An explicit analysis conducted on the crack behavior in chirurgical cement (Polymethylmethacrylate -PMMA) used for Total Hip Prosthesis (THP) is of great importance in collecting information about the nature of the phenomenon of loosening of the cement application. The rupture of the orthopedic cement is practically the main cause of this loosening. Understanding different rupture mechanisms give a great value in advancing the durability of the cemented total prosthesis. The purpose of this study is to analyse cracks behavior, initiated in the cement that links the femoral-stem with the bone, using the Finite Element Analysis Method (FEM). The present study brings into focus the variation of the stress intensity factor in modes I, II and III. This rupture criterion is used according to the nature of crack, its orientation and its location in the orthopedic cement. At first, the level and distribution of the equivalent von Mises stress is analysed, which is induced in the medial, proximal and distal parts of the bone cement. Then, the behavior of different geometric forms of an elliptical crack is evaluated which are located and initiated within the body of these three parts.
Cement is the weakest link in the composition of total hip prosthesis in terms of mechanical properties. The knowledge of the intensity and distribution of stresses on the cement attaching the implant to the bone is of great importance for understanding the condition of the prosthesis and its failure. In this study, the finite element method is used to analyze the magnitude and the equivalent Von Mises stress distribution induced in different components of the total hip prosthesis (THP) as well as the identification of the damage induced in the cement and between two cavities located in the polymethyl methacrylate (PMMA). The crack propagation is determined and localized using the extended element method (XFEM). The results show that the fracture stress of the cement in its proximal part is very important. These stresses increase considerably with the interaction of the cavities in this binder, causing damage to the cement and the loosening of the prosthesis.
This research is based on the study of the fatigue behavior of an aluminum alloy plate with a central crack. The plate is subjected to a tensile loading on its lower and upper parts. Several parameters were highlighted, such as the loading effect with a load ratio R = 0. The effects of the load ratio on both the repaired and not repaired plates, by two composite patches, which are boron/epoxy and graphite/epoxy, were investigated, as well as the effect of the plate material on plate life, comparing different materials
Bone is a living material with a complex hierarchical structure that gives it remarkable mechanical properties. The bone undergoes constant mechanical and physiological stress, so its quality and its resistance to fracture evolve constantly over time through the process of bone remodelling. Bone quality is not only defined by bone mineral density but also by mechanical properties as well as micro architecture. The aim of this work is to model the fracture of the femur bone under a quasi-static and dynamic solicitation in order to create a digital model simulating the fractures of this element due to an accident. This modelling will contribute to improve the design of the means of transport to bring a better security to the passages. To achieve this goal, the modelling by the finite element method is performed to study the mechanical behaviour of bone structure and predict femur fractures.
The post-operative period for a carrier of total hip prosthesis (THP), especially in the first months, remains the most difficult period for a patient after each operation, even if traumatologist surgeons want the relief and success of their operations. In this investigation, selected three of the daily activities for a wearer of total hip replacement (THR), such as, sitting in a chair, lifting a chair and going down stairs, and was performed a numerical simulation by finite elements in based on experimental data by Bergmann (Bergmann 2001) in terms of effort for each activity. Different stresses have been extracted, as well as a detailed comparison between two activities with different induced stresses such as normal, tensile and compressive shear stresses.
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