1,721,218 research outputs found
Chill material and size effects on HTC evolution in sand casting of aluminum alloys
No full textAn extensive experimental investigation on the heat transfer coefficient (HTC) during sand casting of aluminum alloy is presented here; the variation in time of the HTC in the whole cooling process was reconstructed with many kinds of chills, different in size and material. Cast iron, aluminum and copper were used as chill materials, the HTC between aluminum and sand also being considered. In particular, typical foundry practice regarding melt treatment, sand preparation and chill manufacturing and assembly within the mold is considered throughout the analysis, in order to obtain the most reliable HTC values. The evaluated HTC are then put in relation with cast and chill temperature, in order to allow the easiest transportability to simulation codes for foundry. Relevant points of HTC curves and physical behaviors of the interfaces are also discusse
Aluminium Two Thousand World Congress and International Conference on Extrusion and Benchmark ICEB 2015
No full textThis special issue of the journal “Material
s Today: Proceedings”
contain
s selected
peer reviewed papers presente
d at the 2015 edition of the
‘united’
congress
International Confere
nce on Extrusion and Benchmark
(
ICEB
)
5
th
edition and
9
th
edition of
Alu
minium Two Thousand
World Congress
.
The two congresses
were merged together in a single venue
for the edition 2015 in
order to
bring together “aluminium and light
alloys” specialists in a single event,
creating a very attractive
and unique oppo
rtunity for
researchers, technicians
,
technology suppliers
,
industry managers and othe
r qualified
speakers for
discovering
and discussing the latest researche
s
and the trends for the future
Experimental assessment of hot-work tool steels performances under the creep-fatigue regime
Full text linkIn the present research an innovative testing method, specifially developed to characterize the tool steels under creep-fatigue conditions, was carried out an a TQ1 hot-work tool steel. The experimental campaign consisted of different testing conditions and part of the specimens were nitrided to account for the specific surface state of the tools. Tests were performed on a 10tons 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 a hot forging or extrusion tool. Then, under a constant temperature of 520°C, the effects of four different load levels and 2 different values of dwell-times were evaluated. In addition, selected test conditions were replicated with the specimens not nitrided with the aim to evalute and quantify the influence of the superficial treatment. Final results were presented in terms of fatigue curves of the TQ1 and compared to the performances of the H11 tool steel tested in a previous research by the same authors
Multi-objective Optimization of the Extrusion Process
No full textIn the paper a multi-objective optimization of a porthole extrusion die used to manufactured a thick AA7003 round tube is presented. Eight competitive objective functions were selected aimed at increasing the seam weld quality, the die lifetime, the production rate and at restraining the die yielding and the peak process load with respect to an initial already optimized solution. Six geometric input variables were included in the optimization procedure (welding chamber and bridges height, ports width, undercut on ports, die entry angle, mandrel-bridges fillet radius) together with the ram speed. The multi-objective optimization was performed by means of modeFRONTIER® using meta-models generated over a selected set of experimental and numerical training designs
Fonderia e Pressofusione
No full textLA RIVISTA STORICA DEDICATA ALLE FONDERIE
La rivista Fonderia Pressofusione continua a essere un insostituibile strumento per l’aggiornamento professionale delle fonderie ferrose e non ferrose. Con la presentazione di nuove macchine e di nuovi impianti, con ampi articoli applicativi realizzati direttamente nelle fonderie, con gli articoli tecnici dedicati ai processi di fusione e alle tecniche di produzione, Fonderia Pressofusione segue il passo di un settore in continuo rinnovamento e che fa dell’innovazione tecnologica la sua arma vincente
Multi-Goal Virtual Optimization of Industrial Extrusion Dies
No full textIn the design of complex extrusion dies, a number of different and potentially conflicting goals are involved in the process optimization such as profile tolerances, mechanical properties, aesthetic surfaces, and die life. The aim of the present work was to carry out a multi-objective virtual optimization of industrial porthole dies for the maximization of profile quality (seam welds strength), of the production rate (flow balance and ram speed), and of die strength. Two industrial profiles were investigated, a thick round tube and a more complex industrial case of a hollow rectangular profile. In the first case, the gain achieved by the optimal design was compared with the experimental evidence of an already optimized configuration, showing an additional increase in terms of welding strength and flow balance. For the rectangular profile, the most significant improvements were attained not only for the seam weld quality, but also for the die strength, if compared to the performances of a starting configuration
Extrusion research activities at the University of Bologna-Italy
No full textA review of the activities recently performed at the University of Bologna in the field of aluminum extrusion is here presented. A brief description on the state of the extrusion industry in Italy is initially drawn with a particular focus on the Extrusion district located in the north of Italy. There, University of Bologna is the Italian reference point for the research activities in the field of extrusion technology, process optimization and products characterization.
