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The technical achievement described in this paper is to optimize all the variables in the extrusion of complex aluminum profiles using finite element (FE) simulation, statistical regression analysis, and analytical equations in a software platform to account for these variables and their interactions with each other as a group to achieve an ideal extrusion practice. This approach is done by repetitive computer simulations based on varying die modifications conducted through a CAD model of the die and then applying incremental changes to extrusion parameters (several die variables, extrusion speed, temperature, etc.) via an FE code and regression analysis in an optimization program that takes account of thousands of "tweaks" to the die configuration and extrusion process parameters. Computation time varies depending on extrusion complexity but is reasonable in terms of industrial practice. As has been determined in this paper, this optimization procedure was applied to the extrusion of two sample extrusions, a hollow tube and a complex rectangular hollow with screw bosses at its corners. In each case, die pressure was reduced and weld quality and the level of stress in the die were improved, while maintaining or increasing exit speed.

The extrusion of aluminum alloys is a prcess able to manufacture high tolerances and high mechanical properties profiles. However, the main drawback of the process is that many objective functions need to be satisfied at the same time and many of these are potentially conflicting one each other. Example of conflicting objective functions are thre requirement fro high seam welds quality (in hollow profiles), an extended die lifetime and an high productivity. In order to solve the problem, the authors developed a comprehesive mutli-objective optimization of the extrusion process base on meta-models. The proposed procedure has been validated against two industrial profiles of a different complexity and a thrid case in now under investigation. Preliminary experimental analyses of the third case are presented.

Establishing numerical tools able to reliably analyze a manufacturing process takes a long time not only for their development, but also for proper validation through experimental trials in a wide range of processing conditions. In order to provide the extrusion industry and community with a place to discuss numerical techniques and to train users in FEM simulations, the ICEB – International Conference on Extrusion and Benchmark conference series was established in 2007.1 The aim of the conference was, and is still today, to merge the typical conference format (with presentation of papers from academia as well as industry) with a benchmark session where participants are asked to analyze a specific extrusion problem, the results of which are disclosed only during the conference.

Questo lavoro presenta i risultati di un’attività di caratterizzazione numerico-sperimentale di un processo dicolata in sabbia di una ghisa sferoidale ferritico-perlitica. L’indagine si è avvalsa di un’attrezzatura di colataopportunamente progettata e realizzata per fornire moduli termici differenziati, tali da sottoporre il materiale adiverse condizioni di raffreddamento e solidificazione. Il sistema di colata è stato studiato mediante simulazionenumerica, che ha permesso di replicare con adeguata accuratezza le condizioni di processo poi monitorate.Le caratteristiche microstrutturali sono state stimate attraverso modelli numerici implementati nel codice dicalcolo PROCAST™ v.2011 per la previsione delle diverse microstrutture ottenute al variare delle condizionilocali di raffreddamento. La validazione delle simulazioni è stata effettuata comparando i dati ottenuti, conquelli ricavati da un accurato studio microstrutturale svolto su oltre 2000 micrografie ottiche, avvalendosi diun software di analisi d’immagine. Sono stati in particolare valutati: porosità percentuale, numero di noduli digrafite per unità di superficie, area media dei noduli, morfologia media dei noduli, frazioni grafitica, ferritica eperlitica. Sono state quindi sviluppate relazioni empiriche in grado di permettere la valutazione delle proprietà atrazione del materiale noti i soli parametri microstrutturali ottenibili dalla simulazione numerica.

The 4th International Conference on Extrusion and Benchmark (ICEB 2011) will be held in Bologna, Italy from October 3-5, 2011. A large number of extruders, die makers, software houses, and researchers will gather at the event to discuss the core technology of light metal extrusion. More than 50 abstracts have been accepted on light alloy extrusion processing and the first day will be dedicated to these sessions. Papers will be also presented on ultra light alloys and new applications for extruded profiles. Process optimization and solutions to extrusion related issues will be analyzed thoroughly by several contributors. The second day of the event will be mainly dedicated to the benchmark experiment and participant results where the results of two monitored experiments will be discussed. The Scientific Benchmark will focus on the different strategies for balancing the material flow in porthole dies and its die design will deal with issues of hollow profile production, such as seam welding mechanism and material flow. The 4th International Conference on Extrusion and Benchmark (ICEB 2011) will be held in Bologna, Italy from October 3-5, 2011. A large number of extruders, die makers, software houses, and researchers will gather at the event to discuss the core technology of light metal extrusion. More than 50 abstracts have been accepted on light alloy extrusion processing and the first day will be dedicated to these sessions. Papers will be also presented on ultra light alloys and new applications for extruded profiles. Process optimization and solutions to extrusion related issues will be analyzed thoroughly by several contributors. The second day of the event will be mainly dedicated to the benchmark experiment and participant results where the results of two monitored experiments will be discussed. The Scientific Benchmark will focus on the different strategies for balancing the material flow in porthole dies and its die design will deal with issues of hollow profile production, such as seam welding mechanism and material flow.

