基于面板声学贡献度的封闭空腔结构内声场分析的若干关键问题研究

发布时间：2018-05-04 09:14

本文选题：封闭空腔 + 载荷识别　；参考：《合肥工业大学》2014年博士论文

【摘要】：弹性封闭空腔结构在动态载荷激励下产生振动进而形成的空间复杂声场是工程实际中最具代表性的一类声场，如汽车、船舶和飞机的舱内声场。对该类声场的研究一直以来都是振动与噪声控制领域的一个重要研究方向，实现对这类封闭空腔结构内部声场的声学响应预测和分析，具有重要的理论研究意义和广阔的工程应用前景。根据传递路径分析方法的原理，系统响应可认为是外界激励通过多种不同路径传递到响应点的能量贡献叠加。因此通过识别外界激励载荷和计算结构振动声辐射来解决复杂封闭空腔结构的振动噪声分析与控制问题。本文以封闭空腔结构受激所形成的内部复杂声场为研究对象，用结构部件的面板声学贡献度代替先前的传递路径贡献量，以预测和控制封闭结构声腔内的声学响应为目标，深入研究结构外界激励载荷的识别和复杂封闭空腔内部声场响应计算两个关键问题。在激励载荷的识别方面，提出了具有一般意义的结构动态载荷时域识别方法，提高了载荷识别的精度和稳定性。在振动声辐射计算求解方面，提出了用于计算复杂封闭结构振动形成的内部空间声场的等效声传递向量法，避免了边界元法的固有缺点，计算效率更高。在封闭空腔结构内声场预测和声学优化方面，提出了一种基于等效源法的内部近场声全息的面板声学贡献度计算方法，该方法可在重建封闭空腔结构内声场的同时，有效识别出各振动板件对封闭声场的声学贡献度。完成的主要研究工作和成果如下：（1）阐述了封闭空腔结构内部声场分析的研究意义，详细回顾了动态载荷识别方法和封闭空腔结构内部声场计算的研究现状和进展，分析了其中仍然存在的一些值得研究的问题，并以此为基础，确定了本论文所要研究的主要内容。（2）针对响应中带有噪音时载荷识别的困难，提出了联合奇异熵去噪修正和正则化预优的共轭梯度迭代识别方法。系统的振动响应表示为单位脉冲响应函数与激励载荷的卷积，并离散化一组线性方程组，将载荷识别问题即转化为求解线性方程组的反问题。一方面对含噪信号进行基于奇异熵的去噪处理，提高反问题求解中输入数据的精度。另一方面利用正则化方法对共轭梯度迭代算法进行预优，改善反问题的非适定性。由于从输入的响应数据去噪和正则化算法两方面同时改善动态载荷识别反问题的求解，因此可以有效地抑制噪声，提高识别精度。通过数值算例分析，，表明在不同的噪声水平干扰下，其识别精度均优于常规的正则化方法，能够实现有效稳定地识别动态载荷。最后通过实验研究进一步验证了该方法的正确性和有效性。（3）对封闭空腔结构内声场分析计算问题的数值求解方法进行了详细的论述，推导了求解Helmholtz方程的声学有限元法和声学边界元方法的理论公式，并分析了这两种数值计算方法在实际应用中的不足之处。（4）推导了基于边界元法的声传递向量的计算公式。提出了用于分析复杂封闭空腔结构内声场的等效声传递向量法，导出了等效声传递向量和面板声学贡献度的理论公式，研究了等效声传递向量法的数值计算误差影响因素。该方法避免了边界元法中复杂的数值计算和奇异积分的处理过程，简化了计算过程，有利于向工程实际推广。分别以三个不同形状结构形成的声腔模型为例进行声场分析，仿真实验结果证明了该方法的正确性和有效性。（5）基于等效源法的内部声全息技术，提出了一种复杂封闭空腔结构内声场的面板声学贡献度识别方法。首先重构出振动结构表面的法向振速，实现对整个内部封闭声场的预测，再将振动结构的每个面板在腔体内部场点产生的声压分别用位于空腔表面附近的等效源在该点产生的辐射声压代替，将复杂的封闭非自由声场问题转化为简单的内部自由场问题，结合重建出的结构表面法向振速进而识别出封闭振动结构各面板对腔体内任意位置的声学贡献度。研究了等效源的数量及与重建面距离等参数对重建精度的影响，通过复杂结构内声场的数值仿真和实验研究的结果验证了所提方法的正确性和有效性。（6）总结本文的主要研究成果，指出了需要进一步研究和解决的问题。
[Abstract]:The space complex sound field formed by the vibration of the elastic closed cavity structure under the dynamic load excitation is the most representative sound field in the engineering practice, such as the acoustic field in the vehicle, the ship and the aircraft. The prediction and analysis of acoustic response inside the closed cavity structure has important theoretical significance and broad engineering application prospects.
According to the principle of the transfer path analysis, the response of the system can be regarded as the superposition of the energy contribution of the external excitation through a variety of different paths to the response point. Therefore, the vibration noise analysis and control of the complex closed cavity structure can be solved by identifying the external excitation load and calculating the structural vibration sound radiation.
In this paper, the internal complex sound field formed by the excitation of a closed cavity structure is taken as the research object. The acoustic contribution of the panel's panel is replaced by the contribution of the previous transmission path, and the acoustic response in the closed structure sound cavity is predicted and controlled as the target. The recognition of the external excitation load and the internal sound field in the complex closed cavity are deeply studied. In response to two key problems, the time domain identification method of structural dynamic load with general significance is proposed to improve the accuracy and stability of load identification. The equivalent sound transfer of internal space sound field for calculating the vibration formation of complex closed structures is proposed in the calculation of vibration acoustic radiation. The vector method avoids the inherent shortcomings of the boundary element method and has a higher calculation efficiency. In the aspect of acoustic field prediction and acoustic optimization in the closed cavity structure, a method for calculating the acoustic contribution of the panel based on the equivalent source method is proposed. This method can effectively identify the sound field in the closed cavity structure and effectively identify the vibration. The main contributions of the research work are as follows:
(1) the research significance of the internal sound field analysis of the closed cavity structure is expounded. The research status and progress of the dynamic load identification method and the internal sound field calculation of the closed cavity structure are reviewed in detail, and some problems that still exist in the cavity structure are analyzed, and the main contents of the study are determined on the basis of this.
(2) in response to the difficulty of load recognition in response to noise, a conjugate gradient iterative identification method with combined singular entropy de-noising correction and regularization predominance is proposed. The vibration response of the system is expressed as a convolution of the unit impulse response function and the excitation load, and a set of linear equations is discrete, and the problem of load identification is transformed into a solution line. The inverse problem of the sex equation group. On the one hand, the noise signal is denoised based on the singular entropy to improve the accuracy of the input data in the inverse problem solving. On the other hand, the regularization method is used to predominate the conjugate gradient iterative algorithm and improve the inadaptability of the inverse problem. Two aspects of the denoising from the input response data and the regularization algorithm are made. At the same time, it improves the solution of the inverse problem of dynamic load identification, so it can effectively suppress the noise and improve the recognition accuracy. Through numerical example analysis, it shows that the recognition accuracy of different noise level interference is better than the regular regularization method, and it can realize the dynamic load effectively and steadily. Finally, the experimental research is further tested. This method is proved to be correct and effective.
(3) the numerical solution of the analysis and calculation of the acoustic field in a closed cavity structure is discussed in detail. The theoretical formulas for the acoustic finite element method and the acoustic boundary element method for solving the Helmholtz equation are derived, and the shortcomings of the two numerical calculation methods in practical application are analyzed.
(4) the calculation formula of sound transfer vector based on boundary element method is derived. An equivalent sound transfer vector method for analyzing the sound field in complex closed cavity structure is proposed. The theoretical formula of the equivalent sound transfer vector and the acoustic contribution degree of the panel are derived, and the influence factors of the numerical calculation error of the equivalent sound transfer vector method are studied. The method is avoided. In the boundary element method, the complex numerical calculation and the processing of the singular integral are simplified. The calculation process is simplified and it is beneficial to the engineering practice. The sound field analysis is taken as an example of three different shape structures. The simulation results prove the correctness and effectiveness of the method.
(5) based on the internal acoustic holography of the equivalent source method, a method to identify the acoustic contribution degree of the panel in a complex closed cavity structure is proposed. First, the normal velocity of the vibration structure is reconstructed to realize the prediction of the whole internal closed sound field and the sound pressure produced by each panel of the vibration structure in the interior of the cavity. By replacing the sound pressure generated by the equivalent source near the surface of the cavity, the complex closed non free sound field is converted into a simple internal free field problem. The acoustic contribution of the closed vibration structure to any position of the cavity in the cavity is identified by combining the reconstructed structure surface method to the velocity of vibration. The effect of the number of the source and the distance from the reconstruction surface on the reconstruction accuracy is verified by the numerical simulation and experimental results of the sound field in the complex structure.
(6) summarize the main research results of this paper, and point out the problems that need further research and solution.

【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB535

【参考文献】