Four main research directions are actually developed at University of Bologna in cooperation with companies and academia: seam and charge welding, process simulation, die design optimization and microstructural evolution of aluminum alloys during and after hot deformation. The paper summaries each activity with a specific focus on the main results, the applications and the possible developments for each topic
Experimental investigation and numerical analysis of the die deflection in aluminum extrusion
No full textIn order to assess the capability of numerical simulation in industrial hot aluminium extrusion, an extensive comparison was performed between data recorded during the experiment performed at 2009 ICEB conference and the process simulations performed by three FE codes: ALTAIR HyperXtrude®, COMSOL® Multiphysics and DEFORMTM 3D. In the experimental trials, two U-shaped profiles made of AA6082 alloy were extruded under monitored conditions: profiles exit temperature and velocity, extrusion load, die temperature and die deflection by means of an innovative laser-based method were continuously recorded during the trials.
Numerical simulations were performed by means of the decoupled approach: at first, the material flow was computed with each code (DEFORM with an Updated Lagrangian approach, HYPERXTRUDE with an Arbitrarian Lagrangian Eulerian formulation, COMSOL based on a pure Eulerian approach); then the pressure was mapped and applied on the die face for a subsequent die stress analysis
Creep behaviour modeling of the AISI H11 tool steel for extrusion dies applications
No full textAim of an extrusion die is to allow the production of the profile with the required dimension tolerances and quality level. One of the main impediment to achieve this aim could be an excessive die deformation due to the high cyclic loads and temperatures acting on the die during the extrusion process. In order to investigate the mechanisms that influence the die deformation, a physical experiment reproducing the thermo-mechanical conditions of a die was performed on a martensitic tool steel used for extrusion tools (AISI H11). The design of experiment consisted of 4 levels of temperature, 3 levels of stress and 3 types of load, i.e. pure creep, pure fatigue and creep-fatigue. In all cases, the same pattern of the mandrel displacement-time curve was found consisting of 3 stages as those typical of the strain evolution in a standard creep test with a marked primary phase. Thus, with the aim to define an easy-applicable equation to estimate the die deformation, an exponential type law was chosen. In order to obtain the temperature gradient within the specimen coupled thermo-electric simulations were previously performed. The nodal temperature have been then imported within the structural model and the mechanical properties assigned to the each element as a function of these values. Coefficients of the exponential law were optimized, for each testing condition, on the basis of experimental data starting from values for similar alloys found in literature and novel equations formulated to express their dependency on temperature and stress. A good average agreement was found between experimental and numerical results
Code Validation and Development of User Routines for Microstructural Prediction with Qform
No full textAim of the present work is to validate the metal forming FE code QForm and to develop user routine for the prediction of microstructure evolution in 6XXX aluminum alloys. Preliminary simulations are carried out in order to select optimal friction models and coefficients among the several formulations available in the code. Numerical results are compared to grid-based visioplasticity experiments: the comparison is performed in term of grid deformation at the billet-tools interfaces, load-stroke behavior and temperatures evolution of die and profile. The optimized friction model and coefficient are then applied in second series of simulations in order to develop the prediction of microstructure evolution. A theoretical model for the grain size and shape evolution of 6XXX aluminum alloys is finally implemented through the use of user routine and compared with experimental observations. The model is found able to properly predict the deformed state of the grains in the fibrous condition
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