Coupling loss factors for two plates joined at a line (a 90-deg bend), but otherwise free to respond in lateral vibration, have been studied both analytically and experimentally. Two cases have been studied: one with no added damping and one in which one of the plates has a small amount of damping provided by a constrained layer treatment. Statistical energy analysis (using VA ONE) and the finite element method (using NASTRAN) have been used to predict the coupling loss factors. The finite element predictions are based on the averaged responses for a range of boundary conditions on the plates, essentially a “pseudo-statistical” approach. Experimentally, one of the plates was excited while the kinetic energy of the two plates was assessed with a scanning laser vibrometer (scanning a dozen or more points) and four accelerometers on each plate. Both impulse and persistent excitations were used. The coupling loss factors were assessed by balancing the power input with the energies of the plates, also using the estimated modal densities. The estimations from the analytical and experimental approaches compare as well as may be expected for the lightly damped plates case, but very well for the case of one plate having a damping treatment.

Transmission through beams can become a significant path in many structure-borne problems, especially in aircraft or launch vehicles. Statistical energy analysis (SEA) is widely used for the vibro-acoustic modeling of high-frequency problems. However, in a system-level SEA model, even at higher frequencies, some beams can exhibit low-modal behavior and might not be a good SEA representation. Vibration transmission through beams involves both resonant and non-resonant transmission paths. Typically the non-resonant path is dominant at low frequencies and the resonant path at high frequencies. This paper describes various modeling approaches for describing the transmission through beams over a broad frequency range. SEA modeling techniques will be compared to the hybrid FE-SEA method, energy flow method, and the finite element method for various beam configurations. Modeling beams under pre-stressed conditions is also investigated.