Mechanical properties optimization of friction stir welded lap joints in aluminium alloy

This work focuses on the influence of the rotational and travel speed on the strength of AA 2024 T3 friction stir welded lap joints. Tensile tests were carried out on mini-specimens extracted from different welding zones. A central composite design was applied to identify the relative importance of the variable factors’ effects and their interaction on yield/ultimate strength and elongation for both heat affected zone (HAZ) and nugget zone. Surface methods and gradient algorithms were used to optimize the yield strength of the joints. Shear and micro hardness tests were executed to achieve a more complete mechanical characterization

A PFEM approach to the simulation of landslide generated water-waves

A Particle Finite Element Method is here applied to the simulation of landslide-water interaction. An elastic-visco-plastic non-Newtonian, Bingham-like constitutive model has been used to describe the landslide material. Two examples are shown to show the potential of the approach

Selective electrochemical machining of the steel molds in hot isostatic pressing of Ti6Al4V powder

Anodic dissolution is proven to be an effective method to remove stainless steel molds from Ti6Al4V compacts obtained from powder by hot isostatic pressing. Two different working solutions were studied: 2 M NaCl and 2 M NaCl + 0.05 M Na2EDTA. While both were capable of removing the steel mold, the latter was also capable of removing the diffusional layer made by the intermetallic phases generated between titanium and steel during the compaction process

Friction-Stir Welding of AA 2198 Butt Joints: Mechanical Characterization of the Process and of the Welds Through DOE Analysis

In this study, rolled plates of AA 2198 T3 aluminium alloy are friction-stir welded in butt configuration varying two fundamental process parameters: rotational and welding speeds. Two sets of empirical models based on regression analysis are developed. The first one predicts the stationary values of the in-plane and downwards forging welding forces in dependence of the process parameters under investigation. The second one predicts the mechanical strength, in particular yield and tensile strength, of the friction-stir welded joints as function of the same parameters. For the development of the empirical models, two 32 full factorial designs are used: one having the stationary values of the welding forces and the other having the yield and tensile strength as observed responses, respectively. Statistical tools such as analysis of variance, F tests, Mallows’ CP, coefficient of determination etc. are used to build and to validate the developed models. By using the desirability function approach, the optimum process parameters to simultaneously obtain maximum possible yield and tensile strength are found within the investigated range. The developed models can be effectively used to predict the stationary forces and the mechanical proprieties of the joints at 95% confidence level

The influences of the variable speed and internal die geometry on the performance of two commercial soluble oils in the drawing process of pure copper fine wire

The cold wiredrawing process constitutes a classical-tribological system in which a stationary tribe-element (die) is in contact with a tribe-element in relative motion (wire) and both interacting with the interfacial tribe-element (lubricant). This condition is reflected in the effect of friction as a function of the drawing speed and temperature, and directly affects the wearing of the surface into the die and the final quality on the drawn wire. The aim of this work has been to determine the best conditions to process ETP-copper using two different types of oil/water emulsion lubricants. For this purpose, six different die geometries have been proposed and a set of tests have been carried out at different speeds (between 1 and 21 m/s) to determine those combinations that give a lower value in the required drawing force (Fd). The experiments allowed to know the friction coefficient (µ), the temperature profile inside the drawing die and in the lubricant and also the mean roughness (Ra) in the drawn product. The results have shown that drawing speeds above 10 m/s significantly decrease the drawing force and, as a consequence, the friction effect on the interface. The best results have been achieved in the combinations of the lower die angle (2β = 14°) with drawing speeds between 17 and 18 m/s with both types of lubricants used, obtaining the lower values of the friction coefficient between µ = 0.10–0.15 with the lubricant type D (Agip S234-60 oil at 7% concentration). It has been found that those tests carried out with dies with a smaller approach angle have generally made it possible to obtain better qualities in the final product. Additionally, FEM simulations have been done to analyse those cases with the lower values of µ, throwing values of Fd that are consistent with those measured in the experimental setting and allowing to better understand the behavior of the material as it passes through the die

Friction stir welding of AlSi10Mg plates produced by selective laser melting

A preliminary research work is carried out to demonstrate the feasibility of friction stir welding AlSi10Mg plates produced by selective laser melting. The metallurgical evolutions occurring have been studied and discussed on the basis of detailed microstructure observations. The FSW process enhances the structure of the parent material so that the weld presents an overall refinement of the microstructure and a decrease in microporosity in all its zones. Using the friction stir welding technology, sound welds harder than the parent material can be obtained

A general model of dioxin contamination in breast milk: results from a study on 94 women from the Caserta and Naples areas in Italy.

