Self Piercing Riveting for Metal-Polymer Joints

Self-Piercing Riveting (SPR) is a sheet metal joining technique based on the insertion of a rivet into two or more sheets, with no preparatory hole. This process has gained wide diffusion in the automotive industry, due to the increasing use of materials alternative to steel, that are difficult or impossible to join with traditional techniques. In particular, polymeric materials are becoming increasingly used, due to their favorable weight/strength ratio. This paper reports the results of experimental investigations, aimed at identifying the variables affecting the mechanical characteristics of mixed metal-plastic joints. A statistic model for the optimization of the geometrical parameters has been computed. The paper demonstrates that self-piercing riveting appears competitive for metal/polymer junction. The results analyzed in light of statistical techniques show that some geometrical parameters affect joint performance more than others and can therefore be used as independent variables for joint performance optimizatio

Additive manufacturing for the automotive industry: on the life-cycle environmental implications of material substitution and lightweighting through re-design

The automotive sector has recently been taking measures to reduce fuel consumption and greenhouse gas emissions for the mobility of ground vehicles. Light-weighting, via material substitution, and the re-designing of components or even a combination of the two, have been identified as a crucial solution. Additive manufacturing (AM) can be used to technologically complement or even replace conventional manufacturing in several industrial fields. The enabling of complexity-for-free (re) designs is inherent in additive manufacturing. It is expected that certain benefits can be achieved from the adoption of re-design techniques, via AM, that rely on topological optimisation, e.g., a reduced use of resources in both the material production and use phases. However, the consequent higher specific energy consumption and the higher embodied impact of feedstock materials could result in unsustainable environmental costs. This paper investigates the case of the light-weighting of an automobile component to quantify the outcomes of the systematic integration of re-designing and material substitution. A bracket, originally cast in iron, has been manufactured by means of a powder bed-based AM technique in AlSi10Mg through an optimized topology. Both manufacturing routes have been evaluated through a comparative Life Cycle Assessment (LCA) within cradle-to-grave boundaries. A 69%-lightweighting has been achieved, and the carbon dioxide emissions and energy demands of both scenarios have been compared. Besides the use-phase-related savings in terms of both energy and carbon footprint due to the lightweighting, the results highlight the environmental trade-offs and prompt the consideration of such a manufacturing process as an integral part of sustainable product development

Guidelines to compare additive and subtractive manufacturing approaches under the energy demand perspective

In order to characterise the environmental performance of additive manufacturing (AM) processes, comparative analyses are required. Different manufacturing approaches (such as additive and subtractive ones), besides adopting different equipment, use different kinds and amounts of material. Therefore, the material-related flow has to be followed throughout the entire product life. Differences in environmental impact arise at each step of the life cycle: material production, manufacturing, use, disposal, and transportation. A life cycle-based methodology able to take due account of all the factors of influence on the total energy demand for the production of metal components is given in this paper. Decision support tools for identifying the most sustainable manufacturing route (subtractive versus AM-based approaches) are presented for different scenarios. The aim of the present paper is to contribute to the debate concerning the environmental impact characterisation of AM processes

Performance assessment of a vibro-finishing technology for additively manufactured components

Metal components produced by Additive Manufacturing (AM) technologies usually exhibit a rough surface, that in certain applications can result detrimental for the part’s functionality. Thus, it is of great interest to study the finishing processes that can be applied to the surfaces, both external and internal, of AM components. The aim of this work is the evaluation of the capabilities of a vibro-finishing process in the treatment of samples produced by Laser-Powder Bed Fusion (L-PBF) from AlSi10Mg powders. In this research, the abrasive media is identified, and the surface quality improvement is analysed in terms of surface roughness and modifications induced by the finishing treatment (i.e., edge rounding, material loss) against finishing duration. The cost of the treatment is also evaluated

Additive manufacturing for an urban vehicle prototype: re-design and sustainability implications

Additive Manufacturing (AM), allowing the layer-by-layer fabrication of products characterized by a shape complexity unobtainable with conventional manufacturing routes, has been widely recognized as a disruptive technology enabling the transition to the Industry 4.0. In this context, the design of a Portable Assisted Mobile Device (PAMD) prototype was considered as a case study. The best practices of the re-design for AM were applied to three of the main structural components, and the most sustainable manufacturing approach between AM processes and the conventional ones was identified with respect to cumulative energy demand, carbon dioxide emissions and costs. The paper aims to promote the debate concerning the correlation between design choices, process selection and sustainable product development

Wire arc additive manufacturing of Ti-6Al-4V components: the effects of the deposition rate on the cradle-to-gate economic and environmental performance

Wire Arc Additive Manufacturing (WAAM) is a direct energy deposition process based on a wire-shaped metal feedstock which is melted by means of an electric arc to produce and/or repair components in a layer-wise manner. WAAM has shown to be suitable for producing large components, in particular those with a near-to-net shape, at relatively high productivity levels. The aim of this work has been to assess the effects of the WAAM deposition rate on economic and environmental sustainability metrics. A life cycle assessment has been performed under cradleto-gate system boundaries. Three components, with different geometrical characteristics (i.e., dimensions, masses, and solid-to-cavity ratios) and made of Ti-6Al-4V, have been considered as case studies. The effects of different deposition rates have been evaluated on the Cumulative Energy Demand, CO2 emissions, manufacturing times and costs. The conventional manufacturing route for the production of the same components, that is, machining from massive workpieces, has been considered as a benchmark for a process performance comparison. The results show that an increase in the deposition rate determines a significant reduction (up to 25%, on average) in the production time and, consequently, in the manufacturing costs

