A Multi-Point Loaded Piezocomposite Beam: Experiments on Sensing and Vibration Energy Harvesting

A common configuration for a piezoelectric vibration energy harvester is the cantilevered beam with the piezoelectric device located near the beam root to maximize energy transduction. The beam curvature in this configuration is monotonically decreasing from root to tip, so the transduction per unit length of piezoelectric material decreases with increasing patch length. As an alternative to such conventional configuration, this paper proposes a so-called inertial four-point loading for beam-like structures. The effects of support location and tip mass on the beam curvature shapes are analyzed for four-point loaded cases to demonstrate the effect of these configurations on the total strain induced on the piezoelectric patch. These configurations are tested experimentally using several different support locations and compared with results from a baseline cantilevered beam. Performance comparisons of their power ratios are made, which indicate improvement in the transduction per unit strain of the four-point loading cases over the cantilevered configuration. The paper concludes with a discussion of potential applications of the inertial four-point loaded configuration.

Analysis of the Chaotic Dynamics of MEMS/NEMS Doubly Clamped Beam Resonators with Two-Sided Electrodes

We investigate the chaotic dynamics of micro- and nanoelectromechanical (MEMS/NEMS) beam resonators actuated electrostatically by two-sided electrodes, considering devices with realistic physical parameters. We model the resonators using the Euler–Bernoulli beam theory with the addition of viscous damping, midplane stretching and the electrostatic force. For the purpose of numerical simulations, the partial differential equation describing the system is reduced to a one degree of freedom model using the Galerkin method. The resulting nonlinear ordinary differential equation incorporates the main effects of the beam curvature. A comparison with the widely used parallel plate approximation (PPA) evidences the significant effects of the beam curvature. It is also concluded that in the case of resonators with two-sided electrodes special care must be taken when using the PPA. A detailed numerical analysis reveals the region in the relevant parameter space where chaos can be found. Phase portraits, Poincaré sections and bifurcation diagrams are used to characterize the chaotic attractors. The effects of gap asymmetry and damping are also investigated, showing that a stronger chaotic dynamics is favored by small asymmetries and smaller damping. In general, a more complex chaotic dynamics was found, compared to what was initially expected. The results are relevant in view of the potential practical applications in the generation of pseudo-random numbers and chaotic signals for secure communications. The proposed improved model can be easily implemented numerically, helping in the design and simulation of resonators, and the comparison between theoretical and experimental results.

Formulation of a three-dimensional shear-flexible bimaterial beam element with constant curvature

This paper presents the closed-form formulation for a three-dimensional curved beam element with round bimaterial section. The formulation includes the effects of shear forces on displacements and stresses and of the beam curvature on the distribution of bending and torsional stress over the cross section. The element is coherent with the well-known theory for straight beams, which is obtained exactly as the curvature radius becomes infinite. The numerical predictions for a test case compare favourably with published analytical and experimental results and with the outcome of a purposely developed, large-scale FE brick model.

Study on Bend Performence of Binding Bars Prestressed Steel Box Concrete Beam

Put forward binding bars prestressed concrete filled steel box girder and analyses it’s advantage, Study on the bending moment by the fiber model method to analyze the beam-Curvature and load-Relation curves of deflection theory.Through the finite element software analysis of prestressed concrete steel box beam prestressed concrete filled steel tubes and four ways to set binding bars the ultimate bearing capacity of the beam,Analysis of the influence of the thickness of the steel plate and rod diameter, constraint, constraint rod axial spacing on various beam flexural capacity.The results show that,Binding bar has more advantages for prestressed concrete steel box using a thin plate bending ability improvement,Diameter, spacing of the binding bars binding bars as long as not bending capacity of prestressed concrete with binding bars of steel box beam structure under the condition of impact.

The analysis of composite beams with partial interaction using the general technique method

This paper presents a modeling technique that derives from the work of Newmark to describe the behavior of steel-concrete composite beams with elastic shear connection. The model is used to derive expressions for beam curvature, rotation and deflection under monotonic load from which the stiffness matrix is derived and finite element analysis performed on a set of illustrative examples. Model results are compared to those obtained using other method.