An optimization procedure for the friction stir welding FEM model of corner fillet joints

Friction stir welding (FSW) is an energy efficient and environmentally "friendly" (no fumes, noise, or sparks) welding process, during which the sheets are welded together in a solid-state joining process. FSW is mature for simple configurations but a significant lack of knowledge is found when dealing with different designs such as T-sections, box sections and corner welds. Although the latter joint morphology has traditionally been considered unfeasible for the process, it seems to have a great potential to be used also for T-joint configurations, a recurrent design pattern in transport applications. A specific tool has been developed and a set of experimental welds has been produced with…

On the friction stir welding of titanium alloys: Experimental measurements and FEM model fine tuning

Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. Recently, research is focusing on titanium alloys thanks to the high interest that such materials are getting from the industry as welding of titanium alloys by traditional fusion welding techniques presents several difficulties due to high material reactivity resulting in bonding with oxygen, hydrogen, and nitrogen with consequent embrittlement of the joint. In this way FSW represents a cost effective and high quality solution. The study of the temperatures reached at the varying of the …

Microstructural Changes Determining Joint Strength in Friction Stir Welding of Aluminium Alloys

In the paper the results of a wide experimental activity on friction stir welding (FSW) of aluminum alloys are reported. In particular the butt joints of two different materials, namely AA1050-O and AA6082-T6 were considered. Grains dimensions and precipitates density were investigated both in the parent materials and after the welding processes. Furthermore post-welding heat treatments effects on the joint strength were studied.

Il supporto della SISV alla realizzazione di un manuale nazionale per il monitoraggio degli habitat della Direttiva 92/43/EEC in Italia

A partire dall’entrata in vigore della Direttiva 92/43/EEC, la sorveglianza dello stato di conservazione degli habitat elencati nell’Allegato I ed il relativo monitoraggio periodico a intervalli di sei anni sono diventati un obbligo per tutti i paesi membri dell’UE, in base a quanto previsto negli Articoli 11 e 17. Nel 2011 è stato pubblicato un documento che fornisce le linee guida di riferimento europee per il monitoraggio di habitat e specie (Evans & Arvela 2011). Su questa base metodologica, la Società Italiana di Scienza della Vegetazione (SISV), avvalendosi di un ampio gruppo di soci esperti, ha avviato un dibattito interno su principi, criteri, parametri e strumenti per il monitoragg…

Friction stir welding FEM model improvement through inverse thermal characterization

The SISV support to the implementation of a national manual for monitoring the Habitats of the 92/43/EEC Directive in Italy.

The 4th National Report ex Art. 17 of the 92/43/EEC Directive in Italy (period 2013-2018) will try to fill a number of gaps still affecting the former versions of the Italian Reports, where territorial data were still missing for large parts of the country and the assessment was mostly based on the use of the expert opinion. Similar inconsistencies also emerged in other European countries (State of nature in the EU, EEA 2015). In order to reach this aim, a nationally shared protocol for monitoring the vegetation-based Annex I Habitats is currently under development. The most prominent issues addressed by the ongoing project are: i) fixing standardized, updated and scientifically grounded me…

Hybrid prediction-optimization approaches for maximizing parts density in SLM of Ti6Al4V titanium alloy

AbstractIt is well known that the processing parameters of selective laser melting (SLM) highly influence mechanical and physical properties of the manufactured parts. Also, the energy density is insufficient to detect the process window for producing full dense components. In fact, parts produced with the same energy density but different combinations of parameters may present different properties even under the microstructural viewpoint. In this context, the need to assess the influence of the process parameters and to select the best parameters set able to optimize the final properties of SLM parts has been capturing the attention of both academics and practitioners. In this paper differ…

Experimental and numerical analysis on post welding formability of FSWed AZ31 magnesium alloy thin joints obtained using a "Pinless" tool configuration

The post welding formability of friction stir welded AZ31 magnesium alloy thin sheets (1.5 mm thick), obtained using a “pinless” tool configuration, was widely investigated by means of the hemispherical punch method at 350°C, with a constant crosshead speed of 0.1 mm/s. The results were compared with those obtained on the base material. It has shown that formability of the joints is lower than the one of the base material. The experimental work was supported by a numerical investigation based on FEM in order to highlight the material flow occurring during the welding process. Additionally, hemispherical punch tests were simulated starting from the calculated conditions, in terms of accumula…

Joining by forming technologies: current solutions and future trends

AbstractThe progressively more demanding needs of emissions and costs reduction in the transportation industry are pushing engineers towards the use of increasingly lightweight structures. This goal can be achieved only if dissimilar and/or new materials, including polymers and composites, are joined together to create complex structures. Conventional fusion welding processes have often been proven inadequate to this task because of the high heat input reducing the joint mechanical properties or even making the joining process impossible. Joining by forming technologies take advantage on the plastic deformation to create sound joints out of even very dissimilar materials. Over the last 25 y…

First overview on the 4th Annex I Habitats Report in Italy: methods, criticality, results and future prospects

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Key factors for industrial applicability of friction stir welded t-joints of different materials

An overview of the Italian forest biodiversity and its conservation level, based on the first outcomes of the 4th Habitat Report ex-Art. 17

In 2019 the 4th Report ex-Art. 17 on the conservation status (CS) of Annex I Habitats of the 92/43/EEC Directive was expected by every EU/28 country, with reference to the period 2013-18. In Italy, the process was in charge to the Italian Institute for Environmental Protection and Research (ISPRA), on behalf of the Ministry for Environment, Land and Sea Protection (MATTM), with the scientific support of the Italian Botanical Society (SBI). A large group of thematic and territorial experts elaborated the available data concerning the 124 types of terrestrial and inland water Habitats present in Italy, 39 of which are represented by Forest Habitats (Group 9),. The main aim of the work was the…

Numerical prediction of Biphasic Titanium Alloys Microstructure in Hot Forging Operations.

Modern transportation industries shall comply with two demanding requirements: reducing operational consumption together with production costs coming from materials and labour. Current trend of engineering is oriented to meet both requirements increasing the rate of polymer matrix composites which implies association with structures made of titanium alloys. Hot forming can be used to reduce the production costs of titanium components: forging in closed dies of billets or semi finished form, in the temperature range where the Beta phase of titanium is stable, grants an adequate plasticity of the Ti-6Al-4V alloy, the most commercially used, allowing production of complex shapes with limited a…

On the choice of tool material in friction stir welding of titanium alloys

A methodological protocol for Annex I Habitats monitoring: the contribution of Vegetation science.

The methodological foundations of the recently published Manual for Annex I Habitats monitoring in Italy, edited by the Italian Institute for Environmental Protection and Research (ISPRA) with the scientific support of the Italian Society for Vegetation Science (SISV), are here presented, discussed and related to the most consolidated and acknowledged scientific advances in the field of Vegetation science. The proposed methodologies aim at offering simple, yet effective, protocols and procedures towards a harmonized data collection, by way of standardized and shared technical tools, resulting in comparable evaluations of the conservation status of Annex I Habitats. The methodological framew…