无预固化衬层成型工艺对界面粘接强度的影响

采用钢/ 三元乙丙绝热层/ 衬层( K/ J/ B) 粘接试件和钢/ 三元乙丙绝热层/ 衬层/ 推进剂( K/ J/ B/ Y)矩形试件,对三元乙丙(EPDM)绝热层、无预固化衬层界面粘接强度进行测试,研究了EPDM 绝热层表面处 理工艺、衬层成型厚度以及衬层成型后装药间隔时间对界面粘接性能的影响。结果表明:无预固化衬层与表面 未处理的EPDM 绝热层粘接强度约1. 0 MPa,而EPDM 绝热层表面处理后,无预固化衬层与绝热层和推进剂界 面的粘接良好。无预固化衬层成型厚度为0. 3 ~0. 5 mm,界面粘接强度基本不变;衬层成型厚度增大到0. 7 mm,则界面粘接强度逐步增加。K/ J/ B/ Y 断裂面均在推进剂间,界面良好无异常;装药间隔时间从4 h 延长至 24 h,对K/ J/ B/ Y 粘接强度影响较小,无预固化衬层完全可以按照现行装药工艺进行装药。     

Effects of different aging treatments on microstructures and mechanical properties of Al-Cu-Li alloy joints welded by electron beam welding

Post-weld single aging treatment(solution treatment at 510 ℃ for 1 h, water quenching,and aging at 155 ℃ for 16 h) and post-weld double aging treatment(solution treatment at 510 ℃ for 1 h, water quenching, aging at 155 ℃ for 16 h, and aging at 130 ℃ for 12 h) are carried out on Al-Cu-Li alloy joints by electron beam welding(EBW) respectively. The effects of aging treatments on microstructures and mechanical properties of welded joints are investigated. Results show that the mechanical properties of welded joints are obviously improved after both aging treatments. The strength coefficient of joints is increased from 0.64 in an as-welded condition(AW) to 0.90 after post-weld double aging treatment. Microstructure analysis shows that the precipitates of the fusion zone within grains and grain boundaries are less in the AW condition. After post-weld heat treatment(PWHT), a lot of fine needle-like phases T_1(Al_2 Cu Li) precipitate in grain boundaries of the fusion zone, and more horseshoe-shaped β' (Al_3 Zr) particles precipitate within grains. In addition,grains of the fusion zone are refined after post-weld double aging treatment, which leads to an effect of grain refinement strengthening. Consequently, the mechanical properties of welded joints are greatly improved.     

受力刚体拉杆支撑强度与刚度计算

本文对受力刚体应用拉杆支撑的结构进行强度、刚度和自振频率力学进行性能计算,并给出了其计算所依据的应用。     

助烧剂对无压烧结Si3N4力学性能的影响

研究了三种助烧剂MgO、Al2O3+AlN和Y2O3+AlN对1800℃×3h工艺下无压烧结Si3N4力学性能的影响情况。发现材料力学性能主要决定于助烧剂的种类,其次取决于含量。其Y2O3+AlN虽使最终生成的β-Si3N4长径比较小,线度尺寸最短,但最利于致密化,因而使材料力学性能最佳,添加量(质量分数)为12%Y2O3+6%AlN时,陶瓷的抗弯强度、断裂韧性和维氏硬度分别达到431.6MPa、5.10MPa*m1/2和14.52GPa。     

基于BP神经网络的复合材料性能预测

针对复合材料性能表征十分复杂、困难的情况,利用人工神经网络的BP算法,建立了复合材料性能预测模型。模型由3层神经元组成,分别为输入层、隐含层和输出层。以碳/陶瓷复合材料性能与成分的关系为研究对象,选取了38组实验数据作为学习样本,模型总误差为0.18,用建立的网络预测未知,并给出预报曲线。和试验值相比较表明,所建立的网络能反映碳/陶瓷复合材料组分与其材料性能之间的关系,为实验设计提供了新的思路,节省了时间和劳力。     

