Abdelkader Djebli - Academia.edu (original) (raw)

Papers by Abdelkader Djebli

Advances in Materials Science/Advances in Materials Sciences, Jun 1, 2024

International Journal of Architectural Heritage, Dec 16, 2023

A 3-D finite element analysis was conducted on a thin aluminum plate with a 45 ° inclined central... more A 3-D finite element analysis was conducted on a thin aluminum plate with a 45 ° inclined central crack. A modeling of the bonding repair with composite patch of different shapes was carried out. In addition to the patch shapes studied in the literature, a new butterfly shape was proposed. The latter is defined by a length H, a width B and a neck C in the middle. The main objective is to analyze the effect of patch geometry on the rate of decrease of stress intensity factors. This rate is characterized by a coefficient R which combines between the mode I and the mode II of the rupture (KI and KII). Thus, an optimization of the patch shape is made with respect to the effectiveness in decreasing the stress intensity factor. The comparison between the results obtained with the different patch shapes has shown that the butterfly-shaped patch is more effective for relatively small surfaces. On the other hand, the extended octagon shape has been shown to be more effective for higher patc...

International Journal of Engineering Research in Africa, Feb 1, 2016

A method of fatigue damage accumulation based upon application of energy parameters of the fatigu... more A method of fatigue damage accumulation based upon application of energy parameters of the fatigue process is proposed in the paper. Using this model is simple, it has no parameter to be determined, it requires only the knowledge of the curve W–N (W: strain energy density N: number of cycles at failure) determined from the experimental Wöhler curve. To examine the performance of nonlinear models proposed in the estimation of fatigue damage and fatigue life of components under random loading, a batch of specimens made of 6082 T6 aluminium alloy has been studied and some of the results are reported in the present paper. The paper describes an algorithm and suggests a fatigue cumulative damage model, especially when random loading is considered. This work contains the results of uni-axial random load fatigue tests with different mean and amplitude values performed on 6082 T6 aluminium alloy specimens. The proposed model has been formulated to take into account the damage evolution at different load levels and it allows the effect of the loading sequence to be included by means of a recurrence formula derived for multilevel loading, considering complex load sequences. It is concluded that a ‘damaged stress interaction damage rule’ proposed here allows a better fatigue damage prediction than the widely used Palmgren–Miner rule, and a formula derived in random fatigue could be used to predict the fatigue damage and fatigue lifetime very easily. The results obtained by the model are compared with the experimental results and those calculated by the most fatigue damage model used in fatigue (Miner’s model). The comparison shows that the proposed model, presents a good estimation of the experimental results. Moreover, the error is minimized in comparison to the Miner’s model.

Transactions of Famena, 2023

World Academy of Science, Engineering and Technology, International Journal of Civil and Environmental Engineering, 2015

Cmc-computers Materials & Continua, 2015

This work focuses on a linear elastic analysis by the finite element method and the development o... more This work focuses on a linear elastic analysis by the finite element method and the development of a shape function, commonly known as geometrical correction factor, for the case of semi-elliptical crack in a cylindrical rod. We used the same shape function to analyze the behavior of the rod in the case of a viscoelastic medium materialized by a polymeric material such as HDPE. A linear viscoelastic model calibrated from a relaxation test was developed and implemented in Abaqus. Results showed a relatively good performance, compared with finite element method.

Frattura ed Integrità Strutturale, 2019

Through this study, a numerical simulation based on 3D in order to investigate the effect of crac... more Through this study, a numerical simulation based on 3D in order to investigate the effect of crack-front shape on the stress intensity factor and fatigue crack growth behavior of center cracked aluminum plate repaired asymmetrically with bonded composite patch. Consequently, skew degree it is a significant effect on stress intensity factor (SIF) distribution along the crack front in thick panels more than in thin panels. Moreover, fatigue life was calculated using different averaged stress intensity factor of patched panel determined from uniform crack front model and skew crack front model obtained from FEM and when comparing fatigue life values obtained from the finite element model with experimental values were shown a good agreement.

International Journal of Engineering Research in Africa, 2019

A fatigue damage accumulation model for composite materials is proposed. There is unanimity on th... more A fatigue damage accumulation model for composite materials is proposed. There is unanimity on the complex nature of the mechanisms of damage inherent to these types of materials. This led to proposals for nonlinear models, but relatively expensive in experimental requirements and determination of parameters. Thus, the proposed model is simple and does not require parameters apart the ultimate strength and the fatigue curve. A program is developed to allow the follow-up of the damage evolution during the cycles of loading. The proposed model is applied to E-Glass/Epoxy [0°/90°] under two blocks loading. Prediction results are relatively good and fit well with the experimental results compared to similar models.

