随机振动结构声辐射的统计边界点法分析

文章利用作者提出的统计边界点法,对随机振动结构声辐射的计算进行了研究。文中详细地介绍了统计边界点法,并以随机振动球为例,计算了其在表面振速功率谱密度函数分布已知情况下的随机声场,并与解析解以及统计边界元法的计算结果进行了比较。结果表明：该方法与统计边界元法相比,在边界剖分相同的情况下,能够在相当宽的振动频率范围内,给出更加满意的计算结果。     

应用三次B样条函数插值的边界元法计算结构振动声辐射问题

本文通过在边界元方法中采用三次Ｂ样条函数作为插值形函数，对结构振动声辐射的计算进行了研究。并以脉动球作为算例，对其辐射声场中的有关声场参数进行了计算。通过将计算结果与理论解进行比较，结果表明：即使在边界剖分比较粗的情况下，利用该方法计算结构振动声辐射问题在较宽的振动频率范围内，也能给出良好的计算精度。     

随机激励下结构振动声辐射的灵敏度分析和优化设计

基于有限元法、边界元法和虚拟激励法,对随机激励下结构振动声辐射灵敏度分析及优化设计问题进行研究.有限元法用于计算结构谐振响应,边界元法用于计算结构振动声辐射,虚拟激励法结合有限元和边界元计算随机激励下结构振动声辐射问题.提出随机激励下结构振动声辐射问题的优化模型及求解算法流程,重点推导了其灵敏度分析公式.数值算例验证了灵敏度分析的准确性及优化求解算法的有效性.     

边界元法在环境声学中的应用

边界元法是边界积分方程的数值解法 ,是随着计算机技术的发展而出现的。建立声学边界积分方程分两种方法 :直接法与间接法。本文介绍了边界元法在环境声学中的应用 ,如声屏障和不同情况下道路周围的声场分布、复杂气象条件对声传播的影响的问题等。由于边界元法是半解析半数值解法。在解边界积分方程时会遇到解的存在与唯一性问题。     

复杂结构的声辐射解耦及其声辐射效率分析

提出一种用边界元方法与声辐射理论求解复杂结构的声辐射模态与声辐射效率的理论方法。先将结构的声辐射功率表示为一个正定的厄米特二次型，运用广义特征值分解求解了复杂结构的声辐射模态，然后利用声辐射模态关于阻抗矩阵与均方速度耦合矩阵的正交性，求解了复杂结构的声辐射效率，最后用具有解析解的脉动球与辐射立方体验证了该方法的有效性。     

用边界元法计算变压器辐射噪声

本文从半无限域结构体声辐射的理论公式──半无限域Ｈｅｌｍｈｏｔｈｔｚ积分方程入手，采用边界元法（简称ＢＥＭ法）离散积分方程，通过变压器壳体表面振动速度场来计算变压器向外辐射的噪声场。文中讨论了计算变压器辐射噪声场的数值计算模型，变压器体表面振动速度的测试，并将ＢＥＭ法计算结果与实测结果进行了比较，两者基本吻合，最后简要分析了造成误差的原因。     

利用边界元法中的全特解场方法计算结构振动声辐射

本文通过利用边界元法中的全特解场方法，对结构振动声辐射的计算进行了研究，并以脉动球为算例，将计算结果与解析解进行比较，结果表明：该方法与一般边界元法相比，在边界剖分相同的情况下，能够在相当宽的振动范围内，给出满意的计算结果。     

FEM/BEM法计算空调机室外机箱结构噪声辐射

采用有限元与边界元耦合的方法，编写了相应程序对空调室外机箱的激励进行处理并对其结构声辐射进行了计算。试验结果表明该方法具有较高的精度。在此基础上讨论了机箱板厚对噪声辐射特性的影响，为空调机箱的优化设计提供了可靠的基础。     

