Catálogo de publicaciones - libros

This paper deals with the electrical potential drop across a central crack in an infinite plane of piezoelectric material. Three typical electric boundary conditions along the crack surfaces, i.e., the permeable crack model, the impermeable crack model and the so-called exact electric boundary condition accounting for the permittivity of medium inside crack gap, are considered for comparison. The influences of different media on the electrical potential drop are studied. It is found that, even though under moderate mechanical loadings the crack opening displacement jump is small, the electrical potential drop is still very high under highly applied electric field, which may lead to electrical discharge. It is also found that silicon oil inside the crack gap yields much larger values of this drop than those induced from air or vacuum.

The scattering of plane elastic waves by an interface crack between a piezoelectric layer and a homogeneous half-space is analyzed by means of the integral transform and the Cauchy singular integral equation methods. The effects of the crack configuration, the direction of the incident wave and the material combination of the piezoelectric layer and the elastic substrate on the dynamic stress intensity factors are examined. It is found from the numerical calculation that the crack configuration, denoted by the ratio of the crack length to the layer width, and the incident angle of the wave have significant influences on the dynamic response. In addition, the growth of the interface crack may be retarded or accelerated by specifying an appropriate combination of the materials.

The present work deals with the modeling of 1–3 periodic active fiber composites made of piezoceramic (PZT) fibers embedded in a soft non-piezoelectric matrix. We especially focus on predicting the effective coefficients of periodic transversely isotropic piezoelectric fiber composites using representative volume element method (unit cell method). Two ways for calculating the effective coefficients, an analytical and a numerical approach, can be used. In this paper the focus is on a numerical approach based on the finite element method (FEM). The asymptotic homogenization method (AHM) is used to verify the numerical solutions. Special attention is given on definition of appropriate boundary conditions for the unit cell to ensure periodicity. With the method presented the effective coefficients were calculated for different fiber volume fractions and the results are compared and discussed.

A review is given about FEM-techniques to compute the coupled thermoelectromechanical boundary value problem of cracks in three-dimensional thermopiezoelectric structures. The thermoelastic and pyroelectric effects of inhomogeneous temperature fields are considered, assuming that the heat conduction problem can be treated first. In order to calculate the relevant fracture parameters precisely and efficiently, the following specialized techniques are presented in detail: i) special singular crack tip elements; ii) modified crack closure integral; and iii) definition and computation of the thermoelectromechanical J-integral. Special emphasis is devoted to semi-permeable crack face boundary conditions using the iterative capacitor analogy. The accuracy, efficiency and applicability of these techniques are exemplified by various problems.

This paper is concerned with the development of Trefftz -element for two-dimentional piezoelectric materials. Solutions in Stroh formalism for transversely isotropic piezoelectric materials are used for the intra-element displacement and electric potential (DEP) fields together with an independent DEP frame function field along element boundaries. The formulation is based on a modified variational functional in which electric field and strain are taken as basic variables. The final unknowns are the parameters of the frame function field consisting of the usual degrees of freedom (DOF) at corner nodes and an optional number of hierarchic DOF associated with the mid-side nodes. Some numerical examples are considered to show the application of the proposed formulation.

Several numerical examples are presented in which geometrical nonlinearity plays a considerable role when the actuation of piezolaminated plates and shells is considered. In each numerical example the comparison between linear and geometrically nonlinear approximations is drawn. For the numerical simulation of the actuation of piezolaminated shells a geometrically nonlinear finite shell element has been developed based on the total Lagrangian formulation. The strain-displacement relations are based on the assumptions of small strains and moderate rotations of the mid-surface normals. The displacement field in transverse direction is assumed to vary linearly according to the Reissner-Mindlin hypothesis.

Piezoelectric elements are commonly used as sensors and actuators in adaptive structures. Among the many types of piezoelectric elements, solid cylindrical elements are used in a broad range of practical applications. This paper presents a theoretical study of a piezoelectric solid cylinder under electric charge loading applied to the ends. The material is assumed to be transversely isotropic and the general solution of the governing equations is obtained in terms of a Fourier-Bessel series containing Bessel and modified Bessel functions of the first kind. A boundary-value problem corresponding to uniform electric charge loading applied to the ends of a cylinder is solved by expanding the applied load in terms of a Fourier-Bessel series. Selected numerical results are presented to portray the basic features of the electroelastic field of a cylinder for different length-radius ratios of the cylinder and piezoelectric materials.

Piezoelectric material has played an important role of the modern engineering such as ultrasonic transducers, ultrasonic receivers, ultrasonic motors, SAW devices and crystal oscillators to date. An elastic wave analysis of the material is indispensable to enlarge the applicability of the material. In this paper, we investigate a plane-like SH wave obliquely propagating through a periodic piezoelectric composite layered structure and derive a dispersion relation of the wave.

The scattering behavior of elastic waves in piezoelectric composites with 1–3 connectivity is taken into account. As the most utilized two-phase connectivity types, the functional piezoelectric composites with 1–3 connectivity, usually consists of piezoelectric cylinders aligned in a direction parallel to the poling direction and surrounded by polymeric medium, can be found many sensing and actuating applications. The method of wave function expansions is applied to study the scattering of a plane acoustic wave by piezoelectric cylinders surrounded by polymer medium. The dynamic stress concentration factor around the cylinders due to the incident wave is investigated and some other characters are studied.

Stress analysis for anisotropic elastic solids under anti-plane shear deformation is carried out. The axis of anisotropy is varying with depth from horizontal to normal and repeating its variation in the medium. Two problems, stresses in a thick plate and stress distribution around a Griffith crack, are considered. For both problems, exact closed form solutions are obtained and numerical examples show the nature of the variable off-axis of anisotropy.