Damage Initiation and Propagation in Composites Subjected to Low-Velocity Impact:Experimental Results,3D Dynamic Damage Model,and FEM Simulations

A three-dimensional dynamic damage model that fits both small and large damage sizes is developed to predict impact damage initiation and propagation for each lamina of T300-carbon/epoxy laminations. First,13 specimens of the same lamination sequence are subjected to three different impact energies(10 J,15 J,and 20 J).After the impact,the laminates are inspected by the naked eye to observe the damage in the outer layers,and subsequently X-rayed to detect the inner damage. Next,the stress analysis of laminates subjected to impact loading is presented,based on the Hertz contact law and virtual displacement principle. Based on the analysis results,a threedimensional dynamic damage model is proposed,including the Hou failure criteria and Camanho stiffness degradation model,to predict the impact damage shape and area. The numerical predictions of the damage shape and area show a relatively reasonable agreement with the experiments. Finally,the impact damage initiation and propagation for each lamina are investigated using this damage model,and the results improve the understanding of the impact process.     

航天发射塔回转轴承新型清洗剂研制

航天发射塔回转轴承由于尺寸较大、结构复杂等原因,对其直接进行拆卸保养的难度过大。针对航空煤油等传统轴承清洗液存在清洗不彻底、易燃易爆、人身健康危害等缺点,本文通过对轴承润滑脂的化学成分分析研究,配置出了一种新型清洗液,用于对航天发射塔回转轴承进行清洗。经实验验证,该清洗液具有易于配置、便于存储、除油率高等特点。     

Design and application of an air-cooled probe for total pressure measurement at combustor outlet

An air-cooled probe was designed for measurement of total pressure at combustor outlet; its cooling scheme combined the film cooling and convection cooling. With the aid of CFD technique, cooling effectiveness of the coolant jets at various blow ratios was compared; suitable blow ratios and configuration of film holes were chosen accordingly. The overall cooling performance of the probe was evaluated via CFD technique, the design was improved according to the simulation result, and the cooling effect of the leading edge was obviously strengthened by increasing the local coolant mass flow rate. The results of wind tunnel test indicated that, between Mach numbers 0.2 and 0.4, the probe achieved a high accuracy at various attack angles. The probe was utilized in an annular combustor rig test, the highest temperature reached 1760K and total pressure reaches 1036kPa. The result of rig test demonstrates that the coolant film distribution consistent appropriately with the CFD results.      

Z源NPC三电平变换器恒功率并网控制策略研究

Z源中点钳位式(NPC)三电平变换器把逆变和升压两种环节结合在一起,结构简单、工作效率高,但是针对这种结构输出的无功功率研究较少。提出了一种Z源NPC三电平变换器的恒功率并网控制策略。首先对这种变换器的结构及原理进行分析;再把恒功率控制引入到这种变换器的并网控制中,并采用空间矢量脉宽调制(SVPWM)实现了变换器的并网控制。MATLAB/Simulink软件仿真结果证明了这种变换器能够提高电压升压比。该控制策略可使变换器输出的有功功率、无功功率稳定于设定值,且并网电流谐波较低。     

电动汽车用永磁同步电机控制器设计

电动汽车逐渐成为人们出行的交通工具之一,对技术可靠性和安全性的要求较高。电机控制器是实现电池直流电源向三相交流电源转换的装置,驱动永磁同步电机(PMSM)输出力能。设计了一款基于瑞萨单片机的PMSM控制器,从元器件选型、硬件保护电路原理、PCB布局、控制算法、结构强度和热分析方面展开分析。最后生产控制器样机并搭建试验平台,对PMSM控制器进行了效率特性测试、发电测试和温升测试。试验结果验证了设计方案的合理性。     

Effect of W addition on phase transformation and microstructure of powder metallurgic Ti-22Al-25Nb alloys during quenching and furnace cooling

