Studies of a New-style Resonator on Electro-mechanical Coupling Bandgap Control of a Locally Resonant Piezoelectric/elastic Phononic Crystal Double-layer Nonlocal Nanobeam

The paper proposed a model of a locally resonant (LR) piezoelectric/elastic phononic crystal (PC) nanobeam with periodically attached “spring-mass” resonator and additional spring between upper and lower nanobeams, as well as horizontal spring between mass and foundation. Euler beam theory and nonlocal piezoelectricity theory are coupled and introduced to plane wave expansion (PWE) method to calculate the band structures of such a model with different parameters. Numerical results and further analysis demonstrate that all the bands of double-layer nanobeam can be divided into symmetric and antisymmetric ones. Adding additional and horizontal springs play a role in control the symmetric and antisymmetric bands respectively, which make wider band gaps be opened than corresponding single-layer nanobeam. Moreover, the change of parameters of electro-mechanical coupling fields and resonator can be applied to effectively control the starting frequencies and widths of band gaps, which can provide a theoretical basis for active control of vibration. Effects of geometric and non-dimensional nonlocal parameters on band gaps are also discussed. All the studies are expected to be applied to actively control vibration propagation in the field of nano electro-mechanical system (NEMS).

Crack Commencement and Transmissionan Alysison Heavy Vehicle Propeller Shaft by using Wavelet Transform

Present work gives an overview of cracks determination in material usingnatural frequency and wavelet transformation method and its application tocurrent engineering problems. In this technique, comparison between actualnatural frequency (without crack) and frequency due to crack propagation ismade using Euler Beam theory. When cracks are present in structure, natural frequency of material deviates from its original frequencyandresultdifference will measure in term of crack. Whole analysis procedure starting from modeling, meshing and resul tinterpretation done on well-known numerical tool ANSYS. The main aim of proposed study is to detect critical areas especially crack initiativezone before doing actual fabrication of components and avoid the breakage of it. Effects of a breathing crack on thevibratory characteristics of a rotating propeller shaft are investigated. Here three types of load consideration have taken such as axial, bending and torsionloadings. Results of numerical Finite Element Method (FEM) are validatedusingnumericalresultshasdoneusing MATLAB.

Electro-Mechanical Coupling Properties of Band Gaps in an Elastic/Piezoelectric Phononic Crystal Nonlocal Nanobeam With Periodically Attached “spring-Mass” Resonators

The model of a locally resonant (LR) epoxy/PZT-4 phononic crystal (PC) nanobeam with “spring-mass” resonators periodically attached on epoxy is proposed. The corresponding band structures are calculated by coupling Euler beam theory, nonlocal piezoelectricity theory and plane wave expansion (PWE) method. Three complete band gaps with widest total width less than 10GHz can be formed in the proposed nanobeam by comprehensively comparing the band structures of three kinds of LR PC nanobeams with resonators attached or not. Furthermore, influencing rules of the coupling fields between electricity and mechanics, “spring-mass” resonator, nonlocal effect and different geometric parameters on first three band gaps are discussed and summarized. All the investigations are expected to be applied to realize the active control of vibration in the region of ultrahigh frequency.

Substructural Identification of Flexural Rigidity for Beam-Like Structures

This study proposes a novel substructural identification method based on the Bernoulli-Euler beam theory with a single variable optimization scheme to estimate the flexural rigidity of a beam-like structure such as a bridge deck, which is one of the major structural integrity indices of a structure. In ordinary bridges, the boundary condition of a superstructure can be significantly altered by aging and environmental variations, and the actual boundary conditions are generally unknown or difficult to be estimated correctly. To efficiently bypass the problems related to boundary conditions, a substructural identification method is proposed to evaluate the flexural rigidity regardless of the actual boundary conditions by isolating an identification region within the internal substructure. The proposed method is very simple and effective as it utilizes the single variable optimization based on the transfer function formulated utilizing Bernoulli Euler beam theory for the inverse analysis to obtain the flexural rigidity. This novel method is also rigorously investigated by applying it for estimating the flexural rigidity of a simply supported beam model with different boundary conditions, a concrete plate-girder bridge model with different length of an internal substructure, a cantilever-type wind turbine tower structure with different type of excitation, and a steel box-girder bridge model with internal structural damages.

Characterization of Creases in Polymers for Adaptive Origami Structures

Techniques employed in origami are of interest for the design of actuating structures with multiple defined geometric states. Most research in this area has focused on manipulating material chemistry or geometry to achieve folding, but crease development through full material thickness has not been studied in detail. Understanding creasing is crucial for establishing material selection guidelines in origami engineering applications. Identification of the precise failure mechanisms is critical for understanding the residual fold angle and selecting optimal materials for specific origami applications. To characterize crease formation and development, polymer films were folded using a modified parallel plate bending technique which was successfully modeled with Euler beam theory in the elastic regime. Fold angles measured after creasing provided a means to quantitatively describe a material’s ability to retain a fold, and degree of plastic deformation incurred during folding. SEM micrographs of creased regions revealed tensile deformations on exterior crease surfaces while compressive deformations such as wrinkling occurred inside. Profilometry was performed on crease interiors to identify and measure wrinkle topology. It was found that increased dissipative plastic deformation led to retention of smaller fold angles. These characterization techniques can be used as a means of classifying and organizing polymers by potential usefulness in structural origami applications.