飞机进气道流场压力畸变数据采集与处理系统

论述了一个用于飞机进气道出口流场动态压力畸变测试分析的高速数据采集及实时存储处理系统的研制背景、国内外情况、主要技术难题及已完成系统的组成、功能和技术性能，列出了研制中涉及到的若干关键技术     

Galileo系统动态滤波的研究

提出一种Galileo动态定位滤波的方法。该方法从Galileo系统接收机输出的定位结果入手，将各种误差因素的影响等效为一个总误差，对Galileo系统接收机的机动载体加速度采用当前统计模型，利用线性卡尔曼滤波器进行动态定位数据的处理，并将次优加权自适应卡尔曼滤波算法应用到Galileo系统动态定位中。该模型简单，实时性好，滤波后定位精度得到提高。     

动态系统的抗差Kalman滤波及其影响函数

离散历元动态测量及其相应的动态模型可能存在异常，若在数据处理不中考虑对这些异常的特别处理，则动态模型参数估值及其所提供的动态信息将极不可靠。对于GPS动态定位数据的处理，按抗差估计原理，构造了状态向量和观测值对模糊度的影响函数，并由此建立了动态GPS定位的抗差Kalman滤波解法。实际计算验证了该方法的实用性和可靠性。     

纤维增强复合材料高应变率拉伸实验技术研究

本文对基于分离Hopkinson杆的反射式纤维增强复合材料动态拉伸实验技术进行了研究讨论。对加载杆中可能影响拉伸应力波波形实验分析的所有干扰波进行了较系统地定量分析研究,认为产生于试样端头与加载杆界面处的两主要干扰波对希望得到的应力波的测量和判别具有严重的不利影响,因此拉伸实验设计必须避开该主干扰波的重叠影响。文中对动态拉伸实验装置、实验要求及信号采集等作了分析。根据对试验结果的分析,针对复合材料动态拉伸实验技术的若干问题提出了一些处理方法和建议,诸如干扰波的规避、冲击信号合理测点的选取、加载杆长度匹配、复合材料拉伸试样的设计要求以及加载连接等问题。这些方法和建议包括在加载杆特定段上贴应变片,考虑到实验的准确性一般不用反射波进行数据计算处理,尽量缩短试样标距等。     

动态光弹性方法的主应力分离的研究

本文提出了动态光弹性、动态焦散线实验方法同边界元法结合的混合法，并用这种方法解决了动态光弹性主应力分离的问题，首先对现有的多火花高速摄影系统进行了改造，在动态实验过程中，成功地得到了不同瞬时的清晰的动态光弹性的等差线条纹和动态焦散线系列图像，这样，便可提取不同瞬时的边界应力值、全场主应力差值及边界上的外载。继而提出用Ｌａｐｌａｃｅ变换域上的边界元法来求解在冲击载荷作用下二维弹性模型全场的主应力和。最后，以受冲击载荷作用的圆盘为例，进行实验及边界元法计算，得到了分离的主应力场。     

一个新的高速大容量数据采集及实时存储处理系统的构想和实现

本文论述了一个用于飞机进气道流场测试分析的高速大容量数据采集及实时存储处理系统研制中提出的技术难题，系统的构想和实现，功能和应用效果，并展望了它的广泛应用前景     

基于贝叶斯方法的模态参数识别的不确定度分析

振动模态分析和模态参数识别是动态测试的一个重要研究方向。模态参数在模型的修正、响应的预测、系统的健康检测及控制等方面有着重要的作用。但动态测试的不确定度分析,尤其是模态参数的不确定度的研究还十分缺乏。本文主要基于贝叶斯方法,通过傅立叶变换(FFT)建立时域数据和频域数据之间的对应关系。根据共振频带内的多个模态的响应数据得到相对应的模态参数,优化得到模态参数的最佳估计值,评定模态参数识别的不确定度。在固支梁的模态实验中,加速度传感器采集环境激励中的振动数据,运用贝叶斯法进行处理得到模态参数的最佳估计值。在此基础上,通过模态参数的最佳估计值,以及仪器的检定报告数据,结合合成不确度分析方法,系统分析了模态参数识别的不确定度。     

