经典参数在多结构耦合系统统计能量分析中的应用

直接和间接耦合损耗因子是用统计能量分析方法研究多结构耦合系统振动响应的关键参数，也是急待解决的问题之一。本文提出了用经典统计能量分析参数计算多结构耦合系统的直接和间接耦合损耗因子的方法。其优点是利用经典统计能量分析已取得的成果解决了多子结构耦合系统的问题。文中首先推导了经典的双子结构耦合系统的耦合损耗因子和结构参数的关系，然后研究了多子结构耦合系统的直接和间接耦合损耗因子与结构参数的关系，最后推导得到多子结构耦合系统的直接和间接耦合损耗因子和经典统计能量分析中的耦合损耗因子的关系。以三子结构耦合系统为例进行了实验测量，直接、间接耦合损耗因子和结构振动响应的实验测量值与理论预测结果吻合较好。     

不可分离结构的损耗因子测量研究

提出对不可分离结构内损耗因子和耦合损耗因子的测量方法。对于内损耗因子测量，针对实际工程中子结构不可分离的问题，提出了用总损耗因子代替内损耗因子的方法。对于耦合损耗因子测量，利用已测得的内损耗因子结合稳态振动实验测得的能量可计算出结构间耦合损耗因子。同时分析了耦合损耗因子大小对总损耗因子代替内损耗因子差值的影响。仿真结果表明，当耦合损耗因子远小于内损耗因子时，内损耗因子和总损耗因子近似相等。对双圆柱壳耦合结构进行了实验验证，实验结果证明了该方法的正确性。     

梁与正交各向异性板弯曲波的传递特性研究

以正交各向异性板与各向同性梁耦合系统弹性波传递特性为研究对象,基于弯曲波传播的动力学分析,推导出子系统间的功率流传递系数(power flow transmission coefficient,PTC)和耦合边界处的耦合损耗因子(coupling loss factor,CLF)表达式.计算分析了内损耗因子、频率和方向...     

船舶机械设备联接处非保守耦合损耗因子的研究

联接部位传递力、能量和功率，也会把振动能量变成声和热耗散能量，非保守耦合损耗因子是表征这种耦合系统间能量传递特征的重要参数。运用统计能量分析方法分析联结部位的功率流及功率在该处的损耗和传递，建立结构总体SEA模型，根据结构功率平衡方程，推导出非保守耦合损耗因子的计算公式。文章基于这些，对一个实际机械设备联接部位计算例子，进行了仿真数值计算与分析，提出了一些有工程应用价值的结论。     

轴力对梁结构耦合损耗因子的影响研究

以飞行器中经常使用的耦合梁结构为研究对象,使用点阻抗法分析受到轴力作用耦合梁结构的高频振动传递特性。在考虑梁耦合角度和激励频率变化的情况下,分析轴力对结构振动方程的影响,计算了耦合边界处的耦合损耗因子;选用‘一字梁’模型计算了温度变化对梁结构间传递特性的影响,并通过与有限元结果的对比验证了点阻抗法计算的正确性。结果表明:当面外弯曲波入射时,轴力对梁结构间的传递特性有明显的影响,但随着频率的增加逐渐减小;同时,温度对结构间的耦合损耗因子有明显影响,随着温度的升高,结构间的功率传递减弱。     

振动主动控制系统的统计能量分析

基于能量观点对振动主动控制系统进行了统计能量分析。首次推导出振动主动控制系统的统计能量关系式和耦合振子间耦合损耗因子的表达式,并通过实例研究了控制反馈系数对系统耦合损耗因子的影响,分析了阻尼对系统输入功率、子系统间传递功率流以及各子系统振动能量的影响。     

应用结构声强技术测量耦合损耗因子

介绍了一种新的耦合损耗因子测量方法：声强法。以点和线耦合结构为例，应用两点差分技术和单点技术测量弯曲波耦合损耗因子，将测量结果与传统方法获得的测量结果相比较：声强法能较准确地测量点耦合结构间弯曲波耦合损耗因子，其测量精度与能级差分法和直接测量方法的测量精度相似。     

经典参数在我结构耦合系统统计能量分析中的应用

直接和间接耦合损耗因子是用统计能量分析方法研究多结构耦合系统振动响应的关键参数，也是急待解决的问题之一。本文提出了用经典统计能量分析参数计算多结构耦合系统的直接和间接耦合损耗因子的方法。其优点是利用经典统计能量分析已取得的橡胶敢多子结构耦合系统的问题。文中首先推导了经典的双子结构耦合系统的耦合损耗因子和结构参数的关系，然后研究了多子结构耦合系统的直接和间接耦合损耗因子与结构参数的关系，最后推导得到     

