Iskanje po katalogu digitalne knjižnice

Opis: This paper presents an experimental and numerical analysis of the mechanical behaviour of orthopaedic implants with crack-type defects, considering the principles and advantages of the modern X-FEM method, which was used due to limitations of traditional FEM in terms of crack growth simulation, especially for complex geometries. In X-FEM, the finite element space is enriched with discontinuity functions and asymptotic functions at the crack tip, which are integrated into the standard finite element approximation using the unity division property. Though rare, femoral component failures are well-documented complications that can occur after hip prosthetic implantation. Most stem fractures happen in the first third of the implant due to the loosening of the proximal stem and fixation of the distal stem, leading to bending and eventual fatigue failure. The main goal of this paper was to obtain accurate and representative models of such failures. Experimental analyses of the mechanical behaviour of implants subjected to physiological loads, according to relevant standards, using a new combined approach, including both experiments and numerical simulations was presented. The goal was to verify the numerical results and obtain a novel, effective methodology for assessing the remaining fatigue life of hip implants. For this purpose, the analysis of the influence of Paris coefficients on the total number of cycles was also considered. Hence, this simulation involved defining loads to closely mimic real-life scenarios, including a combination of activities such as ascending stairs, stumbling, and descending stairs. The tensile properties of the titanium alloy were experimentally determined, along with the Paris law coefficients C and m. The finite element software ANSYS 2022R2 version was used to develop and calculate the three-dimensional model with a crack, and the resulting stresses, stress intensity factors, and the number of cycles presented in the figures, tables, and diagrams. The results for the fatigue life of a partial hip implant subjected to various load cases indicated significant differences in behaviour, and this underscores the importance of analysing each case individually, as these loads are heavily influenced by each patient’s specific activities. It was concluded that the use of numerical methods enabled the preliminary analyses of the mechanical behaviour of implants under fatigue loading for several different load cases, and these findings can be effectively used to predict the possibility of Ti-6Al-4V implant failure under variable cyclic loads.
Ključne besede: structural integrity, fatigue fracture, extended finite element method (XFEM), experimental testing, DIC, numerical simulations, stress intensity factor, orthopaedic implants, crack-type defect
Objavljeno v DKUM: 21.03.2025; Ogledov: 0; Prenosov: 8
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Opis: Different types of dental restorations are used in the treatment of a unilateral, free-end saddle. A unilateral, complex, partial denture is one of the indications for this case of partial edentulousness. Consequently, the aim of this study was to stress test the unilateral complex partial denture model and its parts, under load, when changing the length of the free-end saddle. The stress distribution in canines and the first premolar, as the retention teeth, was examined under the influence of physiological and excessive occlusal forces by moving the point of attack in a distal direction. CATIA software was used for the creation of the 3D, fixed restoration unit model, in real size, with the appropriate supporting structures (canine and first premolar with present crowns, alveola, periodontal space) that are connected by the SD snap-in-latch attachment to the mobile portion of a partial denture. The mobile portion consists of an acrylate-coated metal base with three teeth (second premolar, first and second molars). The stress analysis, using the finite-element method, was performed under the application of physiological loads of 25 N, 50 N, 75 N and 100 N, and excessive loads of 300 N, 500 N and 700 N in the second premolar region, as well as in the first and second molar region. The results of the analysis showed that the largest amount of load under the application of physiological occlusal forces is positioned on the abutment teeth. Excessive forces are borne by the attachment. The stress analysis, performed on the unilateral complex partial denture model, suggested that the obtained stress values are lower than the limit values at which the plastic deformationin the model occurs.
Ključne besede: enostransko kompleksna proteza, pritrditev SD snap-in-latch, fiziološka obremenitev, prevelika obremenitev, zobotehnika
Objavljeno v DKUM: 10.07.2015; Ogledov: 1710; Prenosov: 92
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