固体火箭发动机燃气二次喷射推力矢量控制试验研究

介绍了固体火箭发动机卧式六分力试车台系统及其测量原理,设计了燃气二次喷射固体发动机试验系统,完成了燃气二次喷射发动机原理性试验。试验结果表明,二次喷射具有放大作用,燃气二次喷射能产生较大的侧向控制力。试验得到的推力矢量控制偏角为7°,二次喷射燃气侧向比冲为2 366.4 N.s/kg,其效率远高于液体二次喷射。     

壁温对压缩拐角流动影响的数值模拟研究

压缩拐角是高超声速飞行器上的典型非连续区域,其分离/再附结构对局部热环境有较大影响。本文采用基于Navier-Stokes方程的自研程序,开展了典型压缩拐角外形的气动热环境数值模拟研究,分析了不同壁温条件下压缩拐角的热环境分布规律。计算结果表明:随着壁温升高,流场整体结构变化不大,但由于近壁面流体物性参数变化较大,导致拐角分离涡分离点向前移动、再附点向后移动,拐角处干扰区扩大;压缩拐角大部分区域的热流随着壁温的升高而减小,且干扰区内热流减小的幅度比无干扰区更大,但热流并不完全遵循随壁温升高而减小的规律。另外,通过对比变壁温计算热流和热壁修正公式修正热流,发现热壁修正公式在干扰区存在精度降低、适用性不足的问题。本文的研究进一步加深了壁温对压缩拐角流动影响的认识,缩小了热壁修正公式的适用范围。     

短舱进气道热气防冰系统传热特性研究

为了研究短舱笛形管热气防冰系统中防冰腔设计参数对进气道唇口表面传热特性的影响，进行了不同设计参数下进气道防冰腔内外流域和固体域的耦合仿真传热计算。分析得出了不同射流孔孔径和射流孔到进气道前缘表面的距离等参数对进气道唇口表面的温度、对流换热系数和Nusselt(Nu)数分布的影响。分析结果表明：射流孔直径和射流孔到唇口表面距离在一定的范围内，进气道蒙皮表面温度和对流换热系数随射流孔直径的增大而升高，随中间排射流孔到唇口表面距离的减小而升高。     

3D打印技术在空间站梦天实验舱上的应用

面对梦天实验舱次结构减重需求，提出了面向3D打印技术的次结构拓扑优化设计的方法，完成并掌握了3D打印次结构从设计、工艺、制造、检验等全周期的研制流程。在梦天实验舱发射载荷条件下，通过结构有限元分析及试验验证，对3D打印次结构性能进行了考核。结果表明:在具有一定强度和刚度裕度的前提下，支架减重效果较为明显，面向3D打印技术的次结构拓扑优化设计的方法具有广阔的工程应用前景。     

基于AMESim的热气防冰系统笛形管设计与仿真

笛形管是飞机热气防冰系统的重要组成部分，笛形管上的孔径、孔间距以及笛形管的引气入口参数决定了防冰供气流量的大小及分配，从而影响防冰性能。本文基于多学科系统建模仿真平台AMESim，建立了笛形管流量分配仿真分析模型，对机翼热气防冰系统笛形管结构参数进行迭代设计。设计参数包括笛形管管径、喷孔孔径及孔间距等参数，最终获得了能够平衡设计状态点防冰热载荷的结构参数和引气流量分配，得到了防冰系统的引气压力制度。本文提出的基于AMESim的笛形管迭代设计方法可为热气防冰系统中笛形管的设计与优化提供参考。     

Investigation of anode shaping process during co-rotating electrochemical machining of convex structure on inner surface

A novel co-rotating electrochemical machining method is proposed for fabricating convex structures on the inner surface of a revolving part. The electrodes motion and material removal method of co-rotating electrochemical machining are different from traditional electrochemical machining. An equivalent kinematic model is established to analyze the novel electrodes motion,since the anode and cathode rotate in the same direction while the cathode simultaneously feeds along the line of centres. Acc...     

低密度镁锂合金性能强化与精密成形技术

针对轻质高强和近成形复杂结构的技术要求，提出一种基于低密度镁锂合金薄壁筒形件的等温超塑性双向挤压近净成形方法，研究了铸态成形性能、铸态和轧制态在不同温度下的力学性能变化规律。研究结果表明，铸态下延伸率约12%，抗拉强度约145 MPa，轧制态下延伸率变化不大，但抗拉强度提升到180 MPa以上。采用本论文方法镁锂合金的延伸率和抗拉强度显著提高，分别达到21%和216 MPa，表明高温大变形过程中，实现了晶粒细化，大量增强相弥散在晶粒内部，起到性能强化作用，成功实现其性能强化和复杂结构件的精密成形。     

带螺旋内筋薄壁筒形件旋压变形特征

采用有限元模拟和实验结合的方法,研究了带螺旋内筋薄壁筒形件旋压变形特征.首先建立带螺旋内筋薄壁筒形件旋压有限元模型,并通过实验验证模型的可靠性.然后基于有限元模拟结果,分析旋轮作用下不同区域的应力特征及成形工件不同区域的应变特征.结果表明:筒壁区材料在旋轮作用下受三向压应力,内筋处外层材料受三向压应力,内层材料径向受压...     

Hot Tearing Behavior of Mg-Gd-Y-X Alloys

Mg-Gd-Y-Zr alloy castings are widely used in the aerospace field owing to their high strength and excellent creep resistance. The castability of these alloys is also an important consideration for engineering application. Thus， the hot tearing susceptibilities (HTSs) of Mg-10Gd-1Y-1Zn-0.5Zr (VW91) alloy and Mg-10Gd-2Y-1Zn-0.5Zr (VW92) alloy are investigated with a constrained rod casting (CRC) mold. The microstructures and fracture surface are characterized by optical microscope and scanning electron microscope. The results unveil that the HTS of VW92 alloy is lower than that of VW91 alloy. The microstructures indicate that obvious tears can be observed in VW91 alloy， while the tears in VW92 alloy are tiny. The tear feeding and healing by eutectic are also observed in VW91 and VW92 alloys. Therefore， the lower hot tearing susceptibility of VW92 alloy is mainly attributed to the high amount of eutectic which feeds and heals tears. Besides， the effects of the coefficient of thermal expansion (CTE) and the fluidity of VW91 and VW92 alloys on their HTSs are discussed.     

Non-isothermal creep age forming of Al-Cu-Li alloy: Experiment and modelling

Non-isothermal Creep Age Forming (CAF), including loading, heating, holding, cooling and springback stages, is an advanced forming technique for manufacturing high performance large integral panels at short production period and low cost. However, the creep deformation and aging precipitation during heating stage is often neglected in experiments and modeling, leading to low forming precision. To achieve shape forming and property tailoring simultaneously, a deep understanding of the non-isothermal creep aging behavior and the establishment of predictive models are urgently required. A new five-stage creep feature of Al-Cu-Li alloy during the non-isothermal creep aging is observed. The microstructural interactions between the dislocations, solute atoms, Guinier Preston zones (GP zones) and T₁ precipitates are found to dominate the five-stage creep aging behavior. The physical-based model considering temperature evolution history is established to describe the five-stage creep feature. The springback and yield strength of non-isothermal creep age formed plates with different thicknesses are predicted and compared by non-isothermal CAF experiments and corresponding simulations. The CAF experiments show that the springback and yield strength of the non-isothermal creep age formed plate are 62.1% and 506 MPa, respectively. Simulation results are in good agreement with experimental results. The proposed model broadens the application of traditional CAF models that mainly focus on isothermal conditions.