Bel Abbes Bachir Bouiadjra

Stress analysis in single molar tooth.

The human tooth faces different stresses under environments of different loading conditions, these loading produces major factors in weakness of the tooth and bone structure. The need to save natural teeth has prompted the development of novel and complex techniques in endodontology, prosthodontics and periodontology. Despite a poor long-term prognosis and some prejudice to local bone, considerable efforts have been exerted for the realization of these techniques. Nowadays, the 3D finite element analysis (FEA) is one of the more recently used techniques for stress analysis in single human tooth under different loading cases. The von Mises stress distribution indicated that the greatest effort area of tooth lies at the base of crown up to the gingival line with varying intensities in the different loading cases. The highest stress in the cortical bone was predominantly found around the cervical region of the tooth and lowest in the cancellous bone and periodontal ligament (PDL). The PDL is a soft tissue, and it could function as an intermediate cushion element which absorbs the impact force and uniformly transfers the occlusal forces into the surrounding bone.

Numerical analysis of the crack growth path in the cement mantle of the reconstructed acetabulum.

In this study, we use the finite element method to analyze the propagations path of the crack in the orthopedic cement of the total hip replacement. In fact, a small python statement was incorporated with the Abaqus software to do in loop the following operations: extracting the crack propagation direction from the previous study using the maximal circumferential stresses criterion, drawing the new path, meshing and calculating again (stresses and fracture parameters). The loop is broken when the users desired crack length is reached (number of propagations) or the value of the mode I stress intensity factor is negative. Results show that the crack propagations path can be influenced by human body posture. The existing of a cavity in the vicinity of the crack can change its propagation path or can absolutely attract it enough to meet it. Crack can propagate in the outward direction (toward the acetabulum bone) and cannot propagate in the opposite direction, the mode I stress intensity factor increases with the crack length and that of mode II vanishes.

Finite Element Analysis of the Mechanical Behaviour of the Different Cemented Hip Femoral Prostheses

The designs of cemented hip femoral stems have an influence on both the quality of the metalbone cement contact and the failure rate of the cement mantle. Finite element stress technique has been used to optimize both design and material selection in load-bearing components in artificial hip joints based on the static load analysis, by selecting the peak load during the patient activity. In this study, two stem shapes (Ceraver Osteal and Charnley stems) for total hip arthoplasty (THA) were modelled. Static behaviour of these designed stem shapes were analyzed using commercial finite element analysis code ABAQUS. Linear elastic analysis is adapted; Von Mises stress and shear stress are the criterions that are of concern. Results show that, the stresses distribution in the femoral arthroplasty components depends on the material and design of the stem. In addition, the cement-bone and cement-stem interfaces seem to be crucial for the success of the hip replacement, hip prosthesis with Charnely stem induces the more stresses on the interfaces cement.

Effects of Voids Growth on the Damage of Polypropylene/Talc Micro-composite

AbstractIn this study, the effect of the voids growth on the damage of PP/talc micro-composite was analyzed using experimental and numerical approaches. Pure PP was filled with four proportions of treated talc: 5, 10, 40 and 50%. Tensile tests were performed on specimens manufactured from this composite. The Gurson–Tvergaard–Needleman model was implemented in FE model to predict the damage of the PP/talc. The predicted results were compared to the experimental ones. There is a good agreement between the numerical and the experimental results for pure PP, PP + 40% of talc and the PP + 50% of talc. We noted a significant divergence between the experimental and the numerical results for the PP reinforced with 5 and 10% of talc.

Optimisation of a Reinforced Cement Spacer in Total Hip Arthroplasty

Infections total hip arthroplasty (THA) are common and can lead to serious complications for patients. Newly developed antibiotic spacers successfully eradicated infection in more than 90 percent of patients. However, the low mechanical strength of the orthopedic cement can be a serious handicap for the success of the surgical operation. The reinforcement of cement spacers with high strength materials can improve the efficiency of this type of surgery. In this study, the three-dimensional finite element method (FEM) is coupled with the experimental design method (EDM) to optimize the geometrical and mechanical properties of the reinforcement that can be applied to cements spacers. The obtained results show that the full stem reinforcement in bio-ceramic with a thickness of 8.2 mm can represent the optimal model to ensure good mechanical resistance of the cement spacer.

Analysis of Crack Propagation by Bonded Composite for Different Patch Shapes Repairs in Marine Structures: A Numerical Analysis

This paper focuses on the cracks repair of A5083 aluminum alloy widely used in marine structures. Indeed, these latter are under continuous high loadings which, with time, cause fatigue of the material and finally damage and crack propagation. Composite patches play an important role in repairing damaged structures by cracking in order to restore them as much as possible to their original operating state. In this study, we compare performance and efficiency between two patches made in carbon-epoxy and boron-epoxy with four different shapes: circular, rectangular, trapezoidal and elliptic. The loading and crack lengths effects on the performance of these patches were also studied. This numerical investigation was carried out to highlight the evolution of the J-integral as a function of the applied load, the geometrical shape of the patch and the crack length for both types of composites. According to the obtained results the best performance for the improvement of crack propagation resistance in aluminum alloy marine structures was achieved by using a circular patch in boron-epoxy.

Stress Distribution of the Variable Dynamic Loading in the Dental Implant: A Three-Dimensional Finite Element Analysis

Stable osseointegration between implant threads and the surrounding marginal bone provides the mechanical base of an implant for daily chewing activity. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. In this work we numerically analyze by the finite element method the distribution of the equivalent stress and their level in the bone the most fragile element of the dental prosthesis. Each set of the model contained a crown, framework, abutment, implant and bone, subjected to variable dynamic loading according to time.

The Effect of Dynamic Loading from Routine Activities on Mechanical Behavior of the Total Hip Arthroplasty

Dynamic loads from routine activities applied to the stem create dynamic stresses varying in time and resulting in the fatigue failure of the prosthesis components. Therefore, a finite element model can be used to predict mechanical failure. The purpose of this study was to develop a three-dimensional model of the cemented hip femoral prosthesis and to carry out finite element analysis to evaluate stress distributions in the bone, the cement and the implant compounds under dynamic loads from different human activities. Linear elastic analysis is adapted; von Mises stress, normal stress and shear stress are the values that are of concern. Results show that the stresses distribution in the femoral arthroplasty components depends on the human activity. The analysis also showed that the stresses are high in the proximal and distal parts of the cement mantle.

Experiments Method Design Applied to Optimization of Patch Repairs for Cracked Plates

The optimization of the patch shape of bonded composite repair in aircraft structures is an efficient way to improve the repair performance. In this study the three-dimensional nonlinear finite element method is used to determine the J integral variation along the front of repaired crack with bonded composite patch in aircraft structures. The experimental design method was applied to optimize the patch shape and size in order to determine the most influencing dimension on the repair efficiency.

J Integral Computation for Repaired Cracks with Bonded Composite Patch in Aircraft Structures

In this study, the three-dimensional and nonlinear finite element method is used to estimate the performances of bonded composite repairs of metallic cracked aircraft structures by analyzing the J integral and at the crack tips of repaired cracks for single and double symmetric patches. Several calculations have been realized to extract the plasticized elements around the crack tip. The obtained results show that composite repair reduces significantly the J integral at the crack tip which can improve the fatigue life of aircraft structures. It was also shown that the double symmetric patch has a considerable beneficial effect on the repair performance compared to the single patch.