一种三点接触球轴承性能试验台的研制

文章针对一种三点接触球轴承,因其运转速度高,且运行在高温工况下,并结合其极限载荷条件及运转特点,研制了一种特殊的轴承试验台。介绍了试验台的技术方案及试验台相关参数计算方法。经实践表明该试验台可靠性良好,运行平稳,可用于三点接触球轴承在特殊运转工况下的研究。     

织机振动各个参数的测试

由于织机的复杂性及其所涉及的机械问题,只有经过许多次的测量才能满意地确定各个参数对织机振动的影响。因此,我们挑选了具有下列条件的工厂进行研究: 1.有大量在相同条件下运转的片梭织机; 2.有不同年代的织机,以便说明织机使用时间和振动的关系; 3.织机上制织的织物品种不同,以利研究织造工艺的影响; 4.织机的转速不同,为了揭示车速的影响。     

机织物与皮肤的摩擦力分布状况及影响规律

为了解机织物与人体皮肤间摩擦力的基本分布状况,对74种常见的服用机织物和皮肤间的摩擦力进行了测试,并应用SPSS统计软件分析了织物结构参数和摩擦力的关系.研究发现,机织物与皮肤间的动摩擦力分布在242～438 cN之间,其中长丝织物与皮肤的动摩擦力普遍较小,短纤织物与皮肤的动摩擦力普遍较大.此外,从纯棉和长丝织物的结构参数与摩擦力间关系的回归分析可看出,纱线直径和纱线间的距离是影响织物和皮肤间摩擦力的主要因素.     

钢丝绳结构与接触应力分析

<正> 钢丝绳按各层股丝间接触状态可分为点、线、面接触。各种接触状态的接触应力有极大差别,使用寿命也不同。各种点接触结构钢绳接触区的接触应力极高,在钢丝承受交变载荷时,即从接触点破坏,据统计若把点接触改为线接触钢丝绳,工作能力可提高25%,面接触绳能力更高。钢丝绳结构从点     

振动力场下挤出胀大测量系统的设计与实现

为研究振动力场对挤出胀大的影响,需要同时测量振动参数、挤出物直径等参数。本文在分析传统测量方法不足的之后,提出采用PCL-812PG数据采集卡,以Delphi作为软件开发平台,对各种传感器信号,特别是激光测径仪的测量信号进行采集,得到了振动力场下挤出胀大物直径、机头压力、螺杆振幅等大量实时数据。同时针对挤出熔体离模后出现的摆动现象,设计了挤出物冷却定型架,提高了测量的精度。     

机械振动对凹版滚筒与刮墨刀间摩擦力的影响

在凹版印刷机运行时产生的各种摩擦力中,凹版滚筒和刮墨刀之间的摩擦力对印刷效果和凹版耐印力影响很大。本研究从微观尺度和宏观尺度,分别对凹印机的振动对凹版滚筒和刮墨刀之间摩擦力的影响进行了理论分析。当振动发生时,凹版滚筒和刮墨刀之间摩擦力会减小,而摩擦力的减小会减少凹版的磨损,但是如果凹版滚筒和刮墨刀之间摩擦力过小,就会影响刮墨刀的刮墨效果,因此摩擦力应该控制在一定范围之内。     

木材刷式砂光机砂光参数的选择(2)

以刷式砂轮砂光试验机为砂光设备,以砂轮转速、进给速度、砂光次数为砂光参数,测量砂光参数与表面粗糙度Ra之间的关系,得出了在本实验条件下较理想的砂光条件.     

木材刷式砂光机砂光参数的选择(1)

以刷式砂轮砂光试验机为砂光设备,以树种(樟子松和柞木)、砂纸目数及接触深度为砂光参数,测量砂光参数与被砂木材表面粗糙度Ra之间的关系,得出了在本实验条件下较理想的砂光条件。     

