Investigation of Experimental Devices for Finger Active and Passive Tactile Friction Analysis

Complicated tribological behavior occurs when human fingers touch and perceive the surfaces of objects.In this process,people use their exploration style with different conditions,such as contact load,sliding speed,sliding direction,and angle of orientation between fingers and object surface consciously or unconsciously.This work addressed interlaboratory experimental devices for finger active and passive tactile friction analysis,showing two types of finger movement.In active sliding experiment,the participant slid their finger freely against the object surface,requiring the subject to control the motion conditions themselves.For passive sliding experiments,these motion conditions were adjusted by the device.Several analysis parameters,such as contact force,vibration acceleration signals,vibration magnitude,and fingerprint deformation were recorded simultaneously.Noticeable friction differences were observed when comparing active sliding and passive sliding.For passive sliding,stick-slip behavior occurred when sliding in the distal direction,evidenced by observing the friction force and the related deformation of the fingerprint ridges.The employed devices showed good repeatability and high reliability,which enriched the design of the experimental platform and provided guidance to the standardization research in the field of tactile friction.

Seismic fragility of structures isolated by single concave sliding devices for different soil conditions

This study deals with the seismic fragility of elastic structural systems equipped with single concave sliding（friction pendulum system（FPS）） isolators considering different soil conditions. The behavior of these systems is analyzed by employing a two-degree-of-freedom model, whereas the FPS response is described by means of a velocity-dependent model. The uncertainty in the seismic inputs is taken into account by considering artificial seismic excitations modelled as timemodulated filtered Gaussian white noise random processes of different intensity within the power spectral density method. In particular, the filter parameters, which control the frequency content of the random excitations, are calibrated to describe stiff, medium and soft soil conditions. The sliding friction coefficient at large velocity is also considered as a random variable modelled through a uniform probability density function. Incremental dynamic analyses are developed in order to evaluate the probabilities of exceeding different limit states related to both the reinforced concrete（RC） superstructure and isolation level, defining the seismic fragility curves within an extensive parametric study carried out for different structural system properties and soil conditions. The abovementioned seismic fragility curves are useful to evaluate the seismic reliability of base-isolated elastic systems equipped with FPS and located in any site for any soil condition.

Mechanical Analysis and Numerical Simulation for New Type of Dynamic Control Devices

The conventional dynamic control devices,such as fluid viscous damper(VFD)and isolating bearings,are unsuitable for the double-deck cable-stayed bridge due to a lack of sustainability,so it is necessary to introduce some high-tech dynamic control devices to reduce dynamic response for double-deck cable-stayed bridges under earthquakes.A(90+128)m-span double-deck cable-stayed bridge with a steel truss beam is taken as the prototype bridge.A 3D finite element model is built to conduct the nonlinear time-history analysis of different site categories in fortification intensityⅨ(0.40 g)degree area.Two new types of dynamic control devices-cable sliding friction aseismic bearings(CSFABs)and elasticity fluid viscous dampers composite devices(EVFDs)are introduced to reduce the dynamic responses of double-deck cable-stayed bridges with steel truss beam.The parametric optimization design for the damping coefficient C and the elastic stiffness of spring K of EVFDs is conducted.The following conclusions are drawn:(1)The hybrid support system by EVFDs and CSFABs play a good function under both seismic and regular work,especially in eliminating the expansion joints damage;(2)The hybrid support system can reduce the beam-end displacement by 75%and the tower-bottom bending moment by 60%under the longitudinal seismic excitation.In addition,it can reduce the pier-bottom bending moment by at least 45%under transverse seismic and control the relative displacement between the pier and beam within 0.3 m.(3)Assuming the velocity indexα=0.3,the parametric optimization suggests the damping coefficient C as 2000 kN·s·m-1in siteⅠ0,4000kN·s·m-1in siteⅡ,6000 kN·s·m-1in siteⅣ,and the elastic stiffness of spring K as 10000 kN/m in siteⅠ0,50000 kN/m in siteⅡ,and 100000 kN/m in siteⅣ.

Seismic performance of cable-sliding friction bearing system for isolated bridges

During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction sliding surface, seismic forces may be reduced but displacements are often unconstrained. In this paper, an alternative seismic bearing system, called the cable-sliding friction bearing system, is developed by integrating seismic isolation devices with displacement restrainers consisting of cables attached to the upper and lower plates of the bearing. Restoring forces are provided to limit the displacements of the sliding component. Design parameters including the length and stiffness of the cables, friction coefficient, strength of the shear bolt in a fixed-type bearing, and movements under earthquake excitations are discussed. Laboratory testing of a prototype bearing subjected to vertical loads and quasi-static cyclic lateral loads, and corresponding numerical finite element simulation analysis, were carried out. It is shown that the numerical simulation shows good agreement with the experimental force-displacement hysteretic response, indicating the viability of the new bearing system. In addition, practical application of this bearing system to a multi-span bridge in China and its design advantages are discussed.

