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The paper presents an innovative approach implemented in QForm UK Extrusion FEM software to analyse one of the core defects encountered in profile extrusion known as billet skin defect. The validation of the algorithm has been performed based on a number of experimental case studies taken from the literature [1,2]. Additionally, the sensitivity of the accuracy of the results to the variation in initial parameters has been analysed for both types of profile shapes: solid and hollow. Based on this, practical recommendations have been formalised for the successful industrial use of the presented algorithm.

The microstructure of Al-Mg-Si alloys is gaining nowadays an increasing industrial interest because it influences the strength, crash, corrosion and esthetic properties of the extruded profiles. In order to investigate and predict the recrystallization behaviour in the extrusion of 6XXX aluminum alloys, experimental and numerical activities are still needed. In this work, the extrusion of an industrial-scale AA6060 aluminum alloy hollow profile was carried out. An innovative recrystallization model was developed and optimized by comparing the microstructural data experimentally acquired with the outputs of the simulation performed using the Finite Element commercial code Qform Extrusion. A good correlation between numerical prediction and experimental data was found, thus proving the reliability of the proposed AA6060 recrystallization model.

During the extrusion process, high temperatures are generated, due to friction and deformation works, potentially leading to profile and die defects. Among the suggested solutions aimed at controlling the thermal field of the process, the most accredited one involves the manufacturing of cooling channels at the mating face between the die and a third plate. Despite the proven efficiency of well-designed channels, the main drawback lies in the managing of the many variables involved that strongly affect the cooling efficiency and balancing. In this frame, aim of the work is to investigate the applicability of the topological optimization tool, proposed by COMSOL Multiphysics software, for the design of cooling channels in extrusion dies. To validate the tool, an industrial case study has been selected and results compared between not optimized and optimized cooling solutions.

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 additive manufacturing technology (AM) is considered to be the fourth-industrial revolution allowing to produce «near net» components almost without geometrical constraints. In contrast to conventional, subtractive technologies, additive manufacturing built up the component layer by layer starting from a 3D CAD model [1]. Due to the capabilities of the technology to face with high performance materials with added functionalities and increased complexity in geometrical designs, AM perfectly fits with the requirement of dies, tools and inserts. The AM technologies first developed in 1990s coming to the tools manufacturing some years later. In this context, the first applications were in low impact processes like plastic injection moulding but rapidly entered in metal working process applications like metal forming and die casting [2]. Nowadays, several metallic materials can be processed to full dense parts with outstanding properties, the most important at the industrial scale being represented by steels, aluminium and titanium alloys as well as Ni-based superalloys and CoCr [3,4].

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.

L’uso di piante nettarifere contro i fitofagi del vigneto

Step-procedure for multi-goal optimum design of a carry-mould

The wedge and bulge expansion tests were compared in the assessment of the seam welds strength in a tubular profile extruded at two ram speeds. In the wedge test, the expansion was determined by moving a conical punch into the tube until the specimen fracture. In the bulge test, a hydrostatic tensile stress state was applied by expanding the specimen with an internal rubber plug. The two methodologies were compared in terms of load and hoop strain at fracture and by detecting the fracture morphology and location. Then, the effect of a number of design parameters was investigated in order to evaluate the robustness of the standard testing conditions. For both tests, ductile fractures appeared in the seam welds location, but the bulge test was more robust and conservative with respect to the wedge test, showing less scattered data. Thus, the performances of a second die for the tube profile, designed to optimize the seam welds quality, have been successfully assessed by the bulge test and results compared to those achieved by a novel numerical quality index, coming to a final good matching.

Liquid nitrogen cooling is widely used in the extrusion industrial practice in order to increase the production rate, to reduce the die temperature and to avoid defects on the profile exit surfaces resulting from an excessive heating. However, the efficiency of the cooling is deeply affected by position and design of the liquid nitrogen channel so that numerical modelling is gaining an increasing industrial interest in relation to the possibility offered to optimize the channel design without expensive and time-consuming experimental trials. In this work, a numerical FE model developed within COMSOL Multiphysics® is proposed and validated against experimental trials performed in industrial environment. The model combines the 3D simulation of the extrusion process with a 1D model of the cooling channel thus allowing the testing of a number of different solutions at the die design stage. The global aim of this work is the assessment of the liquid nitrogen cooling efficiency in the extrusion of an industrial aluminum profile and the proof of the potentials offered by numerical models to get an optimized channel design in terms of cooling efficiency, die thermal balancing and reduction of liquid nitrogen consumption.

The die cooling by means of liquid nitrogen is a widely adopted industrial practice used to increase the production rate in the hot extrusion process of light alloys. The development of a reliable numerical model able to simulate the cooling channel efficiency has become of primary interest for the extrusion sector in order to avoid ineffective die cooling and time-consuming trials and errors. In this work, H13 die inserts with a helicoidally conformal channel were designed and printed by means of the SLM additive technology. Billets of AA6063 aluminum and ZM21 magnesium alloys were extruded at different process speeds under monitored conditions to verify the insert resistance and the cooling effectiveness. A 3D finite element model of the extrusion process coupled with a 1D model of the cooling channel was generated within the COMSOL simulation environment. The experimental outputs were also used to validate the numerical predictions of the developed simulations. The FEM results showed a good matching with the loads and temperatures obtained in the experimental trials. Moreover, the endurance of the AM tool validated the prediction of the stress field, thus proving the reliability of the numerical model for the application in the extrusion of light alloys sector.