During the hot-extrusion manufacturing process, a number of damage and deformation mechanisms act simultaneously to produce cumulative damage to the tools, thus causing the increasing deviations from the original geometry or the final breaking [1-3]. Due to the severe cyclic thermo-mechanical loads, mandrel, i.e. the part of the hollow die that defines the internal shape of the profile, is the most critical component in the extrusion of an hollow profile. Indeed, the high pressure generated during the process creates severe friction conditions that results in longitudinal tensile stress and significant bending stresses can arise in the bridges of the mandrel during extrusion. In addition to the mechanical cyclic load, the total loading/unloading time for the whole batch and the temperature that the die is exposed to are great enough to necessitate the consideration on the creep behaviour of the die material, particularly for hollow dies. Hence, the combination of dynamic, heavy loading and high temperature determines a hostile working condition for the mandrel that is normally designed on the basis of static loading at elevated temperatures on hot-work tool steels that are tempered to reach an adequate balance of hot hardness and toughness. Premature failure may occur after a certain number of loading and unloading cycles as a result of creep-fatigue interaction. The new technologies developed for aluminium extrusion aim to minimize the tool system-material flow interference and optimize the mechanical performance of the die that is related both to design and tool steel. Aim of the present work is to illustrate the steps followed to design an innovative experimental test purposely developed to investigate the deforming mechanisms of the AISI H11 tool steel in the creep-fatigue regime. The specimens replicate the geometry and the loading scheme of a mandrel on a smaller scale and are manufactured following the same working scheme. In such a way the test is able to account for realistic stress and strain distributions and superficial roughness of a real mandrel as well as to investigate different material and heat treatments.

La previsione della microstruttura finale dopo l’estrusione delle leghe di alluminio è un argomento che hasuscitato un grande interesse negli ultimi anni, visto che le proprietà meccaniche e la qualità degli estrusisono fortemente dipendenti dall’evoluzione e del tipo di microstruttura. Questo lavoro pone come obiettivolo studio dell’evoluzione microstrutturale della lega di alluminio AA6060 durante l’estrusione, mediatesimulazioni FEM utilizzando il Codice Deform 3D. Allo scopo di determinare i coefficienti dei modellidi ricristallizzazione da inserire nel codice FEM, sono state prodotte delle prove sperimentali mediantel’estrusione inversa di coppe a diverse temperature e velocità di deformazione. Dall’analisi metallograficadei campioni estrusi è stato possibile determinare i coefficienti del modello dinamico di ricristallizzazione indotazione al codice FEM Deform 3D. Le coppe sono state successivamente trattate termicamente in forno perfar avvenire la ricristallizzazione statica, e sono stati determinati i coefficienti del modello di ricristallizzazionestatica. Una volta convalidati i modelli, si è passato alla simulazione del processo reale di estrusione di unabilletta cilindrica. L’evoluzione della microstruttura presenta delle zone con dei grani allungati ed altre con deigrani ricristallizzati con fenomeni di accrescimento. I risultati delle simulazioni sono stati confrontati con lemicrostrutture delle billette estruse, mostrando una buona corrispondenza.

The increasing demand for reliable simulation of the extrusion process has led to the organization of a biannual international conference, referred as "Extrusion Benchmark", specifically related to the optimization of FEM codes for extrusion analysis. In particular, the Extrusion Benchmark is a conference where the several commercial codes capabilities are analyzed in deep by the comparison with an extrusion experiment. The 2009 edition will be held on 16-17 September 2009 at Technische Universitat Dortmund, Germany, under the chair of Prof. A.E. Tekkaya, more info available at conference website (www.iul.eu/extrusion09). In this preliminary organization phase, more than 60 abstracts have been submitted from all around the world, the 4 biggest software houses have already confirmed their participation and 6 big aluminum extrusion market players have decided to support the conference.