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Monotonic or cyclic uni-axial loading tests on specimens with or without notch are designed to characterize the materials, and to develop in their results a formulation of the material either analytically or by prediction using a numerical technique, by the finite element method and using the ABAQUS calculation code, The novelty in this work lies in the way the notch itself is subjected to stress. Many studies have focused solely on damage to structures caused by the presence of notches, whereas in reality it's the notches themselves that are subjected to sometimes severe and complex loading, The latter rapidly undermines the service life of these structures, strongly destabilizing the notch to the point of damage by a cyclic and uni-axial loading mode is the embodiment by a numerical prediction of this new idea in this work, which is based beforehand under simple condition on a validation of the numerical model to that of the experimental results, The fatigue behavior of the structure under the equivalent Von Mises flow stress is given by the combined hardening law, and the damage to the structure by crack initiation and propagation is also given by the XFEM (Extend Finite Element Method) technique, in the second part of this work, a reinforcement of the notch in the structure by a locally graded concept with another material surrounding the notch is proposed in order to delay damage under these loading conditions, the results of damage under the effect of the proposed parameters (grading concept and volume fraction index) have been highlighted in this work. [ABSTRACT FROM AUTHOR]

Our study delves into analyzing fatigue damage in notched structures, an essential field in structural mechanics. We aim to understand how geometric and dimensional variations in the notches affect fatigue damage under different modes and amplitudes of cyclic loading, focussing on the behavior of steel. Our research methodology integrates experimental and numerical approaches. Experimental validation encompasses material properties, mesh selection, and boundary conditions. The finite element method is tailored to address steel's elastoplastic behavior, employing calibrated parameters for kinematic and isotropic cyclic hardening models within the numerical realm. Specific findings elucidate the cyclic response of notched structures, tracking damage progression to critical thresholds, including the number of cycles to failure (Nf) and the critical crack length (Lc). Hysteresis curves vividly depict stress–strain relationships, offering insight into material behavior under cyclic loading. Implications span engineering domains, focussing on reliability and durability in the aerospace, automotive, and civil engineering sectors. Future directions include real-world applications and advanced techniques such as the Extended Finite Element Method (XFEM). In conclusion, this research enriches our understanding of fatigue damage analysis in notched structures, poised to impact safety and robust engineering design. [ABSTRACT FROM AUTHOR]

The evolution of preexisting voids causes damage to metal structures with large plastic deformation. In the ABAQUS-Explicit computer code, the damage by the Gurson–Tvergaard–Needleman model (GTN model) is included in the porous failure criteria law. The numerical predictions using the GTN model are very sensitive to the calibrations of these parameters of the experimental results. This model describes until the damage, the mechanism of the evolution of the voids, which begins with their growth and their nucleation with the particles until the coalescence of these voids of a critical level, which causes the damage to the structure. This analysis uses Voce's hardening model and von Mises' equivalent stress flow theory. After validation with experimental results, this work aims to analyze the sensitivity of these GTN parameters to the response to damage and to the evolution of the gaps. This objective is applied on a plate notch. [ABSTRACT FROM AUTHOR]

This study introduces an innovative numerical approach, validated through experiments, to incorporate functional graded materials (FGMs) volume fractions into mixing laws for fiber–matrix unidirectional composites. Nonlinear techniques address adhesive ductility, with the cohesive zone modelling (CZM) model integrated into finite element analysis using the ABAQUS code. The CZM model encompasses shear and detachment modes, characterized by adhesive stress increase in a trapezoidal shape. Proposed strategies introduce layer-specific fiber presence; concepts like C-1 exhibit denser fibers toward the middle, while C-2 and C-3 position them nearer to the plate edge. Stiffness from attached plates significantly governs overall responses, particularly under mixed loading conditions. The results have shown that the proposed grading concept C-2 provides an over-resistance capacity compared to other concepts. Additionally, using a special mesh in the composite grading, the results indicate that the adhesive formulation used in this analysis and the approach followed are primarily based on experimental results, demonstrating good agreement with the numerical model employed. [ABSTRACT FROM AUTHOR]

Given the various loading cases possible in tubular structures, cyclic bending moment is one of the frequent cases presented in bent structures attached by straight tubular parts, as in straight tubular structures or a connecting tubular element; their loading is under various cyclic modalities; analyzing these pressurized tubular structures or unlocking the difficulties of numerically predicting or approximating to possible and actual fatigue behavior is of interest to several researchers, this work opts to use 316LN stainless steel, also known as Z2CND18.12 N of an elbow attached by straight parts, the study of the cyclic response up to the damage of the pressurized bend is aimed at evaluating the behavior under the effects of the parameters analyzed, namely the amplitude and the pattern of the cyclic bending moment, The fatigue behavior of the steel is formulated as a combined isotropic and kinematic Ohno-Wang model introduced into the ABAQUS calculation code by parameters calibrated to the experimental, using the finite element method. The damage to the structure under a high cyclic bending moment is introduced into the structure mesh. Of the cyclic accumulation of stress, the damage will occur in the structure by crack initiation and propagation, hence using the XFEM technique. The non-linear behavior, independent of the strain rate, is based on the Von Mises equivalent stress flow theory by mode effect at high cyclic bending moment; the results presented by moment-rotation curves show a significant effect on the response, as well as the level of damage. That damage by crack initiation and propagation precedes excessive ovalization at the level of the elbow cross-section. The approach followed in this analysis and the reliability of the results obtained were previously based on a validation of experimental results, which showed good agreement with the numerical model used. [ABSTRACT FROM AUTHOR]

The objective of this work is to analyze some geometrical effect to predict the damage of aluminum 2024T3 structure after validate numerical model by experimental test. The mechanical of damage behaviour under tensile tests of several plates with notches of various forms are investigated using an XFEM technique. The finite element analysis is performed to determine the failure load of these plates. Four different form of notched plates in another part of this work are reinforced by a thickness augmentation with different shapes around the notch. The results of the tensile analysis show that the reinforcements gives the best increase in failure load of each plates.

