金属增材制造变形与残余应力的研究现状

金属增材制造中的变形及残余应力对于成形过程及零件性能均会产生一定的影响,两者影响因素众多,在增材制造过程中的演化尚未明确揭示。本文综述了国内外关于金属增材制造变形和残余应力的研究现状,提出"约束力"新概念,为金属增材制造变形和残余应力机理的深入研究提供了新的方法。     

Experiment of Hall thruster plume effects on different ground experimental conditions

Reducing the influence of back-sputtering effect can effectively improve the accuracy of the measurement of the Hall thruster plume effect. Quartz crystal microbalance (QCM) was used to measure the deposition and sputtering distribution of HET-40 thruster plume on two different experimental conditions: case 1, using liquid nitrogen heat sinks and case 2, without using liquid nitrogen heat sinks. Meanwhile, X-ray photoelectron spectroscopy (XPS) was used to analyze the composition of the QCM surface after two experiments. The results of the two experiments showed that the sputtering rate under the condition of case 1 was slightly higher than case 2. Especially within the range of 90° to 110° relative to the thruster axis, case 1 experiment result showed sputtering effect, while case 2 experiment showed deposition effect. Through analysis of the experimental results, it can be found that using liquid nitrogen heat sink to reduce the temperature of the inner wall surface of vacuum chamber can effectively adsorb the particles sputtered by the plume and reduce the concentration of back-sputtering particles, leading to the above phenomenon.      

低温共固化高阻尼复合材料

在低温下实现了嵌入式阻尼复合材料的共固化，且共固化层合板具有良好的层间结合性能。通过正交试验研制出一种能够与玻璃纤维/酚醛树脂预浸料在80℃时共固化且力学性能优良的黏弹性材料组分。探索使用强极性的四氢呋喃作为溶剂将黏弹性阻尼材料溶解为阻尼胶浆，然后用刷涂工艺制作带阻尼薄膜的预浸料，最终按照预定的铺层经过共固化工艺制备出嵌入式低温共固化复合材料试件。自由衰减试验及层间剪切试验获得了阻尼性能及剪切性能随阻尼层厚度的变化规律曲线，实验数据表明：随着阻尼层厚度增大，复合材料结构的阻尼系数变大，层间剪切应力逐渐减小。     

基于SAPSO算法的异步电动机参数辨识

异步电动机等效电路参数的准确辨识对电动机的控制具有重要作用,同时,等效电路参数的变化可以反映电动机的运行状态,故参数辨识也被运用到电机故障诊断中。将现代最优化算法应用到三相异步电动机的等效电路参数辨识中。通过将粒子群优化算法(PSO)和模拟退火算法(SA)相结合,可以准确有效地对异步电动机的6个等效参数进行辨识,与遗传算法相比,SAPSO算法易于实现且收敛速度快。算法采用考虑铁耗的异步电机dq坐标系下的模型来实现,将温度对电阻参数的影响考虑在内。通过算例证明了算法能够有效地对电机参数进行辨识及跟踪电阻的变化。     

Service life prediction of AP/Al/HTPB solid rocket propellant with consideration of softening aging behavior

The aging behavior of softening composite solid propellant was investigated by measuring its mechanical and ballistic prosperities during prolonged storage at elevated and room temperatures. Accelerated aging was conducted at 65 °C for 231 days while the normal aging was performed at 25 ± 3 °C and relative humidity less than 50% for 8 years. The mechanical properties were obtained from uniaxial tensile tests for the aged propellant specimens while the ballistic properties were determined from static firing tests of subscale motors aged for 112 days at 65 °C. The mechanical results show that the maximum tensile strength and Young's modulus initially increase and subsequently decrease with increasing aging time, while the maximum tensile strain generally increases with increasing aging time. The ballistic properties like burning rate show a small change which cannot affect the ballistic performance. The experimental results show that the changes in the mechanical properties are significant during the aging period, but the burning rate does not undergo significant changes. From this study, it is observed that the propellant ages through a combination of reactions like post-cure, oxidative cross-linking, chain scission, and hydrolysis. The chain scission and the hydrolysis effect are the most significant process, which makes the propellant soft and extendible. The observed aging mechanism has been modeled using an exponential function with two terms which can describe the complex behavior of the aging. By applying Arrhenius equation,the activation energy values were obtained based on the propellant mechanical properties. The shelf life of this propellant formulation at 25 °C is predicted to be 13 years using the modulus as failure criteria and control parameter.     

快速部署浮空器总体技术研究

快速部署浮空器通过运载器将部署平台投放到预定空域,经过分离、减速伞减速、空中充气、展开等阶段,快速完成浮空平台在平流层的部署,可以实现突发灾难区域的应急通信、应急观测、应急监控等功能,能有效弥补目前平流层浮空器放飞条件限制多、升空过程风险大和部署时间长的不足。对其系统组成、优势进行了介绍,对总体技术进行了研究设计及初步分析验证,并围绕浮力体形式、浮力体充气气体、浮力体表面材料、浮力体载重能力、浮空器分离过程等关键技术开展研究。     

TRIZ理论及其在工装改进设计中的应用

介绍了TRIZ理论的产生与发展,分析了该理论在拓展思维、创造性解决问题方面的特点与优势。某型飞机雷达罩开启装置改进设计案例分析表明,该理论可以解决装备设计中常见的技术问题,提高工作效率,完善产品和工艺,合理利用资源降低成本。     

带攻击角度约束的深度强化元学习制导律

针对执行机构部分失效的速度时变导弹机动目标拦截问题,本文提出一种基于深度强化元学习和剩余飞行时间感知逻辑函数的攻击角度约束三维制导律。首先,采用基于模型的深度强化元学习方法,建立深度神经网络动力学模型;引入模型预测路径积分控制,该深度神经网络动力学模型作为预测模型;采用元学习方法,在线学习执行机构部分失效及目标机动等环境变化。其次,提出基于偏态分布的采样方法,提升模型预测路径积分控制的采样效率。再次,在制导律的指标函数设计中提出一种逻辑函数,降低了制导初始阶段的加速度,提升了末速度。最后,多种情况下的仿真结果及蒙特卡洛仿真校验了方法在提升采样效率与降低初始阶段加速度的有效性。     

Reflected Wavefront Modulation with Phase Array by Using Acoustic Metasurface

Acoustic metasurface has attracted increasing attention due to the ability of manipulating the transmitted and reflected phase of waves to generate various acoustic functionalities with planar layer of sub?wavelength structure.We design an acoustic metasurface with a semi?closed and nested slotted tube array,and it possesses the capacity of modulating the reflected phase with sub ? wavelength thickness(about λ/23). The reflected phase shifts can be obtained from 0 to 2π by different rotation angles of internal slotted tubes. The theoretical results agree well with the numerical results by a finite element method. The results show that some excellent wavefront manipulations are demonstrated with the phase array by using acoustic metasurface such as anomalous reflection and sub?wavelength flat focusing. The design may offer a path for acoustic manipulation and promote the potential applications of acoustic metasurface in low frequency noise control,acoustic imaging and cloaking.     

基于AMESim的火工作动装置仿真方法研究

针对一种小型化、低冲击活塞式火工作动装置,基于AMESim仿真软件建立了火工装置的数学模型,得出了活塞杆推力曲线的影响规律。同时进行试验验证,试验数据与仿真结果高度接近,验证了理论分析与仿真模型的正确性,大幅缩短了火工装置研制周期,并节约了研制成本,为火工装置的研究开拓了一种新型研制模式。