充液航天器质量特性计算方法研究

充液航天器的质量特性对飞行动力学建模和控制设计有着重要影响。质量特性测量装置通常只能测出干重状态下航天器的质量特性，而充液状态下的航天器质量特性只能靠计算给出，其中如何计及各贮箱内液体的惯性张量是此类工程计算的难点。首先采用势流理论推导了任意形状贮箱内液体质量特性的一般表达式，包括全充液情况和部分充液情况，其中对部分充液情况考虑了自由液面小幅晃动的影响；然后采用三维有限元方法建立了液体质量特性的数值计算方法，并通过一个验证算例确认了该计算方法的有效性；最后应用该方法计算了一个充液航天器的质量特性，并研究了不同的液体处理方法对计算结果的影响。研究表明，工程上通常采用的“固化液体”处理方法所计算出来的转动惯量明显偏大，而所提出的计算方法具有更好的理论正确性和工程适用性。     

一种新型铁电移相器材料的第一性原理计算

铁电薄膜移相器是基于铁电材料的新型移相器,被广泛应用于相控阵天线中。对于这类移相器组成材料的性能改进一直是雷达系统在军事、航天等领域的研究热点之一。基于第一性原理密度泛函理论,综合分析了ABi₂Nb₂O₉(A=Ba, Pb, Sr, Ca)材料的电子属性、化学键和极化属性。结果表明:这种体系有着类似的铁电性起源；Nb—O和Bi—O间的杂化对于系统的畸变和铁电相的稳定起着重要作用；随着A位离子半径的增大,体系的畸变参数也随之增大,导致材料有更大的自发极化,增强了铁电移相器的性能。实验结果验证了理论计算的正确性,为新型铁电移相器的研发奠定了基础。     

Nanoparticle type effects on flexural,interfacial and vibration properties of GFRE composites

Damping improvement in composite structures via introducing nanofillers generally has remarkable negative effects on the other mechanical properties. Therefore, in the present work, Si C and Al_2O_3 nanoparticles' infusion effects on the flexural, interfacial and vibration properties of epoxy matrix and glass fiber reinforced epoxy(GFR/E) laminates were investigated. Unidirectional(UD-GFR/E) and quasi-isotropic(QI-GFR/E) laminates with [0/±45/90]sand [90/±45/0]sstacking sequences were hybridized by the optimum nanoparticles percentages. Results from off-axis flexural strengths of UD-GFR/E demonstrate good fiber/nanophased-matrix interfacial bonding.The interlaminar shear stress between the adjacent layers with different orientations/strains of ductile QI-GFR/Si C/E laminates results in decreasing the flexural strengths respectively by 24.3% and9.1% for [0/±45/90]sand [90/±45/0]sstacking sequences and increasing the dissipated interfacial friction energy and thus the damping by 105.7% and 26.1%. The damping of QI-GFR/E,QI-GFR/Si C/E and QI-GFR/Al_2O_3/E laminates with [90/±45/0]sstacking sequence was increased by 111.4%, 29.7% and 32.9% respectively compared to [0/±45/90]sstacking sequence.     

Synthesis and characterization of geopolymer from lunar regolith simulant based on natural volcanic scoria

In this study, a new GVS（Ground Volcanic Scoria） lunar regolith simulant was produced. The similarity between GVS and lunar soil was proved by comparison with Apollo lunar soil samples and other commercial lunar soil simulants. Then, GVS lunar regolith simulant was investigated as the source material for preparing geopolymer to produce building material for lunar colony construction. To study the possibility of preparing geopolymer from GVS lunar regolith simulant and the optimum activator formu...     

多异氰酸酯指标对推进剂力学性能的影响分析

为了确定推进剂中所用固化剂多异氰酸酯的质量指标，采用灰色关联度法分析多异氰酸酯的各项指标对推进剂力学性能的影响，通过计算发现：（1）影响多异氰酸酯粘度的主要因素是高官能度的含量，而二官能度的含量是影响其平均官皮肤度的主要因素；（2）二官能度的含量是影响推进强度的最重要因素，而三官能度的含量和粘度是影响其伸长率的最重要因素。对于不能建立明确回归模型的实验，灰色关联度法可用于原材料多因素实验中的影响因素主次分析。