Structural damping loss factor analysis for beams with a non-constrained damping layer based on spectral finite element

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.