The aim of this work is to analyze the failure behavior of a simple lap joint of type metal / metal consisting of 2024-T3 Aluminum plate bonded with an Araldite adhesive using the finite element method to predict damage of the metal in tensile and compressive load under the effect of geometric parameters such as the length of the overlap and the geometric shape of the two plates according to the overlap length. The numerical analysis is performed by the ABAQUS calculation code. The adhesive was modeled by an element of the CZM cohesive zone. the adhesive will be submitted in mixed mode given the non-linearity of the two applied load. the calculation of the failure load will be determined according to the different parameters mentioned above. It is well demonstrated that the type of loading and the parameters taken into consideration condition the strength of the structure. The effect of these different parameters on the strength of the adhesive joint is presented as results by failure load curves

The objective of this work is to study the effects of contact parameters on the cracking parameters of a specimen and a pad assembly. These parameters have been studied and evaluated by the finite element method analysis in two dimensions fretting fatigue model through the Abaqus calculation code. Different values of the coefficient of friction of 0.1, 0.3 and 0.6 were applied on the various lengths in contact for a = 0.1, 0.5 and 1mm. Thus, on the various values of angle of orientation of the crack equal to 15 °, 30 ° and 45 °. In addition, elements of the type (CPE4R) and the criterion of maximum tangential stress were applied. The curves of the crack parameters such as the SIF coefficients and the integral J were obtained and discussed. [ABSTRACT FROM AUTHOR]

A numerical study on the influence of contact parameters on fretting fatigue behavior is carried out by using a new method SFEM (Stretching Finite Element Method) is presented in this article. Several parameters are made to vary: geometric shapes of the mesh, materials and contact parameters. The three-dimensional parametric model is composed by specimen and a pad in full contact. A Fortran Code is used to generate the parametric mesh. The stress intensity factors are calculated by varying the above contact parameters and the stress intensity factor under modes 1, 2 and 3 are computed. [ABSTRACT FROM AUTHOR]

The volume fraction effect of carbon fiber in an epoxy matrix in the vicinity of the notch on the traction and torsion behavior were studied. This volume fraction which increases with the reduction of the thickness is a parameter which proved effective on the capacity of resistance. The calculations are done with the numerical code ABAQUS 2009 [1]. using the model Hashin with shell elements of the structure. The objective of this study is to simulate the damage of stratified composite materials, the effect of several parameters such as the stacking sequence and the increase of the thickness of the folds having the same orientation of the structure, were evaluated and presented by load-displacement curves. The results obtained from the study illustrate the variation of damage as a function of these effects which act simultaneously and which also show that these modifications have a higher absorption capacity than that without modifications. [ABSTRACT FROM AUTHOR]

Cracking resistance or fracture toughness of brittle materials, such as optical glasses, can be determined by Vickers indentation, which allows generating cracks along the diagonals of the indent whose length depends of the loading rate. Subsequently, a relationship between the crack length and the corresponding indentation load is applied to calculate the indentation fracture toughness. As a result, the precision of the fracture toughness will depend on the accuracy of the crack length measurement. To minimize the uncertainties of this parameter, we propose its measurement more precisely by a profilometric method. On the other hand, as the glass surface roughness is recognized to have an important influence on the crack growth, different surface preparations are studied to minimize this roughness effect. In this work, four types of glasses are studied, namely Classical Crown K5, Borosilicate Crown BK7, Dense Flint SF2, and Ceramic Zerodur® glasses. The surface polishing is performed by using CeO2 pellets, which allow obtaining a roughness value for Ra to be <10 nm. Vickers instrumented indentation tests, allowing the plot of the applied load as a function of the indenter displacement, are performed with various maximum applied loads of up to 90 N. Different relationships based on assumptions on the crack shape (half-penny/median or Palmqvist cracks) are then used to calculate the indentation fracture toughness. Additionally, to accurately measure the crack length, we present an original approach based on the analysis of the interferometry map obtained with an optical profilometer using a monochromatic wavelength. [ABSTRACT FROM AUTHOR]

AbstractThe elbow is presented in pressurized tubular structures as a connecting element, generally subjected to bending moments either out-of-plane or in-plane, in closure or opening. Another mode of bending moment that can also occur in these tubular structures is the combined bending moment between out-of-plane and in-plane in closure, or out-of-plane and in-plane in opening. In this work, to better present the potential severity caused by this loading mode, an elbow structure attached by straight tubular sections made of X60 steel is analyzed and its damage under this combined bending moment with orientations between the plane and out-of-plane of the structure is discussed. A reinforcement proposal will be made in the second part of this work. Indeed, the structure is pretreated thermally at the elbow, resulting in a graded structure along the thickness with two different material constituents: the base metal and the thermally affected zone (HAZ). Based on the concept of Functionally Graded Materials (FGM), the gradation is by volume fraction between the base metal and the HAZ, following a power law function of a volume fraction index (n). This graded property is introduced along the thickness by finite element layers. The elastic-plastic behavior of the HAZ-base metal mixture is modeled using the Voce model and the Von Mises equivalent stress flow theory. Using the XFEM technique(extended finite element method), the damage of the pressurized and thermally treated structure under a combined out-of-plane bending moment shows that these parameters condition the response and the level of damage. [ABSTRACT FROM AUTHOR]