非圆截面弹体法向气动力估算方法研究

从位势理论出发 ,引进小扰动细长体理论中的部分思想 ,建立了任意截面弹体法向气动力的理论基础 ,推导出工程估算方法。该方法通过求解仅与截面形状有关系数 ,对已有的圆截面弹体气动力进行修正 ,很方便得到任意非圆截面弹体气动力特性。该方法预测结果与实验数据进行比较 ,具有较好精度     

X形测力元件标准测力仪

介绍一种配置了分辨力为 0 .1μm的光栅位移传感器作为测量装置的标准测力仪。     

试论预应力锚固技术在我国水利水电工程中的应用与发展

预应力锚固技术是一项潜力很大的工程措施，它效益显著，适应面广，既可对原有建筑物进行加固、补强，又可在新建工程中显示其独特的功能，而且由于须应力锚固具有传递拉应力的特殊优点，在国内外受到各部门的重视，取得了显著的成效。本文主要阐述了须应力锚固技术在我国水利水电工程中的应用和发展前景，并提出了预锚技术发展中值得研究及应注意的若干问题。     

基于XML的飞行仿真气动力模型存储格式

飞行仿真获取气动力/力矩的传统方法主要是将气动力模型硬编码在仿真程序进行求解。由于气动力模型和求解程序耦合,一旦修正或更换气动力模型,需要花费大量代价来重新构建仿真过程,无法满足现代飞行器仿真的需求。根据气动力模型树形结构的特点,提出了气动力模型树的概念并基于XML语言的特点设计了一种模型存储格式（MBX）来存储气动力模型树。MBX存储格式不仅提高了飞行仿真系统更换和修正气动力模型的效率,而且提高了气动力/力矩解算的通用性,使得气动力/力矩的求解能够被标准化。MBX存储格式作为气动力模型交换标准不仅能把不同部门交换气动力模型的时间从几周/人缩短至几天/人,也能加快气动力模型逼近飞机真实气动特性的进程。     

Five-axis flank milling tool path generation with curvature continuity and smooth cutting force for pockets

In order to ensure machining stability, curvature continuity and smooth cutting force are very important so as to meet the constraints of both cutting force and kinematics of machine tools. For five-axis flank milling, it is difficult to meet both of the constraints because tool path points and tool axis vectors interact with each other. In this paper, multiple relationships between tool path points and tool axis vectors with cutting force and kinematics of machine tools are established, and the strategies of corner-looping milling and clothoidal spirals are combined so as to find feasible solutions under both of the constraints. Tool path parameters are iterated by considering the maximum cutting force and the feasible range of the tool axis vector, and eventually a curvature continuity five-axis flank milling tool path with smooth cutting force is generated. Machining experimental results show that the conditions of cutting force are satisfied, vibration during the process of machining is reduced, and the machining quality of the surface is improved.     

Mechanistic identification of cutting force coefficients in bull-nose milling process

An improved method to determine cutting force coefficients for bull-nose cutters is proposed based on the semi-mechanistic cutting force model. Due to variations of cutting speed along the tool axis in bull-nose milling, they affect coefficients significantly and may bring remarkable discrepancies in the prediction of cutting forces. Firstly, the bull-nose cutter is regarded as a finite number of axial discs piled up along the tool axis, and the rigid cutting force model is exerted. Then through discretization along cutting edges, the cutting force related to each element is recalculated, which equals to differential force value between the current and previous elements. In addition, coefficient identification adopts the cubic polynomial fitting method with the slice elevation as its horizontal axis. By calculating relations of cutting speed and cutting depth, the influences of speed variations on cutting force can be derived. Thereby, several tests are conducted to calibrate the coefficients using the improved method, which are applied to later force predictions. Eventually, experimental evaluations are discussed to verify the effectiveness. Compared to the conventional method, the results are more accurate and show satisfactory consistency with the simulations. For further applications, the method is instructive to predict the cutting forces in bull-nose milling with lead or tilt angles and can be extended to the selection of cutting parameters.     

螺旋桨径向力风洞试验方法研究

螺旋桨飞机的研制设计过程中,必须了解和掌握动力系统对飞机气动特性的影响.螺旋桨动力系统对飞机的影响主要包括螺旋桨拉力和扭矩、气流斜吹螺旋桨产生的径向力以及滑流影响.螺旋桨径向力的风洞试验在国内尚属探索研究阶段,本文结合型号研制实际应用,对气流斜吹螺旋桨产生的径向力的机理和试验方法进行了研究探索,提出了一种以螺旋桨直接模拟法为基础的螺旋桨径向力风洞试验方法,并通过理论和试验方法完成了试验结果的相关性修正、全机对螺旋桨径向力的上洗等干扰修正,获得了可以满足工程研制使用的螺旋桨径向力数据,可为同类的螺旋桨飞机总体气动布局设计提供参考.     

火箭贮箱箱底瓜瓣拉深成形数值模拟

基于钣金成形仿真软件,数值模拟了火箭贮箱箱底瓜瓣零件的拉深成形,对瓜瓣拉深模具的拉延筋结构和压边力进行了优化,获得了半圆截面等效拉延筋结构的参数最优组合。     

5000m特大跨度悬索桥空气动力稳定性能理论研究

为研究5000m特大跨度悬索桥的三维空气动力稳定性能,首先实现了考虑竖向、侧向和扭转向三自由度自激力和静风荷载的三维全桥全模态颤振分析方法;其次根据风洞试验获得的气动参数对宽开槽和窄开槽两种方案进行了三维颤振性能分析,并与风洞试验和二维颤振分析结果进行了逐项对比,认为二维和三维颤振分析对于5000m悬索桥有可比性;然后实现了特大跨度悬索桥三维三重非线性静风性能分析方法,并对该方案进行研究发现5000m悬索桥的动力失稳先于静力失稳出现,静风稳定性能不控制设计.最终研究结论:从三维分析的角度看,中央开槽达到足够宽度的方案与窄开槽但设稳定板的方案都能给跨度达5000m的悬索桥提供足够高的颤振失稳临界风速,并能满足世界上绝大多数台风区的要求,5000m特大跨度悬索桥的设计由空气动力稳定性能控制.