International Journal of Engineering Research in Africa, 2017

A nonlinear 3-D finite element analysis was conducted to analyze the crack front behavior of a ce... more A nonlinear 3-D finite element analysis was conducted to analyze the crack front behavior of a center cracked aluminum plate, asymmetrically repaired with composite patch. According to experimental observations, the crack front was modeled as an inclined shape from the initial state where the crack front is straight and parallel to the thickness direction from the patched side toward the un-patched side. The skew degree is found to strongly influence the stress intensity factor (SIF) distribution along the crack front. In effect, the obtained trends of the SIF’s distribution are different and changes during crack growth stages. The main finding is that regardless the crack front shape (inclination), the average stress intensity factor through the crack front remains constant and consequently, it means to be an effective parameter to estimate the fatigue life and crack growth of the asymmetrically patched structures. The performed models gave good results compared to the literature a...

Acta Mechanica Solida Sinica, 2016

In this study, an experimental analysis for determining the fatigue strength of HDPE-100 under cy... more In this study, an experimental analysis for determining the fatigue strength of HDPE-100 under cyclic loading is presented. The curve of cumulative fatigue damage versus number of cycles (D-N)was deduced from stiffness degradation. Based on the three stage damage trend, the remaining fatigue life is numerically predicted by considering a double term power damage accumulation model. This model is found to be accurate, both in modeling the rapid damage growth in the early life and near the end of the fatigue life. Numerical results illustrate that the proposed model is capable of accurately fitting several different sets of experimental data.

International Journal of Non-Linear Mechanics, 2013

Procedia Engineering, 2015

An experimental analysis for determining the fatigue strength of HDPE-100, under constant and var... more An experimental analysis for determining the fatigue strength of HDPE-100, under constant and variable amplitude loading is presented. Further, the cumulative fatigue damage behavior for HDPE-100 was experimentally investigated. First, The S-N curve was obtained to establish the fatigue life of The HDPE-100 subjected to constant stress amplitude. Secondly, the Cumulative fatigue damage was estimated by different cumulative model such as Miner rule, damage stress model and Energy model (Damage energy model). Comparison between predictions and experimental results showed different trends depending on the prediction model used.

Engineering, Technology & Applied Science Research, 2014

In this paper, an experimental analysis for determining the fatigue strength of PE-100, one of th... more In this paper, an experimental analysis for determining the fatigue strength of PE-100, one of the most used High Density Polyethylene (HDPE) materials for pipes, under cyclic axial loadings is presented. HDPE is a thermoplastic material used for piping systems, such as natural gas distribution systems, sewer systems and cold water systems, which provides a good alternative to metals such as cast iron or carbon steel. One of the causes for failures of HDPE pipes is fatigue which is the result of pipes being subjected to cyclic loading, such as internal pressure, weight loads or external loadings on buried pipes, which generate stress in different directions: circumferential, longitudinal and radial. HDPE pipes are fabricated using an extrusion process, which generates anisotropic properties. By testing in the Laboratory a series of identical specimens obtained directly from PE-100 HDPE pipes in longitudinal directions, the relationships between amplitude stress and number of cycles ...

International Journal of Automotive and Mechanical Engineering, 2019

The main objective of this paper is the formulation of analytical expressions for the direct calc... more The main objective of this paper is the formulation of analytical expressions for the direct calculation of fracture parameters for the case of an orthotropic material with elastic behaviour. Numerical simulation by finite element method is performed to evaluate the singular and non-singular terms of William's series. Based on the obtained results, a fitting procedure is performed to propose an analytical formulation involving the geometric parameters of the plate and the crack in the approximate estimation of these parameters. The importance of the proposed analytical expressions is that they do not require a complex and time-consuming numerical analysis for the computation of the stress intensity factors and T-stresses for such an orthotropic cracked panel. A comparative study between the results obtained by the proposed equations and those obtained by finite element procedure has shown a good correlation.

Mechanical and structural components are subject in the most cases during their services to rando... more Mechanical and structural components are subject in the most cases during their services to random loading. For this reason, it is necessary to reduce the complex history of these kinds of loading in a series of constant amplitude cycles. There are several counting methods that lead to different results. Among all these methods, it is recognized that the Rainflow Cycle Counting method provides the most conservative results. In this paper, a finite elements analysis technique is presented to predict the fatigue life using this method associate with the S-N method which is used for high cycle fatigue applications that makes no distinction between initiation or growing a crack, but rather, predicts the total life to failure. Comparison between numerical and experimental results is considering in this paper.