Elastoplastic analysis of cracked Aluminum plates with a hybrid repair technique using the bonded composite patch and drilling hole in opening mode I

The objective of this study is to analyze the performance of composite bonding repair, hole drilling and the combination of the two techniques (hybrid repairs) by tensile tests and to show the interest of a hybrid repair versus to other processes. These repair techniques can apply in different branches of engineering: mechanical, aerospace, civil, naval, etc. The finite element method with the ABAQUS code was used to model the mechanical behavior of the different repair techniques. The Notch Stress Intensity Factor (NSIF) is adopted to model the behavior of the cracked notch based on the volumetric method. The size of the plastic zone, the intensity of the normal σyy stress, the peel stress and CTOD are combined to model the proposed technics repairs. Although the bonded composite is very strong, the application of a drilling hole results in additional energy absorption and reduces the level of the maximum normal stress by about 50% compared to a simple patch only. The use of a hybrid repair has a high resistance compared to other proposed methods, improves the mechanical strength and increases the life of the cracked structure compared to a single composite joint and a repair by drilling hole only

FEM analysis of the tridimensionnel effect of microvoids on the PMMA behaviour in PTH.

The performance and success of cemented total hip arthroplasty is related to the stress fields in the cement mantle due to the loading caused by patient activities. To do this, a three dimensional linear elastic model was developed to investigate the intensity and distribution of equivalent stress in the bone cement (PMMA) between the microvoids. This analysis is made according to several parameters such as the size of the microvoids defects, its direction of the arrangement, its location in the seat of the stress concentration and the volume fraction of the microvoids (the microvoid-microvoid interdistance)

Numerical study of the mechanical behaviour and damage of fgm bent pipes under internal pressure and combined bending moment

The main objective of this work is the numerical prediction of the mechanical behaviour up to the damage of the bends of the functionally graded material (FGM) type ceramic/metal pipes. Firstly, the effective elastoplastic proper-ties of bent FGM pipes were determined using the homogenisation law by the Mori–Tanaka models for the elastic part and TTO (Tamura-Tomota-Ozawa) for the plastic part based on a rule of mixtures per function in the form of a power law. Our work also aims at the use of a meshing method (UMM) to predict the behaviour of the FGM by finite element in the mesh of the model. The analysis was performed using the UMM technique for different loading cases and volume fraction distribution. Two stages are necessary for the analysis of the damage: the first is the model of initiation of the damage established by the criterion of maximum deformation named MAXPE and the second is criterion of the energy of the rupture according to the theory Hillerborg used to determine damage evolution. Both stages involve a 3D finite element method analysis. However, for damage, the XFEM technique was used in our UMM method to predict crack initiation and propagation in FGM pipe bends. The results of the numerical analysis concerning the mechanical behavior showed, that if the nature of the bent pipes is in FGM, a good reduction of the various stresses compared to those where the nature of the pipe is metallic material. The results were presented in the form of a force–displacement curve. The validation of the proposed numerical methodology is highlighted by comparisons of current results with results from the literature, which showed good agreement. The analysis took into account the effect of the main parameters in a bent FGM pipe under internal pressure and bending moment on the variation of the force–strain curves

J-integral evaluation of repaired cracks in AA7075-T6 structures subjected to uniaxial tensile stresses

Bonded repairs using composite patches over metallic structures have been evaluated as a cost effective method to increase the life of damaged structures. The J-integral is a widely applied fracture mechanics parameter relating to the energy release associated with crack growth and is a measure of the deformation intensity at the crack tip. In practice, the calculated J-integral can be compared with a critical value for the material under consideration to predict fracture. This study aimed at providing an overview of the behavior of a cracked plate of AA7075-T6 alloy repaired with a boron-epoxy patch bonded with FM73 Adhesive layer. The Finite Element Method (FEM) using Abaqus Software 6.14 predicted the performance. The results show a considerable decrease in the value of the J-integral. This is due to the beneficial effect of the patch on the stress state at the crack tip. The best results were obtained from a uni-directional composite fibres orientation of 0°, where the fibers oriented parallel to the direction of load. A parametric analysis has been carried out to evaluate the effect of lay-up, load variation and crack mouth opening on the J-integral. It was found that the crack mouth opening displacement (CMOD) was reduced by 90–97%.https://www.elsevier.com/locate/polytest2020-08-01hj2019Materials Science and Metallurgical Engineerin