压剪联合载荷作用下复合材料壁板屈曲及后屈曲性能计算与优化方法研究

复合材料壁板被广泛用于航空航天结构,在外部复杂工况下壁板通常会受到面内压剪载荷的联合作用,其屈曲及后屈曲响应直接影响此类结构的极限承载能力。为此,基于改进的Koiter摄动理论,提出一种能够快速精确地开展复合材料壁板非线性屈曲分析的摄动有限元降阶方法,然后计算获得壁板的屈曲/后屈曲性能指标,即非线性屈曲载荷、后屈曲承载刚度以及承载刚度残余系数,最后将摄动降阶方法嵌套到复合材料铺层优化的分析流程中,获得压剪联合载荷下各种屈曲/后屈曲性能指标的最优铺层信息。数值算例验证了所提出方法的高效性和有效性。     

Aeroelastic effect on aerothermoacoustic response of metallic panels in supersonic flow

A finite element formulation is presented for the analysis of the aeroelastic effect on the aerothermoacoustic response of metallic panels in supersonic flow. The first-order shear deforma-tion theory (FSDT) and the von Karman nonlinear strain-displacement relationships are employed to consider the geometric nonlinearity induced by large deflections. The piston theory and the Gaus-sian white noise are used to simulate the mean flow aerodynamics and the turbulence from the boundary layer. The thermal loading is assumed to be steady and uniformly distributed, and the material properties are assumed to be temperature independent. The governing equations of motion are firstly formulated in structural node degrees of freedom by using the principle of virtual work, and then transformed and reduced to a set of coupled nonlinear Duffing oscillators in modal coor-dinates. The dynamic response of a panel is obtained by the Runge-Kutta integration method. The results indicate that the increasing aeroelastic effect can lead the panel vibration from a random motion to a highly ordered motion in the fashion of diffused limit cycle oscillations (LCOs), and remarkably alter the stochastic bifurcation and the spectrum of the aerothermoacoustic response. On the other hand there exists a counterbalance mechanism between the external random loading and the aeroelastic effect, which mainly functions through the nonlinear frequency-amplitude response. It is surmised that the aeroelastic effect must be considered in sonic fatigue analysis for panel structures in supersonic flow.     

滤基的收敛及其应用

引入滤基和滤基收敛的概念，解决了在一般拓扑空间中讨论点列极限的不能问题，并进一步用滤基的收敛统一了数学分析中的各种极限和黎曼积分的滤基极限。     

液体火箭发动机音叉式涡轮叶盘振动特性研究 (液体火箭推进专刊)

某液体火箭发动机采用整体叶盘音叉式涡轮转子，该转子盘-轴根部圆角试车考核中曾多次出现裂纹故障。为推断裂纹产生原因，通过数值计算及模态实验获取了该转子受力状态、振型、阻尼比等结构振动特性。结合振动信号分析，将裂纹故障原因聚焦到叶盘的二节径型振动。通过高频速变压力测量，得到涡轮流场内压力脉动数据，间接获取了该转子工作状态下的振动特性。试验表明被测涡轮转子流场通道内，分频幅值最大压力脉动对应涡轮转子2节径前行波振动，幅值约为11KPa。分析确定涡轮叶盘二节径振动是故障产生的主要原因。     

A model-based prognostics method for fatigue crack growth in fuselage panels

This paper proposes a model-based prognostics method that couples the Extended Kalman Filter (EKF) and a new developed linearization method. The proposed prognostics method is developed in the context of fatigue crack propagation in fuselage panels where the model parameters are unknown and the crack propagation is affected by different types of uncertainties. The coupled method is composed of two steps. The first step employs EKF to estimate the unknown model parameters and the current damage state. In the second step, the proposed efficient linearization method is applied to compute analytically the statistical distribution of the damage evolution path in some future time. A numerical case study is implemented to evaluate the performance of the proposed method. The results show that the coupled EKF-linearization method provides satisfactory results: the EKF algorithm well identifies the model parameters, and the linearization method gives comparable prediction results to Monte Carlo (MC) method while leading to very significant computational cost saving. The proposed prognostics method for fatigue crack growth can be used for developing predictive maintenance strategy for an aircraft fleet, in which case, the computational cost saving is significantly meaningful.     

吸气式高超声速飞行器纵向机动飞行的鲁棒线性变参数控制

针对一个吸气式高超声速飞行器模型,研究了其鲁棒变增益控制问题。为处理对建模误     

加筋板中超高速撞击声发射源定位方法

加筋板是航天器上的常用结构。为研制基于声发射技术的在轨感知系统,需要研究加筋板中声发射波传播规律及撞击源定位方法。文章测定了断铅信号在加筋板中的传播速度,对沿不同方向传播的波速进行了比较;通过有限元仿真,研究了筋体几何尺寸对板中声发射信号传播规律的影响。试验与仿真的结果表明:筋体对信号压缩波波速影响较小,但会造成信号第一幅值的衰减,在传感器布局设计时需要考虑到该因素。将加筋板中声发射信号传播速度取为沿不同方向传播波速的平均值,可将源定位问题转化成求取函数最小值的优化问题,在加筋板上对断铅波源和超高速撞击波源进行定位效果较好。     

曲线片型加筋壁板的稳定性优化设计

加筋板作为一种典型结构被广泛应用于航空航天领域,为进一步拓展直筋加筋板的设计空间,提出了一套基于ModelCenter设计优化环境、Catia和Abaqus的曲线片型加筋板优化设计框架.一方面,筋条曲线采用参数数目可变的等距剖分三次B样条插值函数,为曲筋加筋板提供了足够大的优化空间.另一方面,采用筋条加载端相聚和筋条垂直于板边2种方式来解决曲线片型加筋板的筋条加载问题,从而产生了一些新的曲筋加筋板布局形式.优化结果表明,对于单向载荷主导的加筋板,曲筋加筋板相对于直筋加筋板稳定性改善不大.但对于复杂组合载荷,曲筋加筋板获得了比直筋加筋板更好的稳定性.      

基于超梁降阶模型的蒙皮加筋圆柱壳频率分析

在基于梁平截面假设的复杂结构动力模型降阶方法基础上,文章提出了建立梁超单元和超梁降阶模型的方法。通过对比考虑剪切变形的Timoshenko梁单元刚度阵,给出了梁超单元刚度矩阵的修正方法,提高了超梁降阶模型的计算精度。以蒙皮加筋圆柱壳为例,对比了超梁降阶模型与几种等效梁模型的频率分析结果。结果表明,超梁降阶模型建立方法灵活简单,具有较高的计算精度,能够为火箭结构动特性分析提供参考。     

铆接加筋板应力强度因子计算中几个问题的研究

给出了采用J积分法计算加筋板应力强度因子时选择积分回路的方法;同时给出了采用刚度导数法计算加筋板应力强度因子时刚度导数的计算方法;另外,还对模拟铆钉连接作用的3种方法进行了初步研究。