钣料压延数值解

本文采用能量条件的硬化模式,考虑到钣料的厚向异性,导出了压延凸缘区和凹模圆角区数值解所需的理论方程以及压延拉伸失稳条件的数学表达式和压延拉伸失稳临界载荷计算公式,在此基础上,利用电子计算机求解了四种钣料(TA1—M、LY12—M、LF2—M、20钢)的压延载荷和极限压延系数。理论和实验结果取得了很好的一致性。     

冲击/发散冷却层板隔热屏冷却性能及对比

为了分析对比新型冲击/发散冷却层板隔热屏冷却性能,论证其应用于加力燃烧室的可行性,在3种不同主次流总压比条件下对其进行了三维流固耦合传热数值模拟研究,并与某型波纹板隔热屏和单层平板隔热屏进行了相同工况的对比分析,得到了冷却效果、冷气用量、冷气热负荷和次流总压损失系数等的对比结果和变化规律.结果表明:冲击/发散冷却层板隔热屏具有较好的冷却效果,但其受主次流总压比变化的影响较大.相比某型波纹板,冲击/发散冷却层板隔热屏的冷气消耗量平均减少41.6%,单位面积冷气热负荷平均降低65.9%.     

水平力下板柱结构等代梁等效宽度系数的研究

指出了水平力作用下板柱结构的等代梁应是变截面梁,与柱相交处的等代梁宽度比跨中的小;同时按刚度相等原则,给出了折算成等截面等代梁宽度的计算方法。提出了影响等代梁等效宽度系数的主要因素为受扭构件的抗扭刚度与板的抗弯刚度的比值,并通过弹性有限元分析,给出了以这个比值作为参数的板柱结构内框架和边框架等代梁等效宽度系数计算公式。     

功能梯度材料夹芯板的后屈曲

基于Reddy高阶剪切理论及Von-Karman大挠度理论,针对以功能梯度材料为面材的夹芯板的后屈曲行为进行了研究,数值算例给出了完善、非完善功能梯度材料夹芯板的后屈曲荷载-挠度曲线以及后屈曲荷载-端部缩短曲线。讨论了初始几何缺陷、材料组分指数、温度相关性、面内边界约束条件等各参数变化所带来的影响。     

点阵结构工艺参数对透波平板电磁波谱的影响

文摘为研究点阵结构工艺参数对透波平板电磁波谱的影响,基于体心立方结构(BCC)点阵基本构型,建立透波平板仿真模型,运用CST仿真软件分别从孔隙率、蒙皮厚度、胞元尺寸、入射角度4方面探究不同结构工艺参数对透波平板共振频率及透射率的影响。并运用选区激光烧结(SLS)制备点阵透波平板结构,用于2～18 GHz透射率对比测试。结果表明,仿真数据与实验结果高度一致;透波平板共振频率随孔隙率增大,第一频率点向低频偏移,第二频率点向高频偏移;随着蒙皮厚度的增加,透射率降低;胞元尺寸与蒙皮厚度决定透射谱的通带共振频率,孔隙率影响较小;入射角增大时,水平极化入射波透射率均大于75%,影响较小;竖直极化入射波透射率在高频处逐渐降低。     

BT-14钛合金舱口外盖白斑问题

BT-14钛板为某产品舱口盖结构用材料,焊前检查时,发现钛板表面有数量不等的白色圆状斑点。文章从白斑的外观形貌、微观组织以及力学性能等方面进行分析,重点研究了白斑组织对钛板使用性能的影响,并提出后续生产中的预防措施。     