平面应力型动态断裂韧度的一种测试方法

1 引言由于试验技术及动态断裂分析上的困难,材料动态断裂韧度的表征与测试方法至今仍然很不成熟,尤其对于弹塑性材料,进展更为缓慢.早期的动态断裂韧度测试多半是在落锤式试验机上进行的,且用表征和测量准静态断裂韧度的方法来处理试验数据,从而     

高速电梯机械系统KED分析与动态性能优化

建立了高速电梯机械系统的运动微分方程，对运动微分方程提出了基于ＫＥＤ分析的求解方法。为了改善高速电梯动态性能，在电梯机械系统ＫＥＤ分析的基础上，提出了一种以降低轿厢最大振动加速度幅值为目标的动态性能优化方法。用本文方法对ＴＫＪＴ１００／１．６－ＪＸＰＣ型电梯进行了ＫＥＤ分析与动态性能优化，得到了令人满意的结果。     

循环神经网络在智能天平研究中的应用

激波风洞地面试验对高超声速飞行器高焓气动特性研究至关重要, 而高精度气动力测量是其中的关键技术. 在脉冲型激波风洞中进行测力试验时, 风洞起动时流场瞬间建立, 对测力系统会产生较大的冲击. 测力系统在瞬时冲击作用下受到激励, 系统的惯性振动信号在短时间内无法快速衰减, 天平的输出信号中会包含惯性振动干扰量, 导致脉冲型风洞测力试验精准度的进一步提高遇到瓶颈. 为了解决短试验时间内激波风洞快速准确测力问题, 发展高精度的动态校准技术是提升受惯性干扰天平性能的关键方法. 因此, 本文采用循环神经网络对天平动态校准数据进行训练和智能处理, 旨在消除输出动态信号中的振动干扰信号. 本文对该方法进行了误差分析, 验证了该方法的可靠性, 并将该方法应用于激波风洞测力试验中, 切实有效降低了惯性振动对天平输出信号的干扰影响. 根据智能模型的样本验证分析, 各分量载荷相对误差比较小, 其中高频轴向力分量处理结果的相对误差约1%. 在风洞试验数据验证中, 也得到了比较理想的结果, 同时与卷积神经网络模型处理的结果进行了对比分析.      

SH waves of an arbitrary frequency in random fibrous composites via the K-K relations

The Kramers-Kronig relations method is shown to provide the dynamic response of a random fibrous composite for the full frequency interval, 0 < ω < ∞. The method yields a conceptually simple way of deriving the dynamic response of random composites if the approximation of an effective homogeneous medium is adopted.It is shown that some of the widely accepted theories may violate the causality and/or linearity of the effective medium. Extensive numerical data are given as well as comparison with other theories and experiments.     

Acoustic waves in a cylindrical duct with periodically varying cross section

The null field approach is used to study the propagation of acoustic waves in a rotationally symmetric hard-walled duct with a periodically varying cross section. For a radius that varies sinusoidally along the axial distance, numerical computations give the axial wave number and the passbands and stopbands of the modes of the duct. In particular, small passbands are seen to exist even for very large variations in radius, and probably all the way to the point where the duct is cut off. We also present some plots which show the pressure pattern inside the duct.     

谐波平衡法在动导数快速预测中的应用研究

谐波平衡法以傅里叶级数展开为基础,将周期性非定常流场的非定常求解过程转化为几个定常流场的耦合求解过程,并通过重建得到整个流场的非定常过程. 建立了基于谐波平衡法的动导数快速预测方法,数值模拟了超声速带翼导弹俯仰的动态流场,并通过积分法获取了俯仰动导数,与实验结果吻合很好;且在同等计算精度下,谐波平衡法的计算效率是双时间步方法的13 倍. 应用谐波平衡法研究了较大范围内减缩频率对俯仰动导数的影响规律. 研究发现,对于本外形,当减缩频率降低到一定值后,俯仰动导数的值迅速变化,甚至发生变号;对此现象产生的原因进行了深入分析,并通过对导弹自激俯仰运动的数值模拟验证了该结果. 此外,针对大攻角条件下动态流场非线性强的特点,开展了谐波平衡法在大攻角下的适用性研究. 结果表明,谐波平衡法在大攻角下也能取得很好的计算结果.      

