鞋底摩擦系数测控系统的设计

鞋底的止滑性直接影响着鞋子穿用时的舒适性和安全性,止滑性主要由摩擦系数来表示,在一定范围内,摩擦系数越大,止滑性越好;系统通过测量作用于鞋的拉力和压力,求得摩擦系数,从而来判断各种鞋子的安全性能,因此对拉力压力的测量显得十分重要;鞋底摩擦系数测控系统通过串口将采集到的拉力和压力数据发送给上位机实时处理、显示、绘图并保存;最后对系统进行了测试,所测得的各种材质的摩擦系数符合国际标准,验证了它的正确性且测量精度高。     

高低温环境下摩擦系数的高准确度测试

在航空要求的高低温环境下(-55～ 125℃)，为实现摩擦系数与接触电阻的高准确度测试，本文研制了适合于在高低温环境下测试摩擦件摩擦系数与接触电阻的测试试验台。通过对试验件载荷和摩擦力矩的测量，测量出试验件在不同温度及不同载荷下的摩擦系数与接触电阻，用试验及曲线拟合方法研究并解决了力传感器的温度补偿问题。为提高测试精度，对测试系统的硬件和软件进行了抗干扰优化设计，通过时某航空产品的试验，数据显示测试台的测试精度达4％。     

火炮后坐特性及平滑性测控系统设计

提出了火炮后坐特性及平滑性测控系统的组成,并对驱动电路、拉力或压力测量及后坐速度测量进行了具体分析,使用结果表明,测控系统设计方案合理,工作稳定可靠.     

基于OpenGL 的数控加工在线测量仿真技术研究

为了实现数控机床在线测量的可视化仿真,开发了一种用于数控机床在线 测量的仿真软件。采用OpenGL 作为图形系统开发环境;通过读取STL 格式的零件模型文 件,来显示零件的三维构造;通过解析含有理论点坐标的XML 格式的测量指导文件,来显 示被测点的理论位置;通过接收数控系统的测量数据,来实现在线测量系统测头的实时仿真。 并使用CATIA 生成的STL 模型验证了该仿真系统的运行。     

基于LabVIEW高温摩擦磨损试验机测试系统

高温摩擦磨损试验机主要用于测试摩擦副材料在高温工况下的摩擦磨损性能.采用LabVIEW软件,通过调用动态链接库驱动数据采集卡,设计开发了用于高温摩擦磨损试验机的虚拟仪器测试系统.测试系统包括摩擦力、温度、载荷、转速等数据采集,数据存储,数据处理、图形显示及生成实验报告等功能.在高温摩擦磨损试验机上,利用该测试系统测量并记录摩擦系数,观察所采集的数据以及多次重复性试验.实验结果表明该测试系统具有较高的稳定性、准确性及可靠性.     

基于Simulink的航空供氧系统加压供氧性能仿真

在座舱高度超过12km后供氧系统需要对飞行员进行应急加压供氧,通过在Matlab/simulink软件上建立仿真模型对加压供氧性能进行数值仿真,分析了面罩余压、拉力管压力及压力比随高度变化的特性,以及结构参数对面罩余压、拉力管压力及压力比的影响.通过仿真结果与试验结果的对比分析,表明所建立的仿真模型是准确的,采用的仿真计算方法符合计算精度要求,为供氧系统的仿真研究提供了一定的参考作用.     

飞机跑道摩擦系数测试车软件设计

研究开发了用于测量飞机跑道摩擦系数的测试车。该测试系统的硬件由机械系统和电气系统组成,主要完成测量轮的升降和上位机与下位机之间的数据通信等任务。软件程序采用基于图形化设计的LabVIEW开发系统,引用双线程的设计思想,提高了程序的运行效率和采集数据的精度。根据阶跃响应不变法自行设计了数字低通滤波器,在计算摩擦系数之前对数据进行滤波,抑制了噪声的干扰,提高了数据的准确性。此软件系统除了能够完成摩擦系数的实时计算、显示、打印和存储外,还在历史数据查询的基础上能够对测量位移范围内任意100 m的摩擦系数进行详细查询。试验证明,该测量系统安全可靠、操作简单方便、数据精确重复性好,能够完成自动连续测量的任务。     

8通道静态应变信号调理模块研究

在航空发动机的测试中,需要测量发动机的各种性能参数,如温度、压力、转速、流量、振动等,其中压力的测试是可以通过测量发动机叶片产生的应变来完成,通常应变测试系统包括应变片、信号调理器、数据采集模块和软件处理几部分;北京长城测控公司结合近几年开发航空发动机测试系统的经验,基于VXI总线测试技术开发了信号调理模块与数据采集模块高度集成的航空发动机测试系统,同时针对测试中存在的多种物理量开发了多种信号调理模块;文章主要针对静态应变信号调理模块的使用方法及在数据采集系统中的应用进行了介绍,并对关键电路的设计方法进行了详细说明。     

