On the natural Fiber (Maize) Composite material

This work is focused on the compressive behavior in the elastic region of a composite material made out of stalk-based maize fiber and unsaturated polyester resin polymer as matrix with methyl ethyl ketone peroxide as a catalyst and Cobalt Octoate as a promoter [1]. Deformation and fracture behavior are investigated by using Extended Finite Element Method (XFEM). XFEM enables the accurate approximation of solutions with jumps, discontinuities or general high gradients across interfaces between the fibers and the matrix [2], [3]. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the response of small buildings to vibrations

In this work, the analysis the response to vibrations of a small building equipped with an electromechanical vibration absorber is investigated. In the first part, the case of harmonic excitation with constant or time dependent frequencies is considered, and in the second part, the case of random earthquakes, respectively. The cross correlation functions and the mean square displacements are calculated for the structure when it is equipped with an electromechanical vibration absorber. The stochastic process which characterizes the earth movements is coupled to the cnoidal method, which delivers the analytical solutions of the nonlinear problem. The interaction between the structure and the energy source is analyzed via the Sommerfeld effect inside the resonance region. The resonance capture and the vibration reduction are displayed by the time history responses of the displacement and angular velocities above the resonance.     

On the free vibrations of a piezoceramic hollow sphere

The aim of the paper is to analyze the free vibrations of a piezoceramic hollow sphere with radial polarization. Using the cnoidal method and a genetic algorithm solves the equations of a radially inhomogeneous spherically isotropic piezoelastic medium. The Reddy and the cosine laws represent the functionally graded property of material. It is seen that for a piezoceramic hollow sphere, the piezoelectric effect consists in increasing the values for the natural frequencies in the specified classes of vibrations.     

Chaos–hyperchaos transition in a class of models governed by Sommerfeld effect

The present paper points out the scenario of the hyperchaotic attractor formation (an attractor with at least two positive Lyapunov exponents) in a class of models governed by the Sommerfeld effects. The Sommerfeld effect is the result of the conservation law of energy. When a dynamical system is coupled to a power source, it acts like a energy sink for which a part of the source energy is spend to deform the system rather than increasing the drive speed. The Sommerfeld effect involves riddling bifurcation which explains the creation of the hyperchaotic attractor.     

On the dynamics of locally resonant sonic composites

The sound attenuation in a sonic composite is studied using a new method that combines the features of the piezoceramic theory, cnoidal method and genetic algorithms. A sonic composite consists of an array of acoustic scatterers embedded in an epoxy matrix. Acoustic scatterers are piezoceramic hollow spheres made from functionally graded materials – the Reddy and cosine graded hollow spheres. We show that stable attenuation bands may coexist with different patterns of dynamics, including chaos. In order to extend the method towards a tool for analyzing the sound attenuation in sonic composites, the behavior of a real sonic composite is simulated. The results concerning the full band-gaps have been validated by experimental data.     

On the non-ideal vibrating structures

In this work, analysis of the response to vibrations of a small building equipped with an electromechanical vibration absorber is investigated. The case of harmonic excitation with constant or time dependent frequencies is considered. The interaction between the structure and the energy source is analyzed via the Sommerfeld effect inside the resonance region. The resonance capture and the vibration reduction are displayed by the time history displacement of the last story. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the piezotronics and tactile sensing virtual simulation

A flexible finger with muscles made of Nitinol wires and the skin made of auxetic material is analyzed from the tactile sensing point of view. The recognizing of the shape and texture of 3D objects is performed by simulation the action of an array of nanopiezotronic transistors integrated into the skin. The array of nanopiezotronic transistors makes possible the detection of the pressure-induced changes in the auxetic skin. The shape and texture of the objects is best estimated by determining the surface and texture as an n-ellipsoid defined by 12 parameters. An inverse problem is solved in order to find these parameters from the condition that the n-ellipsoid best fits the set of data points probed by touch with the finger. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the chaotic behavior of the non-ideal vibrating systems

The paper discusses the chaotic behavior of a vibrating structure coupled to an energy source. The structural response of this system may act like energy sink under certain conditions so that a part of the energy supplied by the source is spend to vibrate the structure rather than increasing the drive speed, according to the Sommerfeld effect [1]. The energy source is influenced by the response of the system and consequently, the system exhibits jumps at critical values of the energy source. The system mimics a disappearance of the energy in the resonance regions which can affect the stability of the system, sending it to chaos [2-4]. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)