飞机结构关键件设计改进后的疲劳寿命评定技术

 结合某型飞机重要疲劳关键件起落架梁设计改进后的寿命评定,建立了在不进行全尺寸试验的情况下,对设计改进结构进行寿命评定的方法。即在结构改进前后关键疲劳薄弱部位细节应力分析的基础上,通过该疲劳关键部位的模拟试件在改进前后应力谱下的寿命分析和疲劳对比试验,综合评定结构改进后的寿命增加系数,参照改进前该结构的全尺寸疲劳试验结果,确定设计改进后该关键件的疲劳寿命。用上述方法完成了对某型飞机重要疲劳关键件起落架梁改进后的寿命评定,其结果也应用到了该型飞机结构的定延寿。     

Analysis Approach to Durability Based on Material Initial Fatigue Quality and S-N Curve

Based on probabilistic fracture mechanics approach, a new concept of material initial fatigue quality (MIFQ) is developed. Then, the relation between S-N curve and crack propagation curve is studied. From the study, a new durability analysis method is presented. In this method, S-N curve is used to determine crack growth rate under constant amplitude loading and evaluate the effects of different factors on durability and then the structural durability is analyzed. The tests and analyses indicate that this method has lower dependence on testing, and higher accuracy, reliability and generality and is convenient for application.     

机身加筋壁板复合加载损伤容限性能试验

为研究机身加筋壁板裂纹扩展规律和剩余强度特性,按照机身壁板承受内压和轴拉载荷边界条件的要求,设计并制造试验装置,通过静力试验验证了试验方案的正确性和合理性。损伤容限试验结果表明:纵向裂纹沿直线扩展,左右两侧裂纹扩展对称性较好,半裂纹长度小于80mm时呈缓慢裂纹扩展特性,该裂纹可检性好,检出概率较高;纵向裂纹失稳扩展导致最终破坏,在最远的框处呈现"T"字状的裂纹扩展破坏模式。研究结果可为新型客机机身结构损伤容限分析与设计提供数据支持。     

地月系共线平动点探测器的星上轨道预报问题

针对定点在地月系共线平动点附近运动的探测器,研究其轨道预报问题,并探讨了星上外推预报时的力模型简化问题。首先定量分析了共线平动点L1和L2附近探测器的受力情形;然后构造了真实力模型下这些点附近的目标轨道并研究了其误差传播规律,指出这类轨道相比一般卫星轨道预报的不同特征;最后结合星上有限的计算和存储资源限制探讨了力模型的简化问题。此项工作可为定点在平动点附近的探测器的星上预报提供参考。     

A novel robust aerodynamic optimization technique coupled with adjoint solvers and polynomial chaos expansion

Uncertainty is common in the life cycle of an aircraft, and Robust Aerodynamic Optimization(RAO) that considers uncertainty is important in aircraft design. To avoid the curse of dimensionality in surrogate-based optimization, this study proposes an adjoint RAO technique called ‘‘R-Opt”. Polynomial Chaos Expansion(PCE) is coupled with the R-Opt technique to quantify uncertainty in the responses of the target(including its mean and standard deviation). Only one process of PCE model construction i...     

基于数据深度加权的卫星轨道确定技术

将统计数据深度理论应用到抗差估计中,用数据深度作为衡量残差在整个样本集中地位的统计量.提出了基于数据深度加权的抗差估计算法.考虑到天基观测结构的复杂性,设计了天基测控的误差传播因子,并构造了模型结构权对定轨模型结构进行加权.在此基础上构造了基于数据深度加权和模型结构加权的M估计算法,证明了该算法的高崩溃点特性.设计了天基测控模式下的轨道确定仿真试验,试验结果表明该估计方法能有效抑制观测粗差和模型结构误差的影响,并且能显著提高定轨算法的鲁棒性.     

Introduction of fretting-contact-induced crack closure: Numerical simulation of crack initiation and growth path in disk/blade attachment

Fretting fatigue crack initiation and growth in titanium alloy dovetail assembly was investigated by the Finite Element Method(FEM). Firstly, contact stress was calculated precisely with an elastic–plastic material model. Secondly, the location and angle of crack initiation were determined by the parameter of the maximum shear stress range on the critical plane, and the angle of crack growth was predicted by the Maximum Tangential Stress(MTS) criterion, which showed agreement with experimental observation. Finally, the fretting-contact-induced crack closure behavior was simulated by the node release technique in software ABAQUS with both elastic and elastic–plastic material models. The simulation shows that the variation of the contact status between fretting surfaces will result in crack closure even for the elastic material model. The fretting crack closure ratio decreases as the crack grows out of the contact area and it has great impact on the effective range of Stress Intensity Factor(SIF) as well as the crack growth rate.     

切向流条件下短舱单/双自由度声衬实验

使用声学流管实验台对一件双自由度（DDOF）声衬和一件单自由度（SDOF）声衬的声学特性进行对比测试。在最大0.26Ma切向流速和管道的截止频率之下,采用直接提取法SFM测得声衬的无量纲声阻抗,同时使用双传声器分解驻波法计算声衬安装段管道的传声损失（TL）和吸声系数等,基于声能量理论的传声损失可直观地展示两件被测声衬的吸声性能差异。结果表明在流管声学实验台上,相较于单自由度声衬,双自由度声衬能够有效拓宽声衬的吸声频带,同时共振频率处的传声损失不如单自由度声衬,切向流也会明显改变声衬的共振频率、弱化吸声能力。基于声能量的传声损失和吸声系数也为无等效阻抗的非均匀结构声衬提供了一种声学性能评估方法。     

水下无线传感器网络目标定位算法

提出了一种基于目标位置的定位转换算法,通过对水下声波传播衰减的研究,推导出距离与声强度的公式,进一步由节点接收到目标强度信息计算出节点与目标的距离进行定位。当目标处在水下传感器网络内部时,根据节点接收到信号强度的大小,进行加权质心定位算法。为解决三维坐标系下目标深度的计算,通过在海面设置大功率骨干节点,通过主动探测声呐测得目标的距离与角度,从而计算出目标深度。仿真验证表明,本文算法的有效性。     

基于电涡流位移传感器的钛合金叶片振动疲劳试验研究

为了研究钛合金叶片振动疲劳特性,基于电磁振动测试平台和非接触式电涡流位移传感器,开展了试验工装和试验程序设计.通过本文的传感器标定和振动应力标定方法研究,发展了基于电涡流位移传感器的非接触测量式钛合金叶片振动疲劳试验手段,进而完成了疲劳考核试验和裂纹扩展试验,研究了裂纹长度和固有频率随疲劳循环数累积的变化规律.试验结果...