Study on the Key Technique of Spinning Fine Tex Yarn on the Friction Spinner

Introducing the key technique of spinning fine tex yarnson the friction spinner, deals mainly with the technologi-cal parameters of the carding device, conducting tubeand spinning drum for the friction spinning. The experi-mental results show that, the combing effect of pin drumis better than that of garnett; the combing length is a im-portant factor. The form and dimension of the conduct-ing tube influence the rate of fiber straightness and thedegree of fiber orientation. The little angle between theconducting tube and drum axis is good for fiber parallel-ism and straightness. The frictional ratio and the rate ofair flow influence the efficiency of twist.

Research on Nonlinear Dynamic Characteristics ofStructures Supported on Slide-Limited Friction Base Isolation System

This paper presents a new type of base isolation system, i. e. , slide-limited friction (S-LF) base isolation system . Based on this system, the harmonic and subharmonic periodic response of S-LF subjected to harmonic motions is investigated by using Fourier-Galerkin-Newton (FGN) method with Flo-quet theory. The dynamic response of S-LF subjected to earthquake ground motions is calculated with a high order precision direct integration method, and the numerical results are presented in maximum acceleration response spectra of superstructure and maximum sliding displacement response spectrum form. The comparison of isolating effects of S-LF, pure-friction base isolation system (P-F) and resilient-friction base isolation system (R-FBI) shows that the isolating property of S-LF is superior to those of P-F and R-FBI. Finally, by analyzing an engineering example, it is observed that the distribution of the maximum shear between floors and absolute acceleration of S-LF to earthquake ground motion is very different from that of traditional structures.

Structural connection with predetermined discrete variable friction forces

This paper presents a simple and practical structural connection able to develop predetermined discrete variable friction forces at target design displacement levels. The innovative connection is termed Modified Friction Device ( Modified FD ). Modified FDs are used to transfer the seismic induced horizontal forces from the floors to the core wall seismic force-resisting system of a building. The schematics of the physical embodiment of the Modified FD are presented. The components and the assembly of the Modified FD are discussed. The mechanics of the Modified FD are explained. Results from static structural analyses of two types of finite element models of the Modified FD are presented. The first model is developed using solid finite elements and it is used to assess the expected kinematics and the expected force-displacement response of the Modified FD. The second model is developed using a truss finite element and it can be used to effciently simulate the force-displacement response of the Modified FD in numerical earthquake simulations of structural systems. The force-displacement response of the Modified FD computed using a numerical earthquake simulation of an eighteen-story reinforced concrete core wall building model is presented. The seismic response of the building model with Modified FDs is compared with the seismic response of the building model with monolithic connections and the seismic response of the building model with friction devices with constant friction forces. The results presented in this paper show that it is possible to develop a simple and practical structural connection with predetermined discrete variable forcedisplacementresponse to limit the seismic induced horizontal forces transferred between the floors of the flexible gravity load resisting system and the core wall piers in high-performance earthquake resilient buildings.

基于摩擦搅拌的金属增材制造实验装置研制

为了研究工艺参数对增材摩擦搅拌沉积工艺的影响,基于摩擦搅拌工艺原理自主研制了金属增材制造实验装置。在主轴转速420 r/min、进给速度72 mm/min、移动速度72 mm/min、增材层厚3 mm、启动时间50 s的工艺条件下,对6061铝合金进行了单层和双层增材沉积初步实验。结果表明,该实验装置实现了良好的铝合金固相增材,可用于增材制造相关领域的科学研究和实验教学工作。

基于负刚度装置的超长联大跨连续梁桥地震反应控制研究

为完善超长联大跨连续梁桥的减、隔震技术,将负刚度装置引入到超长联大跨隔震连续梁桥中组成新型减、隔震系统,并与黏滞阻尼器-摩擦摆支座组合减震系统进行比较。基于CSiBridge软件建立全桥有限元模型,负刚度装置采用弹性多段线模拟,摩擦摆支座采用双线性恢复力模型,黏滞阻尼器采用Maxwell模型,输入3条地震波进行非线性时程分析,考查两种新型减、隔震系统下桥梁结构的地震反应,探究负刚度系统及黏滞阻尼器系统对超长联大跨连续梁桥地震反应的控制效果。研究结果表明:负刚度装置与黏滞阻尼器均可以有效地减小超长联大跨隔震连续梁桥的支座位移。负刚度装置对桥墩内力反应及梁体加速度反应的控制优于黏滞阻尼器。负刚度装置在超长联大跨连续梁桥地震反应控制中有较好的应用前景。

