Samir Khatir

Application of proper orthogonal decomposition and radial basis functions for crack size estimation using particle swarm optimization

Complex engineering problems require simulations, which are computationally expensive in cases of inverse identification tasks since they commonly requires hundreds of thousands of simulations. This paper propose a method based on model reduction for crack size estimation, combining the proper orthogonal decomposition method with radial basis functions. The reduced model is validated by comparing the obtained boundary displacements with the corresponding results from a finite element model. This inverse procedure is formulated as the minimization of the difference between the measured and computed values of displacement at selected boundary nodes, called sensor points, using particle swarm optimization algorithm. Convex and a non-convex specimens have been considered for investigations of crack presence, and identification of its size, different crack sizes have been tested to demonstrate the efficiency of the proposed approach.

Genetic Algorithm Based Objective Functions Comparative Study for Damage Detection and Localization in Beam Structures

The detection techniques based on non-destructive testing (NDT) defects are preferable because of their low cost and operational aspects related to the use of the analyzed structure. In this study, we used the genetic algorithm (GA) for detecting and locating damage. The finite element was used for diagnostic beams. Different structures considered may incur damage to be modelled by a loss of rigidity supposed to represent a defect in the structure element. Identification of damage is formulated as an optimization problem using three objective functions (change of natural frequencies, Modal Assurance Criterion MAC and MAC natural frequency). The results show that the best objective function is based on the natural frequency and MAC while the method of the genetic algorithm present its efficiencies in indicating and quantifying multiple damage with great accuracy. Three defects have been created to enhance damage depending on the elements 2, 5 and 8 with a percentage allocation of 50% in the beam structure which has been discretized into 10 elements. Finally the defect with noise was introduced to test the stability of the method against uncertainty.

Delamination detection in laminated composite using Virtual crack closure technique (VCCT) and modal flexibility based on dynamic analysis

The delamination problem is very important failure mechanism in certain types of composite structures. Detecting this type of damage using vibration data is currently a problem of interest to the structural health monitoring community. In this paper, we used finite element method with embedded interface for analysing damaged laminated composite structures. The flexibly modal method, in which analysis data is related to finite element modelling, is used to detect and localize delamination. Several numerical examples are presented in order to evaluate the accuracy this approach.

Structural Health Monitoring of Beam-Like and Truss Structures Using Frequency Response and Particle Swarm Optimization

In this paper, non-destructive damage identification in beam-like and truss structures using Frequency Response (FR) data is presented. This approach is to formulate an inverse problem using Particle Swarm Optimization (PSO) and Finite Element Method (FEM) to identify the presence, location and quantification of the damage. PSO is one of the most efficient bio-inspired methods. It is used to minimize the objective function, which is based on FR data. The damage in structure is caused by loss of rigidity at a specific location. The capability and efficiency of this application to identify the location and severity of damage are demonstrated by means of several numerical examples. The results of the proposed approach show good accuracy.

Crack Identification Using eXtended IsoGeometric Analysis and Particle Swarm Optimization

The eXtended isogeometric analysis (X-IGA) combined with Particle swarm optimization (PSO) is used for crack identification in two-dimensional linear elastic problems based on inverse problem. The application of fracture mechanics test under mode II loading is performed. The X-IGA possesses the advantages of the combination between eXtended Finite Element Method (X-FEM) and the Isogeometric Analysis (IGA). The objective function minimizes the gap between the calculated and measured displacements. Convergence studies at various positions of crack on the plate are calculated and the results shows that the proposed technique can detect damage with minimum accuracy 95% for the position and maximum accuracy 98%.

Numerical Simulation of cracked orthotropic materials using extended isogeometric analysis

In the present study, extended isogeometric analysis (XIGA) is used to analyse cracks in orthotropic media. NURBS and T-splines geometric technologies are used to define the geometry and the solution. Knot insertion and order elevation are used in NURBS models, while a new local refinement algorithm is applied to T-spline models. In XIGA, the basic idea of the extended finite element method (X-FEM) is used along with isogeometric analysis for modelling discontinuities by including enrichment functions. Special orthotropic crack tip enrichments are used to reproduce the singular fields near a crack tip, and fracture properties of the models are defined by the mixed mode stress intensity factors (SIFs), which are obtained by means of the interaction integral (M-integral). Results of the proposed method are compared with other available results.

Influence of Thermal Fatigue on the Wear Behavior of Brake Discs Sliding against Organic and Semimetallic Friction Materials

ABSTRACT In this article, brake discs are exposed to high thermal stress, causing thermal fatigue damage. The aim of this work is to study the evolution of the wear behavior of brake disc materials, such as cast iron, chromium steel, and metal matrix composites, under the influence of thermal fatigue. The brake disc specimens are heated and then cooled rapidly. Then, wear tests are carried out using a pin-on-disc-type tribometer. Organic and semimetallic friction materials are used for all wear tests. The results show that thermal fatigue affects the structure of the contact surfaces of all of the disc specimens by increasing their roughness. Furthermore, the wear rate of the friction materials increased, except a reduction of the wear rate is noted for the semimetallic friction material rubbing against cast iron. Moreover, thermal fatigue has no significant influence on the coefficient of friction. The worn surface of the metal matrix composite sliding against semimetallic friction material is characterized by abrasive and adhesive wear mechanisms.

Optimization of IGA Parameters Based on Beam Structure Using Cuckoo Search Algorithm

In this study, free vibration analysis of Timoshenko beams is presented in order to determine the error in natural frequencies of a beam using experimental and numerical analysis based on Isogeometric analysis (IGA). Numerical modeling based on IGA has been updated using Cuckoo search algorithm according to the results found by experiments. NURBS order and sensitivity of discretization in the longitudinal and transversal directions are updated by Cuckoo search to identify the IGA best parameters. The results show that higher accuracy is achieved by using optimization technique for a beam structure to identify the best IGA parameters.

A proposal application based on strain energy for damage detection and quantification of beam composite structure using vibration data

In this research paper, the damage in Carbon Fibre Reinforced Polymer (CFRP) laminate beams under free vibration and simply supported conditions, is investigated numerically by Finite Element Method (FEM) using Matlab program. The developed Cornwell Indicator is used for damage detection and quantification in the considered composite beams. The data was acquired by developing a software that performs dynamic analysis of composite beams based on FEM. The results show that the efficiency of the developed indicator.