开孔蜂窝夹芯结构的声振耦合疲劳寿命分析

Acoustic fatigue analysis for perforated honeycomb sandwich structure based on vibro-acoustic coupling

摘要:

为研究蜂窝夹芯结构上面板开孔直径大小对结构的声疲劳寿命的影响,采用了声振耦合的分析方法. 首先对结构进行有限元分析,得到结构的低阶模态以及其对应的频率；随后对声场进行边界元单元划分,建立声场-结构的耦合动力学模型；为降低计算量,对于输入的噪声载荷进行主成分分析,提取各阶主成分作为输入条件,通过数值分析得到结构在各频率、各主成分下的动力学响应；通过基于模态叠加法的随机声场后处理得到结构危险点的功率谱密度函数；最后结合P-M线性累计损伤理论、概率密度函数等作为功率谱密度法的输入条件计算结构的声疲劳寿命.结果表明,虽然结构表面开孔,会使结构刚度降低、孔边应力集中,但开孔直径较小时,每一个蜂窝单胞都是一个天然的赫姆霍兹共鸣器,声波在开孔结构中传播时受到空气粘滞性的影响,传播过程中将产生热损耗,能够吸收部分声能,降低噪声,因此对结构的声疲劳寿命具有积极作用.

Abstract:

To analyze the influence of different opening diameters in the upper panel of the honeycomb sandwich structure on its acoustic fatigue life, the vibro-acoustic coupling analysis was adopted in this study. First, the finite element analysis of the structure was performed to obtain low-order modes and corresponding frequencies. Next, the sound field was divided by boundary element, and a dynamic model of acoustic-structure coupling was built. In order to reduce calculation, principal component analysis was performed on the input noise load, the principal components of each order were extracted as input conditions, and the dynamic responses at each frequency and each principal component were obtained by numerical analysis. Then, the power spectral density (PSD) function of structural dangerous points was obtained by post-processing based on modal superposition. Lastly, the PSD method which combines P-M linear cumulative damage theory and probability density function was used to calculate the acoustic fatigue life of the structure. Result shows that although the structural panel opening caused the reduction of structural rigidity and the stress concentration of the hole edge, when the diameter of the opening was small, each honeycomb cell was a Helmholtz resonator. Consequently, the acoustic wave was affected by the viscosity when it propagated in the opening structure, and heat loss occurred during the propagation, which could absorb part of the acoustic energy and reduce noise. Therefore, the small open-cell structure has a positive effect on the acoustic fatigue life.