星载大型网状天线非线性结构系统有限元分析

论述了大型网状可展开天线的非线性理论模型及其非线性模拟有限单元模型,并以一副4．2m天线为例进行了有限元建模分析,获得了这类天线的动力学振动特性。研究结果表明：拉索几何非线性和间隙接触非线性对大型网状天线系统的动力学特性具有较大影响。     

Nonlinear aeroelastic analysis of the folding fin with freeplay under thermal environment

The nonlinear aeroelastic behavior of a folding fin in supersonic flow is investigated in this paper. The finite element model of the fin is established and the deployable hinges are represented by three torsion springs with the freeplay nonlinearity. The aerodynamic grid point is assumed to be at the center of each aerodynamic box for simplicity. The aerodynamic governing equation is given by using the infinite plate spline method and the modified linear piston theory. An improved fixed-interface modal synthesis method, which can reduce the rigid connections at the interface, is developed to save the problem size and computation time. The uniform temperature field is applied to create the thermal environment. For the linear flutter analyses, the flutter speed increases first and then decreases with the rise of the hinge stiffness due to the change of the flutter coupling mechanism. For the nonlinear analyses, a larger freeplay angle results in a higher vibration divergent speed. Two different types of limit cycle oscillations and a multiperiodic motion are observed in the wide range of airspeed under the linear flutter boundary. The linear flutter speed shows a slight descend in the thermal environment, but the effect of the temperature on the vibration divergent speed is different under different hinge stiffnesses when there exists freeplay.     

一般线性阻尼系统的预解式以及模态正交性

本文研究一般线性阻尼系统的振动问题。仅假定系统的质量矩阵非奇异,将系统模态的加权正交关系式作了拓广,并利用相互等价的一次本征方程与二次本征方程间的转换关系,简捷地求得了预解式的各种模态展开式。     

系统测试性建模及验证方法

通过研究系统级测试性建模的基本原理,主要包括数学模型和图示模型,从结构、故障和测试三个方面给出了系统测试性建模的流程,最后给出了系统级测试性模型的验证方法,包括模型整体有效性验证、基于测试性分析报告的测试性模型验证等。     

基于交叉验证的陀螺仪温度漂移建模方法

根据k次交叉验证思想,分别在测量方差已知与未知的情况下引入了一种模型选择准则,该准则充分考虑了模型的拟合能力与预测能力,在获得极大似然估计的同时,避免了参数估计中的过拟合问题。利用这一准则,对陀螺仪误差系数温度漂移建模进行了分析,获得了温度漂移的最优多项式模型。并与传统的AIC准则、MDL准则进行对比,通过Monte Carlo仿真说明了该选择准则在样本较小的情况下具有更好的性质。     

Computational study of wing deformation and sting interference effects with the CAE-AVM test case

A modern transonic computational fluid dynamics test case is described in this paper, which is the Aerodynamic Validation Model (AVM) from the Chinese Aeronautical Establishment (CAE). The CAE-AVM is a representation of a modern transonic business jet aircraft with a design Mach number of 0.85. Numerical simulations for the AVM are conducted for two geometries: one baseline geometry, and one geometry that includes the applied model support system of the wind tunnel as well as the deformed wing shape that occurred during wind tunnel testing. The combined influence of wing deformation and model support interference on local and integral aerodynamic features is presented. Comparisons between CFD and experimental results are made; reasons of discrepancy between results from considered cases are analyzed.     

某型穿甲弹试验模态分析

本文通过试验模态分析的方法，得到了某型反坦克穿甲弹的结构参数，进而为了解该穿甲弹的动态特性以及改进弹体的结构提供了依据。     

基于有限元方法的并联机床模态分析

并联机床的模态分析有着重要的意义。本文针对3—HSS型并联机床,利用大型有限元软件ANSYS,对此并联机床进行了模态分析,分别获得了该机床的低阶固有频率及其对应的振型图,通过振动动画,分析了六阶模态的振动规律,找到了机床的薄弱环节,为机床的结构设计和动力学分析提供了依据。     

An adaptive sequential experiment design method for model validation

Efficient experiment design is of great significance for the validation of simulation model with high nonlinearity and large input space. Excessive validation experiment raises the cost while insufficient test increases the risks of accepting an invalid model. In this paper, an adaptive sequential experiment design method combining global exploration criterion and local exploitation criterion is proposed. The exploration criterion utilizes discrepancy metric to improve the space-filling property of the design points while the exploitation criterion employs the leave one out error to discover informative points. To avoid the clustering of samples in the local region, an adaptive weight updating approach is provided to maintain the balance between exploration and exploitation. Besides, the credibility distribution function characterizing the relationship between the input and result credibility is introduced to support the model validation experiment design. Finally, six benchmark problems and an engineering case are applied to examine the performance of the proposed method. The experiments indicate that the proposed method achieves satisfactory performance for function approximation in accuracy and convergence.     

航空发动机支点同心度的数值仿真及试验验证

为了在设计初期准确地分析支点同心度的大小,提出了一种基于蒙特卡洛的仿真计算方法,通过对影响因素进行分析,建立了支点同心度大小的数学表达式,讨论了各个影响因素的分布规律,并采用蒙特卡洛法进行了仿真计算,同时,对计算结果的正确性进行了试验验证。结果表明,该方法能够正确、方便、迅速完成支点同心度大小的计算,为优化设计参数、评估设计结果提供依据。