BackgroundThe Caserta and Naples areas in Campania Region experience heavy environmental contamination due to illegal waste disposal and burns, thus representing a valuable setting to develop a general model of human contamination with dioxins (PCDDs-PCDFs) and dioxin-like-PCBs (dl-PCBs).Methods94 breastfeeding women (aged 19-32 years; mean age 27.9 ± 3.0) were recruited to determine concentrations of PCDDs-PCDFs and dl-PCBs in their milk. Individual milk samples were collected and analyzed according to standard international procedures. A generalized linear model was used to test potential predictors of pollutant concentration in breast milk: age, exposure to waste fires, cigarette smoking, diet, and residence in high/low risk area (defined at high/low environmental pressure by a specific 2007 WHO report). A Structural Equation Model (SEM) analysis was carried out by taking into account PCDDs-PCDFs and dl-PCBs as endogenous variables and age, waste fires, risk area and smoking as exogenous variables.ResultsAll milk samples were contaminated by PCDDs-PCDFs (8.6 pg WHO-TEQ/98g fat ± 2.7; range 3.8-19) and dl-PCBs (8.0 pg WHO-TEQ/98g fat ± 3.7; range 2.5-24), with their concentrations being associated with age and exposure to waste fires (p < 0.01). Exposure to fires resulted in larger increases of dioxins concentrations in people living in low risk areas than those from high risk areas (p < 0.01).ConclusionsA diffuse human exposure to persistent organic pollutants was observed in the Caserta and Naples areas. Dioxins concentration in women living in areas classified at low environmental pressure in 2007 WHO report was significantly influenced by exposure to burns

is 18f fluorodeoxyglucose uptake by the primary tumor a prognostic factor in breast cancer

Abstract Background We retrospectively investigated 18F-FDG uptake by the primary breast tumor as a predictor for relapse and survival. Patients and methods We studied 203 patients with cT1-T3N0 breast cancer. Standardized uptake value (SUVmax), was measured on the primary tumor. After a median follow-up of 68 months (range 22–80), the relation between SUVmax and tumor factors, disease free-survival (DFS) and overall survival (OS) was investigated. Results In the PET-positive patients, the median FDG uptake by the tumor was 4.7. FDG uptake was significantly related to tumor size, number of involved axillary nodes, grade, negative ER, high Ki-67 and HER2 overexpression. No distant metastases or deaths occurred in the PET-negative group. Five-year DFS was 97% and 83%, respectively in the PET-negative and PET-positive groups (P = 0.096). At univariate analysis, DFS was significantly lower in patients with SUVmax >4.7 compared to the patients with negative PET (P = 0.042), but not to the patients with SUVmax ≤4.7 (P = 0.106). At multivariable analysis, among PET-positive patients, SUVmax was not an independent prognostic factor for DFS (HR>4.7 vs ≤4.7: 1.02 (95% CI 0.45–2.31)). Five-year OS was 100% and 93%, respectively, in the PET-negative and PET-positive groups (P = 0.126). Conclusion FDG uptake by the primary lesion was significantly associated with several prognostic variables, but it was not an independent prognostic factor

Economic impact of the use of Hyalubrix® in the treatment of hip osteoarthritis in Italy

The present study aims at evaluating the economic impact of the use of hyaluronic acid (Hyalubrix®60/HyalOne) as an alternative to surgery in the treatment of hip osteoarthritis, consistently with the therapeutic protocol envisaged in the Ortobrix study. To quantify the cost and efficacy of the treatment options under evaluation, the perspective of both the Italian NHS and the Society was considered. To this end, a decision analysis model was created over a 4-year period, to quantify the cost of treatments, procedures and adverse events, as well as the benefits expressed as survival rates and reduced lost workdays. The results show that, since the treatment with Hyalubrix® enables to avoid or delay the need for Total Hip Replacement (THR) surgery, it is possible to reduce mortality, adverse events and total costs. Hyalubrix®, given in the hip by ultrasound-guided intra-articular injection as an alternative to surgery is the most favourable option, helping preserve the survival rate over a 4-year period, of approximately 1 in 100 patients considered candidates for THR, preserve work capacity for a total differential amount of 500 days, and achieve considerable savings in economic terms, of approximately 550,000 € and 600,000€ euros from the NHS and the Societal perspectives, respectively