置,这时需将其转化为力-距离曲线.本文首先从力曲线的测定原理得出了典型的力曲线,之后从理论上分析了力曲线、力位移曲线和力-距离曲线间的转化,从中得出了转化过程中需要的两个重要参量:灵敏度和零距离,并提出了确定方法.最后,利用MATLAB实现了曲线的自动转化.     

刮板输送机链条预紧力和紧链力计算

1引言 刮板链为一弹性体,运行时因受到拉力会产生弹性伸长,这个伸长量会使刮板链在驱动链轮分离点处松弛,甚至发生堆积而导致断链、卡链或断齿等事故的发生。为了防止这种现象,在初安装刮板链或运转一段时间后,要给其一初张力,使之产生一预加的弹性伸长。初张力（输送机静止时,封闭链条内的张力）的形成,是靠拉紧装置实现的。虽说目前使用的液压缸紧链器、液压马达紧链器和盘闸紧链器等均能准确地反映出拉紧力的大小,但对于某一特定的刮板输送机,究竟需要多大的拉紧力才满足要求,需要进行专门的计算。     

Advanced cantilevers for magnetic force microscopy and high frequency magnetic force microscopy

In order to improve the spatial resolution achieved by magnetic force microscopy (MFM) technique and its derivatives, we employ here advanced MFM tips fabricated by means of focused ion beam (FIB) milling. The magnetic coating applied on these tips is a CoCr film of 10 nm thickness. The MFM measurements on hard disk test samples reveal the achieved high resolution, and the measurement on a garnet film demonstrates the low invasiveness. High-frequency MFM (HF-MFM) is a development of the MFM technique to observe the HF stray fields emerging from magnetic recording writer poles at their operating conditions. By means of HF-MFM, magnetic recording writer poles are characterized in the frequency range 100-1,000 MHz. Up to now, all HF-MFM experiments conducted were using standard MFM cantilevers. From the HF-MFM images obtained using the advanced MFM cantilevers, it is clearly seen that the spatial resolution is considerably improved over the images obtained using standard MFM tips. However, the 10 nm thick magnetic coating of the cantilevers is found to work properly only at frequencies of up to about 500 MHz.     

Easy and direct method for calibrating atomic force microscopy lateral force measurements

We have designed and tested a new, inexpensive, easy-to-make and easy-to-use calibration standard for atomic force microscopy (AFM) lateral force measurements. This new standard simply consists of a small glass fiber of known dimensions and Young's modulus, which is fixed at one end to a substrate and which can be bent laterally with the AFM tip at the other end. This standard has equal or less error than the commonly used method of using beam mechanics to determine a cantilever's lateral force constant. It is transferable, thus providing a universal tool for comparing the calibrations of different instruments. It does not require knowledge of the cantilever dimensions and composition or its tip height. This standard also allows direct conversion of the photodiode signal to force and, thus, circumvents the requirement for a sensor response (sensitivity) measurement.     

Calibration of lateral force measurements in atomic force microscopy with a piezoresistive force sensor

We present here a method to calibrate the lateral force in the atomic force microscope. This method makes use of an accurately calibrated force sensor composed of a tipless piezoresistive cantilever and corresponding signal amplifying and processing electronics. Two ways of force loading with different loading points were compared by scanning the top and side edges of the piezoresistive cantilever. Conversion factors between the lateral force and photodiode signal using three types of atomic force microscope cantilevers with rectangular geometries (normal spring constants from 0.092 to 1.24 N/m and lateral stiffness from 10.34 to 101.06 N/m) were measured in experiments using the proposed method. When used properly, this method calibrates the conversion factors that are accurate to +/-12.4% or better. This standard has less error than the commonly used method based on the cantilever's beam mechanics. Methods such of this allow accurate and direct conversion between lateral forces and photodiode signals without any knowledge of the cantilevers and the laser measuring system.     

