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The evolution of grain size in AA6XXX extruded profiles is a critical factor for enhancing mechanical, thermal and surface properties. Traditional methods for microstructure control rely on extensive experiments requiring significant time and resources. To address this issue, the present work proposes a method for microstructure prediction combining numerical data from Finite Element Method (FEM) simulations with experimentally acquired microstructure data to train an Artificial Neural Network (ANN) capable of predicting grain size. Data was acquired for three distinct AA6063 aluminum alloy profiles extruded under various process conditions in terms of profile and tool geometry, ram speed, billet pre-heating temperature and extrusion ratio, representing a diverse and heterogenous dataset comprising grain size (55–228 µm), strain (2.8–28), maximum strain rate (2–190 s−1), exit temperature (480–580 °C), Zener-Hollomon parameter (4 × 1015–4 × 1017) and Stored Energy (170–480 kJ/mol*K) for training and testing different ANN configurations. The final trained ANN was able to accurately predict grain size in regions of normal grain growth but was less reliable at foreseeing formation of the largest and smallest grains due to limited data points within this range. A Mean Absolute Percentage Error (MAPE) of 13.9% was achieved for predictions in the test set with an ANN comprising two fully connected layers with 9 and 19 neurons, respectively, Rectified linear unit (ReLU) activation functions and a ridge L2 penalty term of 10−6 for regularization. The presented methodology provides a foundation for the development of new data-driven approaches aimed at facilitating microstructure prediction in industrial settings. [ABSTRACT FROM AUTHOR]

This study examines a numerical method to simulate the production of novel multi-material metal-composite components, where an additive-manufactured cellular solid is infiltrated by a sheet molding compound (SMC) in a single-step compression molding operation. A single-fiber numerical approach is adopted to predict microstructural changes, such as fiber orientation, fiber-matrix separation, and fiber volume content variations during molding. The accuracy of the numerical predictions is confirmed by physical samples using micro-computed tomography and optical microscopy investigations at both the qualitative and quantitative scales. From optical microscopy observations, there emerged a positive correlation between experimental outcomes and simulation results, accurately capturing fiber swirling, wrinkling, and draping that occurred during molding. At a quantitative scale, a 0.6% mismatch was observed when void volume and unfilled areas were compared, as measured by micro-computed tomography and numerical simulation. [ABSTRACT FROM AUTHOR]

The distribution of fibers in injection-molded thermoplastic-reinforced parts is known to significantly affect both the final mechanical properties and the appearance of defects related to undesired shrinkages and warpages. Even if the numerical modelling of the process is in the state of the art, the selection criteria of the model for the fiber orientation predictability and the influence of the models' parameters are not yet clearly understood. The complexity of the matter increases further considering that, inside the same injection-molded part, the fiber orientation distribution could differ from one region to another depending on the local melt shear flow type. In this context, the aim of this study is to investigate the orientation of fibers in regions of non-simple shear flow in an injection-molded short glass fiber-reinforced part. X-ray microcomputed tomography is used to experimentally investigate fiber distribution and orientation. Furthermore, a number of numerical simulations of the injection molding process are performed in Moldflow® by varying the mesh type (2D/3D), the selected predictive model, and the models' coefficients. The main findings indicate that, in regions with non-simple shear flow, a 2D mesh fails to capture accurate fiber orientation. A 3D mesh is essential for reliable predictions. MRD-specific parameters from the literature reduce prediction error by 37.5% compared to Moldflow's default MRD parameters. Regarding the RSC model, both Wang's optimal retarding rate parameter and AMI's default retarding rate parameter result in similar 5% prediction errors. However, employing a literature-suggested interaction coefficient raises the prediction error to 26%. [ABSTRACT FROM AUTHOR]

The microstructure of 6xxx aluminum alloys deeply affects mechanical, crash, corrosion and aesthetic properties of extruded profiles. Companies, especially in the transportation sector, require control over the grain structure in order to ensure the quality and the performance of the products. A main challenge for the extrusion companies is to accurately predict the profile microstructure at the design stage, trying to limit the formation of coarse grains and, consequently, the reduction of the mechanical properties of the component. In this work, the modeling of the stored energy, driving force for the recrystallization, was carried out and implemented within the Qform Extrusion FEM code. A novel approach for the evaluation of fibrous and recrystallized microstructures in 6XXX aluminum alloy profiles was proposed and tested in a campaign of experiments involving the extrusion of AA6082 round bars under several die designs and processing conditions. The outcomes proved the good accuracy of the recrystallization predictions during the extrusion of AA6082 aluminum alloy. [ABSTRACT FROM AUTHOR]

The present review paper would celebrate the 25 years anniversary of the ESAFORM association by summarizing the studies performed by the delegates of the ESAFORM conference series within mini-symposium “Extrusion and Drawing” and of the papers published in the International Journal of Material Forming in the same fields. The 160 analyzed papers have been divided in four main categories corresponding to the paper main chapters (Hot Metal Extrusion, Cold Metal Extrusion, Polymer Extrusion and Drawing) then further divided in sub-chapters in order to group them in more specific research subjects. The aim of this review paper is then to provide to the reader a complete overview of the investigated topics and of the research trends over the years within the ESAFORM associate researchers. [ABSTRACT FROM AUTHOR]