多绳摩擦提升机多连杆锁绳装置的设计与优化

针对现有锁绳装置锁绳低效、松绳困难、锁绳力不足等问题,设计出一种能够实现在各种载荷工况(尤其重载)下安全、高效地进行锁绳作业的提升钢丝绳锁紧装置(简称锁紧装置)。使用SolidWorks对锁绳装置进行三维建模,采用ANSYS对锁绳装置进行有限元分析;然后对锁绳装置关键部位第一连杆进行优化设计,采用中间复合材料设计方法获得初始优化数据组,并且使用Kriging模型建立响应面模型;最后采用多目标遗传算法进行优化。优化结果显示:第一连杆变形量减小17.46%,最大等效应力减小16.18%,显著提高了锁绳装置的综合性能,为矿井的安全、高效生产提供了保障。

大跨度钢箱系杆拱桥减隔震措施对比研究

以某跨河大跨度钢箱系杆拱桥为研究对象,研究不同措施下桥梁的减隔震性能。通过“m”法,利用桥梁有限元软件Midas Civil进行动力分析;通过人工合成地震波,采用FDB模型、粘滞阻尼器MAXWELL模型进行模拟,对大跨度钢箱系杆拱桥进行非线性时程分析,对比分析摩擦摆支座、速度锁定器、拉索减震支座的减震效果。研究结果表明:三种减隔震措施下,墩柱所受的轴力差异较小,摩擦摆支座及拉索减震支座所受的剪力、弯矩差异较小,速度锁定器作用下,墩柱所受的剪力及弯矩差异较大。通过对比分析,选用摩擦摆支座能较好地满足工程需求,减震效果良好。

沉井侧摩阻力监测装置设计及应用研究

针对现有沉井施工过程中侧摩阻力测试方法要求高、难度大的问题,自主设计研发一套侧摩阻力直接测试装置,并提出输出电压与侧摩阻力的理论转化公式。通过有限元软件对不同传感器平行梁尺寸下梁端应变和最大应力、不同密封材料下装置的应变损失进行分析,指导传感器平行梁尺寸及密封材料的选择,并利用大型直剪仪对装置进行精准标定,最后在哈尔滨某沉井工程中进行现场应用。研究结果表明:1)平行梁的厚度越小、长度越大,弹性元件在荷载作用下微应变越大,但同时最大应力会增大;2)传感器内填充密封材料后,会存在一定应变损失,采用硅酮结构胶对装置进行密封应变损失最小;3)不同法向应力加载条件下侧摩阻力监测装置标定曲线的一致性较好,线性拟合系数均大于0.99,装置稳定性好。现场应用结果表明,通过侧摩阻力监测装置获取的沉井侧摩阻力与侧壁土压力的分布规律基本一致,且装置易于安装,可靠性好。

规则连续梁桥质量转动缠绕索装置减震效果及影响参数研究

为解决连续梁桥纵向地震惯性力仅由固定墩承受的抗震设计难题,充分发挥与固定墩相同截面的活动墩的抗震潜能,基于缠绕索原理,研发了利用附加质量惯性力的质量转动缠绕索装置,从而实现固定墩与活动墩协同受力和限制梁端相对位移的目的。在阐述装置工作原理及构造特点的基础上,提出了装置的恢复力模型,并通过对一座三跨规则连续梁桥建立全桥有限元模型,研究了连续梁桥质量转动缠绕索装置的减震效果,系统分析了附加质量、摩擦系数和初始松弛系数取值对装置减震性能的影响。结果表明,质量转动缠绕索装置对于减小固定墩地震响应,提升活动墩参与连续梁桥纵向整体协同受力的效果较为明显,值得注意的是,不同地震波作用下减震装置参数对结构地震响应的影响略有不同。

织物摩擦性能测试系统的研究进展

织物表面摩擦性能是织物最基本的力学性能之一,为更好地评估该性能,文章对织物摩擦性能测试系统的研究和发展情况进行了综述,介绍了织物摩擦的研究背景、摩擦机理和研究历程,以及织物表面摩擦性能测试装置和织物摩擦声测试方法,分析了织物摩擦性能测试装置及织物摩擦声的研究现状及不足。分析发现:织物摩擦性能测试装置在不断改进,但依旧存在精度问题;KES系统被广泛应用,但KES系统价格昂贵且不能进行实时测量,目前国际上并没有通用织物摩擦声测试装置。文章最后展望了织物摩擦性能测试系统未来的研究方向。