基于DFM/FEM铝蜂窝夹层结构耦合损耗因子预测

在使用统计能量分析对复杂的蜂窝夹层结构进行高频动力学响应预示的关键环节之一在于准确估算耦合损耗因子。本文研究应用对偶模态/有限元法（DFM/FEM）估算铝蜂窝夹层结构之间的耦合损耗因子,通过算例对该方法进行仿真验证,结果表明,该方法可行且高效准确。最后对L型耦合铝蜂窝夹层板结构进行振动实验,并使用功率输入法辨识试件间的耦合损耗因子,比较功率输入和和对偶模态/有限元法结果,两者一致性好,进一步验证了对偶模态/有限元法估算铝蜂窝夹层板系统耦合损耗因子的可行性,扩展了统计能量分析在复杂结构上的应用。     

基于统计能量法的变速箱振动特性研究

应用统计能量分析方法对变速箱结构进行高频振动特性的分析。通过有限元计算得到1/3倍频程频带内的模态数目,确定适合统计能量分析的频率范围。研究复杂结构等效质量的试验方法,测量得到两个子系统的等效质量、内损耗因子和耦合损耗因子。结合测量结果,在VA One中建立统计能量分析模型,计算得到随机激励力作用下的振动响应,并与试验测量结果进行对比,验证结果表明所建模型是正确且有效的。运用所建立的变速箱SEA模型计算在实际工作激励下的振动响应。结果表明统计能量分析方法可以有效地对复杂结构的高频振动特性进行分析。     

Wirksame Auflagebreite Balliger Metalldichtungen

Effective Sealing Area of Osculating Metallic Gaskets The question of importance in the design of flanged joints using metallic osculating gaskets is the contact area and the effective width of the gasket. For the three important sealing materials armco iron, austenitic steel X 10 CrNiTi 189 and high-temperature steel 12 CrMo 195 the dependence of the effective gasket width on pressure was determined experimentally through variation of the radius of curvature. The comparison of the measured data with existing numerical approaches is not congruent to a sufficient degree. New formulations of the relations, which correspond better to the experimentally determined results, are developed on the basis of material mechanics.     

Vibrational Spectroscopy of Water with High Spatial Resolution

The ability to examine the vibrational spectra of liquids with nanometer spatial resolution will greatly expand the potential to study liquids and liquid interfaces. In fact, the fundamental properties of water, including complexities in its phase diagram, electrochemistry, and bonding due to nanoscale confinement are current research topics. For any liquid, direct investigation of ordered liquid structures, interfacial double layers, and adsorbed species at liquid–solid interfaces are of interest. Here, a novel way of characterizing the vibrational properties of liquid water with high spatial resolution using transmission electron microscopy is reported. By encapsulating water between two sheets of boron nitride, the ability to capture vibrational spectra to quantify the structure of the liquid, its interaction with the liquid‐cell surfaces, and the ability to identify isotopes including H₂O and D₂O using electron energy‐loss spectroscopy is demonstrated. The electron microscope used here, equipped with a high‐energy‐resolution monochromator, is able to record vibrational spectra of liquids and molecules and is sensitive to surface and bulk morphological properties both at the nano‐ and micrometer scales. These results represent an important milestone for liquid and isotope‐labeled materials characterization with high spatial resolution, combining nanoscale imaging with vibrational spectroscopy.     

Core material effect on wave number and vibrational damping characteristics in carbon fiber sandwich composites

