Modeling of Transport Phenomena in Metal Foaming

ude gas voids in the material structure with the real possibility to modify ad hoc their physical properties. During the foaming process of a metal, simultaneous mass, momentum and energy transport mechanisms arise. In this work we propose a model considering mass transfer phenomena coupled to the growth and motion of a gas bubble in the liquid metal. The diffusion of the gas in the liquid is studied by applying the Fick's law and convective transport. The equilibrium concentration at the gas-liquid interface is modeled by the Sievert's law with surface tension effects included. The numerical results of the simulation show that the computational model, using the phase field method for capturing the phase interface, can be effective. The computations simulate satisfactorily mass transfer, bubble expansion, interface movement and fluid flow. In this way other physical mechanisms of foaming could be included in a future more comprehensive model

A novel application of cryogenics in dieless sheet metal piercing

In tube punching, if the internal die is necessary to properly pierce the tube avoiding its collapse, it also represents a bottleneck to a rapid change of the punching set. In this research an innovative dieless tube punching approach has been conceived and studied. The use of a cryogenic fluid to force the material ductile-brittle transition is a way to limit the sheet deformation during the piercing process. The analysis of the innovative cryogenic punching was carried out both adopting numerical and experimental methodologies. A finite element FE model of the cryogenic punching was developed and updated in two stages. First, experimental tensile tests, performed at cryogenic temperatures, were used to characterize some material properties. Secondly, some piercing tests in cryogenic conditions were performed at different velocities and temperatures to fine update the model. A validation session was carried out to assess the model and the process feasibility. It was found that the FE model reproduced the experimental results within a maximum estimation error of 10% on both the punching force and tube deflection. Results showed that both the increment of the punching velocity and especially the decrement of the punching temperature could be the only viable solution for making the tube dieless punching industrially feasible

The analysis of tool life and wear mechanisms in spindle speed variation machining

Regenerative chatter vibrations generally limit the achievable material removal rate in machining. The diffusion of spindle speed variation (SSV) as a chatter suppression strategy is mainly restricted to academy and research centers. A lack of knowledge concerning the effects of non-stationary machining is still limiting its use in real shop floors. This research is focused on the effects of spindle speed variation technique on tool duration and on wear mechanisms. No previous researches have been performed on this specific topic. Tool wear tests in turning were carried out following a factorial design: cutting speed and cutting speed modulation were the investigated factors. The carbide life was the observed process response. A statistical approach was used to analyze the effects of the factors on the tool life. Moreover, the analysis was extended to the wear mechanisms involved during both constant speed machining and SSV. The worn-out carbide surfaces were examined under a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. Significant differences were appreciated. It was observed that SSV tends to detach the coatings of the inserts, entailing a mechanism that is quite unusual in wet steel turning and thus fostering the wear of the tool. The performed analysis allowed to deduce that the intensified tool wear (in SSV cutting) is mainly due to thermo-mechanical fatigue

Robust tool condition monitoring in Ti6Al4V milling based on specific force coefficients and growing self-organizing maps

Tool condition monitoring (TCM) is a mean to optimize production systems trying to use cutting tool life at its best. Nevertheless, nowadays available TCM algorithms typically lack robustness in order to be consistently applied in industrial scenarios. In this paper, an unsupervised artificial intelligence technique, based on Growing Self-Organizing Maps (GSOM), is presented in synergy with real-time specific force coefficients (SFC) estimation through the regression of instantaneous cutting forces. The conceived approach allows robustly mapping the SFC, exploiting process parameters and similarity to manage the variability of their estimation due to unmodelled phenomena, like machine dynamics and tool run-out. The devised approach allowed detecting the tool end-of-life in cutting tests with variable lubrication, machine tool and cutting speed, through the adoption of a self-starting control chart running on real-time clustered data. The solution was validated through the comparison of the GSOM framework with respect to the optimized self-starting control chart applied without GSOM clustering. The GSOM reached a root mean squared percentage error (RMSPE) of 13.2% with respect to 56.1% obtained with the analogous control chart in a full-set optimization scenario. When optimised on tests for a unique machine tool and tested on another machine tool, GSOM scored an RMSPE of 34.5%, whereas the optimized control chart scored 64.5%

Diffuse Interface Models for Metal Foams

le interest because of their potential applications in many fields of the industry. To produce a metal foam, a well-established process is starting with a molten metal, then introducing blowing agents to create gas bubbles inside the metal. In this work we use COMSOL Multiphysics® and apply the diffuse interface methods of the phase field technique, in order to model the properties of metal foams and describe the movement of the gas-liquid interfaces. A metal foam represented by a number of bubbles moving in a laminar flow is modeled and simulated. Surface tension effects are considered and repulsive forces between neighboring bubbles are expressed through the disjoining pressure. The numerical results show that diffuse interface methods are effective to model this kind of complex phenomena and that fundamental mechanisms due to surface tension effects an

