Contact fatigue behavior of nano-ZrO2/Ni coating prepared by electro-brush plating

Nano-ZrO₂/Ni composite coatings were prepared through co-depositing nano-ZrO₂ particles and pure nickel by electro-brush plating (EBP). By analyzing the effects of microstructure, annealing and load on contact fatigue life, the contact fatigue behavior of the nano-ZrO₂/Ni EBP coating was investigated. Furthermore, the contact fatigue behaviors of the nano-ZrO₂/Ni EBP coating and the nickel EBP coating were compared. The results show that the nano-ZrO₂ particles in the as-deposited nano-ZrO₂/Ni EBP coating were partially conglomerated, and the microstructure of the annealed nano-ZrO₂/Ni EBP coating was finer. Under the as-deposited condition, the contact fatigue life of the nano-ZrO₂/Ni EBP coating was much lower than that of the nickel EBP coating. After the annealing process, the contact fatigue life of the nano-ZrO₂/Ni EBP coating was greatly increased and much higher than that of the nickel EBP coating. The scanning electron microscope (SEM) images of the fatigue fracture zones and the transmission electron microscope (TEM) images of microstructure of the deformation layer show that the annealing could improve the ductility of the nano-ZrO₂/Ni EBP coating, and the nano-ZrO₂ particles could restrain the propagation of the fatigue cracks, which contributed to the enhancement of the contact fatigue properties of the nano-ZrO₂/Ni EBP coating.     

精密分度装置中蜗轮副的啮合分析

对新型蜗轮剐齿面啮合进行理论分析，指出它的一些特性：齿面容易获得较高精度；接触线走向容易形成油膜；齿面诱导曲率小，可承受较大载荷，使用寿命长。     

表面工程系统接触力学模型

在任何严峻条件下现代机械运行中综合性能的迫切需求促进了许多先进表面工程技术的迅速发展。因而，设计者在结构设计时将有许多表面工程技术可以选择。但是，怎样为一种特定的应用选择一种最优化的表面工程方法对设计者来说又是一种挑战。为了这个目标，在现代多层表面接触理论的基础上建立起一种接触力学模型，考虑到了多层结构、真实表面粗糙度和摩擦影响。这种力学模型可以成功地预测表面工程结构的性能。文中首先回顾了赫兹接触理论的发展过程，然后讨论了伯明翰多层真实粗糙表面接触力学模型，并用实例示范了一系列关于动载荷下表面工程结构设计的主要步骤。     

Analysis of thermo-mechanical wear problems for reciprocal punch sliding

The relative sliding motion of two elastic bodies in contact induces wear process and contact shape evolution. In the case of a punch sliding on a substrate the transient process tends to a steady state for which the fixed contact stress and strain distribution develops in the contact zone. This state usually corresponds to a minimum of the wear dissipation power. The optimality conditions of the wear dissipation functional provide the contact stress distribution and the wear rate compatible with the rigid body punch motion. The present paper is aimed to extend the previous analyses [1], [2], [3], [4], [5] of steady state conditions to cases of periodic sliding of punch, assuming cyclic steady state conditions for both mechanical and thermal fields.     

Critical stress and load conditions for pitting calculations of involute spur and helical gear teeth

Calculation methods of spur and helical gear drives for preliminary designs or standardization purposes available in technical literature, use the Hertz equation to evaluate the contact stress, assuming the load to be uniformly distributed along the line of contact. However, this model presents some discrepancies with experimental results because the changing rigidity of the pair of teeth along the path of contact produces a non-uniform load distribution, which implies that some load distribution factors are required to compute the contact stress. In this paper, a non-uniform model of load distribution along the line of contact, recently developed, obtained from the minimum elastic potential criterion, has been used. This model combined with the Hertz equation yields more accurate values of the contact stress. As the load per unit of length at any point of the line of contact and any position of the meshing cycle has been described by a very simple analytic equation, a complete study of the location and value of the critical contact stress has been carried out. From this study, a recommendation for the calculation of the pitting load capacity of spur and helical gears is proposed.     

Caustic imaging of gallium droplets using mirror electron microscopy

We discuss a new interpretation of mirror electron microscopy (MEM) images, whereby electric field distortions caused by surface topography and/or potential variations are sufficiently large to create caustics in the image contrast. Using a ray-based trajectory method, we consider how a family of rays overlaps to create caustics in the vicinity of the imaging plane of the magnetic objective lens. Such image caustics contain useful information on the surface topography and/or potential, and can be directly related to surface features. Specifically we show how a through-focus series of MEM images can be used to extract the contact angle of a Ga droplet on a GaAs (001) surface.     

基于IMS移动终端的即时通信联系人列表管理器

本文主要介绍基于IMS移动终端的即时通信联系人管理器,该管理器主要由XML搜索器、XML解析器、XML管理模块、XCAP通信模块构成。分析联系人列表中联系人的XML片段的定长特性,设计了XML搜索器,实现了节点的快速查找。在XML管理器模块中,以节点路径和消息片段的方式提交联系人修改,减少XML消息传输的字节数,从而提高了消息的传输速率。     

Full perimeter obstacle contact sensor based on flex sensors

This paper presents an obstacle contact sensor system that can detect both the contact state and the direction of contact parallel to the movement plane of a mobile system carrying the sensor. This sensor system is based on a regular- or irregular-shaped ring surrounding the mobile system’s perimeter, connected to the mobile system’s body by a set of soft springs and also coupled mechanically to a set of four flex sensors measuring the relative displacement and direction of the ring when contacting an obstacle. The set of flex sensors is connected to a low-cost electronic module that implements a data acquisition block and a fuzzy processing block, delivering a value representing the estimated contact zone of the ring. Some experiments show how this detection system effectively reduces the sensor count needed for full coverage of the mobile system’s perimeter. Despite the kind of output implemented in the experiments, the contact force can also be estimated.     

Controller design for flexible structure vibration suppression with robustness to contacts

Model-based feedback control of vibration in flexible structures can be complicated by the possibility that interaction with an external body occurs. If not accounted for, instability or poor performance may result. In this paper, a method is proposed for achieving robust vibration control of flexible structures under contact. The method uses robust linear state feedback, coupled with a state estimation scheme utilizing contact force measurement. Uncertain contact characteristics are modelled by a sector-bounded non-linear function, such that state feedback gains can be synthesized using a matrix inequality formulation of the Popov stability criterion. A separation theorem is used to establish a robust H₂ cost bound for the closed loop system. Experimental results from a multi-mode flexible structure testbed confirm that vibration attenuation and stability can be maintained over a broad range of contact characteristics, in terms of compliance and clearance.     

基于小世界模型的传感器网络节能查询策略

查询处理是传感器网络中最重要的技术之一。以降低查询能耗为目的,提出了一种基于小世界模型的查询策略（CardSN）。该策略以关联作为长程连接,降低了网络平均路径距离;将各节点的邻居相对定位,使查询处理获得了方向性。仿真实验结果表明：CardSN具有良好的可扩展性,且能耗明显低于ZRP和CAPTURE。