镁合金表面铬掺杂类金刚石薄膜的制备与性能研究

本文利用阳极层离子束混合磁控溅射技术在AZ31镁合金表面制备了类金刚石涂层（DLC）和Cr掺杂DLC膜（Cr-DLC）,并利用Raman光谱、残余应力仪、划痕仪、摩擦磨损仪和电化学工作站等,对薄膜的碳结构、残余应力、结合力、摩擦学性能和耐腐蚀性进行了研究。结果表明：相比纯DLC膜,Cr-DLC膜具有较低的残余应力,较高的膜/基结合力。Cr-DLC膜能显著提高镁合金的抗摩擦磨损性能,但对改善镁合金耐腐蚀性能影响不大。     

基于弹性形变摩擦力的光学天线伺服系统建模

提出了一种弹性形变摩擦力模型,用于描述光学天线伺服系统的非线性效应。弹性形变摩擦力模型将摩擦力表示为相对运动物体表面接触形变产生的弹性力,与Stribeck模型相比,弹性形变在相对运动过程中连续变化,消除了零速度摩擦力不连续性,与LuGre模型相比,参数较少且无需求解微分方程,降低了模型辨识难度。以伺服系统模型输出速度与实测输出速度的误差平方和为评价函数,采用遗传算法辨识基于三种摩擦力模型的伺服系统参数。实验结果表明:在相同的遗传进化迭代次数下,弹性形变摩擦力模型精度比Stribeck模型提高2.3倍,比LuGre模型提高4.6倍。验证了弹性形变摩擦力模型用于伺服系统非线性建模的可行性。     

浅谈电刷-导电环摩擦副使用寿命的影响因素

主要从电刷-导电环材料配对和工作环境两方面探讨了电刷-导电环电接触滑动摩擦副使用寿命的影响因素,认为其使用寿命是多种因素综合作用的结果,包括电刷-导电环配对材料的选择,周围气体环境和湿度环境,电接触摩擦副的压力以及相对滑动速度,电刷的加工方法和烧结密度及其中石墨的含量、晶粒大小和晶粒取向等。对于获得高可靠长寿命的滑环具有一定的指导意义。     

Biomimetic Bidirectional Switchable Adhesive Inspired by the Gecko

The gecko adhesive system has attracted significant attention since the discovery that van der Waals interactions, which are always present between surfaces, are predominantly responsible for their adhesion. The unique anisotropic frictional–adhesive capabilities of the gecko adhesive system originate from complex hierarchical structures and just as importantly, the anisotropic articulation of the structures. Here, by cleverly engineering asymmetric polymeric microstructures, a reusable switchable gecko‐like adhesive can be fabricated yielding steady high adhesion ( ≈ 1.25 N/cm²) and friction ( ≈ 2.8 N/cm²) forces when actuated for “gripping”, yet release easily with minimal adhesion ( ≈ 0.34 N/cm²) and friction (≈ 0.38 N/cm²) forces during detachment or “releasing”, over multiple attachment/detachment cycles, with a relatively small normal preload of 0.16 N/cm² to initiate the adhesion. These adhesives can also be used to reversibly suspend weights from vertical (e.g., walls), and horizontal (e.g., ceilings) surfaces by simultaneously and judiciously activating anisotropic friction and adhesion forces. This design opens the way for new gecko‐like adhesive surfaces and articulation mechanisms that do not rely on intensive nanofabrication in order to recover the anisotropic tribological property of gecko adhesive pads, albeit with lower adhesive forces compared to geckos.     

Normally Oriented Adhesion versus Friction Forces in Bacterial Adhesion to Polymer‐Brush Functionalized Surfaces Under Fluid Flow

Bacterial adhesion is problematic in many diverse applications. Coatings of hydrophilic polymer chains in a brush configuration reduce bacterial adhesion by orders of magnitude, but not to zero. Here, the mechanism by which polymer‐brush functionalized surfaces reduce bacterial adhesion from a flowing carrier fluid by relating bacterial adhesion with normally oriented adhesion and friction forces on polymer (PEG)‐brush coatings of different softness is studied. Softer brush coatings deform more than rigid ones, which yields extensive bond‐maturation and strong, normally oriented adhesion forces, accompanied by irreversible adhesion of bacteria. On rigid brushes, normally oriented adhesion forces remain small, allowing desorption and accordingly lower numbers of adhering bacteria result. Friction forces, generated by fluid flow and normally oriented adhesion forces, are required to oppose fluid shear forces and cause immobile adhesion. Summarizing, inclusion of friction forces and substratum softness provides a more complete mechanism of bacterial adhesion from flowing carrier fluids than available hitherto.     

Bondability analysis of bond pads by thermoelectric temperature measurements

To reduce cost and enhance reliability for microelectronics applications, a complete understanding of the thermosonic bonding process is required. In particular, the question of whether melting, diffusion, or significant heating occurs along the interface during friction has often been raised. We present results obtained with a new device based on thermoelectric temperature measurements to determine the temperature at the bond interface. In addition to the temperature information, the data characterizes the bonding process in real time on a micrometer scale. The basic principle of the developed apparatus is temperature measurement by an Au-Ni thermocouple fixed within the inside chamfer of a bonding capillary. Different bond substrates with high and low bond contact quality have been investigated. The thermoelectric temperature measurements very precisely determines the bonding behavior of the bond pads. A few nanometers surface contamination on a bond pad significantly reduces the temperature rise at the bond interface and therefore impairs bondability of the substrate. These results demonstrate the sensitivity and accuracy of the measurement principle. The apparatus is a powerful tool to measure the tribology of the bond system and to characterize the bondability of different bond pads.     

扩张式自激超越弹簧离合器超越摩擦力矩计算

扩张式自激超越弹簧离合器是一种新型离合器。在对其进行受力分析的基础上 ,推导出超越时摩擦力矩计算式 ,为该种离合器的设计与应用奠定基础。     

矿山机械液压系统的摩擦磨损分析

对矿山机械液压系统的摩擦磨损进行了分析和探讨。分析表明:矿山机械工作环境恶劣,液压元件的磨损主要是油液污染造成的[1],其元件磨损失效形式通常有4种:磨粒磨损、疲劳磨损、粘着磨损和腐蚀及侵蚀磨损。     

TA19钛合金线性摩擦焊接试验研究

为了探索TA19钛合金线性摩擦焊合适的工艺规范,在不同摩擦压力下进行了TA19钛合金线性摩擦焊接试验,并对焊接接头的组织特征和力学性能进行了分析。组织分析结果显示,焊缝区为再结晶组织,晶粒有所细化;热力影响区晶粒发生不同程度的变形,晶粒沿摩擦方向伸长;热影响区β相含量增加,推测发生了β相转变,β相层片状组织变厚,使等轴初生的α相晶粒有所减小。力学性能试验结果显示,焊接接头各区显微硬度均高于母材;拉伸试样断在母材区,接头强度不低于母材;接头平均冲击韧性均大于母材,冲击性能良好。研究结果表明,TA19钛合金线性摩擦焊焊接工艺窗口宽,在差异较大的摩擦压力下均能获得高质量接头。     

喷嘴与水平圆管的气－液两相流动阻力特性

本文应用一维变密度气－液两相流动量方程于喷嘴和水平圆管的气水两相流动，建立了喷嘴进出口压力及流速之间的关系，将动量方程在有限管道长度内积分，从而可由试验测得的压力差计算通过水平回管的气－液两相流阻力系数，并在大量试验的基础上建立了考虑截面含气率的喷嘴动量修正系数的相关关系式和水平因管中气水两相流阻力系数与雷诺数之间的关系式。