A sandwich composite is typically designed to possess high bending stiffness and low density and consists of two thin and stiff skin sheets and a lightweight core. Due to the high stiffness-to-weight and strength-to-weight ratios, sandwich composite materials are widely used in various structural applications including aircraft, spacecraft, automotive, wind-turbine blades and so on. However, sandwich composite structures used in such applications often suffer from poor acoustic performance. Ironically, these superior mechanical properties make the sandwich composites “excellent” noise radiators. There is a growing interest in optimizing and developing a new sandwich composite which will meet the high stiffness-to-weight ratio and offer improved acoustic performance. The focus of this study is to investigate the structural–vibrational performance of carbon-fiber face sheet sandwich composite beams with varying core materials and properties. Core materials utilized in this study included Nomex and Kevlar Honeycomb cores, and Rohacell foam cores with different densities and shear moduli. The structural–vibrational performance including acoustic and vibrational damping properties was experimentally characterized by analyzing the wave number response, and structural damping loss factor (η) from the frequency response functions, respectively. It was observed that the relationship between the slopes of the wave number data for frequencies above 1000 Hz is inversely proportional to the core material’s specific modulus (G/ρ). The analysis also showed the importance of using a honeycomb core’s effective properties for equal comparison to foam-cored sandwich structures. Utilizing analytical modeling, the loss factors of the core materials (β) was determined based upon the measured structural loss factors (η) for a frequency range up to 4000 Hz. It was determined that low shear modulus cores have similar material damping values to structural damping values. However as the core’s shear modulus increases, the percent difference between these values is found to increase linearly. It was also observed that high structural damping values correlated to low wave number amplitudes, which correspond to reductions in the level of noise radiation from the structure.     

复合材料连接结构健康监测技术研究进展

连接结构是大型复合材料结构的关键环节,对保证复合材料结构的完整性具有重要作用。由于复合材料连接结构存在复杂的非线性耦合因素,使得复合材料连接结构的强度和破坏模式分析十分困难,因此,必须对复合材料连接结构的健康状态进行监测、诊断、评价和预测,通过在线监测获得的信息实时掌握结构的健康状况与对外界载荷的响应,并在此基础上对未来可能发生的缺陷和故障进行预报,以便能在合适时间段内采取措施,以保证复合材料结构的安全服役并取得最大的经济效益。以飞行器复合材料连接结构为背景,首先简要分析了复合材料胶接连接、机械连接和混合连接形式的损伤和失效模式,然后重点介绍了基于波传播法、阻抗法、智能涂层监测法、真空比较监测法、光纤传感监测法和混合集成监测法的复合材料连接结构健康监测(SHM)技术的研究进展,最后讨论了飞行器复合材料连接结构健康监测技术的发展趋势和面临的挑战。      

导电衬垫材料的屏蔽效能研究

导电衬垫材料是计算机防信息泄漏研究中应用最广泛的一类屏蔽材料，在研制TEMPEST计算机中发挥了重要的作用，本文通过对6种常用的导电衬垫材料的屏蔽效能的测试研究，得出了一些有工程参考价值的结论。     

Invariants of electromechanical coupling coefficients in piezoceramics

The relationships between coefficients of electromechanical coupling (CEMC) of various types of piezoceramic resonator (PR) vibrations are considered. Being constant for a given piezoceramic state, the range of variation of piezoceramics dielectric permittivity from a mechanically "free" condition at relatively low frequencies up to an "overall clamped" condition at high frequencies is determined by a consecutive "clamping", caused by a complex of CEMCs of various particular vibrational modes peculiar to the resonator. As the difference between "free" and "overall clamped" permittivities is always determined by the maximal piezomaterial /spl kappa//sub i3/ coupling coefficient, the difference does not depend on the path that was gone through the low-high frequency range, which includes all the vibrational modes possible for a particular PR. The influence of the piezoelectric and elastic anisotropy of lead-zirconate-titanate (PZT) piezoceramic materials on relative CEMC variations was experimentally investigated.     

利用波的反射和透射系数确定波导结构不连续点的动力学参数

截面均匀的梁、管道等细长结构在工程中有着广泛应用,这类结构具有沿结构伸展方向长距离传递机械波的波导特性,称为波导结构。此类结构通常包含联结件、支撑件等不连续点,这些不连续点的动力学参数,如质量,刚度,阻尼等,是波导结构动力学建模的关键参数。由于实际不连续点结构复杂,往往需要用实验方法确定其动力学参数。基于行波分析方法,本文建立了波导结构不连续点的动力学参数与不连续点处的反射、透射系数之间的一般性解析关系式。根据此关系式,提出了通过测量有效频率范围内的不连续点处的反射、透射系数,结合最优化曲线拟合,进行不连续点动力学参数识别的方法。文中以无限长梁附加质量块不连续点为例,用该方法测量附加质量块的质量和转动惯量参数。蒙特卡罗法仿真结果表明,该方法受测量噪声的影响较小。用该方法对不同附加质量块进行参数识别的实验结果表明,质量误差在5%以内,转动惯量误差在15%以内,测量准确度与所选择的识别频率范围有关。