Development of a microlateral force sensor and its evaluation using lateral force microscopy

A microlateral force sensor (MLFS) was developed and evaluated using atomic force microscopy (AFM). The sensor was attached to a sensing table supported by a suspension system. The lateral motion of the sensing table was activated by a comb actuator. The driving voltage to the comb actuator was controlled to maintain a constant position of the sensing table by detecting the tunneling current at a detector, which consisted of two electrodes where the bias voltage was applied. An AFM was used to apply a lateral force to the sensing table of the sensor. When the probe of a cantilever was pressed against the sensing table and a raster scanning was conducted, the driving voltage of the comb actuator changed to compensate the friction force between the probe and sensing table. AFM measurements of an asperity array on the sensing table were conducted, and a lateral force microscopy image (LFM) was obtained from the change in driving voltage. The image by MLFS was very similar to the LFM image that was conventionally obtained from torsion of the cantilever. The LFM image strongly correlated with the gradient image calculated from the AFM topographic image. The force sensitivity of the MLFS was determined by comparing the LFM image obtained by using the MLFS with the tangential force derived from the gradient of the AFM image.     

Experiments and analysis of force transmission in force transducers to improve their characteristics

The influence of force transmission and transducer dimensions on the accuracy of the force measurement is studied experimentally by testing several force transducers designed and built by VTT. The results are analysed with a FEM-analysis of the transducer body. The transducers operate on the principle that the applied force creates shear forces in the transducer and these are registered with strain gauges. The testing of the transducers was performed so that the force was applied in different directions towards the transducer. In this way the inaccuracy resulting from the calibration method used can be reduced.     

人脐静脉内皮细胞形貌与表面粘附力的原子力显微镜表征

目的:探讨原子力显微镜(AFM)在研究人脐静脉内皮细胞(ECV304)表面形貌、超微结构及纳米机械性质等方面的应用,讨论ECV304超微结构和机械性质与其功能的关系。方法:利用AFM对ECV304细胞的表面形貌及生物机械性质进行表征与测量。结果:在AFM下观察到用普通光学显微镜难以观察到的ECV304细胞的独特的形态结构,如细胞骨架、伪足及细胞边缘微丝等。ECV304细胞呈现长梭形、多角形、圆形等多种形态,细胞表面平均粗糙度为320.52±75.98 nm,表面均匀分布微绒毛,细胞周围有铺展的圆盘状物质。力曲线定量分析得出针尖与细胞表面的非特异性粘附力为75±14 pN。结论:通过AFM成像和力曲线测量表明,ECV304细胞呈圆形,多角形,梭形等多种形态,针尖与细胞膜表面问的粘附力比较小,约75±14pN。     

Surface charges and adhesion measured by atomic force microscope influence on friction force

A good correlation has been found between friction force measured using a ball-on-disc tribometer (normal load 200 mN) and adhesion hysteresis measured by atomic force microscopy. Both adhesion and friction forces were investigated in liquid media (water, ethanol, formamide, ethylene glycol) and involved interactions between silicon nitride and several materials (Si(1 0 0), Si(1 1 1), silica glass, DLC and TiN coatings). Despite the difference between the two scales of measurement, comparison between the measured friction force and the dissipated energy during the adhesion process has shown that the two quantities follow the same trend. Additional experiments were conducted in NaCl 10⁻³ M at various pH values in order to investigate surface charge effect on adhesion and friction.     

压电式力接收器在测力与称量技术中的可能性与范围

压电式力接收器基于其小型结构和很高的机械刚性，所以特别适宜于动态测量。例如，在生产监控、Crash检验以及生物机械方面，用这种力接收器测量脚踏力。这种力接收器因其不利的漂移特性，迄今很少适宜于静态应用。然而，使用现代的电荷放大器，似静态测量将会成功，其时间特性曲线不再用指数减小表示，而是用线性漂移表示。所以，与现代的电荷放大器组合的压电式力接收器应用在测力与称量技术中已越来越引人注意，此时测量时间或负荷变换时间在几分钟之内。     

Quality of motion and force transmission

Actual mechanism performance can differ markedly from the performance expected from a theoretically perfect model. A good quality design is one which not only theoretically solves the design problem but actually does so reliably when installed in its applications. This paper summarized work done by the author in developing merit functions which reflect motion and force transmission quality, and in combining these quality merit functions with primary design merit functions to form viable mechanisms design algorithms.     

