铁路客车内场噪声预测与控制

统计能量分析方法适于解决高频高模态密度的复杂动力学问题。采用该方法对25型铁路客车进行研究。用模态相似群法建立整车统计能量分析模型,仿真预测客车内场噪声的分布情况和噪声的主要传播路径,进而提出降低车内噪声的措施,尽管得出的是相对的结果,但是这些结论可以使设计者在设计初期考虑噪声指标成为可能。     

铁路空调客车车内气流组织的数值模拟

本文以铁路空调客车为研究对象．采用k-ε双方程模型，对客车室内的气流组织进行数值模拟，得到了有车内热负荷存在时的车内温度、速度场分布模拟计算结果。通过与试验结果的对比，对影响车内温度、速度场的因素进行了初步分析。     

客车车内降噪设计

首先针对某型客车建立了汽车车身结构的有限元模型,对建立的模型进行了有限元模态分析;通过比较计算得出的模态数据和实车试验得出的模态数据,验证了该车身结构有限元模型的正确性。基于模态分析的结果,提出了车身减振降噪的改进方案, 在车身模型上对结构进行了改进并且对改进前后的车内噪声进行分析。分析结果表明,该改进方案能有效降低车内的低频噪声。     

客车车内降噪设计

首先针对某型客车建立了汽车车身结构的有限元模型,对建立的模型进行了有限元模态分析;通过比较计算得出的模态数据和实车试验得出的模态数据,验证了该车身结构有限元模型的正确性。基于模态分析的结果,提出了车身减振降噪的改进方案, 在车身模型上对结构进行了改进并且对改进前后的车内噪声进行分析。分析结果表明,该改进方案能有效降低车内的低频噪声。     

中低速无障碍旅客列车研究

为了提高铁路客车的服务质量,体现铁路旅客运输的人性化,在中低速旅客列车上设置了无障碍设施,本文详细介绍了25型硬座和硬卧客车上残障人士专用的无障碍通道、卫生装置、呼唤装置、车门、车窗、车内设备和专用标识等设施。     

豪华大客车车内声场的模态分析

结合典型豪华大客车采用有限元法进行了车内声场的模态分析.文中对内部纯流体声场,考虑座椅影响和考虑声场与车身结构之间耦合作用这三种情况分别建立了车内部声场的三维有限元计算模型,并对车内声场进行了声学的模态分析.     

铁路客车车内噪声分布规律研究

运用多通道噪声测试与分析系统,对运行中的铁路客车进行了多点同步车内噪声测试和分析,得出了在不同工况和不同运行速度时的车内噪声的现状和分布规律,确定出车内噪声发生的主频带,对既有线铁道车辆和将来的高速铁道车辆进行防噪降噪设计具有较高的参考价值。     

轿车车内空腔声模态测量

介绍了轿车车内空腔声学模态,对实车的声模态进行了测试与分析,获得了车内空腔的声学共鸣频率和模态形状;提出了利用LMSTest_lab对轿车车内空腔声学模态进行测试的试验方法,为车内空腔的低频噪声研究提供了参考。     

A型地铁车体结构动态特性及车内声学模态研究

建立A型地铁车体结构和车内空腔有限元模型,应用模态分析技术分别对车体结构模态和车内空间声学模态进行了研究。结构模态分析表明：车体满足结构动态设计要求,但要加强端墙刚度、车顶与侧墙连接强度,以提高其疲劳寿命。声学模态分析表明,地铁车体对称的结构特点决定车内声场在横向、纵向和垂向同样具有对称性,使车内声场的各阶模态形状基本上呈前后、左右和上下对称分布,说明车内声场共鸣频率和模态形状主要由其几何形状决定。     

空调客车车内计算参数的优化与节能

本文根据PMV—PPD指标，分析了K25型软卧客车的车内空调计算参数——空气温度和湿度对热舒适性的影响，并通过计算软卧客车的负荷和制冷量分析了温、湿度对空调能耗的影响。最后指出：优化车厢内空调计算参数，对铁路客车空调的节能有重要的意义。     

Shunting operations at flat yards: retrieving freight railcars from storage tracks

OR Spectrum - In this paper, we study the railcar retrieval problem (RRT) in which specified numbers of certain types of railcars must be withdrawn from the storage tracks of a flat yard. This task...     

Characterisation of Strength Behaviour of Aluminium Foam Sandwiches Under Static Load

Abstract: Cellular metals, particularly aluminium foams, are increasingly used in automotive, railcar and aircraft industries due to their advantages such as low density, comparatively high stiffness, noise damping or non‐flammability. From this point of view a new powder‐compact forming and foaming technique has been developed to manufacture 3D‐aluminium foam sandwich (AFS) parts for components of railcars without glued joint between the foamed core layer and both cover sheets. Three different stages of foam expansion have been analysed to describe the material properties. We have characterised samples made of plane AFS panels by compression, bending and shear tests. The shear strain is optically measured by digital image correlation to estimate the shear modulus of foamed sandwiches. Furthermore, these experimentally determined values and curves are the basis for the verification and optimisation of finite element models by design of experiments. As a result of this work, recommendations could be derived for improving technological parameters.     

Measuring the package shipping environment in refrigerated ocean vessels

The dynamic and climatic environments inside the cargo holds of regrigerated ships carrying bananas from Central America to destinations in Europe and the United States were measured. The same environments inside individual packages of bananas were also measured for comparison. Among the variables studied were shock and vibration G-levels, temperature, humidity, and air velocity. Three different types of shipments were monitored: break-bulk, palletized, and containerized. The results show that the average G-levels are similar to those found on trailers and railcars and that the vibration levels in the packages themselves were amplified by up to as much as eight times.     