一种摩擦力演示装置设计

摩擦力是一种常见的力,同时也是一种多因素共同决定的力。很多人认为摩擦力的概念抽象而不容易理解,尤其是摩擦力的大小与接触面的关系问题。为了辅助摩擦力教学,设计了一台摩擦力演示装置。同时介绍了该演示装置的设计原理、装置构成、制作方法以及仪器的详细使用方法。它适用于学生做基础的摩擦力验证实验。

新型装配式自复位RC剪力墙设计与性能研究

为满足结构施工效率高、震后功能可恢复的多重目标,提出了一种新型装配式自复位RC剪力墙。该新型剪力墙主要包含RC墙板、碟簧复位装置和摩擦耗能装置,三者仅通过高强螺栓组装而成,施工方便且效率高;在地震作用下,主要由碟簧复位装置和摩擦耗能装置提供抵抗弯矩和恢复力,能减小整体剪力墙构件的震后残余变形和损伤,有效提高其震后功能可恢复性。该文分析了新型装配式自复位RC剪力墙的截面受力形式,提出了其截面承载力计算公式;设计了一新型装配式自复位RC剪力墙构件进行数值模拟,获得了其滞回性能,对比分析了其与普通剪力墙的承载力、耗能能力、自复位性能。结果表明:在相同位移角下,新型装配式自复位RC剪力墙的承载力小于普通剪力墙,但其极限承载力与普通剪力墙的峰值承载力相当,且其在超大震(2.0%位移角)下的残余位移角仅为0.31%,具有优异的自复位能力,能使结构在震后具有低损伤、功能可恢复的特点。增大碟簧复位装置的预压力,可有效提高新型剪力墙构件的承载力和累积耗能,但残余变形也相应增大。

煤矿长距离带式输送机线摩擦驱动增压装置设计与应用

针对线摩擦带式输送机运行过程中,空载、少载时承载带与传动带间摩擦产生的驱动力不足,导致主机系统能耗增加,以及满载时承载带与传动带间摩擦力激增造成的皮带过度磨损问题,设计了带式输送机线摩擦驱动增压装置,并通过模拟软件对其进行仿真分析.结果表明,摩擦驱动增压装置可按照预先设定的压力大小,自动调节皮带的法向力,能够改善驱动力不足的现象,有利于输送机长距离、大运量运输.同时为类似工况下线摩擦带式输送机的大规模投产使用提供借鉴.

圆-椭圆垂直复合微孔织构对密炼机端面密封装置摩擦性能的影响

建立密炼机端面密封装置圆-椭圆垂直复合微孔织构(简称复合织构)的流体动压润滑模型,研究织构参数和工况参数对复合织构摩擦性能的影响。结果表明:当复合织构深度为5μm时,复合织构端面密封装置具有最好的减摩性能;当复合织构面积率为43.96%时,润滑油膜平均无量纲压力(P_(a))最大和摩擦因数(μ)最小;复合织构的μ随着动密封环转速(n)和润滑油粘度(η)的增大而增大;密封间隙(h_(0))为3和6μm时,复合织构的P_(a)和μ都随着n和η的增大而增大;在不同的n和η下,复合织构的P_(a)和μ随着h_(0)的增大而减小。

盘形螺旋棘轮注射模设计

分析盘形螺旋棘轮结构特点和功能作用,介绍了其注射模结构,通过简易的滚珠旋转结构实现成型塑件倒扣处的脱模,并对模具中的关健零件齿圈研制了特殊的磨削加工方法,降低了加工成本。模具经实际生产验证:模具零件动作可靠,成型的塑件质量合格,对类似塑件的模具设计具有一定的参考作用。

滚动轴承摩擦力矩和旋转灵活性检测装置

针对滚动轴承摩擦力矩和旋转灵活性检测精度低,效率低,测量方法复杂等问题,基于自由减速法设计了滚动轴承摩擦力矩与旋转灵活性同步检测的试验装置。利用高压喷气的方式驱动被测轴承高速运转,以省去动力离合装置,简化检测步骤;利用空气静压轴承支承旋转轴构建无摩擦环境,以提高滚动轴承摩擦力矩的测量精度;结合自动上下料装置和电磁阻尼器,实现装配线上滚动轴承旋转灵活性的在线检测。该检测装置测量不同型号深沟球轴承的试验结果表明:同一型号轴承的摩擦力矩最大平均偏差为7.18N·mm,最大相对平均偏差为3.97%,测量精度较高,可重复性强;滚动轴承旋转灵活性的检测效率为每分钟10~12个,满足装配线需求。