Fatigue behavior of dual-phase and TWIP steels for lightweight automotive structures

Presentazione orale al convegno Euromat 2011, svoltosi a Montpellier, Francia, dal 12/09/2011 al 15/09/201

Room temperature plastic flow localization in a Mn-alloyed austenitic steel

A fully austenitic steel containing 0.5 wt.% C and 22 wt.% Mn was recently proposed for the fabrication of automotive body structures by room-temperature sheet forming, the goal being weight reduction and better crash performance owing to its much higher yield stress and elongation (as compared to presently employed ferritic and multiphase steels). Full-thickness tensile specimens, cut from as-produced sheets, were polished and tested at different strain rates, and the macroscopic surface relief eventually induced by the plastic deformation was recorded with a video camera. Between 0.3 and 0.4 true strain, successive macroscopic deformation bands (forming about 45° angle with the tensile axis and involving the full specimen width) travel along the specimen, a new one being nucleated as the previous reaches one of the specimen heads, whereas the gage displacement vs. stress curve shows a series of steps, each corresponding to the transit of a band through the gage length, and the cross-head displacement vs. stress curve shows isolated stress peaks, each immediately preceding the nucleation of a new band. Afterwards, and up to rupture, a series of stationary deformation bands appear, most being immediately adjacent to the preceding ones, with the stress vs. strain curve showing a series of serrations with large stress drops. As the strain rate is increased from 0.0004 to 0.4 s-1, the overall flow stress slightly decreases and the mentioned plastic localization phenomena become less evident

Estimation of contact lens friction coefficient: The need for a protocol

Contact lens discomfort (CLD) is a sporadic or frequent condition that affects millions of contact lens users worldwide. The experience of the contact lenses (CLs) wearers is strongly influenced by many factors, among these the physical properties of lens materials. Especially, the friction coefficient (CoF) plays a critical role in the balance between lenses and ocular environment. The aim of our study is to quantify the CoF for different CLs by means of a nano-tribometer. Three experiments were performed following protocols already published in the literature, in order to evaluate the CoF dependance on testing parameters, such as sliding speed, applied normal force and number of sliding cycles. Our results identify a lack in the reproducibility of already published experiments and the necessity to identify a measuring standardized protocol

Aloe vera silver nanoparticles addition in chitosan films: improvement of physicochemical properties for eco-friendly food packaging material

In recent times, the searches for alternative materials to plastic is a popular topic, due to the danger that synthetic materials cause to the environment and humans. Among the promising natural polymers, chitosan (CS) is certainly one of the most suitable since it it is edible, non-toxic and derives from crustacean waste.- However, it is necessary to improve its physical properties to be widely applied in food packaging, whose market is dominated by synthetic plastic. In this work we have synthesized silver nanoparticles (AgNPs) using hot-plate and microwaves-based techniques, using Aloe Vera leaves extracts. The synthetic process follows the principles of green chemistry, since no toxic substance is used to obtain nanomaterials. These NPs, having dimensions <20 nm, were characterized by TEM, zeta potential, UV-vis, FTIR, and then added to CS having low and medium molecular weight to develop thin films after its polymerization. These films were evaluated in terms of swelling ratio, optical properties, thermal stability, wettability, roughness, and friction coefficient, understanding that the physical properties of the films improved after the intercalation of the AgNPs, albeit differences were observed using the two NPs type. Subsequently, the release of silver ions from films using different pH as well as in vitro toxicity tests were carried out to evaluate their applicability. Largely, the excellent properties of new com- posite materials make them promising materials for packaging of different kinds of foods

Caratterizzazione di leghe Zama 2 pressocolate in riferimento a fenomeni connessi con l’invecchiamento

