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3D non-linear MSD crack growth simulation for a riveted aeronautic reinforcement by DBEM
No full textNon-linear models for assessing the fatigue crack behaviour under cyclic biaxial loading in a cruciform specimen
No full textThis work addresses FEM-based numerical simulations of fatigue crack propagation in a cruciform specimen under biaxial loading and small scale yielding (SSY) conditions. Three non-linear models are used as fatigue crack propagation laws. The cruciform specimens are made of aluminium alloy D16T and modelled with non-linear material properties. In the experimental tests, starting from a surface flow mechanically created in the centre of the cruciform specimen, biaxial loading conditions are applied to create various pre-cracked configurations that correspond to different values of initial crack aspect ratios. In the numerical simulations, the material behaviour is modelled with a low hardening bilinear law. Each simulation is carried out with one of the established non-linear laws. At the end of the fatigue crack propagation simulations, several crack aspect ratios are obtained. Finally, these aspect ratios are compared with the corresponding experimental tests available in the literature
Surface flaw behavior in a round bar under combined tension and torsion loading
Full text linkThe subject for studies is a steel bar of circular cross-section with straight-fronted edge transversal notch undergoing fatigue loads. Both the optical microscope measurements and the crack opening displacement (COD) method are used to monitor and calculate both crack depth and crack length during the tests. The variation of crack growth behaviour is studied under axial and combined axial+torsional fatigue loading. Results show that the cyclic Mode III loading superimposed on the cyclic Mode I leads to a fatigue life reduction. In parallel to the experimental activity, numerical calculations are performed based on three-dimensional DBEM-analysis to determine the crack path (based on three distinct criteria from literature) and fatigue life. The experimental fatigue crack growth curve obtained from round bar specimens have been compared with the numerical predictions. The computational DBEM results are found to be in good agreement with the experimental findings
ANALISI BEM DELLE SOLLECITAZIONI A CARICO DEL NERVO TRIGEMINO CAUSATE DA IMPIANTI DENTALI MULTIPLI
No full textIn this work an elastic-static analysis is developed in order to assess how the masticatory loads, applied on a system of multiple independent implants in a mandible, are transferred to the trigeminal nerve. The simulation is based on the Boundary Element Method (BEM) and consider a perfect osteo-integration between implant and bone (continuity condition for traction and displacement at the implant-bone interface). The analysis considers the mandible segment containing two adjacent implants at different distances, each one loaded with a vertical load. Both the cortical and spongy bone are modeled as transversally isotropic. A non linear contact analysis is needed in order to properly model the nerve-canal interactions. The results obtained show the pressure on the trigeminal nerve against a varying distance between implants. Such information is useful for a correct surgical planning
Hybrid technique to assess the fatigue performance of multiple cracked FSW joints
Full text linkIn this paper a numerical-experimental procedure useful to numerically assess the fatigue performance of friction stir welded aluminium joints is presented. The impact of manufacturing residual stresses on crack propagation in the joint driven by a remote fatigue load can be predicted. The proposed sequential procedure starts with the experimental residual stress assessment by the contour method and proceeds through the multiple crack growth simulation by the Dual Boundary Element Method. In the frame of Linear Elastic Fracture Mechanics, the superposition principle is invoked to provide the mathematical foundation supporting the proposed modelling strategy. In order to validate the proposed procedure, simple specimens are fatigue tested, obtaining multiple crack propagation scenarios that are monitored, in order to compare experimental and predicted crack growth rate
DBEM Crack Path Predictions Against Experimental Findings And FE Results in a Shaft Under Torsion
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