Powder metallurgic Ti2 AlNb alloys with W addition are sintered at 900, 1000, 1070 °C,and 1150 °C(i.e., in the O + B2, a_2+ B2 + O, a_2+ B2, and single B2 phase regions, respectively)for 12 h, followed by water quenching and furnace cooling. Comparisons of phase and microstructure between quenched and furnace-cooled W-modified alloys are carried out to illustrate the phase transformation and microstructure evolution during the cooling process. Furthermore, a comparison is also made between W-modified and W-free alloys, to reveal the function of the W alloying.W addition accelerates the solutions of a_2 and O phases during the high-temperature holding, and a Widmannsta¨tten B2 + O structure, which contributes to the properties, is induced by furnace cooling from all the phase regions. The Widmannsta¨tten structure includes a B2 matrix, primary O, and secondary O precipitates. However, W alloying refines the Widmannsta¨tten structure only when the alloys are solution-treated and then cooled from the single B2 phase. Although the hardness of the W-modified alloys is lower than that of the W-free alloys sintered in the same phase region, an enhancement of hardness, 489 ± 18 HV, is obtained in the alloy solution-treated in the single B2 phase region for only 0.5 h.     

A quantum inspired genetic algorithm for multimodal optimization of wind disturbance alleviation flight control system

This paper develops a Quantum-inspired Genetic Algorithm (QGA) to find the sets of optimal parameters for the wind disturbance alleviation Flight Control System (FCS). To search the problem domain more evenly and uniformly, the lattice rule based stratification method is used to create new chromosomes. The chromosomes are coded and updated according to quantum-inspired strategies. A niching method is used to ensure every chromosome can converge to its corresponding local minimum in the optimization process. A parallel archive system is adopted to monitor the chromosomes on-line and save all potential feasible solutions in the optimization process. An adaptive search strategy is used to gradually adjust the search domain of each niche to finally approach the local minima. The solutions found by the QGA are compared with some other Multimodal Optimization (MO) algorithms and are tested on the FCS of the Boeing 747 to demonstrate the effectiveness of the proposed algorithm.     

冶金法提纯多晶硅退火工艺优化的数学模型分析与试验验证

冶金法制备多晶硅过程中,通过对不同退火温控方案进行数学建模,探求优化的退火理论温度控制函数与曲线。数学模型表明,对硅铸锭直接进行保温,依靠自然热平衡退火,会使内部应力大于产生位错的临界应力;采用加热元件对硅铸锭适当加热保温可减缓降温速率。通过比较,选择较低的退火温度1 236℃和较短的退火时间8.52 ks作为试验退火温控方案。试验验证表明,该退火方案得到的多晶硅铸锭目视裂纹较少,少数载流子寿命与电阻率具有明显优势。     

基于改进遗传算法的物料配送路径实时规划方法

针对离散制造车间环境复杂、外部干扰因素众多的情况,提出基于改进遗传算法的物料配送路径实时规划方法。该方法以工作中心为物料配送基础,对离散制造车间物料配送环境进行了分析,阐述了物料配送参数的多样性。在此基础上,结合物料配送时间窗要求,以最小物料配送成本为优化目标,建立了车间实时环境下的物料配送模型。采用改进遗传算法对模型进行求解,通过实例验证了该模型的可行性和有效性。     

多种软磁合金及金属非晶材料的磁屏蔽性能研究

针对部分航天器组件易受磁场影响的问题,文章选取了6种目前常用的软磁合金及金属非晶材料,研究了它们对于弱磁场波动、稳恒磁场以及低频交流磁场的屏蔽效果,结果表明,材料的磁导率与矫顽力对磁屏蔽性能有较大影响,其中矫顽力与磁屏蔽性能的负相关性更好,即矫顽力越低,材料的磁屏蔽性能越好。对于测试的6种材料,铁镍合金材料与钴基非晶材料的磁屏蔽性能优于其他4种,铁镍合金材料在1 kHz以下磁屏蔽性能更佳,钴基非晶材料在50 kHz以下具有一定磁屏蔽效果。