Horacio Sosa

Plane problems in piezoelectric media with defects

Abstract A two-dimensional electroelastic analysis is performed on a transversely isotropic piezoelectric material containing defects. A general solution is provided in terms of complex potentials, with emphasis being placed on stress concentrations that arise in the vicinity of circular and elliptical holes. It is shown that for this genre of problem both mechanical and electrical variables are responsible for the peak stresses.

On the fracture mechanics of piezoelectric solids

Abstract A fracture mechanics analysis is developed within the realm of two-dimensional linear piezoelectricity. The asymptotic expressions for the electromechanical fields in the vicinity of the crack are deduced, and their behavior is illustrated through several examples. The modelling of the electric fields effects on crack arrest and crack skewing constitutes one of the important features of this article.

Three-dimensional eigenfunction analysis of a crack in a piezoelectric material

Abstract A three-dimensional analysis of a semi-infinite crack embedded in a transversely isotropic piezoelectric material was performed by means of the eigenfunction expansions method. The results show the characteristic 1/√r singular behavior of the stress tensor in the vicinity of the crack. A similar behavior is also revealed for the electric field. In addition the study demonstrates that coupling (or decoupling) of the mechanical and electrical variables is a function of the distance to the crack tip as well as of the crack orientation.

New developments concerning piezoelectric materials with defects

The problem of a piezoelectric body with an elliptic cavity is revisited within the frame-work of two-dimensional electro-elasticity. In contrast to our previous formulation, the present analysis is based on the use of exact electric boundary conditions at the rim of the hole, thus avoiding the common assumption of electric impermeability. Expressions for the elastic and electric variables induced inside and outside the cavity are derived in closed form in terms of complex potentials. Comparisons between present (exact) and previous (approximate) models are effected to establish the limitations associated with the assumption of the impermeable hole, in particular when it becomes a slit crack.

Dynamic representation formulas and fundamental solutions for piezoelectricity

Abstract Representation formulas and fundamental solutions of the governing equations of transient piezoelectricity are obtained through a generalization of the reciprocal theorem and the plane wave transform method. It is shown that dynamic fundamental and singular solutions can be reduced to one-dimensional integral expressions by means of a slowness surface. The article provides the necessary mathematical foundations towards the development of the boundary element method for nonstationary, three-dimensional electroelastic problems.

Transient dynamic response of piezoelectric bodies subjected to internal electric impulses

Abstract The response of piezoelectric bodies disturbed by internal electric sources is investigated using integral representations of Greens functions and their derivatives. The emphasis of the article is placed on transient dynamic phenomena promoted by high intensity electric discharges applied over very short intervals of time. To that end closed form integral representations of the electro-elastic variables are derived and applied to investigate the behavior of transversely isotropic piezoelectric ceramics. In particular, the characteristics of the induced stress and electric field components are investigated numerically for the case of charge impulses of triangular shape.

Approximate Green's functions and a boundary element method for electro-elastic analyses of active materials

Abstract A boundary element method (BEM) for the analysis of two-dimensional, time independent problems of linear electro-elasticity is presented. Emphasis is given to the derivation of representation formulas and fundamental solutions as well as to the construction of an efficient numerical algorithm. The method is particularly suitable for studying the behavior of active materials such as electrostrictive, ferroelectric and piezoelectric ceramics. Two numerical examples with direct impact on the structural safety and reliability of piezoceramics are provided to demonstrate the virtues of the new BEM.

Further analysis of the transient dynamic response of piezoelectric bodies subjected to electric impulses

Electric and acoustic transient waves induced by an impulse point charge are represented and studied by means of dynamic Greens functions and their derivatives. Numerical results using such functions are generated to illustrate important features associated with the electroacoustic waves. In particular, the attenuation characteristics of the waves with distance from the source are analyzed for a class of material and electric load.

Remote Control of Quality Using Ethernet Vision and Web-enabled Robotic System

A dynamic, globalized and customer driven market brings opportunities and threats to companies, depending on the response speed and production strategies. One strategy is concurrent engineering (CE) that focuses on improving the product development process, by the consideration of various factors associated with the life cycle of the product from the early stages. Design for manufacturing (DFM) has proven to be an effective approach to implement CE concept. Recently, an important DFM concept in product quality has drawn much attention from both academia and industry. This is because intense domestic and international competition has put more emphasis on quality. This study investigates the feasibility of integrating Ethernet-based vision system and assembly robot for the purpose of remote quality control. The accuracy and repeatability of the system were tested and verified over the Internet, prior to the quality inspection. The web-enabled quality check and robotic operations present many benefits, such as ubiquitous access, remote control/programming/monitoring capability, and integration of production equipment into information networks for improved efficiency and product quality within the framework of CE and DFM.

Conservation laws in plate theories

SummaryThree conservation laws, expressed in terms of line and surface integrals, are derived for Reissners transverse shear theory of plates. Mindlins and Kirchhoffs (or classical) theories are included as particular cases. A physical interpretation of three plate transformations used to obtain the conservation laws is proposed. The path-domain independence property of the integrals, their connection to energy release rates due to cavity motions and their relationships with stress intensity factors are also discussed.ÜbersichtFür Reissners Theorie von Platten mit Querschub werden drei Erhaltungssätze, die durch Linien- und Flächenintegrale dargestellt werden, hergeleitet. Mindlins und Kirchhoffs Theorie sind als Sonderfälle enthalten. Vorgeschlagen wird eine physikalische Deutung von drei Variablentransformationen der Platte, die zur Herleitung der Erhaltungssätze benutzt werden. Weiterhin wird die Weg-Bereichsunabhängigkeit der Integrale, ihre Verknüpfung mit Energiefreisetzungsraten bei bewegten Löchern und der Zusammenhang mit Spannungsintensitätsfaktoren erörtert.