某调距导管桨系泊工况水力性能和流激直发声预报

采用经验证的计算流体力学方法,对某艏辅推调距导管桨设计螺距和系泊工况螺距的水动力性能进行了有效预报,并对系泊工况装船桨流激噪声进行了分析。系泊工况下,由于导管桨的抽吸作用在导管外壁近壁面区域存在与导管内部流动方向相反的逆向流动,且导管桨尾流场速度梯度分布不均匀、流动紊乱,此时桨叶与导管的推力之比约为1.2∶1。系泊工况船+桨的瞬态流场脉动信息表明,导管桨各部件噪声源强度均表现出从1倍到4倍叶频依次下降的规律,最强幅值集中在桨叶导边和导管内壁;在远场声源级频谱曲线中轴向测点线谱较高峰值位置体现出导管桨进流流场的流动特性。对比分析该艏辅推整体和各部件宽带声源级指向性,可知旋转部件(桨叶、桨榖)对总噪声级的贡献较大,静止部件是径向测点噪声的主要贡献源。     

Recent advances in wave energy converters based on nonlinear stiffness mechanisms

Wave energy is one of the most abundant renewable clean energy sources, and has been widely studied because of its advantages of continuity and low seasonal variation. However, its low capture efficiency and narrow capture frequency bandwidth are still technical bottlenecks that restrict the commercial application of wave energy converters (WECs). In recent years, using a nonlinear stiffness mechanism (NSM) for passive control has provided a new way to solve these technical bottlenecks. This literature review focuses on the research performed on the use of nonlinear mechanisms in wave energy device utilization, including the conceptual design of a mechanism, hydrodynamic models, dynamic characteristics, response mechanisms, and some examples of experimental verification. Finally, future research directions are discussed and recommended.

     

动态结构系统的频率可靠性稳健设计研究

针对随机动态结构系统振动问题进行研究,提出了系统避免共振的频率可靠性分析方法;在此基础上,推导出频率可靠性灵敏度计算公式,研究设计参数的改变对随机动态结构系统频率可靠性的影响,给出各随机参数可靠性灵敏度的变化规律;并将频率可靠性及其灵敏度分析方法与可靠性优化设计方法相结合,提出了频率可靠性稳健优化设计方法,同时以一简化的两自由度的车身-车轮-路面关系的1/4离散系统模型为例,对该模型进行了频率可靠性稳健设计的研究,其理论计算结果与工程实际情况完全一致,也说明了所提方法的有效性和实用性,为随机动态结构系统的设计、制造、使用和评估提供了合理和必要的理论依据。     

Amplitude dependence of filler-reinforced rubber: Experiments,constitutive modelling and FEM – Implementation

The focus of the present paper is the experimental investigation, the constitutive representation and the numerical simulation of the amplitude dependence of filler-reinforced elastomers. A standard way to investigate the dynamic properties of viscoelastic materials is via the dynamic modulus which is obtained from stress signals due to harmonic strain excitations. Based on comprehensive experimental data, an amplitude-dependent constitutive model of finite viscoelasticity is developed. The model is based on a modified Maxwell chain with process-dependent viscosities which depend on additional internal state variables. The evaluation of this thermodynamically consistent model is possible in both the time domain, via stress-time signals, and in the frequency domain, via the dynamic modulus. This property is very profitable for the parameter identification process. The implementation of the constitutive model into the commercial finite element code ANSYS with the user-programmable feature (UPF) USERMAT for large deformations in updated Lagrange formulation is presented. This implementation allows simulating the time-dependent behaviour of rubber components under arbitrary transient loading histories. Due to physical and geometrical nonlinearities, these simulations are not possible in the frequency domain. But, transient FEM computations of large loading histories are sometimes not possible in an acceptable time. In the context of the parameter identification the fundamental ideas are presented, how this problem has been solved. Transient FEM simulations of real rubber components are also shown to visualize the properties of the model in the context of the transient material behaviour.     

