scholarly journals Dynamic Characterization of Microstructured Materials Made of Hexagonal-Shape Particles with Elastic Interfaces

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1781
Author(s):  
Marco Colatosti ◽  
Nicholas Fantuzzi ◽  
Patrizia Trovalusci
Keyword(s):  
Mechanical Behavior ◽  
Discrete Model ◽  
Natural Frequencies ◽  
Constitutive Behavior ◽  
Dynamic Characterization ◽  
Hexagonal Shape ◽  
Macro Scale ◽  
Elastic Interfaces ◽  
Micropolar Model

This work aims to present the dynamic character of microstructured materials made of hexagonal-shape particles interacting with elastic interfaces. Several hexagonal shapes are analyzed to underline the different constitutive behavior of each texture. The mechanical behavior at the macro scale is analyzed by considering a discrete model assumed as a benchmark of the problem and it is compared to a homogenized micropolar model as well as a classical one. The advantages of the micropolar description with respect to the classical one are highlighted when internal lengths and anisotropies of microstuctured materials are taken into consideration. Comparisons are presented in terms of natural frequencies and modes of vibrations.

Operational Modal Analysis for Dynamic Characterization of a Ro-Lo Ship

2014 ◽  
Vol 58 (04) ◽  
pp. 216-224 ◽  
Author(s):  
Esben Orlowitz ◽  
Anders Brandt
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Operating Conditions ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Dynamic Characterization ◽  
Sea Trial ◽  
Global Modes ◽  
Bending Modes

The dynamic characteristics of ship structures are becoming more important as the flexibility of modern ships increases, for example, to predict reliable design life. This requires an accurate dynamic model of the structure, which, because of complex vibration environment and complex boundary conditions, can only be validated by measurements. In the present paper the use of operational modal analysis (OMA) for dynamic characterization of a ship structure based on experimental data, from a full-scale measurement of a 210-m long Ro-Lo ship during sea trial, is presented. The measurements contain three different data sets obtained under different operating conditions of the ship: 10 knots cruising speed, 18 knots cruising speed, and at anchor. Natural frequencies, modal damping ratios, and mode shapes have been successfully estimated for the first 10 global modes. Damping ratios for the current ship were found within the range 0.9%–1.9% and natural frequencies were found to range from 0.8 to 4.1 Hz for the first 10 global modes of the ship at design speed (18 knots). The three different operating conditions showed, in addition, a speed dependency of the natural frequencies and damping ratios. The natural frequencies were found to be lower for the 18-knots condition compared with the two other conditions, most significantly for the vertical bending modes. Also, for the vertical bending modes, the damping ratios increased by 28%–288% when the speed increased from 10 to 18 knots. Other modes were not found to have the same strong speed dependency.

Static and Dynamic Characterization of Some Tensegrity Modules

2000 ◽  
Vol 68 (1) ◽  
pp. 19-27 ◽  
Author(s):  
H. Murakami ◽  
Y. Nishimura
Keyword(s):  
Static Loading ◽  
Natural Frequencies ◽  
Singular Value ◽  
Dynamic Characterization ◽  
Order Of Magnitude ◽  
Equilibrium Matrix ◽  
Value Decomposition ◽  
Deformation Modes ◽  
Stiffening Effect

A set of procedures was presented for characterizing static and dynamic response of tensegrity modules. The procedures were applied to two tensegrity modules: a six-bar spherical module and a two-stage cylindrical module with three bars at each stage. The singular value decomposition of the initial equilibrium matrix revealed prestress and infinitesimal mechanism modes. The prestress stiffening effect of infinitesimal mechanism modes was found to be isotropic at each node. In the initial quasi-static loading, infinitesimal mechanisms exhibited soft response. As the deformation advanced, the stiffness of tensegirty modules increased almost quadratically with infinitesimal mechanism amplitudes. Modal analyses revealed that the lowest modes were those of infinitesimal mechanism modes and their natural frequencies were an order of magnitude smaller than those of higher deformation modes.

