1,354,327 research outputs found
A sperm cell toxicity test procedure for the Mediterranean species Paracentrotus lividus
No full textMessa a punto del test Microtox solid-phase per la valutazione del rischio tossico dei sedimenti della laguna di Venezia
No full textParameter identification of elastoplastic materials by simulation of static and dynamic indentation tests
No full textThis work presents a numerical optimisation procedure for the identification of elastoplastic material parameters by inverse analysis, through both static and dynamic indentation tests. A Finite Element Method modelling of the indentation test is put in place, by analysing first macroscopic effects (indentation curve, residual imprint geometry) at variable constitutive parameters (elastic modulus, yield stress, hardening coefficient). The FEM solver is then linked to an optimisation routine, by assembling an integrated loop towards the solution of the inverse problem. Later, the FEM solver is replaced by a Radial Basis Function (RBF) Network interpolation of pre-calculated data, combined to a Principal Component Analysis (PCA), allowing to reduce the computational burden of each non-linear analysis. Next, a detailed study on the identification procedure is performed, by applying it to pseudoexperimental data generated numerically priory to the inverse analysis, possibly affected by random uncertainty at given variance. The reliability of the inverse procedure is then demonstrated, for both static and dynamic indentation tests, which appears to be a necessary condition for further validations based on true experimental data
L'impiego di Photobacterium phosphoreum nella determinazione del rischio tossico dei sedimenti
No full text
Elastoplastic parameter identification by simulation of static and dynamic indentation tests
No full textThis work presents a numerical optimization procedure for the identification of elastoplastic material parameters by means of inverse analysis, through both static and dynamic indentation tests. A finite element method (FEM) modelling of the indentation test is put in place by analysing first macroscopic effects (indentation curve, residual imprint geometry) at variable constitutive parameters (elastic modulus, yield stress, hardening coefficient). The FEM solver is then linked to an optimization routine by assembling an integrated loop towards the solution of the inverse problem. Later, the FEM solver is replaced by a radial basis function network interpolation of pre-calculated data, combined to a principal component analysis, allowing the reduction on computational burden of each non-linear analysis. Next, a detailed study on the identification procedure is performed by applying it to pseudo-experimental data that is generated numerically prior to the inverse analysis, which is possibly affected by random noise with given variance. The reliability of the inverse procedure is then demonstrated for both static and dynamic indentation tests as a necessary condition for further validations with true experimental data. The information from only the imprint geometry is shown to be sufficient for consistent material parameter identification
Identificazione parametrica di materiali elastoplastici mediante prove di indentazione statica e dinamica
No full textIl presente lavoro espone gli esiti di una procedura di ottimizzazione volta all’identificazione di parametri elastoplastici di materiale tramite analisi inversa, applicata a prove di indentazione statica e dinamica. Si sviluppa una modellazione delle prove agli elementi finiti, analizzando gli effetti macroscopici (curva di indentazione, impronta residua) dei parametri costitutivi elastoplastici (modulo elastico, sforzo di snervamento, coefficiente di incrudimento). Il solutore FEM viene integrato all’interno di una procedura di ottimizzazione in ambiente MATLAB. Successivamente, esso viene sostituito con un’interpolazione tramite funzioni a base radiale (RBF Network), abbinata ad analisi alle componenti principali (PCA), di un set di soluzioni FEM appositamente precalcolate. Si procede, quindi, ad uno studio dettagliato delle prestazioni della procedura di identificazione parametrica, applicandola a dati pseudo-sperimentali, generati numericamente a monte dell’analisi inversa, eventualmente affetti da incertezza a varianza imposta. Si dimostra l’estrema efficacia ed affidabilità della procedura approntata, ciò che appare condizione necessaria per successive validazioni con dati sperimentali reali
Friction coefficient measurements to assess tooling behaviour in hot rolling processes
No full textIn hot rolling, tool wear is an important issue, as well as friction and lubrication phenomena. An adhoc designed tribometer, able to reproduce industrial contact conditions, was applied to investigate a variety of tool-workpiece surface interactions during hot rolling. In this work, the experimental methods were tailored to assess friction coefficient for the severe case of piercing of hot steel billets by means of plugs in seamless pipe production. Tool samples were machined from commercial steel plugs. Before testing against the counterbody representing the steel billet, they were subjected to the same industrial treatment performed on the plugs to develop a proper oxide acting as lubricant and thermal barrier. Through ring-on-ring tribological experiments, factors affecting friction such as surface oxide, temperature, billet material (0.40%C steel vs. high-alloy P91 steel), sliding speed and contact pressure were investigated, even when surface plastic deformation occurred. The set-up methodology was also demonstrated to be suitable to investigate wear resistance of hard chromium coatings for mandrels
The manufacture of natural hydraulic limes: Influence of raw materials' composition, calcination and slaking in the crystal-chemical properties of binders
Get PDFThis study aims to achieve an in-depth understanding of the manufacturing process of natural hydraulic lime
(NHL) by assessing the influence of raw materials' chemical- mineralogical composition and the effect of the
slaking process. NHLs with variable hydraulicity were manufactured using 56 raw materials from carbonate
outcrops in Andalusia (Spain). This study shows that siliceous limestones with microcrystalline quartz generate
hydraulic phases after calcination. However, when the amount of this reactive silica exceeds 18% by weight, CaO
is not formed, and only calcium silicates appear. It was also found that slaking of NHL leads to partial hydration
of the most reactive calcium silicates, reducing the expected reactivity of the lime. Instead, exposure of NHL
quicklimes to environmental relative humidity promotes the formation of disordered portlandite and reduces the
partial hydration of hydraulic phases. Our findings demonstrate that standard slaking can be replaced by
alternative methods for the studied binders.State Research Agency (SRA) and the
Ministry of Science and Innovation under the Research Project PID2020-
119838RA-I00Regional Ministry of University Research and
Innovation of the Junta de Andalucía and FEDER (a way of making
Europe) B-RNM-188-UGR20Junta de Andalucía Research
Group RNM17
Effects of using tea waste as an additive in the production of solid bricks in terms of their porosity, thermal conductivity, strength and durability
Get PDFIn this paper, we investigated the use of tea waste as an additive in the production of traditional bricks. This could provide several environmental and economic benefits, as well as improving thermal insulation in construction. To this end, we produced brick samples with 0, 5 and 10 w% of tea waste mixed with a clayey material from Teruel (Spain) that was rich in quartz and phyllosilicates and had smaller amounts of carbonates. These samples were fired at 800, 950 and 1100 °C in an electric oven. We then analysed and discussed their chemical, mineralogical, textural and physical-mechanical behaviour and evaluated their durability in response to salt crystallization. The pore system of the bricks was examined using a combination of different analytical techniques (hydric tests, mercury intrusion porosimetry and digital image analysis). We also evaluated their thermal conductivity and observed that an increase in the firing temperature and the amount of tea waste altered the texture of the bricks, increasing their porosity. This happened above all at 1100 °C, where it led to the appearance of a new family of pores and increased the porosity to about 39% for bricks made with 10 w% added tea waste. The increased porosity made the bricks lighter. The bricks made with tea waste showed higher levels of water absorption and poorer mechanical strength. Our results suggest that the addition of tea residues strongly decreases the thermal conductivity and heat diffusion capacity of the bricks. They could therefore be used as lightweight bricks for the thermal insulation of buildings
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