Similitude theory can be used to extrapolate the experimental data of a small, inexpensive, and easily tested model into design information for a large prototype. Scaling laws provide the relationship between a full-scale structure and its scale models. However, one challenging issue is the similitude of complex structure. To address the problem, an energy similarity method is presented based on the principle of conservation of power flow. The emphasis is to predict the vibroacoustic characteristic of beam-plate coupled structure in an effective and convenient way. The vibration response and radiated sound are investigated on the beam-plate coupled structure under random excitation. Numerical simulation and model test are both implemented, which validate the effectiveness and efficiency of the proposed method. Both aluminum and honeycomb materials are considered in beam-plate coupled structures. In addition, the comparison between the classic similitude method and the presented method (energy similarity) is illustrated. The results show that the energy similarity presented in this study can achieve a better performance in reproducing the vibroacoustic characteristic of beam-plate coupled structure than the classic similarity method.

To address the problem that complex bearing faults are coupled to each other, and the difficulty of diagnosis increases, an improved envelope spectrum–maximum second-order cyclostationary blind deconvolution (IES-CYCBD) method is proposed to realize the separation of vibration signal fault features. The improved envelope spectrum (IES) is obtained by integrating the part of the frequency axis containing resonance bands in the cyclic spectral coherence function. The resonant bands corresponding to different fault types are accurately located, and the IES with more prominent target characteristic frequency components are separated. Then, a simulation is carried out to prove the ability of this method, which can accurately separate and diagnose fault types under high noise and compound fault conditions. Finally, a compound bearing fault experiment with inner and outer ring faults is designed, and the inner and outer ring fault characteristics are successfully separated by the proposed IES-CYCBD method. Therefore, simulation and experiments demonstrate the strong capability of the proposed method for complex fault separation and diagnosis.