高密肋结构整体壁板VARI成型技术研究

高密肋壁板结构可采用真空辅助树脂渗透工艺（VARI）整体一次成型，但成型过程中存在加筋区预定型困难、树脂流动控制复杂等问题，导致制件尺寸精度和孔隙缺陷难以保证。为此，本文根据高密肋壁板多特征区域的特点，采用压实实验和注胶仿真模拟分析方法，优化预定型工艺参数、分区注胶方案。结果表明，选择定型剂浓度4%、温度120 ℃、压力0.1 MPa、保压时间60 min的压实参数，可有效保证纤维体积分数；采用线注射、线冒口与筋条点冒口结合的分级注胶方案，可实现壁板结构的有效浸润。优化设计的工艺方案与工装成功应用于某型号高密肋整体壁板VARI成型制造，验证了本文分析方法的有效性，研究结果对壁板类结构低成本整体成型技术在军民飞机上的应用与发展具有重要参考价值。     

Influence of sub boundary layer vortex generator height and attack angle on cross-flows in the hub region of compressors

It has been recently shown that Sub Boundary layer Vortex Generator (SBVG, abbreviated as VG hereafter) can suppress the Cross-Flow (CF), and therefore, can eliminate corner separation and increase aerodynamic loading when installed on the end wall inside middle-load compressor passages. However, when VGs are applied in high-load compressors, it is difficult to achieve ideal results. This is because the definition of the VG attack angle in the presence of CF in existing research is confusing, and the stronger CF in high-load compressors worsens the problem and results in an improper design and optimization range of VG attack angle. Therefore, this paper clarifies the definition of the VG attack angle in the presence of CF and reveals the CF controlling mechanism of VG on a flat plate. The differences in the flow phenomena around a VG both with and without CF are also studied. The numerical results show that a larger height or attack angle of the VG generates a greater CF suppression effect. However, the cross velocity increases when surmounting the primary vortex induced by the VG, except that this enhanced CF is less conspicuous for larger VG heights. Compared to the cases without CF, the VG suffers an additional loss because of the stronger separation and primary vortex loss caused by the CF.     

2219铝合金厚板TIG焊接头组织与力学性能研究

采用氦弧打底+氩弧填充、盖面的焊接工艺对2219-T87铝合金15 mm厚板进行TIG焊接试验，研究其焊缝成形和组织力学性能。结果表明，此工艺焊缝成形美观，无可见焊接缺陷，气孔抑制效果好，接头平均抗拉强度为278.22 MPa，平均断后延伸率为3.89%，接头平均强度系数达到58.94%。接头硬度整体表现为焊缝中心最低，从焊缝中心到母材呈现先增大后局部降低再增大的趋势；且焊缝中心填充层硬度高于打底层和盖面层。熔合区的微观组织为柱状树枝晶和胞状树枝晶，且垂直于熔合线生长，在靠近熔合区两侧出现了等轴细晶带。焊接接头断面有较多撕裂棱和韧窝，局部发现第二相粒子和微孔，其断裂机制为典型的韧性断裂。     

Higher-order vibration of thick composite and sandwich plates based on an alternative higher-order model

The transverse stretching vibration of thick sandwich plates, which is attributed to largely different stiffness at the adjacent layers, is a challenging issue, and efficient approach for such issue is less reported in the published literature. Thus, natural frequencies corresponding to stretching vibration modes are generally neglected in engineering design, which might impact structural safety as frequencies of the exciting force are close to transverse stretching vibration frequencies. This paper proposes an alternative higher-order model for dynamic analysis corresponding to the higher-order vibration modes. The proposed model is classified in the displacement-based equivalent single-layer theory, as the number of displacement parameters in the proposed model is independent of the layer number. The continuity of displacements and transverse shear stresses can be fulfilled at the interfaces between the adjacent layers of structures. To demonstrate the capability of the proposed model, typical examples are analyzed by utilizing the proposed model, the three-dimensional finite element method and the chosen higher-order models. By comparing with the exact three-dimensional elasticity solutions, it is found that the proposed model can yield more accurate natural frequencies corresponding to the higher-order displacement modes than the selected models. Moreover, the factors influencing reasonable prediction of the higher-order frequencies are investigated in detail, which can provide a reference for the accurate prediction of the higher-order frequencies.