Vibration monitoring using sensors mounted on machines is widely used for rotating machinery fault diagnosis. The periodic overlapping group sparsity (POGS) method has been developed in previous work of authors, and is an effective technique for detecting faults induced in rotating machines. However, the regularization parameter of the POGS problem is roughly specified via a look-up table provided in the original work. To address this problem, a data-driven diagnostic method, which is termed the adaptively regularized periodic overlapping group sparsity (ARPOGS), is proposed in this paper. The non-stationary fault feature ratio which is defined in the Hilbert domain is employed to guide the optimal regularization parameter. The criterion of setting the interval of candidate regularization parameters is also discussed. The ARPOGS is developed in terms of a convex optimization problem, while non-convex regularizations are used to further promote the sparsity. Since the non-convex penalty term is used and the whole objective function is constrained as a convex optimization problem, the sparsity of useful fault features is maximally induced. A simulated signal is formulated to verify the performance of the proposed method for periodic feature extraction. Finally, the effectiveness of the proposed ARPOGS method is validated by analyzing real data collected from a wind turbine transmission system. The results demonstrated that the proposed method can effectively and automatically extract periodic-group-sparse features from noisy vibration signals.

In recent years, the micromechanics model plays an important role in investigating the mechanical properties for particle-reinforced composite (PRC) materials. In this article, through discretizing the representative volume element (RVE) with eight-node hexahedral isoparametric elements, as well as expressing the higher-order displacement functions as the function of surface-averaged displacements for the subcell, a new parametric micromechanical model is presented to investigate the elastic constant variations of the three-dimensional PRC. For validating the proposed method, the finite element method (FEM) is employed for solving the PRC without consideration of interphase. The calculated results by employing the FEM show a good consistency with the proposed micromechanical method. Furthermore, interphase thickness, as well as interphase modulus effect on elastic constant are further predicted and discussed.

The aim of this present article is to improve an effective model for analyzing the mechanical properties of hybrid smart composites in a fully coupled magneto-electro-elastic field. To this end, a three-dimensional micromechanical model is established by employing the displacement continuity, electric potential continuity, and magnetic potential continuity among adjacent sub-cells in a representative volume element. The numerical results of the effective elastic constants for three-dimensional smart composites, as well as continuous fiber-reinforced composites, are validated by the finite element method. On this basis, the micromechanical theory is employed at each integration point along lamina thickness for establishing the model of smart composite laminates. The numerical results revealed that the mechanical properties of piezoelectric–piezomagnetic hybrid smart composites are closely dependent on working temperature, and the internal force tends to be decreased with the raising of working temperature.

Microscopic voids/defects always occur in brittle piezoelectric fiber during the preparation. In addition, inconsistent material properties between the reinforced fibers and the matrix led to some microcracks located at the interface in matrix materials. In order to obtain equivalent properties of piezoelectric composites with respect to initial voids/defects, a parametric microscopic finite-volume model was constructed in this paper. To this end, the mechanical-electric coupling constitutive relation was implanted into the parametric FVDAM model to describe their piezoelectric characteristics. To verify the presented coupled mechanical-electric model, the numerical results of local stress and electric field distributions acquired by finite element method were also indicated for a comparison. On this basis, equivalent modulus and equivalent electrical properties with full consideration of local damages were also investigated by the presented microscale model.

This work improved upon an effective micromechanical method to analyze the mechanical properties of three-dimensional particle-reinforced composites (PRC) with consideration of the interfacial debonding. By incorporating the interfacial debonding model, Mises yield criterion, and failure theory, the effects of particle shape, particle volume fraction, and loading condition on the mechanical properties are studied. A comparison of simulation results obtained from the established method and published experimental data is presented. Good consistency can be found in this study. On this basis, the interfacial cohesive strength and particle shape effects on the biaxial failure strength of particle-reinforced composites with interfacial debonding were also studied. The results revealed that both interfacial strength and particle shape have significant effects on biaxial tensile failure strength. However, the different interfacial strength influence on failure envelope can hardly be discerned in biaxial compressive loading.