纤维质多孔材料中纤维间接触点数量的理论模型

为深入研究纤维质多孔材料的微观结构,通过建立纤维间接触点数量的理论模型,分别研究纤维在空间中三维和二维分布情况下,纤维间接触点数量的理论值。根据泊松分布的特点,结合Sampson等的研究结论,建立纤维间接触点数量、纤维直径和孔隙率的函数关系。使用Geo-Dict软件模拟纤维结构,同时计算纤维间接触点数量,再分别将纤维不同取向的理论预测值和前人研究结果相比较。结果表明:当纤维长径比不变时,纤维数量与纤维间接触点数量呈线性正比关系;当孔隙率不变时,纤维直径与纤维间接触点数量呈反比关系;当纤维直径固定时,纤维间接触点数量随孔隙率增加而减少;当纤维直径大于40 μm时,接触点数量不随孔隙率的变化而改变。     

接触式纱线张力传感器动态测量模型

纱线变化张力的准确测量和有效控制对纺织品质量有重要影响。基于霍尔效应的接触式张力传感器通过霍尔元件检测由纱线张力引起的悬臂梁挠度,进而获得纱线张力。但是随着张力变化频率的增高,因悬臂梁机械振动所造成的系统张力误差也随之增大。为此,本文对接触式张力传感器检测单元建立动力学模型,并在此基础上分析振动对张力信号检测的误差影响,进而提出动态张力测量模型以及相应的振动误差抑制算法。通过建立张力测试实验台,对不同条件下的测试结果进行了振动误差抑制前后的张力信号对比研究。结果表明基于动态张力辨识测量模型的误差抑制算法能够有效地消除振动所产生张力检测误差。该项研究为动态条件下的接触式张力传感器运用提供了理论参考。     

航空用精密轴承定位包装的装置设计

设计一种采用预紧力对精密轴承定位的包装装置,该装置通过对轴承滚动体和内圈施加预紧力来消除游隙,减小运输过程中冲击和振动对接触部件表面产生的损伤影响。利用有限元软件对定位包装装置的工作状态进行仿真模拟分析,结果显示定位装置能够通过应力-应变方式减小游隙,所产生的预紧力不会对轴承接触表面产生损伤。     

PEACH VIBRATION BRUISING: THE EFFECT OF PAPER AND PLASTIC FILMS BETWEEN PEACHES1

Laboratory vibration bruising trials were conducted to determine the effectiveness of polypropylene film and paper between peaches in reducing the vibration bruising of peaches. Kinetic coefficient of friction (KCOF) values for peaches in contact with peaches and in contact with a variety of paper and plastic materials were also determined using a modification of ASTM D 1894. The data produced were combined to test the hypothesis that the amount of vibration bruising is proportional to the KCOF of peaches in contact with packaging materials. It was determined that lower KCOF values did correspond to less bruising. This result suggests that the use of paper or film to minimize vibration bruising should be investigated further. Important KCOF values determined were approximately 0.7 for peach-to-peach, 0.4 for peach-to-paper, and 0.2 for peach-to-polypropylene contact. The KCOF value for peach-to-polypropylene contact is a function of the anti-block additives in the particular film utilized. KCOF values were found to be independent of cultivar and maturity. Although KCOF values are a factor in vibration bruising of peaches, other important factors and their effects remain to be identified.     

Friction characteristics of fabrics in the presence of air

High frictional force between the skin and the air bag greatly influences the scratch damage to human skin when an air bag inflates and rubs against the skin. The coefficient of friction should therefore be reduced. In this study, we propose a new method to reduce frictional force by producing air lubrication between an air bag made of a non‐coated fabric and the human skin. Air was generated, and an experimental device that could measure frictional force was produced. The frictional force of the air bag with air was measured, and the effectiveness and efficiency were confirmed. In the presence of air, the friction disk materials, fabric materials, and fabric structure do not influence the frictional force and coefficient of friction. Instead, the coefficient of friction is influenced by air mass flow passing through the fabric.     

Measurement of the Transverse Yarn-on-solid Coefficient of Friction

Abstract

The transverse friction coefficient of a yarn sliding on a surface is much more difficult to measure than its lengthwise coefficient. A method based on the transverse sliding of the yarn on the cylindrical balloon limiter of a two-for-one twister is proposed to measure this coefficient. A simple yarn ballooning apparatus based on a hollow spindle was built and tested. A top picture of the cylindrically constrained yarn balloon is taken and the final yarn angle is measured. This angle can be theoretically correlated to the other easily measured parameters of the simplified balloon and to the desired transverse friction coefficient. This method was experimentally verified and found to be both practical and highly accurate.     