基于LabVIEW的自由射流风洞系统加热气流模拟软件设计

目前设计的自由射流风洞系统加热气流模拟软件测量得出的气流面受力值容易发生耦合共振,导致测量流量误差较大;为解决上述问题,基于LabVIEW设计一种新的自由射流风洞系统加热气流模拟软件,软件程序包括自由射流风洞系统加热气流流量调节、加热气流时序控制、气流模拟软件等,通过与采集节点的配合完成数据采集、处理、分析等工作;利用Lab-VIEW技术,在程序软面板显示加热气流压力、增益频率等数据,直观地表现加热气流的压力大小以及变化;根据加热气流模拟软件,简化开发测试以及控制系统的程序,使软件调试过程更加简单,容易操作,实现了软件测试程序以及控制程序流程开发的平台化和通用化;实验结果表明,基于LabVIEW的自由射流风洞系统加热气流模拟软件能够减少气流面受力值耦合共振,测量误差在0.2％以内,实现自由射流风洞系统加热气流的准确模拟.     

混合总线分布式测试技术研究及应用

在飞机液压系统试验中不但要完成流体特性参数的测量,还要完成机械运动参数的测量,如何对这些种类繁杂、数量多、分散的信号进行测量,研究和开发混合总线的分布式测试系统就成为最佳选择,在测试软件设计开发中,采用面向对象框架的软件方法,开发具有良好复用性、扩展性和维护性的软件组件模块,减少了软件开发的工作量,提高了软件开发效率,通过实际应用表明,混合总线测试系统在试验中的实际应用,提高了测试效率,缩短了试验周期.     

Mechanisms of friction and assessment of slip resistance of new and used footwear soles on contaminated floors

Abstract

The great number of slipping accidents indicates that footwear providing good slip resistance must be rare. Slip resistance seems to be a purely physical phenomenon, however, more knowledge of the mechanisms of friction is needed to develop slip-resistant footwear and to ensure safer walking in slippery conditions. In the present study the influence of the normal wear of shoe heels and soles on their frictional properties was clarified. The slip resistance of three types of new and used safety shoes on four relatively slippery floor-contaminant combinations, was assessed with a prototype apparatus, which simulates the movements of a human foot and the forces applied to the underfoot surface during an actual slip. The used shoes were collected from 27 workers in a shipbuilding company and classified by sight into four wear classes: Good, satisfactory, poor, and worn-out. The assessed shoe heels and soles were in general more slippery when new compared to used heels and soles. However, footwear must be discarded before the tread pattern is worn-out. Used microcellular polyurethane (PU) heels and soles gave a considerably higher coefficient of kinetic friction (μ_k) on contaminated floors than used heels and soles made of compact nitrile (NR) and compact styrene rubber (SR). The heel-slide coefficient of kinetic friction (μ_kl) for used versus new shoes was on average 66% higher for PU (0·216 versus 0·130), 27% higher for SR (0·143 versus 0·113), and 7% lower for NR (0·098 versus 0·105). The fundamental mechanisms of friction between shoe soles and contaminated floors were also discussed, and experiments with seven slabs of sole materials were carried out to assess contact pressure effects from the viewpoint of slipping. Slip resistance particularly seemed to depend on the squeeze film and the contact pressure effects between the soling materials and the floor. An increasing contact pressure dramatically reduced the μ_k, thus indicating that the slip resistance varies considerably during the normal gait cycle. Hence, average friction readings are probably not at all decisive from the slip resistance point of view. An instantaneous coefficient of friction may be more relevant, because in walking the time available to achieve a sufficient coefficient of friction to avoid a slip is only a few tenths of a second.     

Observation of the floor surface topography changes in pedestrian slip resistance measurements

This study is concerned with the changes of the floor surface topography in the early stage of repetitive wear rubbings and the relationships between slip resistance properties and operationally defined geometric characteristics of the floor surfaces. It was assumed that: (1) alterations in surface topography will be associated with changes in the DFC; and (2) wear process will be accompanied by changes in surface topography. For the analysis of initial characterization on the surface topography, specially prepared, dry and clean metal and perspex specimens were chosen. The surface profiles of the fresh and rubbed flooring specimens were recorded using a laser scanning confocal microscope. From the profile ordinate data read at 1 μm intervals, a number of surface roughness parameters – centre line average, root-mean-square roughness, maximum height, maximum mean peak height, maximum mean depth, and absolute average asperity slope were calculated using a computer program. The skew and the kurtosis of the statistical distribution of each surface profile were also computed. The results indicate that the asperity height and the maximum mean depth were significantly reduced after the friction tests. The average slope of asperities was the parameter that most highly correlated with the dynamic friction coefficient. The analyses also showed that the surface parameters underwent large variations initially, but subsequently these changes were less marked, which was explained by the transition from unsteady-state friction to steady-state friction. These results found that slip resistance properties between the shoes and the floor counterfaces were greatly influenced by the manner in which the geometry of the floor surface was modified. It was suggested that measurement of changes in the surface geometry provides additional information on the analysis of slip resistance and could usefully be reported with friction measurements.