Effective mass density of rigid sphere-reinforced elastic composites

An analytical model is presented to study metaelastic dynamic behaviors of rigid sphere-reinforced elastic random composites. The model is based on the concept that the deviation of the displacement field of embedded rigid spheres from the displacement field of the composite is responsible for novel metaelastic dynamic behaviors of stiff sphere-reinforced composites. Compared to the existing models, the present model offers a simple general method to analyze various 3D metaelastic dynamic problems of rigid sphere-reinforced random composites, and its validity and efficiency are demonstrated by comparing the predicted results with known experimental or numerical data on several typical steel/glass/lead-polymer composites. Several basic dynamic problems of rigid sphere-reinforced composite beams and rods are investigated, and some metaelastic dynamic phenomena (such as vibration isolation, localized buckling, and natural frequency within the bandgap caused by an attached concentrated mass) of stiff sphere-reinforced composites are demonstrated.

     

Investigation of the linear flow regime of commercial polymers by numerical conversion of MVM creep measurements

A new experimental and numerical method has been developed to characterize the terminal flow behavior of polydisperse, commercial grade polymer melts over a wide dynamic range of time/frequency scales. Experimentally, an MVM rheometer specifically designed for long time scale (t 10⁴ s) creep measurements is used to measure the creep compliance of three commercial polymers: two high density polyethylenes and one polystyrene. The long time scale MVM creep data are complemented in the short time scale regime by creep data from an industrial plate-plate rheometer. The time-dependent creep data is combined and converted to a discrete retardation spectra using a nonlinear regularization algorithm to address the ill-posed nature of the interconversion. The retardation spectrum is analytically converted to dynamic moduli and compared with independently measured dynamic moduli. In the overlapping frequency region, calculations and measurements show excellent agreement and the combined data span a much larger dynamic range than either independent data set. The calculated and measured dynamic moduli data are combined and a retardation spectrum with a vastly expanded dynamic range is generated. Combining long time scale MVM creep compliance data and dynamic moduli data exploits the intrinsic sensitivities of controlled strain and controlled stress rheological experiments and is a powerful means to greatly expand the experimentally accessible dynamic range of time/frequency. This approach is particularly useful for commercial polymers with broad molecular weight distributions and commensurately large distributions of relaxation times.     

The application of interferometric techniques to the nondestructive inspection of fiber-reinforced materials

A method for increasing the sensitivity of dynamic materials evaluation (DME) to localized damage in fiber-reinforced composites was examined. To obtain this improved sensitivity, different aspects of DME were examined. These included an increase in the frequency used to evaluate the dynamic properties, utilization of mode-shape information and different procedures for evaluating the experimental data.The extent of the internal damage was determined using measured changes in the dynamic properties of the system (loss factor, dynamic stiffness and mode shape). To obtain the response information at higher frequencies a modalanalysis system was built around the performance characteristics of a laser doppler vibrometer (LDV) and an electronic speckle pattern interferometer (ESPI). These two devices provided complementary information for the determination of the dynamic characteristics of each vibration mode. With this system, damage-induced changes in the dynamic characteristics of composite materials were measured at frequencies up to 10 kHz.The results of this study showed the following. (1) Torsion modes provide the most sensitivity to localized internal damage. (2) The evaluation of higher frequency NDI data requires the ability to correlate the measured loss factor and resonant frequencies with the actual mode shape. (3) The data obtained over the frequency range of the test could be reduced to a series of slopes that provide a sensitive indication of the material condition. (4) The sensitivity of the dynamic method to localized damage is limited by the measurement of the loss factor.