EFFECT OF FRICTION ON THE PERFORMANCE OF TEXTURE TEST CELLS*

The relationship was measured between the normal contact force and the force required to overcome friction between food samples and a surface simulating a typical texture test cell. Peas produced frictional behavior that combined the characteristics of dry friction and fluid flow. Friction coefficients for selected foods ranged from 0.04 to 0.52. Friction force was linearly related to the normal contact force and non-linearly to the area of contact between the sample and the surface, and the speed of the sample relative to the surface. This verifies the fact that, with empirical texture test devices, these test variables must be held constant. The estimated friction forces represented a significant amount of the total force required to operate a wire extrusion cell and a back extrusion cell. It was concluded that standardization of the test cell would be easier to achieve if the contact area between the sample and the cell surfaces was minimized and if low friction materials were used to construct the cells.     

实验参数对高性能石英纤维摩擦性能的影响

针对立体织物织造过程中高强高模纤维束间相互摩擦而导致织物性能下降的问题,以石英纤维为例,设计了一种用于测试纤维束间摩擦性能的摩擦磨损试验机夹具,使纤维束或单根纤维能够以相互正交或一定角度相接触,在纤维尺度上研究了摩擦角度、摩擦频率和法向载荷对纤维束间摩擦性能的影响。结果表明:3种实验参数对纤维束表面的磨损程度不同;摩擦角度为70°时的摩擦因数是90°时的1.2倍,即摩擦角度越小,磨损程度越大;在一定范围内,摩擦频率和法向载荷对摩擦因数没有影响;在立体织物织造过程中,应尽可能减少纤维束间倾斜接触,从而降低织物性能下降,还可在一定范围内提高织造频率和法向载荷,提高生产效率。     

转轮集聚纺纱装置与工艺设计

针对目前负压式集聚纺能耗大的问题,设计了转轮集聚纺纱装置。选用粗纱定量为6.33 g/(10 m)的普梳棉粗纱为原料,采用转轮集聚纺纱装置与传统环锭纺,设计纺纱线密度分别为32.4、24.3、19.4 tex纺制纱线,并对其单纱线密度、断裂强度、毛羽、条干均匀度和捻度进行测试对比,客观评价该转轮集聚纺纱装置的应用效果。结果表明：与环锭纱相比,转轮集聚纱4 mm以上有害毛羽减少量达40%～80%,单纱断裂强度下降1%～3%,断裂强力不匀率下降25%～50%,24.3和19.4 tex的单纱条干均匀度有3%～6%的轻微恶化,捻度基本无影响,说明使用转轮集聚纺纱装置可显著减少纱线的有害毛羽;转轮集聚纺纱装置安装在前罗拉下方,可在环锭细纱机上快速安装与拆卸,实现传统环锭纺与集聚纺的便捷切换,同时该装置具有构造简单、能耗低等优点。     

基于动力学有限元分析的实木地板损伤检测

介绍了脉冲锤击法检测实木地板损伤及测定其动态弹性模量的理论依据，并通过有限元模拟与试验验证了其可行性。试验结果表明：脉冲锤击法能有效地测得实木地板的固有频率与动态弹性模量，所得动态弹性模量值比静态弹性模量值稍大；测试中，拾振点应选择在主振频率振型的最大振幅处或其附近区域，激振点应选择在离拾振点较远且振幅较大的区域；固有频率可对实木地板的损伤程度进行较好的判定。     

Hydrophobic properties of textile materials: robustness of hydrophobicity

Extremely hydrophobic surfaces have been receiving considerable interest, such as in the contexts of self-cleaning glass or clothes, antifouling paintings, and the reduction of friction drag. A large variety of treatments permits the obtainment of (super)hydrophobic textile surfaces. The point here is to investigate the role of different geometrical textile parameters on the hydrophobicity, and more particularly, on the robustness of this property. The influences of solid surface roughness on the wetting behavior are commonly studied for model solid textures while textile roughness is largely deformable. A laboratory test method is suggested to evaluate this robustness. Some hydrophobic fibrous structures were prepared (using classical woven fabrics and pile fabrics) to investigate the influence of textile structures on their static and forced wetting properties. Static contact angles, contact angle hysteresis, and the contact angle after compression were measured. The meso- and micro-structures appeared to influence either the static wetting or the robustness of the hydrophobicity after compression.