Relevance to industry

Slipping and falling accidents are a major ergonomic and safety concern in the workplace and the general community. Prevention of slip hazard has focused on designing “slip resistant” footwear and floor surfaces. This study is primarily concerned with the understanding of friction and wear mechanisms from a tribological point of view. A tribological approach may provide additional useful information about slip resistance performance.     

Progress in the prevention of falls caused by slipping

Initial research by the INRS showed the importance of biomechanical factors in the causes of accidents by slipping. Dynamic friction was shown to be far more significant than static fraction. The measuring procedure which has been developed does not provide a model of walking or slipping but a physical measurement giving the same ranking as subject evaluation methods.

Systematic measurements show the effect on slip resistance of the material used and the configuration of the sole. Following publication of these results, manufacturers have improved the slip resistance of shoes. An internationally acceptable method (ISO) should, however, be developed so that slip resistance, which is such an important factor in accident prevention, can be given as much attention as other features of the sole.

Scientific research on the psychophysiology of equilibrium on slippery surfaces is needed, as is applied research on friction with lubricated elastomers and on-site research into floor-surface friction.     

The effect of roughness, floor polish, water, oil and ice on underfoot friction: current safety footwear solings are less slip resistant than microcellular polyurethane

Research over a period of about 18 years has shown that a microcellular polyurethane known as AP66033 is the most slip-resistant safety footwear soling material on oily and wet surfaces. In recent years it has been replaced in commercially available footwear by a dual density polyurethane (DDP) which has a dense outer layer and a soft microcellular backing. This research programme has compared the slip resistance of AP66033 with DDP and some rubber solings. In addition, data were obtained on the effects of soling and floor roughness, and floor polish on slip resistance. Some data were also obtained for walking on ice. The coefficient of friction (CoF) of the solings was measured on 19 water wet surfaces in three conditions: (I) when the solings were new, (II) following abrasion to create maximum roughness and (III) after polishing. The CoF was measured on four oily surfaces after each of 11 abrasion or polishing treatments. The profound effects of the roughening of all soles and of floor roughness on the CoF were demonstrated for both wet and oily surfaces. The superior slip resistance of AP66033 was confirmed for oily and wet conditions; however, some rubbers not suitable for safety footwear achieved higher CoF values on wet floors. All of the floor polishes reduced the CoF of all floors when contaminated with water. The mean CoF of DDP solings was lower than the mean for AP66033 on wet and oily surfaces. No safety footwear soling provided adequate grip on dry ice and the CoF was reduced by water on the ice. A rubber used for rock climbing footwear was one of the most slip-resistant solings on wet surfaces in the laboratory but recorded the lowest CoF on ice. It is concluded that the incidence of occupational injuries caused by slipping could be reduced by the following: (A) returning to safety footwear soled with the microcellular polyurethane AP66033; (B) abrading all new and smooth footwear solings with a belt sanding machine coated with P100 grit; (C) avoiding the use of floor polish; (D) informing the general public about the poor slip resistance of ordinary footwear on ice and the lowering of slip resistance in cold weather.     

Development and validation of a novel portable slip simulator

The objective was to develop, construct and validate a portable device suitable for measurements of pedestrian slip resistance in situ. The developed device proved to be precise enough and easy to use. The dynamic coefficient of friction (DCOF) values measured by it showed strong correlation (r> or = 0.990, p < 0.001) with the values measured by the force platform used as a reference. In addition, the measured DCOF values were in good consistency with those obtained when using the older laboratory device of the Institute, the slip simulator. Based on the use of the new, developed device it can be concluded that accurate friction measurements with actual footwear can be performed even with a moderate-sized but portable device. The developed slipmeter will be used to measure slipperiness of various walking surface conditions, e.g. at different work places and in walkways, in the near future.     

基于深度学习的X射线鞋底异物检测系统

在服饰鞋厂的加工生产过程中经常会出现断针现象,残留在鞋子里的多余断针等金属异物会威胁人们的人身安全.针对这一问题,本文提出了一种基于深度学习的鞋底金属异物检测系统.首先,将鞋子依次放在传送带上送入检针机,经过X光照射采集图像.之后对采集到的图像进行预处理操作,使金属异物变得清晰.最后通过深度学习网络模型识别当前图像是否含有金属异物,并检测异物所处位置.实验结果表明,经过图像预处理和微调标注框的做法,能有效提高模型识别的精度.本文提出模型的平均精度为97.6%,该结果表明此模型可以有效检测遗留在各种鞋类中不同形状的金属异物,具有很好的商业价值.     