Multi-criteria environmental and economic impact assessment of wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) is a fusion- and wire-based additive manufacturing technology which has gained industrial interest for the production of medium-to-large components with high material deposition rates. However, in-depth studies on performance indicators that incorporate economic and environmental sustainability still have to be carried out. The first aim of the paper has been to quantify the performance metrics of WAAM based manufacturing approaches, while varying the size and the deposited material of the component. The second aim has been to propose a multi-criteria decision-analysis mapping to compare the combined impacts of products manufactured by means of the WAAM-based approach and machinin

A novel method of assessing and predicting coated cutting tool wear during Inconel DA 718 turning

This work investigates the wear characteristics of two different coating systems deposited on cemented carbide tools and used in the finish turning of an Inconel DA718 aerospace alloy. The two coatings were: (a) a new nanocomposite multilayer Ti25Al65Cr10 N/Ti20Al52Cr22Si8N PVD coating, and (b) an AlTiN benchmark coating. Four different cutting speeds (60, 80, 100 and 120 m/min) were employed during this study. Wear behavior was characterized using three-dimensional volumetric wear progression, as well as flank wear progression, wear mechanism evaluation, and cutting force analysis. A tool life predictive model was created for this process based on both 3D and flank wear patterns. The tool with the nanocomposite coating outperformed the AlTiN benchmark coating under higher speed conditions, and both tools performed best under a surface speed of 80 m/min. The primary wear mechanisms responsible for the performance of these coatings differ in relation to the adaptive behavior of the nanocomposite coating. In addition, tool wear predictions modeled under different cutting conditions demonstrated an estimated accuracy of 93%

Metereological conditions and psychiatric emergency visits in Messina, Italy

Objective: The aim of this study is to examine the association between psychiatric disease, climatic and seasonal factors in patients recorded to the Emergency Unit, in Messina Hospital (Italy). Method: A total of 6565 psychiatric patients were recorded to the Emergency Unit in Messina from January 2005 and December 2010. Each psychiatric visit in emergency, was categorized by date of appearance and admitting diagnosis according to diagnostic categories: Anxiety, Mood Disorders and Psychosis. Local weather data were obtained from the Metereological Instituted "Aereonautica Militare" station in Messina, Sicily, In addition, to gathering data on the state of the sky, temperature, atmosphericpressure with the normalized value at sea level, relative humidity, rainfall, wind direction and speed, the station is connected to a buoy located on the eastern sector of Tyrrhenian Sea. Results: In anxiety disorders we have found relevant results comparison between winter and spring (p=.007) and spring and fall (p=.001). In affective disorders the differences occur in relation to winter and fall (p=.002), spring and fall (p=001), spring and summer (p=002). The psychotic disorder presents significant differences between summer and fall (p=.001) and spring and fall (p=.002). Conclusions: We can observe a similarity of affective disorders, i.e. anxiety and mood disorders compared to psychosis, which have different influences and probably according to dissimilar etiopathogenetic ways. In our research, the distribution of anxiety disorders is higher than depressive disorders in terms of delivering emergency room visits. The major differences occur comparing spring and fall, the seasons when all pathological classes have significant differences. It follows that the most abrupt climate change, typical of these seasons, as a whole, cause psychopathological emergencies. The study is important for planning a more effective assistance for patients needing psychiatric support

Effects of Hydrogenized Water on Intracellular Biomarkers for Antioxidants, Glucose Uptake, Insulin Signaling and SIRT 1 and Telomerase Activity

Abstract Hydrogen has been shown in several clinical trials to be completely safe without adverse events and there are no warnings in the literature of its toxicity or adverse effects during long-term exposure. Molecular hydrogen has proven useful and convenient as a novel antioxidant and modifier of gene expression in many conditions where oxidative stress and changes in gene expression result in cellular damage. Our intracellular biomarker studies have shown that a hydrogenized water drink formula containing 2.6 ppm dissolved hydrogen was able to penetrate cellular membranes and function as an antioxidant in human liver cells (HePG2) utilizing the Cellular Antioxidant Assay (CAA). This assay uses the protection of a florescent probe as a marker for cellular damage by reactive oxygen species (ROS), such as peroxyl radical, and compares this to the known antioxidant standard, Quercetin. Using this system oxidative damage was reduced in a dose-dependent manner. One ml of hydrogenized water was found to possess antioxidant capacity equivalent to 0.05 µmole of quercetin. When examined in a human colon cell line (Caco-2 cells), hydrogenized water demonstrated a dose-and time-dependent permeability inhibition of an intracellular fluorescent glucose derivative (2-NBDG), indicating decreased glucose uptake. In another study, the impact of hydrogenized water on Akt phosphorylation (Ser473), a biomarker for insulin signaling, was monitored in human skeletal muscle cells. The hydrogenized water treatment markedly elevated the level of phosphorylation of Akt (Ser473) in a dose-dependent manner. The anti-aging effects of hydrogenized water were examined utilizing SIRT1 expression as a biomarker of aging in human umbilical cells (HUVECs). Hydrogenized water increased dose-dependent SIRT1 gene expression. Hydrogenized water also increased telomerase activity (an anti-aging biomarker in HUVEC cells) up to 148% when cells were treated with media containing 25% hydrogenized water formula. Increased telomerase activity caused by hydrogenized water may be able to protect telomeres from degradation, suggesting the possible use of hydrogenized water in therapeutic interventions of age-related diseases. These studies show that commercial hydrogenized water improved the levels or activities of a few intracellular biomarkers specific for antioxidant activity, glucose uptake, insulin signaling and SIRT 1 and telomerase activities. Industrial Relevance: The molecular hydrogen used in this study indicates that certain commercial sources of hydrogenized water can provide similar antioxidant and gene expression modifications seen in other sources of molecular hydrogen. The biomarkers evaluated here lend well to hydrogenized water's biological activity relating to health conditions and aging