1,721,076 research outputs found
Deformazione a caldo e mappe di processo di un composito 6061 rinforzato dal 20% di particelle Al2O3
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Comportamento a creep e fenomeni di precipitazione nella lega Ni-22Cr-12Co-9Mo A 700 e 800°C
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Comparison of compression and torsion constitutive analyses of Al-Mg-Si alloy at elevated temperature
No full textIn the last decade several papers dealing with FEM simulation of bulk forming processes have been presented and
discussed in literature [1-2]. FEM simulations became a very useful tool for process analysis and optimization,
especially in such cases, like extrusion, where on-plant experiments are complex, expensive and their results are
of difficult interpretation. In order to perform reliable and accurate FEM simulations, a correct definition of the
flow stress dependence on thermo-mechanical parameters is an essential prerequisite. In this context several
equations have been defined and included in FEM codes. In particular, the Garofalo relationship [3] is widely used
for modeling the flow stress behavior of aluminum alloys. In this equation the peak flow stress (sigma)) dependence
on strain rate (ε̇) is described by the Garofalo expression:
ε= A sinhασ exp( Q / RT) (1)
where n is the stress exponent, Q is the activation energy for high-temperature deformation, R is the gas constant,
T is the absolute temperature, A and are material parameters. Other equations were developed recently taking
into account the strain dependence on the flow stress behavior[4].
Several testing methods, both in cold or hot conditions, can be used in order to determine the flow stress. Tensile
testing is the most popular but can be used only when small true strains (below 0.5-0.8) are accounted for, since
the limit of this technique is the occurrence of necking which limits the maximum attainable strain. Compression
testing requires an excellent lubrication of the specimen, since severe barreling of the specimen usually occurs at
strain around 1. Torsion is a pure shear mechanical testing, permits to reach a high strain before rupture and
frequently exceeds 5; these very high strains can be favorably compared with those typical of bulk processes like
extrusion, where the strain field can reach values up to 10.
The aim of the present paper is thus to study the hot deformation behavior of Al AA6063 alloy by means of hot
compression and torsion tests in the 350-550°C temperature range, typical of real extrusion temperatures. The
behavior of the alloy, in terms of equivalent stress vs equivalent strain, was modelled by different constitutive
equations: a modified and strain dependent form of the Garofalo’s equation and the Hensel and Spittel equation. The experimental flow stress curves obtained by compression and torsion were compared with the curves
predicted by the developed models and discussed in order to define the goodness of the models in predicting the
materials hot flow stresses
Interpretation of the creep behaviour of a 9%CrMoNbV (T91) steel using threshold stress concept
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Assesment of the creep response of new Powder Metallurgy Rapid Solidification Al-Si-Ni-Cr and Al-Si-Cu-Fe alloys
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