凸轮铰杆增力夹具

介绍铰杆与偏心凸轮机构组成的夹紧装置的工作原理，给出相应的计算公式，并用实例证明，给手柄施加很小的力可以获得较大的输出力。该夹具结构简单，制造方便。     

Quantification of the lateral detachment force for bacterial cells using atomic force microscope and centrifugation

To determine the lateral detachment force for individual bacterial cells, a quantitative method using the contact mode of an atomic force microscope (AFM) was developed in this study. Three key factors for the proposed method, i.e. scan size, scan rate and cantilever choice, were evaluated and optimized. The scan size of 40×40 μm² was optimal for capturing sufficient number of adhered cells in a microscopic field and provide adequate information for cell identification and detachment force measurement. The scan rate affected the measurement results significantly, and was optimized at 40 μm/s considering both force measurement accuracy and experimental efficiency. The hardness of applied cantilevers also influenced force determination. The proposed protocol for cantilever selection is to use those with the lowest spring constant first and then step up to a harder cantilever until all cells are detached. The lateral detachment force of Escherichia coli cells on polished stainless steel and a glass-slide coated with poly-l-lysine were measured as 0.763±0.167 and 0.639±0.136 nN, respectively. The results showed that the established method had good repeatability and sensitivity to various bacteria/substrata combinations. The detachment force quantified by AFM (0.639±0.136 nN) was comparable to that measured by the centrifugation method (1.12 nN).     

Error analysis of indirect force determination and a regularisation method to reduce force determination error

Accurate estimation of dynamic forces acting on a structure is very difficult, since, at certain frequency regions, the identified forces may contain an unacceptable amount of error. In this study, by investigating the characteristics of the inverse transfer function and frequency response function (FRF) error, the indirect force determination error is analysed statistically, and the special frequency regions where force determination error is very large are searched for each case of the number of response measurements and applied forces. It is shown that the large force determination error near the first kind of inverse pole frequencies is mainly due to the rank deficiency of the FRF submatrix, while the large error in the vicinity of resonance frequencies comes from the larger FRF error. The idea was tested both analytically and experimentally. Also a regularisation process to reduce the error especially near the first kind of inverse pole frequencies is proposed. Since the degree of singularity of the FRF submatrix near the first kind of inverse pole frequencies is mainly related to system damping, a regularisation procedure is suggested by adding additional damping. An optimal regularisation constant is also derived. It is shown that, the greater the order of magnitude of the FRF error is than that of modal damping ratio, the larger the force determination error reduction is obtained with the suggested regularisation procedure. The proposed regularisation method was tested experimentally and its effects examined.     

A new device for simultaneous measurement of friction force,normal force and friction coefficient

To meet the demands for higher accuracy in the measurement of forces in tribological experiments a force transducer has been developed which allows the simultaneous measurement of friction force, normal force, and, via an electronic divider, the friction coefficient. The device consists essentially of four bending rods notched at four points to localize strains monitored at these points by strain gauges. Tilting and bending of the probe is avoided by this construction. The details, performance and formulae for dimensioning are given.     

Development and metrological characterization of a precision force transducer for static force measurement related applications

The present paper discusses design and development of a force transducer of octagonal ring shape, which is a modified version of ring shaped force transducer. Nominal capacity of the force transducer designed and developed is 25 kN. This force transducer has been investigated for its utilization as force transfer standard for static force measurement and related applications. This force transducer is studied using dial gauge and strain gauges for its metrological characterization according to the calibration procedure based on standard ISO 376:2011/IS 4169:1988 (reaffirmed 2003) and is found to have good metrological results as compared to the existing ring shaped force transducers.     

Current and potential characterization on InAs nanowires by contact-mode atomic force microscopy and Kelvin probe force microscopy

We fabricated InAs nanowires on GaAs giant step structures, and studied their surfaces by two methods; one was current detection by contact-mode atomic force microscopy, and the other was surface potential measurement by Kelvin probe force microscopy (KFM). In the current detection method, the regions where the large current flowed were distributed along the step edges, and these regions agreed well with the expected distribution of InAs. This result confirms that the InAs nanowires were formed along the GaAs giant step edges. The KFM measurements showed that the potential value became more negative along each step edge, where the InAs nanowire was expected to be formed. The surface potential of the InAs nanowires is more negative than that of the surrounding GaAs, which may result from the electron accumulation in the InAs nanowires.