1,354,529 research outputs found
3D nonlinear coupled modelling of geomaterials using the unconventional Subloading Surface approach
No full textThe purpose of the work presented in this thesis is aimed to investigate the nonlinear behaviour of porous media, in detail soils, by means of an unconventional plasticity model named subloading surface.
The main feature of this model is the abolition of the neat distinction between elastic and plastic domains by assuming that plastic deformations occur whenever a change in the stress state is induced. Inside the conventional yield surface a new surface is create by means of a similarity transformation. This new surface, named subloading surface, expands or contracts depending on the stress evolution, leading to a gradual and smooth development of permanent deformations in the granular material.
Besides the more realistic answer of the simulations this theory allows a simpler numerical computation without the recourse of special techniques to define if the stress lies or not on the yield surface. In fact the subloading surface is such to pass always to the current stress point assuming the role of driving and measuring how the stress evolves in the analysis.
Many unconventional plasticity models can be found in literature but, except for the present, they all show some defects which may be relevant in cyclic plastic analyses where the accumulation of errors can produce a significant mistake in the forecast of the simulations.
As it will be shown in the following chapters the simple subloading surface model and the extended subloading surface one have been implemented in a fully coupled hydro-(thermo)-mechanical three dimensional F.E. research code, PLASCON 3D, in several scenarios dealing with: consolidation problems, subsidence at regional scale, numerical triaxial tests, tensile strength for particular soils and finally cyclic plasticity investigations. All the results show a good accordance with experimental data proving the reliability both of the theoretical model and of its implementation in the F.E. cod
A Chrome extension for managing work activities
No full textopenIl presente documento fornisce una descrizione del lavoro svolto durante il periodo di stage, della durata di circa trecentodieci ore, dal laureando Fincato Alessandro presso l’azienda Wavelop Srls.
Il progetto prevedeva l’analisi, la progettazione e l’implementazione di una estensione per Google Chrome che permetta la pianificazione e la consuntivazione di attività lavorative svolte dai dipendenti.
Il tutto utilizzando tecnologie attuali come ReactJS, TypeScript, HTML5 e CSS.This document describes the work accomplished during the internship period, lasting about three hundred and ten hours, by the graduate student Fincato Alessandro at the company Wavelop srls.
The project involved the analysis, design and implementation of an extension for Google Chrome that allows the planning and reporting of work activities performed by employees. All using current
technologies such as ReactJS, TypeScript, HTML5 and CSS
3D subsidence analyses above gas reservoirs accounting for an unconventional plasticity model
No full textThe coupled hydro-mechanical state in soils coming from consolidation/subsidence processes and undergoing plasticity phenomena is here evaluated by means of the subloading surface model. The most important feature of this theory is the abolition of the distinction between the elastic and plastic domains, as it happens in the conventional elastoplastic models. This means that plastic deformations are generated whenever there is a change in stress and a smoother elastoplastic transition is produced. The plasticity algorithm has been implemented in the PLASCON3D FE code, coupling hydro-thermo-mechanical fields within a saturated (locally partially saturated) porous medium subjected to external loads and water/gas withdrawals from deep layers (aquifers/reservoirs). The 3D model has been first calibrated and validated against examples taken from the literature, and then subsidence analyses at regional scales due to gas extractions have been developed to predict the evolution of settlements and pore pressure in soils for long-term scenarios
Numerical study on fatigue notch sensitivity of high and middle strength carbon steels for welded structures
No full textA numerical study of the return mapping application for the subloading surface model
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Purpose
Many practical problems in engineering require fast, accurate numerical results. In particular, in cyclic plasticity or fatigue simulations, the high number of loading cycles increases the computation effort and time. The purpose of this study is to show that the return mapping technique in the framework of unconventional plasticity theories is a good compromise between efficiency and accuracy in finite element analyses.
Design/methodology/approach
The accuracy of the closest point projection method and the cutting plane method implementations for the subloading surface model are discussed under different loading conditions by analyzing the error as a function of the input step size and the efficiency of the algorithms.
Findings
Monotonic tests show that the two different implicit integration schemes have the same accuracy and are in good agreement with the solution obtained using an explicit forward Euler scheme, even for large input steps. However, the closest point projection method seems to describe better the evolution of the similarity centre in the cyclic loading analyses.
Practical implications
The purpose of this work is to show two alternative implicit integration schemes of the extended subloading surface method for metallic materials. The backward Euler integrations can guarantee a good description of the material behaviour and, at the same time, reduce the computational cost. This aspect is particularly important in the field of low or high cycle fatigue, because of the large number of cycles involved.
Originality/value
A detailed description of both the cutting plane and closest point projection methods is offered in this work. In particular, the two integrations schemes are compared in terms of accuracy and computation time for monotonic and cyclic loading tests.
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A return mapping algorithm for elastoplastic and ductile damage constitutive equations using the subloading surface method
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