Damage Zone Size Limit During the Crack Propagation

The principal goal of this work is to limit the damage zone length during the crack propagation in brittle materials. This study is based on the determination of stress fields by varying the distance between a semi-infinite crack and a neighboring dislocation. The model suggested is a rectangular element (a dish), having a semi-infinite crack in one of its ends and a dislocation located in the vicinity of a crack-tip, subjected to a tensile stress on mode I. The problem is treated numerically using Finite Element Method.For each distance between the two cracks (semi-infinite crack and dislocation), stress fields are given. On the basis of these stress fields, a limiting damage zone length is obtained.

Vibration Analysis of Piezolaminated Plates for Sensing and Actuating Applications Under Dynamic Excitation

The vibration characteristics of piezolaminated plates under coupled electromechanical loading are investigated using the finite element method. Higher order shear deformation theory is adopted to incorporate the effect of shear in the formulation. In the finite element formulation, an isoperimetric eight-nodded rectangular element is employed with linear through-the-thickness electric potential distribution. In the parametric study, the influences of geometry and boundary conditions on the vibration characteristics of piezolaminated plates are evaluated. Numerical results are presented for the frequencies of simply supported, clamped plates fitted with piezoelectric patches at the top and bottom surfaces of the laminate. For this, a model simulating the effect of the electromechanical loading with control potential is developed. Studies are also performed for piezolaminated plates with various thickness-to-span ratios, along with convergence test. The effect of the provision of piezoelectric layers to improve the vibration response of plates is investigated. This analysis reveals that the electro-mechanical coupling can strengthen the plate’s resistance to vibration.

A modified four-node rectangular element

The sensitized principle of virtual work is applied to modify the stiffness matrix of the ordinary four-node rectangular element by sensitizing terms. The sensitizing parameter values are determined by the single-element strain energy test. The reference solutions used are of bending mode types and their application removes the so-called parasitic shear behavior. A stiffness matrix of good quality is obtained corresponding exactly to an earlier formulation using incompatible modes.

Double-arm steel connector of glass façades

This paper presents a numerical analysis of a steel double-arm connector, according to the authors’ solution, designed for fixation of glass façades. The analysis was carried out in order to obtain a distribution of stresses and displacements, on the basis of which global displacements and maximum stresses were determined. An additional element of the solution was the use of the M8 bolt, as a linking element of the steel walls of both arms. The numerical simulation was performed using the ADINA program, which is based on the finite element method (FEM). The dynamic effect of wind gusts on the glass façade was assumed, taking into account both wind pressure and suction. The adoption of a rectangular element of the glass façade causes an unfavorable load distribution at the connection point. The conducted research allowed to determine displacements and stresses in a steel connector made of S355JR steel. The applicability of the proposed solution for glass façades with a height of up to 100 m has been demonstrated.

Approximating Bending Stiffness for Structural Optimization of Double-skin Hollowed Car Body Panels

This paper presents the construction of the approximate equivalent bending stiffness of double-skin hollowed rectangular plates. For this purpose, the equivalent bending stiffness of the plate are expressed first in the quadratic polynomial form with respect to the design parameters for structural optimization by using the Response Surface Method (RSM). Finite element formulation for bending problem of the plate is also formulated by using the ACM rectangular element, and then FE source code is developed by incorporating the equivalent stiffness obtained by the RSM. Finally the numerical results obtained from the present FEA with the equivalent stiffness are compared with the ones by a commercial FE software, ANSYS, and then the applicability of the approximate equivalent stiffness are studied.

A four-node quadrilateral element for vibration and damping analysis of sandwich plates with viscoelastic core

Constrained layer damping treatments have been widely used as an effective way for vibration control and noise reduction of thin-walled plates and shells. Despite extensive application in vibration and damping analysis of sandwich plates with viscoelastic core, the rectangular element is challenged by irregular structural forms in practical engineering. In this paper, a three-layer four-node quadrilateral element with seven degrees of freedom at each node is presented. Compared with classical rectangular element, the four-node quadrilateral element has stronger adaptability in complex structural forms and boundary conditions. Based on the layer-wise theory where the constrained layer and the base layer meet Kirchhoff theory and the viscoelastic layer satisfies first-order shear deformation theory, the finite element formulation of the sandwich plate with viscoelastic core is derived by the Hamilton principle in variational form and based on the generalization of the discrete Kirchhoff Quadrilateral plate element. The complex modulus model is employed to describe the viscoelastic core of sandwich plates, allowing for the material’s frequency dependent characteristics. The natural frequencies and associated modal loss factors are computed based on the complex eigenvalue problems. The frequency dependent characteristic of the viscoelastic core is considered and an iterative procedure is introduced to solve the nonlinear eigenvalue problem. At last, six verification numerical examples that include three sandwich beam-plates and three sandwich plates are provided to compare present method with experiment, analytical method, Galerkin method, finite element methods and commercial software (NASTRAN). The results show that the proposed finite element can accurately and efficiently simulate the sandwich plates treated with constrained layer damping with a variety of structural forms and boundary conditions.