Campioni di lega Zama 2 (ZP0430: Zn-4Al-3Cu) opportunamente prodotti con processo di pressocolata, sonostati sottoposti a differenti condizioni di invecchiamento naturale (tempi da 21 a 330 giorni) ed artificiale (tempidi 1, 3, 8 e 20 ore e temperatura di 100 °C). Nelle varie condizioni di trattamento i campioni sono stati sottopostiad analisi metallografica, roentgenografica, a misure dimensionali ed a caratterizzazione meccanica per valutarel’influenza delle condizioni di invecchiamento sulle caratteristiche microstrutturali, meccaniche e dimensionali ditale lega. Si sono riscontrate significative diminuzioni di caratteristiche meccaniche e resistenziali nel processodi invecchiamento, una dimensione dei cristalli primari della fase più ricca in Zn (h) fortemente influenzata dalladistanza dalla superficie oltre che dalla massività del singolo componente, mentre le variazioni dimensionalimisurate, in alcuni casi anche del 3% relativo, non evidenziano un andamento continuo. Analisi roentgenografichesono state effettuate per individuare la costituzione della lega e gli stati tensionali conseguenti al processoproduttivo che possono giustificare la non continuità delle variazioni dimensionali

Caratterizzazione di leghe Zama 2 pressocolate in riferimento a fenomeni connessi con l’invecchiamento

Campioni di lega Zama 2 (ZP0430: Zn-4Al-3Cu) opportunamente prodotti con processo di pressocolata, sonostati sottoposti a differenti condizioni di invecchiamento naturale (tempi da 21 a 330 giorni) ed artificiale (tempidi 1, 3, 8 e 20 ore e temperatura di 100 °C). Nelle varie condizioni di trattamento i campioni sono stati sottopostiad analisi metallografica, roentgenografica, a misure dimensionali ed a caratterizzazione meccanica per valutarel’influenza delle condizioni di invecchiamento sulle caratteristiche microstrutturali, meccaniche e dimensionali ditale lega. Si sono riscontrate significative diminuzioni di caratteristiche meccaniche e resistenziali nel processodi invecchiamento, una dimensione dei cristalli primari della fase più ricca in Zn (h) fortemente influenzata dalladistanza dalla superficie oltre che dalla massività del singolo componente, mentre le variazioni dimensionalimisurate, in alcuni casi anche del 3% relativo, non evidenziano un andamento continuo. Analisi roentgenografichesono state effettuate per individuare la costituzione della lega e gli stati tensionali conseguenti al processoproduttivo che possono giustificare la non continuità delle variazioni dimensionali

Conservazione e sicurezza strutturale di colonne in ghisa prodotte e montate in opera nel XIX secolo

riassunto esteso e presentazione orale al convegno Workshop IGF - Problematiche di Frattura nei Materiali per l’Ingegneria, Forni di Sopra (UD), 7/1/2010 - 9/1/201

Outdoor particulate matter (PM10) exposure and lung cancer risk in the EAGLE study

Objective Cohort studies in Europe, but not in North-America, showed an association between exposure to outdoor particulate matter with aerodynamic diameter ≤10 μm (PM10) and lung cancer risk. Only a case-control study on lung cancer and PM10 in South Korea has so far been performed. For the first time in Europe we analyzed quantitatively this association using a case-control study design in highly polluted areas in Italy. Methods The Environment And Genetics in Lung cancer Etiology (EAGLE) study, a population-based case-control study performed in the period 2002-2005 in the Lombardy Region, north-west Italy, enrolled 2099 cases and 2120 controls frequency-matched for area of residence, gender, and age. For this study we selected subjects with complete active and passive smoking history living in the same municipality since 1980 until study enrollment. Fine resolution annual PM10 estimates obtained by applying land use regression modeling to satellite data calibrated with fixed site monitor measurements were used. We assigned each subject the PM10 average estimates for year 2000 based on enrollment address. We used logistic regression models to calculate odds ratios (OR) and 95% confidence intervals (CI) adjusted for matching variables, education, smoking, and dietary and occupational variables. Results We included 3473 subjects, 1665 cases (1318 men, 347 women) and 1808 controls (1368 men, 440 women), with PM10 individual levels ranging from 2.3 to 53.8 μg/m3 (mean: 46.3). We found increasing lung cancer risk with increasing PM10 category (P-value for trend: 0.04). The OR per 10 μg/m3 was 1.28 (95% CI: 0.95-1.72). The association appeared stronger for squamous cell carcinoma (OR 1.44, 95% CI: 0.90-2.29). Conclusion In a population living in highly polluted areas in Italy, our study added suggestive evidence of a positive association between PM10 exposure and lung cancer risk. This study emphasizes the need to strengthen policies to reduce airborne pollution