Mohammed Ouali

MODELING AND ANALYSIS OF BEAMS WITH DELAMINATION

In this paper, a mathematical model for beams with partially delaminated layers is presented to investigate their behavior. In this formulation account is taken of lateral strains. The principal advantage of the element is that it allows the modeling of delamination anywhere in the structure. Numerical results of the present model are presented and its performance is evaluated for static problems.

Effect of various parameters on delaminated actuators with piezo-beams

Several researches treated last years the introduction of the piezoelectric actuators in the engineering domains, and studied its behaviors under the effect of many parameters. A bimorph beam made of two piezoelectric layers with a delamination zone between them is studied using the FOSDT (First Order Shear Deformation Theory), the F. E. M. to modeling the problem, the obtained equation of motion are solved using Newmark method and Matlab to establish the calculations. A piezoelectric actuator made of a PVDF bimorph beam, and subjected to a delamination zone between its upper and lower layers is considered to study the influence of several parameters. Like the changes of the ambient temperature, the structural damping coefficient and some geometrical parameters. Using the FOSDT to model the axial and vertical displacements of this actuator, we used the F.E.M. method to discretize the beam. The delaminated beam presents more actuation than the perfectly bonded one.

Dynamic Analysis of Delaminated Beams

To investigate the dynamic behavior of beams with partially delaminated layers, a model is presented in this work. This model takes into account the lateral strains. The principal advantage of the element is that it allows the modeling of delamination anywhere in the structure. The region without delamination is modeled to carry constant peel and shear stresses. Numerical results of the present model are presented and its performance is evaluated.

Analysis of Delaminated Composite Plates

A mathematical model for plates with partially delaminated layers is presented to investigate their behavior. In this formulation account is taken of lateral strains. The principal advantage of the element is that it allows the modeling of delamination anywhere in the structure. The region without delamination is modeled to carry constant peel and shear stresses; while the region with delamination is modeled by assuming that there is no peel and shear stress transfer between the top and bottom layers. Numerical results of the present model are presented and its performance is evaluated for static problems. Laminated beams and plates are often used as primary load-carrying structures. However, the mechanical properties of composite materials may degrade severely in the presence of damage. One of the common types of damage modes in laminated composites is delamination. The presence of delamination is one of the most prevalent life-limiting failure modes in laminated composite structures. Many researchers had been studying the effect of delamination. Wee and Boay [1] developed an analytical model to predict the critical load of a delaminated composite laminated beam. Lee et al. [2] investigated the buckling behavior of the beam plate with multiple delaminations under compression. Kapania and Wolfe [3] examined the buckling behavior of a beam plate with two delaminations of equal length. Wang et al. [4] improved the analytical solution by including the coupling between the flexural and axial vibrations of the delaminated sub-laminates. Lee et al. [5] studied a composite beam with arbitrary lateral and longitudinal multiple delamination. Finite-element methods have been developed using the layerwise theory by Kim et al. [6]. Tan and Tong [7] developed a dynamic analytical model for the identification of delamination embedded in a laminated composite beam. To investigate the effects of delamination of a plate layers, a finite-element model is developed. Both displacement continuity and force equilibrium conditions are imposed between the regions with and without delamination. The accuracy of the approach is verified by comparing results with previously published data.

Introduction of Mass Points Into the Finite Element Method for the Dynamic Behavior Modeling of Rotating Machine

The dynamic modeling of the rotating machines system is required to understand their dynamic behavior and the associated vibration problems. Fortunately, this modeling has seen a great development, since the use of Timoshenko or Euler-Bernoulli beam, followed by the Jeffcott and Laval rotor until using fine and complex techniques these days.Unfortunately, this development remains still insufficient to describe in a realistic way the dynamic behavior, in particular the rotor.Nowadays, the using of the finite element method, which is considered as the powerful numerical tool, gave a great help. This method can model as real as possible the phenomena that influence the rotor behavior, but this tool remains inapplicable to describe its behavior when it undergoes at the same time motion, deformations and the faults effects.To resolve these problems, a number of mathematical artifices are used, but, these methods are some times very difficult or are too complex and the result obtained is not always as good as it hopes. In fact, the deformed rotor resolution method is reduced to a modal solution, which does not show the real deformations during time in many cases.In order to simplify the resolution and to show rotor movement with deformation under faults effects, a method is proposed to allow a better approach of this problem. This method is based on subdividing the structure to mass-point sections that make possible to consider the rotational motion with deformations of the rotors.In this work, the above method is implemented on engineering simulation software dedicated for rotordynamics, and the calculation results are validated against experimental data of fault simulations in rotors as presented in the following sections of this paper.Copyright