242 research outputs found
Structural-Damage Detection by Distributed Piezoelectric Transducers and Tuned Electric Circuits
A novel technique for damage detection of structures is introduced and
discussed. It is based on purely electric measurements of the state variables
of an electric network coupled to the main structure through a distributed set
of piezoelectric patches. The constitutive parameters of this auxiliary network
are optimized to increase the sensitivity of global measurements- as the
frequency, response functions relative to selected electric degrees of
freedom-with respect to a given class of variations in the
structural-mechanical properties. Because the proposed method is based on
purely electric input and output measurements, it allows for accurate results
in the identification and localization of damages. Use of the electric
frequency-response function to identify the mechanical damage leads to
nonconvex optimization problems; therefore the proposed sensitivity-enhanced
identification procedure becomes computationally efficient if an a priori
knowledge about the damage is available.Comment: 18 page
Optimal piezo-electro-mechanical coupling to control plate vibrations
A new way of coupling electrical and mechanical waves, using piezoelectric
effect, is presented here. Since the energy exchange between two systems
supporting wave propagation is maximum when their evolution is governed by
similar equations, hence, an optimal electromechanical coupling is obtained by
designing an electric network which is "analog" to the mechanical structure to
be controlled. In this paper, we exploit this idea to enhance the coupling,
between a Kirchhoff-Love plate and one possible synthesis of its circuital
analog, as obtained by means of a set of piezoelectric actuators uniformly
distributed upon the plate. It is shown how this approach allows for an optimal
energy exchange between the mechanic and the electric forms independent of the
modal evolution of the structure. Moreover, we show how an efficient electric
dissipation of the mechanical energy can be obtained adding dissipative
elements in the electric network.Comment: 9 page
Synthesis of electrical networks interconnecting PZT actuators to damp mechanical vibrations
This paper proves that it is possible to damp mechanical vibrations of some
beam frames by means of piezoelectric actuators interconnected via passive
networks. We create a kind of electromechanical wave guide where the electrical
velocity group equals the mechanical one thus enabling an electromechanical
energy transfer. Numerical simulations are presented which prove the technical
feasibility of proposed deviceComment: International Symposium on Applied Electromagnetics and Mechanics in
honor of Professor K.Miya, Tokyo: 2000. 9 page
Analytical continuum mechanics \`a la Hamilton-Piola: least action principle for second gradient continua and capillary fluids
In this paper a stationary action principle is proven to hold for capillary
fluids, i.e. fluids for which the deformation energy has the form suggested,
starting from molecular arguments, for instance by Cahn and Hilliard. Remark
that these fluids are sometimes also called Korteweg-de Vries or Cahn-Allen. In
general continua whose deformation energy depend on the second gradient of
placement are called second gradient (or Piola-Toupin or Mindlin or
Green-Rivlin or Germain or second gradient) continua. In the present paper, a
material description for second gradient continua is formulated. A Lagrangian
action is introduced in both material and spatial description and the
corresponding Euler-Lagrange bulk and boundary conditions are found. These
conditions are formulated in terms of an objective deformation energy volume
density in two cases: when this energy is assumed to depend on either C and
grad C or on C^-1 and grad C^-1 ; where C is the Cauchy-Green deformation
tensor. When particularized to energies which characterize fluid materials, the
capillary fluid evolution conditions (see e.g. Casal or Seppecher for an
alternative deduction based on thermodynamic arguments) are recovered. A
version of Bernoulli law valid for capillary fluids is found and, in the
Appendix B, useful kinematic formulas for the present variational formulation
are proposed. Historical comments about Gabrio Piola's contribution to
continuum analytical mechanics are also presented. In this context the reader
is also referred to Capecchi and Ruta.Comment: 52 page
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