汽车消声器声学特性的数值分析与结构改进

利用Sysnoise软件对一汽车消声器进行声场计算,得到消声器的声压分布和传递损失曲线;对消声器结构进行改进,在其内部增设一块隔板和两个穿孔管,并对改进结构进行数值计算。结果表明：低频时声波以平面波的形式向前传播,高频时声波主要以高次谐波的形式向前传播。与原始消声器相比,在600-1 200 Hz的中低频段,以及1 700-1 800 Hz,2 700-2 800 Hz的中高频段,改进消声器的传递损失提高20 dB以上;且在20-3 000 Hz总频段,改进消声器的传递损失平均提高19.8 dB。故改进消声器的消声效果良好。     

基于无单元声波叠加的自辐射近似解析表达研究

传统波叠加法中虚拟声源必须设于结构体内离表面一定距离处,否则会使算法中的自辐射项中的格林函数产生奇异性,无法正确计算声场。针对这一问题,研究了针对振动结构辐射表面离散化域形成的无单元空间离散域波叠加计算方法,采用奇异点挖去法、部分积分区域替换法和不变量嵌入法克服当声源点与接收点重合时格林函数的奇异性问题,得到自辐射声压项和速度项的非奇异表达。然后利用速度边界条件确定声源强度和声压。通过具有解析解的脉动球源的例子验证,该近似解析表达式能较好地代表声压和速度自辐射项,从而实现声场的预测。     

Excitation of acoustic waves from cylindrical polyvinylidene fluoride (PVDF) film confined in a concentric wall

This paper investigates acoustic wave radiation from cylindrical polyvinylidene fluoride (PVDF) film mounted inside a concentric wall with a small air gap. In such a structure, propagation is allowed only in the gap between the film and the wall surface, and the wave propagates in the axial direction of the cylinder. The radiation impedance of the cylindrical transducer inside the concentric wall has been calculated using a one-dimensional propagation model. After calculating the mechanical impedance of the cylindrical PVDF film, the generated acoustic wave has been calculated as a function of frequency with various air gaps between the PVDF film and the wall. It has been found that the excited acoustic wave becomes stronger for a narrower air gap and shows a maximum at a specific air gap. This phenomenon has been explained as the match between the transducer impedance and the radiation impedance of the air gap. When the gap is too small, the radiation impedance exceeds the transducer's mechanical impedance, the acoustic wave radiation decreases with the decreasing gap, and the resonance frequency increases due to loading by the imaginary part of the excessive radiation impedance. All these theoretical results have been experimentally confirmed.     

Integrated FEM/BEM approach to the dynamic and acoustic analysis of plate structures

An integrated finite element/boundary element method approach to the prediction of the interior acoustic radiation of open ended box structures is presented. Dynamic response of the structure is predicted in terms of the nodal displacements under sinusoidal point force excitation using the finite element method. Theoretical results obtained in terms of frequency response functions are verified using the results from tests performed on a box structure. The interior acoustic field is then examined by the boundary element method using the boundary conditions obtained from the finite element analysis. Sound pressure levels produced inside the structure are calculated and the results are compared with the experimental measurements.     

Ultrasound Manipulation and Extrusion of Active Nanorods

Synthetic self-propelled nano and microparticles have a growing appeal for targeted drug delivery, collective functionality, and manipulation at the nanoscale. However, it is challenging to control their positions and orientations under confinement, e.g., in microchannels, nozzles, and microcapillaries. This study reports on the synergistic effect of acoustic and flow-induced focusing in microfluidic nozzles. In a microchannel with a nozzle, the balance between the acoustophoretic forces and the fluid drag due to streaming flows generated by the acoustic field controls the microparticle's dynamics. This study manipulates the positions and orientations of dispersed particles and dense clusters inside the channel at a fixed frequency by tuning the acoustic intensity. The main findings are: first, this study successfully manipulates the positions and orientations of individual particles and dense clusters inside the channel at a fixed frequency by tuning the acoustic intensity. Second, when an external flow is applied, the acoustic field separates and selectively extrudes shape-anisotropic passive particles and self-propelled active nanorods. Finally, the observed phenomena are explained by multiphysics finite-element modeling. The results shed light on the control and extrusion of active particles in confined geometries and enable applications for acoustic cargo (e.g., drug) delivery, particle injection, and additive manufacturing via printed self-propelled active particles.     

基于FEM/BEM法的模拟舱室结构声辐射仿真与试验

针对机舱结构辐射噪声问题,基于有限元/边界元法,对模拟舱室结构进行辐射声场仿真与试验。首先建立模拟舱室结构的有限元模型,对模拟舱室结构进行模态试验,将仿真计算与模态试验进行对比,验证了有限元模型的正确性。然后进行模拟舱室结构的声辐射试验,得到模拟舱室结构内部的声压频响特性。最后在ANSYS中对模拟舱室结构进行瞬态响应计算,将结构受节点力激励的响应导入Virtual Lab中,采用间接边界元法计算空腔结构内部的辐射声场。仿真与试验有较好的一致性,表明该方法是正确、可行的。     

双层弹性-非弹性封闭腔体的内部声场研究

从球坐标中声波波动方程出发，利用本征函数展开方法和界面边界条件，导出了双层弹性封闭球壳的内部散射声场表达式。对于单位源强度的点声源，本文计算了分别由弹性/粘弹性和弹性/吸声材料组成的双层封闭球壳的内部散射声压随频率的变化关系。计算结果表明，粘弹性材料和吸声材料在某些频段对散射声压有十分明显的抑制作用。