Numerical study of eddy current by Finite Element Method for cracks detection in structures

In this paper, we try to use the finite element method of 2-D axisymmetry to solve problems in eddy current testing problems where the main idea is detecting crack's shape using the NDT-EC. Results are given for a simple eddy current problem using the finite element method as a tool to control cracks and defects in materials and eventually, to study their propagation as well as their shape classification. These latest can be described as the task of reconstructing the cracks and damage in a tube’s profile of an inspected specimen in order to estimate its material properties. This is accomplished by inverting eddy current probe impedance measurements which are recorded as a function of probe position. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products

Eddy current modelling using multi-layer perceptron neural networks for detecting surface cracks

A new method for computing fracture mechanics parameters using computational Eddy Current Modelling by Multi-layer Perceptron Neural Networks for detecting surface cracks. The method is based upon an inverse problem using an Artificial Neural Network (ANN) that simulates mapping between Eddy current signals and crack profiles. Simultaneous use of ANN by MLP can be very helpful for the localization and the shape classification of defects. On the other side, it can be described as the task of reconstructing the cracks and damage in the plate profile of  an  inspected  specimen  in  order  to  estimate  its  material properties. This is accomplished by inverting eddy current probe impedance measurements that are recorded as a function of probe position, excitation frequency or both. In eddy current nondestructive evaluation, this is widely recognized as a complex theoretical problem whose solution is likely to have a significant impact on the detection of cracks in material

On Numerical Assessment of Stress Intensity Factor in the Cracking of Brittle Materials

The present study evaluates the Stress Intensity Factor (SIF) during the propagation of a crack interacting with a nearby circular dislocation. The problem is formulated using a numerical approach such as FEM along with the software (ABAQUS). The stress field and the SIF are determined for different crack's length. A brittle material such as a glass having an equivalent elasticity modulus and a Poisson rain this research work. Besides, the proposed model is a rectangular specimen with an edge crack subjected to tensile stresses according to the mode 1 opening. Obtained results are compared and agreed with those determined by other researchers

Use of scanning electron microscope and the non-local isotropic damage model to investigate fracture process zone in notched concrete beams

In this study, a Scanning Electron Microscope (SEM) is used to understand the micro level aspect of the Fracture Process Zone (FPZ) in a concrete beam. It is mainly based on the preparation and analyzing samples which are considered as being a very important part of SEM (poor preparation techniques can lead to erroneous diagnosis of the concrete study). Numerically, the fracture of concrete requires the consideration of progressive damage, which is usually modeled by a constitutive law. This latest relies on numerical methods to obtain adequate solutions. It is shown herein that by using the Object Oriented Finite Element Method (OOFEM), obtained results agreed more or less with those of others researchers. On the other side, experimental results compromise those obtained by the use of the non-local isotropic damage model. It is finally proven throughout this study that the FPZ is defined by two parameters: the length and the width

Detecting the fracture process zone in concrete using scanning electron microscopy and numerical modelling using the nonlocal isotropic damage model

This paper deals with two aspects of the characterization of the fracture process zone (FPZ) in quasi-brittle materials such as concrete. An overview is given of the possibility of using a destructive technique, such as the scanning electron microscope, and a numerical model, such as the nonlocal isotropic damage model (NLIDM), to detect FPZ characteristics, e.g., length and width of the FPZ. The fracture of concrete requires the consideration of progressive damage, which is usually modelled by a constitutive law and can be studied by a numerical method. The object-oriented finite element method (OOFEM) has recently been used in damage studies, and thus the FPZ is calculated on the basis of one of the damage models (the NLIDM). The results obtained from the experimental investigation are similar to those obtained using the NLIDM, which has proven to be a useful tool for analysis of the cracking process

The use of acoustic emission to investigate fracture process zone in notched concrete beams

Acoustic emission (AE) has been used to investigate characteristics of the fracture process zone (length, width and macro crack propagation) in a concrete specimen subjected to four-point bending, using probability and statistical methods. To understand the process' of crack growth and fracture, a technique based on AE has been developed. The results are treated according to the laws of probability and statistics. It is shown that these results agree more or less in comparison to those obtained using other techniques