1,720,995 research outputs found
Design and manufacturing of anti-intrusion bars made of aluminium foam filled tubes
No full textThe role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. The aim of this paper is to investigate the performances of anti-intrusion bars, made by tubes filled with aluminium foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is mainly conducted by evaluating some key technical issues of the manufacturing problem and by
running experimental and numerical analyses. The evaluation
of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH2 blowing agent. Empty and foam filled tubes are tested in three point bending, in order to evaluate their performances in terms of several performance parameters. Different manufacturing conditions, geometries and tube materials
are investigated. The option of using hydroformed tubes, with non constant cross section, for the production of foam filled side structures id also discussed
The effect of cold rolling on the foaming efficiency of aluminium precursors
No full textThe objective of the present study is to investigate the role of cold rolling on the foaming ability (or foamability) of aluminium precursors, made by continuous rotary extrusion, a process performed at elevated temperature, starting by powder. For this purpose, the effect of different parameters including initial shape of precursors, rolling direction, amount of deformation in each rolling pass and final thickness of rolled specimens are experimentally investigated. Furthermore, the foaming efficiency of both rolled precursors and as-received extruded ones is compared. To clarify the role of secondary processing operations on the foaming efficiency, precursor samples are prepared following different forming and machining process chains, before the final foaming operation. Finally, hardness tests are performed on as-received precursors and rolled samples to notice the correlation between rolling parameters, state of strain, foaming efficiency and hardness. The results of the study show that: (a) cold rolling considerably improves foamability, (b) rectangular precursor bars have higher foaming efficiency than round ones, both before and after cold rolling. Besides, the improvement in foamability due to cold rolling is greater if precursors are rolled in the extrusion direction, rather than the orthogonal direction. © 2013 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved
The analysis of tool life and wear mechanisms in spindle speed variation machining
Full text linkRegenerative chatter vibrations generally limit the achievable material removal rate in machining. The diffusion of spindle speed variation (SSV) as a chatter suppression strategy is mainly restricted to academy and research centers. A lack of knowledge concerning the effects of non-stationary machining is still limiting its use in real shop floors. This research is focused on the effects of spindle speed variation technique on tool duration and on wear mechanisms. No previous researches have been performed on this specific topic. Tool wear tests in turning were carried out following a factorial design: cutting speed and cutting speed modulation were the investigated factors. The carbide life was the observed process response. A statistical approach was used to analyze the effects of the factors on the tool life. Moreover, the analysis was extended to the wear mechanisms involved during both constant speed machining and SSV. The worn-out carbide surfaces were examined under a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. Significant differences were appreciated. It was observed that SSV tends to detach the coatings of the inserts, entailing a mechanism that is quite unusual in wet steel turning and thus fostering the wear of the tool. The performed analysis allowed to deduce that the intensified tool wear (in SSV cutting) is mainly due to thermo-mechanical fatigue
CFD and experimental analysis of the coolant flow in cryogenic milling
Full text linkCryogenic cooling could improve the machining performance for hard-to-cut materials. Deployment of this modern technology for milling applications, specifically because of their severe working conditions and complicated physical phenomena inside cryogenic fluids, requires further research to become credible for industrial applications. Obtaining accurate models for coolant behavior is essential for optimum design, prediction of operational limits, and safe control of the cooling process. In this paper, Computational Fluid Dynamics (CFD) were used to determine the behavior of the liquid nitrogen (LN 2 ) inside the coolant delivery system and the interaction of the coolant jet with the cutting area. The role of working conditions as well as nozzle geometry, formation of cavitation inside the tool, coolant pressure, and wall temperature on the efficiency of the coolant delivery were investigated in this study. Initial experimental flow measurements were used to predict the simulation setup and evaluate the results. Experimental milling tests were performed to verify the numerical findings. Cutting forces, coolant mass flow rate, temperature, and pressure were measured during the tests. A mechanistic cutting force model and the morphology of the chips were used to interpret the effect of liquid nitrogen on the cutting mechanisms. Results of this study offer three main suggestions for reliable industrial cryogenic milling: using liquid nitrogen in the range of 2–4 bar, improving the insulation of the feeding line and finding a technical solution for non-insulated parts, and increasing the quality of the liquid in the coolant mixture close to the milling head. Outcomes of this study could help to improve the cooling performance and implement a reliable industrial solution for cryogenic milling
Microstructural Study of the Intermetallic Bonding Between Al Foam and Low Carbon Steel
Full text linkBonding between a metal foam core and a metallic skin is a pre requisite for the technological application of aluminum foam as filling reinforcement material to improve energy absorption and vibration damping of hollow components. This work is a preliminary study for the microstructural characterization of the interface layer formed between a commercial powder metallurgy (PM) precursor and a steel mould during foaming. The microstructure of the intermetallic layer was characterized by scanning electron microscopy, electron probe microanalysis and nanohardness measurements on the cross section. X-ray diffraction measurements, performed on the foam/substrate surface after stepwise material removal, allow the identification of the intermetallic phases. Two intermetallic layers, identified as Fe2Al5 and FeAl3, characterize the low Si foam/substrate while the AlSi10 foam/substrate interface evidences the presence of three Fe(Si, Al) intermetallic layers with different composition. Two and three different phases of increasing hardness could be distinguished going from the foam to the steel substrate for AlMg1Si0.6 and AlSi10 precursors respectively. The results suggest the importance of elemental diffusion from steel substrate in the molten aluminum matrix (foam). The possibility to control and tailor the microstructural properties of the interface between foam and steel skin is of fundamental importance in the technological process of foam filled structures manufacturing
On the influence of some process parameters in aluminum foam/steel bonding
No full textBonding between foam core and metallic skin is a pre requisite for the technological application of aluminium foam as filling reinforcement material. An intermetallic layer formed at the interface during foaming should make the foam firmly fixed to the skin improving its bending and torsional strength and stiffness. The formation, growth and metallurgical properties of this layer are strongly related to the process parameters. This work aims to contribute to understand how some parameters and the possible correlations between them influence the process. DOE and ANOVA statistical techniques highlighted that argon
flux helps the formation of a continuous layer, foaming time and temperature strongly affect its thickness and morphology
Energy measurements and LCA of remanufactured automotive steel sheets
Full text linkNew paradigms based on Circular Economy (CE) principles are needed for boosting the ecological transition and improving the energy and material efficiency. In this paper, a novel remanufacturing process chain for End-of-Life (EoL) automotive panels is first presented. The core of the recycling strategy is the reshaping of curved EoL automotive sheets through flattening by means of a hydraulic press. Flattening experiments together with press power consumption measurements have been performed on thin steel parts. While the experimental procedure demonstrated the technical feasibility of flattening “small-scale” steel parts, a more complete analysis on environmental sustainability was required. For this purpose, a Life Cycle Assessment (LCA) of the remanufacturing process chain proposed was set up. The results of the study demonstrated that flattening is a viable solution for reshaping EoL automotive panels, and that, for one kg of reshaped steel, approximately 2.2 kg CO2 and 24 MJ could be saved
Procedures for Damping Properties Determination in Metal Foams to Improve FEM Modeling
Full text linkThe aim of this work is to review the available procedures suitable for the determination of damping parameters in literature and standards for porous and dense materials and to evaluate their applicability to metal foams.
Preliminary experimental setup and characterization data obtained with the selected procedures are presented and compared with representative FEM models. The experimental dynamic measurement on a test structure is compared with the simulated ones in order to validate the chosen procedure
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