Infection caused by Sporothrix schenckii: an autochthonous case in Bari, Southern Italy

An autochthonous case of lymphocutaneous sporotrichosis caused by Sporothrix schenckii is reported. The patient developed skin lesions localized along the lymphatics that appeared after he suffered an injury while collecting wicker canes in marshy water. The fungus was identified as Sporothrix schenckii by MALDI-TOF and sequencing. Phylogenetic analysis was also performed. Low MIC values were detected for all tested echinocandins and azoles except for fluconazole. The patient was treated with itraconazole without significant improvement. A regression of lesions was observed after 3 months of therapy with voriconazole. Few cases of sporotrichosis have been reported in Europe. However, several cases of sporotrichosis have been described in Italy. The incidence of sporotrichosis in Italy may be underestimated and microbiologists, and clinicians must be aware of this fungal infection

Applicability of abrasive waterjet cutting to irradiated graphite decommissioning

Characterization, dismantling and pre-disposal management of irradiated graphite (i-graphite) have an important role in safe decommissioning of several nuclear facilities which used this material as moderator and reflector. In addition to common radiation protection issues, easily volatizing long-lived radionuclides and stored Wigner energy could be released during imprudent retrieval and processing of i-graphite. With this regard, among all cutting technologies, abrasive waterjet (AWJ) can successfully achieve all of the thermo-mechanical and radiation protection objectives. In this work, factorial experiments were designed and systematically conducted to characterize the AWJ processing parameters and the machining capability. Moreover, the limitation of dust production and secondary waste generation has been addressed since they are important aspects for radiation protection and radioactive waste management. The promising results obtained on non-irradiated nuclear graphite blocks demonstrate the applicability of AWJ as a valid technology for optimizing the retrieval, storage, and disposal of such radioactive waste. These activities would benefit from the points of view of safety, management, and costs

Antibiotic use in departments of internal medicine of Lazio

Antimicrobial therapy is inappropriate in 9 to 64% of the patients hospitalized. We evaluated the antibiotic use in Internal Medicine wards of an Italian region (Lazio) by a prospective multicenter, observational study. One thousand and nine patients were evaluated. Patients under antimicrobial treatment (PUAT) were 588 (58.2%), patients without treatment (PWT) 421 (41.8%). Infections were classified as community acquired (47.8%), hospital acquired (10.3%) or healthcare-associated (11.4%); the remaining 30.5% of infections did not receive any epidemiological classification. Samples for microbiological examination were collected in 41.6% of PUAT. The antibiotic choice was empiric in 94.8% of the cases and protected penicillins were selected in 48% of the cases. The mean duration of treatment was 9.5±6 standard deviation (SD) days. Only 6% of the patients switched from intravenous to oral therapy. Age, length of hospital stay and mortality were higher for PUAT than for PWT (mean age: 75.9±15 SD vs 74.2±15 SD years, P<0.02; length of hospital stay: 13.7±10.4 SD vs 10±8.4 SD days, P<0.01; mortality: 15.9% vs 3.1%). Antibiotic stewardship needs to be implemented all over the hospitals of Lazio region

Time to redefine endometriosis including its pro-fibrotic nature

Endometriosis is currently defined as presence of endometrial epithelial and stromal cells at ectopic sites. This simple and straightforward definition has served us well since its original introduction. However, with advances in disease knowledge, endometrial stromal and glands have been shown to represent only a minor component of endometriotic lesions and they are often absent in some disease forms. In rectovaginal nodules, the glandular epithelium is often not surrounded by stroma and frequently no epithelium can be identified in the wall of ovarian endometriomas. On the other hand, a smooth muscle component and fibrosis represent consistent features of all disease forms. Based on these observations, we believe that the definition of endometriosis should be reconsidered and reworded as 'A fibrotic condition in which endometrial stroma and epithelium can be identified'. The main reasons for this change are: (1) to foster the evaluation of fibrosis in studies on endometriosis pathogenesis using animal models; (2) to limit potential false negative diagnoses if pathologists stick stringently to the current definition of endometriosis requiring the demonstration of endometrial stromal and glands; (3) to consider fibrosis as a potential target for treatment in endometriosis. This opinion article is aimed at boosting the attention paid to a largely neglected aspect of the disease. We hope that targeting the fibrotic process might increase success in developing new therapeutic approaches