基于单片机控制的角度自动调整系统设计

本系统采用单片机STC12C5A08S2作为主控芯片,输出可控的PWM信号,通过L298N专用驱动电路对风扇的转速进行控制,调节风力大小,改变帆板偏转角度。使用WDD35D4角度传感器检测帆板偏转角度,检测信号送回单片机控制系统,形成闭环系统。系统可通过键盘输入进行风力控制达到自动调整帆板偏转角度目的。同时系统还可通过显示电路实时显示帆板偏转角度值。     

含地下水的回填砂土中重力式岸墙地震残余角位移的拟静力计算

地震残余角位移的预测是重力式岸墙地震工程设计中的关键问题。引用液化度指标考虑含地下水的回填砂土地震过程中的超静孔隙水压力对墙体运动的影响,基于Mononobe-Okabe拟静力法修正考虑液化度的动主动土压力,基于静力水压力理论近似计算土颗粒里的动水压力。同时考虑了水平与竖向地震载荷,根据力矩极限平衡确定旋转门槛加速度系数,采用旋转块体方法初步推导出岸墙主动旋转运动下的地震残余角位移的简单计算法。选用一理想的地震运动特征,应用该简单预测位移的方法对一算例进行了推算;并对回填砂土内摩擦角、墙体与土间摩擦角、水平与竖向地震加速度系数、回填土地下水位、墙前自由水位和码头墙宽高比多种参数下对旋转角位移的影响作了详细的定性分析。     

Feasibility study on optical vortex generation at Shanghai deep ultraviolet free-electron laser

Coherent light with orbital angular momentum （OAM） is of great interest. Recently, OAM light generation by coupling a relativistic electron beam with a Gaussian mode laser pulse at the high harmonics of a helical undulator has been demonstrated experimentally. In this paper, the possibility of delivering coherent OAM light at the 3rd harmonic of the Gaussian mode seed laser is discussed for the Shanghai deep ultraviolet free- electron laser （SDUV-FEL）. Considerations are given on the experiment setup, the expected performance and the possible measurement method.     

Rotor fault condition monitoring techniques for squirrel-cage induction machine—A review

Nowadays, manufacturing companies are making great efforts to implement an effective machinery maintenance program, which provides incipient fault detection. The machine problem and its irregularity can be detected at an early stage by employing a suitable condition monitoring accompanied with powerful signal processing technique. Among various defects occurred in machines, rotor faults are of significant importance as they cause secondary failures that lead to a serious motor malfunction. Diagnosis of rotor failures has long been an important but complicated task in the area of motor faults detection. This paper intends to review and summarize the recent researches and developments performed in condition monitoring of the induction machine with the purpose of rotor faults detection. The aim of this article is to provide a broad outlook on rotor fault monitoring techniques for the researchers and engineers.     

Improving corrosion resistance of Al‐11mass%Si alloy through a large number of ECAP passes

Ultrafine‐grained (UFG) Al‐11mass%Si alloy, processed by multi‐pass equal‐channel angular pressing (ECAP) at 573 K, was investigated on corrosion behavior in 0.6 M NaCl solution. Potentiodynamic polarization tests and scanning electron microscopy observation showed that a large number of ECAP passes resulted in lower corrosion current density, more positive corrosion potential, and rather smooth corroded surface with shallow corrosion pits. The uniform distribution of fine secondary‐phase particles on UFG Al matrix weakened the susceptibility to pitting corrosion while inhibited general microgalvanic reactions. The present results indicate that grain refinement of aluminum matrix to the UFG state and uniform redistribution of broken particles (including eutectic silicon and secondary phases), via severe plastic deformation at elevated temperature undergoing dynamic recrystallization, can significantly improve the corrosion resistance of Al alloys, besides the known exceptional mechanical advantages. The simple and effective ECAP procedure makes UFG Al alloys more attractive for high strength structural application in corrosive environment.     

楔形头部试样的ECAP变形行为有限元模拟

应用三维有限元方法对楔形头部试样在等径弯曲通道挤压(ECAP)中的变形行为进行了模拟分析,以比较不同楔形方案(前楔形、后楔形以及楔形头部大小)对金属ECAP变形的影响.结果表明:试样头部为后楔形可以有效的降低加工载荷,显著改善应力/应变分布的均匀性,消除应变集中,避免折叠缺陷,从而获得组织性能较为均匀的试样.     

A modification on ECAP process by incorporating torsional deformation

In the present study, integration of equal channel angular pressing (ECAP), as a well known severe plastic deformation (SPD) technique, and torsion deformation, is studied by using three dimensional finite element analysis. This process is to be named as torsional-equal channel angular pressing (T-ECAP). In this modification a part of the exit channel in the ECAP die is rotating around its axis, to impose extra shear strains to the samples. To study deformation behavior in the T-ECAP process, three-dimensional finite element analysis (FEA) was carried out by using the elasto-plastic finite element analysis ABAQUS/Explicit Simulation. To investigate the validity of the simulation results, experimental studies were furthermore performed on commercially pure aluminum (AA 1050). Vickers hardness test was used to determine the distribution of hardness on both normal and longitudinal sections of the deformed samples with respect to the exit channel of the die. The hardness test results showed more uniform distribution of hardness in both sections of the T-ECAP processed samples regarding the ones produced by ECAP process. The load requirement comparison for performing both processes showed lower value for the T-ECAP with respect to the ECAP process. The simulation results for the strain values showed higher magnitude and more uniform distribution for the T-ECAP with respect to the ECAP process.     

Microstructure control during severe plastic deformation of Al-Cu-Li and the influence on strength and ductility

The microstructure and mechanical behaviour of an Al-Cu-Li alloy has been examined after processing over a wide range of conditions involving severe deformation at elevated temperatures with prior or subsequent heat treatments. Dislocation cellular or subgrain structures are obtained, with varying degrees of precipitation. High strength, as well as poor ductility, can be correlated with the presence of a high density of fine T₁ phase precipitates, with the dislocation substructure playing a smaller role. Careful control of processing conditions allows a suitable combination of good strength with ductility to be obtained.     

步进电动机的失调角及精度

步进电动机象同步电动机一样,在负载转矩的作用下,转子磁极中心线将滞后于气隙磁场的中心线一个角度,称为失调角。在开环控制系统中,负载失调角对应于一定的失动量。用脉冲当量来衡量失动量的值时,它与电动机的通电方式,主要是逻辑通电状态数,即通常所说的运行拍数有关。由此明确了微步驱动技术在开环控制系统中应用的局限性。