Displacement boundary method for vibrations of piezoelectric materials

UNA FORMULAZIONE BEM ALTERNATIVA PER LA MECCANICA DELLA FRATTURA

MULTIDOMAIN BOUNDARY ELEMENT MODEL FOR CRACKS IN MAGNETO-ELECTRO-ELASTIC MATERIALS

Analysis of piezoelectric composite laminates with edge delamination

Composite piezoelectric laminates play a crucial role in the development of the smart structures technology for aeronautical and aerospace applications, since they combine the mechanical features of the classical laminates with the additional capability to sense deformation and to adapt the structural response accordingly, allowing in this way an efficient structural control, which is achieved by exploiting the features of the electromechanical coupling. In piezoelectric devices the electrical and mechanical loads give rise to stresses whose intensity can be sufficiently high to lead to the failure of the material, especially if damage is present. In this framework, a topic of great relevan…

Free vibrations of anisotropic panels

A meshfree approach, called Displacement Boundary Method, for the analysis of in-plane and out-of-plane free vibrations of anisotropic plates is presented. The discretization process is based on the use of a modified variational principle and the static fundamental solutions of the problem operators. The stiffness and mass matrices are frequencyindependent, symmetric and positive definite and their computation requires boundary integrations of regular kernels only. Thus, the final resolving system can be solved with classical approaches by using standard numerical procedures. Numerical results are presented to show the accuracy and effectiveness of the method.

Dynamic analysis of magneto-electro-elastic structures by a meshless approach

A Theory for Multilayered Composite Beams

Composite laminates are nowadays widely employed as lightweight components in civil engineering, automotive and aerospace applications due to their excellent mechanical properties, such as, the high strength and stiffness per unit weight, the path loads management capability. Moreover by using composite laminated materials it is possible to manufacture large size structures with less riveted joints, which leads to a reduction of the overall structural complexity and of the manufacturing and inspection times and costs. A drawback of layered composites is represented by the the low values of throughthe-thickness tensile and shear strengths, with respect to the in-plane ones, that affect the o…

On the transient response of actively repaired damaged structures by the boundary element method

The transient fracture mechanics behavior of damaged structures repaired through active piezoelectric patches is presented in this paper. The analyses have been performed through a boundary element code implemented in the framework of piezoelectricity to take account of the coupling between the elastic and the electric fields, which represents the peculiar feature of piezoelectric media. The multi-domain technique has been also involved to assemble the host structures and the active patches and to model the cracks. Moreover, the patches have been considered elastically bonded to the damaged structure by means of a zero thickness adhesive layer. This has been achieved through the implementat…

A Theory of Laminated Beams Subjected to Axial, Bending and Shear Load

A theory of laminated beams subjected to axial, bending and shear loads is presented in this paper. The kinematical model employed to describe the laminated beam displacement field is layer-wise in nature. Moreover it is such that the equilibrium equations and the continuity of the stress components at plies interfaces are satisfied. By using the whole set of interface continuity conditions in conjunction with the traction –free conditions on the beam top and bottom surfaces the layer-wise kinematical quantities are written in terms of the mechanical primary variables pertaining to one layer only, which are then expressed in terms of the laminated generalized displacements. The solution for…

An alternative 2D BEM for fracture mechanics in orthotropic materials

An original and alternative single domain boundary element formulation and its numerical implementation are presented for the analysis of orthotropic two-dimensional cracked bodies. The problem is formulated employing the classical displacement boundary integral representation and an alternative integral equation deduced on the basis of the stress function theory. This integral equation written on the crack provides the relations needed to determine the problem solution in the framework of linear elastic fracture mechanics. Numerical examples are reported and discussed to demonstrate the accuracy of the proposed approach.

BE contact analysis of delamination cracks actively repaired trhough piezoelectric active patches

Boundary Element Analysis of Magneto-Electro-Eleastic Bimorph Actuators

Magneto-electric laminates free vibration characterization by dual reciprocity BEM

Analytical solution for Magneto-Electro-Elastic Bimorph

Active repair technology applied to delaminated composite structures

The main target of the present paper is represented by the fracture mechanics charac-terization of delaminated composite structures actively repaired through piezoelectric patches. A boundary element code, formulated for anisotropic piezoelectric solids, including, as limiting case, the applicability to linear elastic anisotropic materials has been then imple-mented. The modeling of the delaminated composite structures as well as of the assembled structures, made of the damaged components and the patches, has been achieved through the multidomain technique. Moreover, to take into account for the adhesive layer between the host structures and the piezoelectric patches, a "spring-model" has b…

A NUMERICAL APPROACH FOR THE PREDICTION OF SOUND GENERATED BY A MISTUNED ROTOR CASCADE

A numerical investigation on the effects of blade frequency mistuning on the acoustic emission of a rotor cascade in subsonic flow is shown. A numerical method has been developed and implementd to obtain the mistuned rotor aeroelastic response and the associated acoustic waves. Both the aeroelastic and acoustic models are based on a linear unsteady small perturbations theory. The dynamic aeroelastic coupling between bending and torsional responses of each blade and the aerodynamic coupling among the blades are included in the formulation.

An alternative BEM for fracture mechanics in orthotropic materials

A model for multilayered beams undergoing end loads

A formulation for layered beams undergoing end loads, namely axial, shear and bending actions, is developed and presented in this paper. A layer-wise kinematical model is first derived so that the point-wise balance relationships are fulfilled at the layer level. Successively, by enforcing the interface continuity conditions and taking the traction–free conditions on the top and bottom surfaces of the laminate into account, the layer-wise kinematical quantities are written in terms of generalized kinematical variables representative of the beam displacements field. The beam problem is then formulated in terms of these generalized variables leading to a model that shows the positive characte…