航空铝合金板材搅拌摩擦连接有限元分析

根据搅拌摩擦连接特点,充分考虑搅拌摩擦连接过程中搅拌针各部位与连接板材之间的摩擦生热及在连接过程中连接板材摩擦系数随温度变化规律,建立了适合搅拌摩擦连接自身特点的动态热元模型,并利用此模型进行了航空铝合金板材搅拌摩擦连接过程的有限元分析模拟.通过模拟结果和试验结果对比验证了所建立的动态热源模型和有限元分析过程是合理的.模拟结果显示搅拌摩擦连接残余拉应力主要集中在连接区,且在连接区中间位置出现最大残余拉应力区,连接区两端及其它部位出现残余压应力.     

Effect of bark fiber content and size on the mechanical properties of bark/HDPE composites

Black spruce and trembling aspen bark fibers and high density polyethylene were used to process bark–plastic composites by extrusion. Fibers of fine, medium, and coarse size and contents of 50% and 60% based on oven-dry weight were used. The effects of species, fiber content and size on the flexural and tensile properties of the composite were investigated and were found to be highly significant. Black spruce bark composites exhibited higher strength but showed more brittle behavior than aspen bark composites. The effect of content on mechanical properties was more important than size. Compared to wood flour composites, those from bark showed lower strength.     

Modeling and prediction of surface roughness in ceramic grinding

Surface quality of workpiece during ceramic grinding is an ever-increasing concern in industries now-a-days. Every industry cares to produce products with supposedly better surface finish. The importance of the surface finish of a product depends upon its functional requirements. Since surface finish is governed by many factors, its experimental determination is laborious and time consuming. So the establishment of a model for the reliable prediction of surface roughness is still a key issue for ceramic grinding. In this study, a new analytical surface roughness model is developed on the basis of stochastic nature of the grinding process, governed mainly by the random geometry and the random distribution of cutting edges on the wheel surface having random grain protrusion heights. A simple relationship between the surface roughness and the chip thickness was obtained, which was validated by the experimental results of silicon carbide grinding.     

Design and hybrid control of the pneumatic force-feedback systems for Arm-Exoskeleton by using on/off valve

This article models a pneumatic force-feedback system consisting of the double-acting cylinder and a set of high-speed on–off valves, and its fuzzy controller in order to provide an insight into pneumatic system design and force-feedback control requirements of the Arm-Exoskeleton, which is applied in robot-teleoperation and robotics. In modeling, effects of nonlinear flow through the valves, air compressibility in cylinder chambers, and time delay and attenuation of the pressure input in the connecting tubes are considered. Based on this mathematical model, the hybrid fuzzy control method for the precise force-feedback control is proposed and the fuzzy controllers are realized with the Mega8 MCUs as the units of the distributed control system in the Arm-Exoskeleton. At last a series of experiments validated the models and control method.     

Wear Resistance Analysis of a Lightweight Aluminum Alloy Sheet Friction Stir Joint Area

Strength of Materials - The friction stir joining experiment was performed on a 6061-T6 aluminum alloy sheet 1 mm thick by optimization of different process parameters, and the microstructure and...     

基于激素调节机制改进型自适应粒子群算法在置换流水车间调度中的应用研究

研究以最小化最大流程时间为调度目标的离散型生产作业中的置换流水车间调度问题,将基于激素调节机制的改进型自适应粒子群算法应用到其中。在该算法中,粒子群算法的个体最优初始值不再是随机生成,而是由基于启发式信息的贪婪随机自适应算法得到的工件加工顺序转换而成,同时借鉴激素调节机制,引入激素调节因子,根据单个粒子周围的粒子的信息,对粒子的飞行方程进行改进,以提高搜索效率和搜索质量。对置换流水车间调度实例Rec系列基准问题进行测试,结果验证算法的有效性。     

Flow Field Simulation and Experimental Study of Friction Aided Jet-Electro-Deposition Based on the Wireless Information Networks

By analysing the system of friction aided jet-electro-deposition, this research developed a simulate model of the flow field to simulate the velocity of the electroplating solution and investigate the influence of flow field on electro-deposition at different electrode gaps. Simulate Results indicated that velocity of the electroplating solution was high in areas affected by jet-electro-deposition. With increased electrode gap, the velocity of the electroplating solution on the cathode surface decreased gradually, but its velocity distribution became uneven. Analyses using scanning electron microscopy and transmission electron microscopy demonstrated that choosing an appropriate electrode gap could result in both a high, and a well-distributed, velocity profile conducive to the production of nickel films with fewer defects.     

The effect of light scattering in stereolithography ceramic manufacturing

This research simulated the light scattering caused by ceramic particles' presence during stereolithography ceramic manufacturing and revealed the phenomena in the process. The theoretical derivation and calculation of a classic single-particle scattering model were used to verify the reliability of the simulation model. The light scattering simulation confirmed the effects of particle distribution, input energy, and relative refractive index, which were all supported by experiments. The simulation also showed the different scattering edge and the surface roughness at the micron level with verified experiment. Besides, as the particle size of Al2O3 particles increased, the curing thickness increased, the degree of side scattering increased slightly, and the regularity of the curing edge decreased. It was found through simulation that adding an appropriate amount of carbon powder can solve SiO2 inability to print. This study provides valuable guidance to the control of the light-cured 3D printing process for ceramics.     

人眼像差探测哈特曼波前传感器的质心优化

为提高自适应光学系统中Hartmann-Shack波前传感器的动态测量范围和测量精度,对由CCD采集的波前光斑图进行了质心探测研究.介绍了波前传感器的工作原理,根据127单元传感器的结构特征和实际人眼光斑图的畸变特点,提出了一种动态定位光斑区域、动态分割区域内部阈值以及锁定最优探测窗口的自适应光斑质心探测方法.讨论了该...