1,720,986 research outputs found
Phase Field Method for the Assessment of the New-Old Billet Material Interaction during Continuous Extrusion Using COMSOL Multiphysics
No full textDuring the hot extrusion process of metals, billets are continuously loaded into the press and joined together under high hydrostatic pressure, forming a single extruded profile. Contamination at the billet-to-billet interface, such as oxides and dust residues, produces a welded zone (i.e. charge welds) with compromised mechanical properties, leading to the scrap of the resulting profile portion. To optimize the discharging process, the exact starting point and the extent of the billet-to-billet interaction must be precisely identified. This study aims to develop an innovative model based on phase field method to capture the interaction between immiscible fluids at high viscosity, capable of predicting the charge welds evolution within the COMSOL Multiphysics FEM code. To validate the model, two industrial case studies were experimentally investigated, involving the extrusion of AA6060 and AA6082 profiles with different process parameters and cooling conditions. The collected data were compared with simulation outcomes, revealing a good agreement with errors always below the 8% both in terms of charge welds onset and extent. This validation proved the reliability of the proposed model in accurately predicting extrusion defects
Efficiency of conformal cooling channels inserts for extrusion dies
Full text linkDuring 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
Predicting grain size in extruded AA6063 profiles: A unified approach based on finite element analysis and machine learning
Full text linkThe 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 mu m), strain (2.8-28), maximum strain rate (2-190 s-1), exit temperature (480-580 degrees C), Zener-Hollomon parameter (4 x 1015-4 x 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
A Reference Framework For Looking At Business Sustainability
No full textSustainability is a key issue of today society. Within this context, business sustainability is part of the problem, and can be part of the solutions. Recent researches have demonstrated that companies affect and are affected by sustainability, and that sustainability opens both opportunities and threats. Business sustainability is a challenge that require an holistic approach to business and managerial practices, as well as the contribute of academics from different backgrounds and with different research approaches. In this paper, the authors propose a framework for looking at sustainability based on the well know value chain scheme. Potential initiatives to increase the sustainability of value creation processes are highlighted based on practice. The framework represents just a starting point to look at business sustainability, but offers a methodological
approach to face such a complex challenge
Experimental investigation and numerical prediction of the peripheral coarse grain (PCG) evolution during the extrusion of different AA6082 aluminum alloy profiles
No full textPeripheral Coarse Grain (PCG) is an undesirable defect that may occur in the extrusion of medium-strength Al-Mg-Si aluminum alloys. This phenomenon usually degrade extruded profiles in mechanical, crash, corrosion, fracture and surface quality properties thus precluding their applicability in the automotive sector. In this work, an experimental campaign was carried out involving the extrusion of two different AA6082 profiles in a wide range of process parameters. The microstructural analysis of these profiles was conducted in order to investigate the impact of die design and process parameters on PCG occurrence. According to this analysis, it was detected a clear influence of the ram speed and of highly dynamic recrystallized (DRX) zones on the PCG. The modeling for the PCG evaluation was then developed and implemented into the commercial FEM code Qform Extrusion® for the simulation of the extrusion process together with the DRX and the PCG predictions. The numerical results were further compared to the collected experimental data thus proving the reliability of the proposed model
Liquid nitrogen in the industrial practice of hot aluminium extrusion: experimental and numerical investigation
Full text linkNowadays, 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
Assessment of the Optimization Strategy for Nitrogen Cooling Channel Design in Extrusion Dies
Full text linkAluminum extrusion is an efficient industrial process. However, one of the main problems is related to the temperatures developed during the process that can detrimentally affect the achievable productivity, profile quality and/or die life. Cooling of the die with liquid nitrogen represents an efficient solution to overcome this limit but a further issue arises lying in the number of process and design variables that need to be managed in order to set-up of an efficient system. In this context, a 3D FE model of the extrusion process, coupled with a 1D model of the cooling channel, previously proposed by the authors, has been integrated in an optimization platform in order to iteratively and automatically adjusts the channel geometry and the process variables gaining to a final optimal solution in terms of thermal balance, cooling efficiency and nitrogen consumption. The original channel design used during the extrusion of industrial hollow AA6060 profile guaranteed an efficient but unbalanced cooling with a maximum temperature deviation of 60 °C registered by the thermocouple positioned around the bearings. The optimized designs showed temperature deviations below the 16 °C as well as the reduction of 50% in terms of nitrogen consuming
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
FEM validation of front end and back end defects evolution in AA6063 and AA6082 aluminum alloys profiles
Full text linkThe 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
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