1,721,049 research outputs found
Simultaneous Effect of Plunger Motion Profile, Pressure, and Temperature on the Quality of High-Pressure Die-Cast Aluminum Alloys
No full textHigh-pressure die casting has been used widely to manufacture a large variety of products with high dimensional accuracy and productivity. Although this process has a considerably lower cycle time than the other metal forming processes, it is not yet optimized, due to the complexity of the process and the number of parameters to be controlled. Hence, the identification of the parameters affecting quality of castings is the current challenge toward efficient and effective production. In their previous work, the authors proposed and validated some novel kinematic parameters of the plunger, which explain and forecast both the static mechanical properties and the internal quality of castings. The present work extends such an approach by including two other meaningful parameters, which describe the effect of upset pressure and temperature on the final outcome. These parameters are here formulated and have been validated by means of a statistically significant sample manufactured with different plunger motion profiles, upset pressures, and temperatures of the melt and die. The quality of the castings was assessed through static mechanical properties and density measurements. As further proof, internal defects were analyzed on the fracture surfaces of some meaningful castings
Lightweight design versus raw materials criticalities
Full text linkThe 4th list of Critical Raw Materials has been published by the European Commission at the beginning of September 2020. A trend of increased criticality is observed for all raw materials in 2020 compared to 2017 and four new critical raw materials appeared (bauxite, titanium, lithium, and strontium) that pose new restrictions in lightweight design of metallic components. Based on a materials selection methodology developed in literature to face such emerging issues, the criticality assessment of light alloys is evaluated and rationally considered in lightweight design by using a trade-off material selection strategy. A simplified case-study is proposed as an example
HPDC foundry competitiveness based on smart Control and Cognitive system in Al-alloy products
No full textHigh Pressure Die Casting (HPDC) technology is facing new challenges in terms of quality requirements from the end-users, production rate achievable, process monitoring and control, in a complex worldwide scenario. A relevant contribution to HPDC competitiveness has been offered by the EU-FP7-funded MUSIC Project It is probably the biggest research project ever carried out in the field of HPDQ with 16 partners and an effort of about 1000 person-months MUSIC developed a totally new Control and Cognitive system, giving an integrated and multi-disciplinary answer to the most relevant issues for HPDC industry: "zero-defect" production, real time process control, understanding the role of process variables, process optimization and real time cost evaluation. The basics about this new Control and Cognitive system are presented in this paper
Materials selection in a critical raw materials perspective
Full text linkCritical Raw Materials (CRMs) are those raw materials that are economically and strategically important for the European economy but have a high-risk associated with their supply. Used in environmental technologies, consumer electronics, health, steel-making, defence, space exploration, and aviation, these materials are not only ‘critical’ for key industry sectors and future applications, but also for the sustainable functioning of the European economy. In this scenario, ‘mitigating actions’ need to be developed to reduce criticalities linked to the use of those raw materials. Recycling and substitution, when possible, are strategic solutions but a more efficient use of such CRMs in design, obtained by a correct alloy selection, is become nowadays mandatory. A method for metallic alloys selection in a CRMs perspective, based on the definition of the alloy critical index, is described. The proposed method allows selecting the alloy for the current application that minimizes its criticality associated to CRMs. The method is illustrated with example
Process parameters affecting quality of high-pressure die-cast Al-Si alloy
No full textIn the last years, aluminium alloys have become more and more relevant because of their low density, coupled with good mechanical and corrosion properties. Different processes are available for the production of aluminium alloy components, but a very significant role is played by foundry processes. However, defects and imperfections are physiologically generated by foundry techniques, as a result of the process itself, of the alloy properties and of the die design. Particularly, high-pressure die-casting (HPDC) is considered a “defect generating process”, since an average of 5 - 10 % scrap is typically generated by this process. Several process parameters need to be controlled in order to obtain sound and reliable castings. Among the different process variables, the determination and control of the injection parameters remain a key requirement throughout the HPDC process. In this work, a statistically significant sample of castings in AlSi9Cu3(Fe) alloy has been manufactured through different injection parameters in order to identify the most relevant process parameters and estimate their correlations with the quality of the casting. In particular, the plunger I and II phase velocities (v1 and v2), the switch point between two phases (SW) and the intensification pressure (IP) have been varied randomly in accordance to the Design of Experiment methodology. The static mechanical properties of the castings have been measured using the bending test. Furthermore, the castings have been analysed by X-rays and their percentage of porosity has been estimated by means of image analysis software. Some novel aggregate parameters, representing a measure of the mechanical energy related to the plunger motion and the thermal energy exchanged with the die have been extracted from the plunger displacement curves and from thermocouple signals. The application of statistical concepts, methods and models demonstrates that these novel parameters allow explaining and forecasting both the mechanical properties and the porosity, and therefore the overall quality of the castings
Experimental and numerical analysis of TIG-dressing applied to a steel weldment
Full text linkFatigue strength of welded joints is controlled above all by notch defects such as weld toe and weld root that act as stress concentrators. This is the reason why over the last years different post-weld fatigue improvement techniques have been developed with the main propose of reducing geometrical discontinuities. Among these, TIG-dressing is the most used because of its simplicity and effectiveness in lowering the residual stress concentration. By this process the weld toe is re-melted to provide a smoother transition between the plate and the weld crown and to beneficially modify the residual stress redistribution. However, because of the intrinsic difficulty to numerically simulate the TIG-dressing process due to the high coupling between fluid and mechanical analysis, the effects of a weld toe remelting in terms of residual stress redistribution is hardly quantified in literature. The present paper is aimed to analyse the influence of TIG-dressing process on metallurgical and mechanical properties of a steel T-joint. Finally, a numerical model, recently published in literature, was used to quantified the residual stress redistribution.publishedVersion© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/)
Digital transformation to foundry 4.0
No full textThe competitiveness of the foundry sector is driven by innovation oriented to quality and production efficiency. The deeper knowledge of foundry process supports the introduction of optimal solutions to high quality products as requested from different global markets. The ability to manage all the stages of foundry production, based on advanced monitoring and cognitive platform, is fundamental to be able to react in real-time with a positive impact in terms of energy, environment and cost. Nowadays, the challenge is the digitalisation of real processes introducing intelligent systems to control the stability and the efficiency of production lines, along with being able to enable quality assessment and predictive maintenance. The application of the new ICT platform, Smart Prod ACTIVE, is oriented to zero defect manufacturing as demonstrated and validated at the foundry
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