Nowadays, the liquid nitrogen cooling in aluminium extrusion is a widely adopted industrial practice to increase the process productivity as well as to improve the extruded profile surface quality by reducing the profile exit temperatures. The cooling channels are commonly designed on the basis of die maker experience only, usually obtaining modest performances in terms of cooling efficiency. Trial-and-error approach is time and cost consuming, thus providing a relevant industrial interest in the development of reliable numerical simulations able to foresee and optimize the nitrogen cooling effect during the die design stage. In this work, an extensive experimental campaign was performed during the extrusion process of an AA6060 industrial hollow profile, in different conditions of nitrogen flow rate and ram speed. The monitored data (die and profile temperatures and extrusion load) were compared with the outputs of a fast and efficient numerical model proposed by the authors, and developed in the COMSOL Multiphysics code, able to compute not only the effect of nitrogen liquid flow but also the gaseous condition. The results of the simulations showed a good agreement with experimental data, and evidenced how far the experimental cooling channel design from an optimized condition was. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Charge welds are unavoidable defects of the continuous extrusion process whose extension needs to be accurately predicted in order to avoid profile mechanical failures or to minimize unrequired scrap of material. The aim of this work was then to evaluate the accuracy of the charge welds FEM predictions and their applicability in the industrial field. Two different industrial cases involving A6082 and AA6063 aluminium alloys were analysed. The data of charge welds behaviours were experimentally collected, discussed and then innovatively compared to the predicted outcomes of FEM simulations performed using QForm Extrusion® software and of theoretical formulas reported in the literature. As main results, a very good numerical-experimental matching was found, with a peak discrepancy of 122 mm in terms of charge weld extent, while theoretical formulas returned a significant underestimation. [ABSTRACT FROM AUTHOR]

Background and objective: In a proof-of-concept study, we aimed to verify whether the wearable haptic anklets, a device that delivers personalized suprathreshold alternating exteroceptive stimulation at the anklets on demand, may improve the quality of walking, including the freezing of gate (FOG), in idiopathic Parkinson's disease (PD) patients. The clinical relevance of the presented device as a walking pacemaker to compensate the disturbed locomotion through the generation of a more physiological internal walking rhythm should be verified in a dedicated clinical trial. Methods: We tested 15 patients diagnosed as idiopathic PD, during their regular treatment regimen. Patients were evaluated during walking with the device switched on and off, personalized at their most comfortable cadence. Stride velocity, variance, and length, as well as FOG episode duration during walking or turning of 180°, were quantified by an optical high-performance motion capture VICON system. Results: The alternating, rhythmic, sensory stimulation significantly improved either walking velocity or reduced inter-stride variance. Effects were more variable on stride length. The significant reduction of FOG episodes' duration correlated with clinical severity of scales rating gate and balance. No safety problems occurred. Conclusions: The WEARHAP-PD device, whose Technology Readiness Level (TRL) is 6, significantly improved some walking abilities (walking velocity and stride variance) and reduced the duration of FOG episodes in idiopathic PD patients. Unlike the traditional auditory and visual explicit cues that require the user's allocation of attention for correct functioning, the interaction of the patients with the surrounding environment was preserved, due to the likely implicit processing of haptic stimuli. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Charge welds are unavoidable product defects generated during the continuous extrusion of metallic materials that extend to a certain variable length and that are marked by lower mechanical properties than the base material. The portion of the profile containing the charge welds thus needs to be scrapped and an accurate prediction of this portion becomes mandatory, not only for the final user of the profile, in order to avoid in-service product failures, but also for extruders and die makers in order to increase the process efficiency. In the present work, four case studies carried out in the years by the authors on the prediction of the charge weld extension are reviewed and systematically compared in terms of experimental and numerical results. Data are furthermore compared with the predictions of analytical models reported in literature for the scrap length calculation and of an industrial empirical rule based on the extrusion ratio. Final aim of the work is to highlight potentials and limits of each predictive method and to assess their applicability in the everyday industrial practice. [ABSTRACT FROM AUTHOR]

This work investigated issues for an efficient and reliable embedding and use of Fiber Bragg Grating (FBG) sensors for strain monitoring of composite structures with particular regard to the manufacturing process of components in the nautical field by means of the vacuum bag technique in autoclave. CFRP material laminates with embedded FBGs were produced and the effect of the curing process parameters on the light transmission characteristics of the optical fibers was initially investigated. Two different types of coating, namely polyimide and acrylate, were tested by measuring the light attenuation by an Optical Time Domain Reflectometer. Tensile specimens were subsequently extracted from the laminas and instrumented also with a surface-mounted conventional electrical strain gage (SG). Comparison between the FBG and SG measurements during static tensile tests allowed the evaluation of the strain monitoring capability of the FBGs, in particular of their sensitivity (i.e., gage factor) when embedded. [ABSTRACT FROM AUTHOR]

In direct extrusion of aluminum alloys, billets are discretely loaded into the press and joined by the high hydrostatic pressure field. The contamination of the billet-to-billet interface by oxides, dust, or lubricant produces a welded zone (charge weld) with reduced mechanical properties that requires profile discharge. For an efficient material scrapping, both the position of the transition zone and its extent in the profile must be accurately identified. In industrial practice, in relation to a lack of experimental and numerical studies on this specific matter, the determination of the zone to be discarded is still performed mainly by experience or labor-intensive analyses. The aim of the present study is to bridge this gap by investigating the evolution of the charge welds inside an industrial multi-profiles and determining their exact position and extension by experimental microstructural analyses coupled with comprehensive 3D FE simulations performed with the Arbitrary Lagrangian-Eulerian code HyperXtrude®. Skin and rest defects are also experimentally investigated and a numerical sensitivity study on the influence of the friction model selection is performed. Comparison between numerical and experimental results shows a good agreement both in terms of general trend and exhausting points of the charge welds. The results prove that the FE code is a reliable tool in assisting and driving the die and process design stages, not only for process optimization as reported in literature but also for the scrap length determination. Finally, a process efficiency index is defined and, for the specific case study, it is found to be increased from 82.6 %, as resulting from the actual industrial practice, to a 88.3 % as optimized by the performed coupled experimental and numerical activities. [ABSTRACT FROM AUTHOR]