The reduction of scraps related to back end defects (i.e. billet skin contamination) and front end defects (i.e. charge welds) is gaining nowadays an increasing industrial interest in order to obtain greater process efficiency. Today, extrusion industrial practice faces the issue by means of technician’s experience, empirical rules or, in most critical profiles, through time consuming and expensive experimental analyses. On the other side, FEM simulation of extrusion dies is becoming a common support tool for the design of new critical dies. Stating this scenario, the possibility to include the prediction of front end and back end defects evolution as simulation output can then be easily obtained at almost comparable computational costs. In this paper the FEM code Altair HyperXtrude® is used for the simulation of 2 industrial cases made by AA6063 and AA6082 alloys following the transient moving boundaries approach. Experimentally, the profiles were extruded, sectioned, polished and etched with caustic soda in order to reveal and measure front and back end development in front of and behind the profile stop mark. The data obtained from experimental analyses are initially discussed referring to billet skin contamination and charge weld evolution, then compared to industrial experience, to theoretical and empirical methods available in literature and to FEM results in order to evaluate pros and cons of each evaluation method.

During aluminum extrusion process, critical temperatures can be reached both in the profile and in the tooling set due to the high pre-heating temperatures and to the work spent in overcoming friction at the workpiece/tool interfaces and in deforming the billet that is converted into heat. By considering that especially the rising of temperature in the profile can represents a critical aspect of the process strongly limiting the maximum achievable extrusion speed, liquid nitrogen die cooling is becoming a consolidated industrial practice in order to increase the process productivity. If cooling channels are traditionally manufactured by subtractive technologies on a third plate (the backer), a more flexible and efficient solution is offered by the selective laser melting (SLM) technology. SLM allows the design of free-form channels with the opportunity to efficiently remove the heat as near as possible to the bearing zones where the highest temperatures are reached. In the present work, the design approach and the manufacturing parameters of an SLM printed H13 die insert for the extrusion of a 10 mm round bar are presented. In addition, the extrusion process is simulated by means of the COMSOL code accounting for the nitrogen cooling effect. Experimental extrusion trials have been furthermore performed with ZM21 magnesium and 6063 aluminum alloys to assess the potentiality of the conformal cooling channel design and to validate the developed numerical model. As main result, a good experimental numerical matching has been achieved with peak errors of 7.5% and 14% in terms of temperature and extrusion load respectively.

The continuous direct extrusion is an economic and efficient process to manufacture high-quality aluminium profiles. However, because of multiple billets processing, transient defects (coring and charge welds) can be generated affecting portions of the profiles and deteriorating their mechanical properties. In case of structural applications, the reliable prediction of the onset and extend of these portions is therefore mandatory in order to be scrapped by the commercialized length. In this context, the present work has been aimed at examining the dynamic evolution of the coring and charge weld defects in the direct extrusion of an industrial solid profile. Both experimental and numerical activities have been performed and results evaluated in terms of coring and charge welds defect evolution achieving a good agreement for both phenomena. Results have been also compared with the outcomes of the analytical models available in literature. For the charge weld extension, the analytical model returned a poor predictably while a very good match with numerical data was obtained for the coring defect.

The temperature monitoring during aluminum extrusion is a crucial task performed in order to avoid profile defects, to increase the die life and to optimize the process productivity. Among the different available systems used to control the process temperatures, in the last decade, the die cooling through liquid nitrogen has been installed on several extrusion plants. In order to provide extruders and die makers with a modelling tool able to gain a better understanding of the extrusion and die thermal field, a numerical model of the extrusion that accounts for liquid nitrogen cooling has been developed in the present work. A simplified 1D modelling of the cooling channel was used and validated against an experimental investigation previously specifically carried out to evaluate the cooling efficiency in a multi-hollow industrial profile. Results showed a significant impact of the design aspects of channel on the thermal efficiency of the cooling and an important heat removal when the liquid nitrogen cooling is used. A good experimental-numerical agreement was achieved in terms of temperature map and extrusion load both in cooled and uncooled conditions, thus suggesting the reliability of the developed simulation tool and its potential integration in a flexible procedure to be used for die/cooling system design and process optimization.

The Extrusion Benchmark 2017 is focused on the evaluation of different die design strategies for the production of two AA6005A thin C-shaped hollow profiles. The process was monitored in term of press load, profiles speed, profiles exit temperature, die temperatures (with specific focus not only on the die but also on the external die ring) and die deflection. Extruded profiles were analyzed in term of geometrical tolerances, microstructure evolution and profile distortions for both air and water quench; the profiles were also be analyzed for retrieving seam welds positions and charge welds extent.

The simulation of microstructural evolution during the extrusion of an AA6063 industrial profile with the commercial Qform VX code is presented and discussed. The description of the grain shape evolution model through specifically developed user-routine is initially presented, then the experimental setup is described in details. Predicted numerical results are compared and discussed with respect to experimental data: relevant outputs like load-stroke diagram, profile speed and thermal distribution in the profile well match with the experimental data. The prediction of the final grain size obtained by the code with air quenching conditions is then compared to experimental measurements. A discussion on potentials and limits of the proposed model is finally presented

In the present research, an innovative testing method, specifically developed to characterize the tool steels under creep-fatigue conditions, was carried out on a TQ1 (X36CrMoV5-2) hot-work tool steel in cooperation with Constellium R&D center. The experimental campaign consisted of different testing conditions, and most of the specimens were nitrided to account for the specific surface state of the tools. Tests were performed on a 100 kN MTS fatigue machine equipped with a heating furnace. A creep-fatigue loading type was applied to the specimens, i.e., a cyclic load with a dwell time, in order to properly reproduce the conditions acting on extrusion tools and dies. Under a constant temperature of 520 °C, the effects of four different load levels and two different values of dwell times were evaluated. In addition, selected test conditions were replicated with specimens not nitrided with the aim to evaluate and quantify the influence of the superficial treatment. Final results were presented in terms of fatigue diagram of the TQ1 steel and compared to the performances of the H11 tool steel tested in a previous research by the same authors.