Static and Dynamic Characterization of Tensegrity Modules

1999 ◽  
Author(s):  
Hidenori Murakami ◽  
Yoshitaka Nishimura
Keyword(s):  
Static Loading ◽  
Natural Frequencies ◽  
Singular Value ◽  
Dynamic Characterization ◽  
Order Of Magnitude ◽  
Equilibrium Matrix ◽  
Value Decomposition ◽  
Deformation Modes ◽  
Stiffening Effect

Abstract A set of procedures was presented for characterizing static and dynamic response of tensegrity modules. The procedures were applied to two tensegrity modules: a six-bar spherical module and a two-stage cylindrical module with three bars at each stage. The singular value decomposition of the initial equilibrium matrix revealed pre-stress and infinitesimal mechanism modes. The pre-stress stiffening effect of mechanism modes was found to be isotropic at each node. In the initial quasi-static loading, infinitesimal mechanisms exhibited soft response. As the deformation advanced, the stiffness of tensegirty modules increased almost quadratically with infinitesimal mechanism-mode amplitudes. Modal analyses revealed that the lowest modes were those of mechanism modes and their natural frequencies were an order of magnitude smaller than those of higher deformation modes.

Simulation and Dynamic Characterization of a 3-Layer Piezo-Actuated Valveless Micropump System

2010 ◽  
Author(s):  
Hamid SadAbadi ◽  
Arvind Chandrasekaran ◽  
Muthukuraman Packirisamy ◽  
Rolf Wuthrich
Keyword(s):  
Natural Frequencies ◽  
Dynamic Properties ◽  
Simulation Method ◽  
Piezo Actuator ◽  
Dynamic Characterization ◽  
Actuation Frequency ◽  
Valveless Micropump ◽  
Actuation System ◽  
Output Flow

In order to design the valveless micropump with a Piezo actuator, it is essential to understand the dynamic properties of the actuating system. Besides several other considerations in designing of microfluidic systems, the efficiency of valveless micropumps also strongly depends on parameters of the actuation system including the actuation frequency. Cleary, higher displacement of the diaphragm results in higher output flow rate of the pump. Thus, studying the dynamic behavior of the actuation system forms one of the important considerations for the design of micropumps. Three different models of the actuating system for the fabricated micropump system are proposed with different boundary conditions and are simulated by finite element method using ANSYS. Comparison of the experimental results and the simulation results of the natural frequencies of the system shows that the proposed simulation method can also be now used as a tool to optimize the design of the actuation system in terms of natural frequency of the system.

scholarly journals New insights on homogenization for hexagonal-shaped composites as Cosserat continua

Meccanica ◽  
2021 ◽  
Author(s):  
Marco Colatosti ◽  
Nicholas Fantuzzi ◽  
Patrizia Trovalusci ◽  
Renato Masiani
Keyword(s):  
Continuum Theory ◽  
Representative Elementary Volume ◽  
Elementary Volume ◽  
Displacement Fields ◽  
Micropolar Continuum ◽  
Rigid Particles ◽  
Hexagonal Shape ◽  
Classical Models ◽  
Elastic Interfaces ◽  
Cosserat Continua

AbstractIn this work, particle composite materials with different kind of microstructures are analyzed. Such materials are described as made of rigid particles and elastic interfaces. Rigid particles of arbitrary hexagonal shape are considered and their geometry is described by a limited set of parameters. Three different textures are analyzed and static analyses are performed for a comparison among the solutions of discrete, micropolar (Cosserat) and classical models. In particular, the displacements of the discrete model are compared to the displacement fields of equivalent micropolar and classical continua realized through a homogenization technique, starting from the representative elementary volume detected with a numeric approach. The performed analyses show the effectiveness of adopting the micropolar continuum theory for describing such materials.

Sign in / Sign up

Export Citation Format

Share Document