基于快速多极子边界元法的齿轮箱声场分析

齿轮箱是广泛应用的工程机械零部件,准确地模拟其辐射声场对后续的降噪优化设计有着重要作用。边界元方法非常适合分析此类无限域下的声辐射问题。但传统边界元方法有着计算效率低、内存占用高的缺点。该研究发展了宽频的快速多极子边界元方法,并运用该方法计算了齿轮箱在特定频率下的场点声压以及辐射声场。通过对比商用软件的分析结果,验证了所提快速边界元方法的准确性。此外,运用多核并行计算方法,对计算量较大的扫频分析进行加速计算,最终快速、准确地获取了齿轮箱辐射声场的扫频结果。     

夹层边界上布置主动声学边界的有源隔声双层板结构EI北大核心CSCD

在双层板结构中夹层声场边界上布置平面声源作为主动声学边界,构成有源隔声双层板结构,提出基于主动声学边界方法的有源隔声双层板结构。在双层板结构中夹层边界上布置四边简支板,用来代替主动声学边界,控制力作用到该简支板上,采用声弹性理论建立了有源隔声双层板结构的计算模型,分别以辐射声功率最小和夹层声功率最小作为控制目标来优化控制力,计算分析控制前后夹层结构的传声损失以及各子系统的响应,并研究了主动声边界尺寸大小对系统隔声性能的影响。计算结果表明:主动声边界控制策略可以有效提高双层板结构的隔声性能,且以辐射声功率最小为控制目标要优于以夹层声场的声功率最小为控制目标;控制后,主动声边界对入射板振动响应几乎没有影响,辐射面板的振动动能和夹层声场的声功率均被有效地抑制;不同尺寸主动声边界都提高了夹层结构的隔声性能;对于低频率段,不同尺寸主动声边界对夹层结构的隔声性能提高的程度相同;对于其他频率段,主动声边界对传声损失和各子系统响应的影响并没有一定的规律,可以对主动声边界的尺寸进行优化设计,达到提高特定频段隔声性能的目的。     

计算随机振动结构声辐射的统计体积源边界点法

机器的机械振动在单频范围内大多是具有明显随机性的随机过程,单纯通过有限元、边界元等传统的数值方法不能计算这类具有随机边界条件的结构声辐射问题。本文提出将体积源边界点法和统计方法相结合的统计体积源边界点法,导出了求解随机振动物体辐射声场的计算公式。通过求解随机声算例的计算,表明本文所提出的方法是有效的。     

On the calculation of boundary stresses with the Somigliana stress identity

The computation of boundary stresses by Boundary Element Method (BEM) is usually performed either by expressing the boundary tractions in a local co-ordinate system, calculating the remaining stresses by shape function differentiation and inserting into Hooke's law or recently also by solving the hypersingular integral equation for the stresses. While direct solution of the hypersingular integral equation, the so-called Somigliana stress identity, has been shown to be more reliable, the interpretation and numerical treatment of the hypersingularity causes a number of problems. In this paper, the limiting procedure in taking the load point to the boundary is carried out by leaving the boundary smooth and the contributions of all different types of singularities to the boundary integral equation are studied in detail. The hypersingular integral in the arising boundary integral equation is then reduced to a strongly singular one by considering a traction free rigid body motion. For the numerical treatment, an algorithm for multidimensional Cauchy Principal Value (CPV) integrals is extended that is applicable for the calculation of boundary stresses. Moreover, the shape of the surrounding of the singular point is studied in detail. A numerical example of elastostatics confirms the validity of the proposed method.     

