基于谱有限元的自由阻尼梁结构损耗因子分析

摘要

The spectral finite element method was used to analyze propagating wave types and their damping loss factor (DLF)in a beam with a non-constrained damping layer (NCDL).Every wave type's exciting condition was studied by analyzing characteristic wave shapes.The finite element method was used to compute the strain energy for every element of a long beam with a NCDL,the DLF was computed with the strain energy method and the relationship between structure DLF and load types was studied.In the end,the boundary reflected waves' effect on the DLF was studied.The study showed that the vertical excitation mainly excites the highest order bending wave or some lower order longitudinal waves whereas the longitudinal excitation mainly excites the highest order longitudinal wave;when the beam becomes longer and the distance between the exciting point and the boundary becomes farther,the effect of boundary reflection on the structural DLF becomes smaller;the DLFs under different boundary conditions are always the same except at some special frequencies;the structural DLF of a beam with a NCDL is decided mainly by the wave types and it is influenced a little by boundary reflection.%使用谱有限元分析了自由阻尼梁中扩散波类型及其损耗因子，通过对其特征波形的分析探讨了各个频率下每种波的激励条件，然后使用有限元对自由阻尼长梁做谐响应分析得到各个单元的应变能，根据应变能法计算得到该长梁分别在垂直和水平激励下的结构损耗因子，对结构损耗因子同激励起的波类型之间的关系进行了讨论，最后分析了边界反射对结构损耗因子的影响。研究表明：垂直激励主要激励起最高阶弯曲波或者某些低阶纵波，水平激励主要激励起最高阶纵波；边界反射对结构损耗因子的影响随着梁长增大以及激励点远离边界而变小；不同边界条件的结构损耗因子一般情况下比较接近，但在一些频率点处会存在一定的差异；自由阻尼梁的结构损耗因子主要由激励所能激励起的波类型所决定，在一定程度上受到边界反射影响。