挠性板弯折的数值分析方法

基于材料力学中梁弯曲的挠曲线方程,利用数值积分方法计算特定弯矩和剪力时挠性板的弯折曲线,同时利用曲线积分计算挠性板的长度,最终确定在给定长度和跨度情况下挠性板的弯折曲线以及对应的弯矩和剪力。利用有限元软件对相同模型在同一条件下进行模拟分析。将数值计算与有限元分析结果对比,发现两者变形曲线非常吻合,弯矩和剪力数值精度满足实际工程需求。基于上述数值计算方法,可以对挠性板弯折的各种参数进行分析和预估,对实际工程应用具有重要的指导意义。     

Effects of surface roughness on the aerodynamic performance of a high subsonic compressor airfoil at low Reynolds number

The aerodynamic performance of compressor airfoil is significantly affected by the surface roughness at low Reynolds number (Re). In the present study, numerical simulations have been conducted to investigate the impact of surface roughness on the profile loss of a high subsonic compressor airfoil at Re = 1.5 × 10⁵. Four roughness locations, covering 10%, 30%, 50% and 100% of the suction surface from the leading edge and seven roughness magnitudes (R_a) ranging from 52 to 525 μm were selected. Results showed that the surface roughness mainly determined the loss generation process by influencing the structure of the Laminar Separation Bubble (LSB) and the turbulence level near the wall. For all the roughness locations, the variation trend for the profile loss with the roughness magnitude was similar. In the transitionally rough region, the negative displacement effect of the LSB was suppressed with the increase of roughness magnitude, leading to a maximum decrease of 14.6%, 16.04%, 16.45% and 10.20% in the profile loss at R_a = 157 μm for the four roughness locations, respectively. However, with a further increase of the roughness magnitude in the fully rough region, the stronger turbulent dissipation enhanced the growth rate of the turbulent boundary layer and increased the profile loss instead. By comparison, the leading edge roughness played a dominant role in the boundary layer development and performance variation. To take fully advantage of the surface roughness reducing profile loss at low Re, the effects of roughness on suppressing LSB and inducing strong turbulent dissipation should be balanced effectively.     

飞机飞行姿态系统控制律设计分析及仿真

飞机的飞行性能与其相关系统控制律设计密切相关.基于飞机俯仰姿态系统基本状态及工作原理,构建了飞机比例式/积分式姿态系统结构框图,对比例式/积分式控制律进行设计,分析了 2种控制律的演变思路及其优缺点.大量仿真数据显示:在比例式/积分式控制律传动比选取恰当时,飞机姿态系统品质良好,具有较好的动态和稳态性能.     

耗散大气中风场对内重力波传播的影响

使用考虑大气耗散的射线跟踪算法,计算了风场作用下重力波的传播情况.结果表明,风场对快速重力波分量影响较小,但对反射和传播区域的慢速波的影响较大,表现在顺风时使反射区范围缩小,逆风时使反射区范围扩大.在传播区,顺风场使慢速波分量的传播距离变小,传播高度降低,而逆风则使慢速重力波分量的传播距离明显增大,传播高度上升.分析表明,重力波传播的丰富多样性是由风场对波的衰减和反射等滤波作用引起的.     

一类有理函数的不定积分

目的为了简单地求解有理函数P(x)/Q(x)的积分;方法对∫P(x)/(x-a)mdx∫,P(x)/(x-a)m(x-b)ndx型有理函数的积分给出一般计算公式;结果通过实例说明该公式简捷、对称,避免以往待定系数法带来的诸多不便;结论具有较强的实用性。     

高温合金复杂薄壁零件多道次充液拉深技术

充液拉深(HDD)技术是薄壁零件成形的一种有效方法.针对难成形,复杂薄壁结构的某型发动机高温合金板材零件,通过分析锥面自由悬空区的起皱失稳现象,设计了多道次充液拉深结合刚模成形的技术方案,并建立了有限元分析模型.基于有限元模拟和工艺验证试验,研究了预成形高度和终成形液室压力等关键工艺参数对零件最终成形质量的影响,探讨了...     

纤维增强复合材料币状I型裂纹桥联问题

利用平面等效方法，将轴对称币状裂纹问题转化平面裂纹问题，由此给出复合材料内币状Ⅰ型裂纹的桥联积分控制方程。对权函数法应用于求解币状裂纹问题的可行性提出质疑，并给出修正的建议。然后对币状Ⅰ型裂纹桥联问题给予了断裂力学分析。利用一种新的分段插值方法求解了桥联积分控制方程。针对该积分程提出了一种近似分析解法，其结果与数值结果符合得相当好。     

求极限的若干技巧

在求极限基本方法的基础上，阐述了运用泰勒公式，导数定义，定积分先化简等技巧来求极限。     

飞机整体壁板广义槽分层识别方法及其实现算法(英文)

To automatically obtain a machining area in numerical control （NC） programming, a data model of generalized pocket is established by analyzing aircraft integral panel characteristics, and a feature recognition approach is proposed. First, by reference to the practical slice-machining process of an aircraft integral panel, both the part and the blank are sliced in the Z-axis direction; hence a feature profile is created according to the slicing planes and the contours are formed by the intersection of the slicing planes with the part and its blank. Second, the auxiliary features of the generalized pocket are also determined based on the face type and the position, to correct the profile of the pocket. Finally, the generalized pocket feature relationship tree is constructed by matching the vertical relationships among the features. Machining feature information produced by using this method can be directly used to calculate the cutter path. The validity and practicability of the method is verified by NC programming for aircraft panels.     

二维连续型随机变量函数的概率密度

本文利用分布函数与概率密度之间的关系,以曲线积分为工具,导出随机变量Z=g(X,Y)的概率密度的一般公式。然后对概率统计中的一些重要分布给予比较简单的证明。