结构振动辐射声场的预估——边界积分方程中奇异积分的间接处理

本文讨论了利用边界积分方程和边界元技术计算结构的稳态外辐射声场的方法,同时,对边界元方法所固有的奇异数值积分提出了一种简单方便的间接处理方法。计算实例证明所编计算程序和奇异积分处理方法是成功的。利用该程序在已知结构表面振速分布的条件下,可以求出该结构在自由声场中的声功率、表面辐射效率以及声场中任意点的声压值和相位。对一个实际钢质空心封闭圆筒作了计算与实测的比较,结果显示了该方法可应用于实际结构或机器的前景。     

形状记忆合金-玻璃纤维/环氧树脂复合材料在振动边界条件下的低速冲击数值模拟

采用有限元方法（FEM）研究了振动边界条件对形状记忆合金（SMA）-玻璃纤维/环氧树脂复合材料的抗低速冲击性能的影响。在数值模拟过程中,将改进的三维Hashin失效准则和Brinson模型分别应用于玻璃纤维/环氧树脂复合材料层合板和SMA,以表征其本构关系。首先通过与固定边界条件下的SMA-玻璃纤维/环氧树脂复合材料板低速冲击实验进行比较,验证了数值模拟过程中所用模型及材料参数的准确性。其次,在模拟过程中,应用了包含不同振幅的一系列振动边界条件,对其进行模拟,揭示了振动边界条件对其抗低速冲击性能的影响。数值模拟结果表明,在大振幅条件下,无SMA复合材料的抗冲击性能比小振幅条件下弱;在相同振动边界条件下,SMA-玻璃纤维/环氧树脂复合材料与无SMA复合材料相比,其抗低速冲击性能提高。      

A wall boundary treatment using analytical volume integrations in a particle method

Numerical treatment of complicated wall geometry has been one of the most important challenges in particle methods for computational fluid dynamics. In this study, a novel wall boundary treatment using analytical volume integrations has been developed for two-dimensional (2D) incompressible flow simulations with the moving particle semi-implicit method. In our approach, wall geometry is represented by a set of line segments in 2D space. Thus, arbitrary-shaped boundaries can easily be handled without auxiliary boundary particles. The wall's contributions to the spatial derivatives as well as the particle number density are formulated based on volume integrations over the solid domain. These volume integrations are analytically solved. Therefore, it does not entail an expensive calculation cost nor compromise accuracy. Numerical simulations have been carried out for several test cases including the plane Poiseuille flow, a hydrostatic pressure problem with complicated shape, a high viscous flow driven by a rotating screw, a free-surface flow driven by a rotating cylinder and a dam break in a tank with a wedge. The results obtained using the proposed method agreed well with analytical solutions, experimental observations or calculation results obtained using finite volume method (FVM), which confirms that the proposed wall boundary treatment is accurate and robust.     

The Boundary Contour Method for Piezoelectric Media with Quadratic Boundary Elements

This paper presents a development of the boundary contour method (BCM) for piezoelectric media. Firstly, the divergence-free of the integrand of the piezoelectric boundary element method is proved. Secondly, the boundary contour method formulations are obtained by introducing quadratic shape functions and Green's functions (Computer Methods in Applied Mechanics and Engineering1998;158: 65-80) for piezoelectric media and using the rigid body motion solution to regularize the BCM and avoid computation of the corner tensor. The BCM is applied to the problem of piezoelectric media. Finally, numerical solutions for illustrative examples are compared with exact ones. The numerical results of the BCM coincide very well with the exact solution, and the feasibility and efficiency of the method are verified.     

An alternative approach to shape design sensitivity analysis

A novel method is presented in this paper for calculating shape design sensitivity, which is based on the finite difference method (FDM). By analysing the numerical procedure of the FDM, the perturbation of the geometry is replaced by a perturbation load which can be calculated once the stress field of the initial problem and the design boundary perturbation are known. The final shape design sensitivity is obtained by solving the perturbation problem which has the same geometry and the kinematical boundary condition as the initial problem, but under the perturbation loads. Therefore the new method does not require the calculation of the matrices of the perturbed structure, and is independent of the perturbation step. A numerical implementation of the finite difference load method (FDLM) is described in which the boundary element method is used to evaluate the structural response. The numerical examples demonstrate that this new method for shape design sensitivity analysis is very accurate.