Iskanje po katalogu digitalne knjižnice

Opis: The fabrication of pressure vessel heads with large diameters necessitates the production from a starting sheet composed of two sections with weld joint. Subsequent plastic deformation may influence changes in the mechanical properties of the sheet, particularly the welded joint. The subject of this research is the effect of incremental plastic deformation (known as Incremental sheet forming) and post weld heat treatment on the mechanical properties of the heat-affected zone in the welded joint, as well as an assessment of the structural integrity. One of the goals of the work is to show that in certain circumstances heat treatment is not necessary. The researches focus on destructive and semi destructive testing of samples extracted from an actual pressure vessel head structure. The material of the vessel head is steel grade P460 NL1, and the heads are manufactured in two thicknesses: 6 mm and 14 mm. The results of the structural integrity assessment are presented in the form of a FAD diagram.
Ključne besede: incremental sheet forming, post weld heat treatment, residual stress, steel grade P460 NL1, structural integrity, welded vessel heads
Objavljeno v DKUM: 19.08.2025; Ogledov: 0; Prenosov: 4
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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
Celotno besedilo (5,22 MB)
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Opis: This paper presents measurement of strain using stereometry method. It describes the use of digital stereometry to measure microstrains on the surface. This can be achieved by comparison of the images of point distribution on faced surface at different load levels. The examples present the possibility to measure strain concentration in the vicinity of crack tip on metallic sample. Applying two video cameras and corresponding software the image of strain distribution can be obtained in different forms, in 2D and 3D formats.
Ključne besede: stereometric measurement, stress, strains, structural integrity
Objavljeno v DKUM: 31.05.2012; Ogledov: 1534; Prenosov: 75
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