Slipperiness of the shoe-floor interface: comparison of objective and subjective assessments

Tribollogically and biomechanically valid slip-resistance measurement methods are needed urgently to facilitate new developments for improving the safety of footwear and floor coverings. Objective coefficient-of-friction measurements and subjective walking experiments were compared to scrutinize and validate anti-slip assessments of the shoe-floor interface. Four shoe types were tested on a smooth stainless steel floor contaminated with viscous glycerol. The friction utilization ratio during one step, the sliding distance, and the subjective rating of slipperiness were evaluated by seven test subjects in 420 walking trials. All subjects assessed the footwear in the same rank of slipperiness. The friction utilization ratios during the walking trial were a poor indicator for anti-slip assessments. The apparatus-based kinetic friction values mu(k1), however, were more valid and, in particular, more reproducible. The safe level of mu(k1) was approximately 0.22, which is in accordance with previous slip-resistance clasification of shoes and floors. Futher trials in other shoe-contaminant-floor conditions and walking tasks are needed to verify the findings in this study.     

Functional levels of floor surface roughness for the prevention of slips and falls: Clean-and-dry and soapsuds-covered wet surfaces

Literature has shown a general trend that slip resistance performance improves with floor surface roughness. However, whether slip resistance properties are linearly correlated with surface topographies of the floors or what roughness levels are required for effective slip resistance performance still remain to be answered. This pilot study aimed to investigate slip resistance properties and identify functional levels of floor surface roughness for practical design applications in reducing the risk of slip and fall incidents. A theory model was proposed to characterize functional levels of surface roughness of floor surfaces by introducing a new concept of three distinctive zones. A series of dynamic friction tests were conducted using 3 shoes and 9 floor specimens under clean-and-dry as well as soapsuds-covered slippery wet environments. The results showed that all the tested floor-shoe combinations provided sufficient slip resistances performance under the clean-and-dry condition. A significant effect of floor type (surface roughness) on dynamic friction coefficient (DFC) was found in the soapsuds-covered wet condition. As compared to the surface roughness effects, the shoe-type effects were relatively small. Under the soapsuds-covered wet condition, floors with 50?μm in Ra roughness scale seemed to represent an upper bound in the functional range of floor surface roughness for slip resistance because further increase of surface roughness provided no additional benefit. A lower bound of the functional range for slip resistance under the soapsuds-covered wet condition was estimated from the requirement of DFC?>?0.4 at Ra???17?μm. Findings from this study may have potential safety implications in the floor surface design for reducing slip and fall hazards.     

The effect of shoe soling tread groove width on the coefficient of friction with different sole materials, floors, and contaminants

Tread groove design is very common in footwear. However, coefficient of friction (COF) measurements between the footwear material and floor using a slipmeter were commonly performed using flat footwear pads. Such measurements might underestimate the actual slip resistance of the footwear pad. This research investigates the effects of the tread groove width on the measured COF using four footwear materials, three floors, and four liquid-contamination conditions using a Brungraber Mark II slipmeter. The analysis of variance results indicated that the footwear material, floor, contamination conditions, and groove width were all significant (p<0.0001) factors affecting the measured COF. The hypothesis that wider tread grooves result in higher COF values was true with some exceptions especially on oil contaminated floors. A regression model, with an R² of 0.91, was established to describe and predict the relationship between the COF and the tread groove width under footwear material/floor/contamination conditions.     

The effect of surface roughness and contaminant on the dynamic friction of porcelain tile

Surface roughness affects friction, but it is not clear what surface roughness characteristics are better correlated with friction. The average of the maximum height above the mean line in each cut-off length (Rpm) and the arithmetical average of surface slope (deltaa) had the highest correlation with dynamic friction coefficient in a previous study. The previous study was expanded to two different footwear materials and four different contaminants on a porcelain tile in the current investigation. The results showed that dynamic friction decreased as the interface speed and glycerol content in the contaminant were increased due to the hydrodynamic lubrication effect. Deltaa had the highest correlation with friction for most of the test conditions with neolite. For Four S rubber, friction coefficient appeared to have the highest correlation with the parameters related to the surface void volume at 30% glycerol content, related to the surface slope at 70 and 85% glycerol contents, and related to the peak to valley distance at 99% glycerol content. A good indicator of surface slip resistance probably should consist of the surface parameters representing the surface slope, the surface void volume and the surface peak-to-valley distance with the coefficients determined by the system parameters.