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  • Liu, J., et al. (författare)
  • Finite element modeling of a non-isothermal superplastic-like forming process
  • 2010
  • Ingår i: AIP Conference Proceedings. - Paris : AIP. - 0094-243X. ; , s. 377-382
  • Konferensbidrag (refereegranskat)abstract
    • Conventional superplastic forming (SPF) has been modified to increase the productivity and reduce some of the drawbacks, such as high forming temperature and high percentage thinning, to suit the automotive industries. One of the modifications was to combine between the conventional SPF and the use of a mechanical preformed blank to form the non-superplastic grade aluminum alloy (AA5083-O). The requirement of high temperature usually results in microstructural defects during forming process. In this paper, finite element modeling was adopted to investigate the superplastic-like forming process using the non-isothermal heating system. In the simulation, two phases (mechanical pre-forming and gas blow for ming) of the process were conducted under different temperatures, where the material was mechanically drawn into the die cavity at 200°C in the first phase, and it formed with gas pressure applied at a global temperature increasing from 400°C to 500°C. Because of the non-isothermal heating of material, it was found that it had enough ductility to flow more easily in the specific zones (die corners and radius). Additionally, FEM results showed that a better formed part can be obtained by the increasing temperature forming, compared to the stable temperature phase. © 2010 American Institute of Physics.
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5.
  • Rigopoulou, D., et al. (författare)
  • The far-infrared spectroscopic surveyor (FIRSS)
  • 2021
  • Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 51:3, s. 699-728
  • Tidskriftsartikel (refereegranskat)abstract
    • We are standing at the crossroads of powerful new facilities emerging in the next decade on the ground and in space like ELT, SKA, JWST, and Athena. Turning the narrative of the star formation potential of galaxies into a quantitative theory will provide answers to many outstanding questions in astrophysics, from the formation of planets to the evolution of galaxies and the origin of heavy elements. To achieve this goal, there is an urgent need for a dedicated space-borne, far-infrared spectroscopic facility capable of delivering, for the first time, large scale, high spectral resolution (velocity resolved) multiwavelength studies of the chemistry and dynamics of the ISM of our own Milky Way and nearby galaxies. The Far Infrared Spectroscopic Surveyor (FIRSS) fulfills these requirements and by exploiting the legacy of recent photometric surveys it seizes the opportunity to shed light on the fundamental building processes of our Universe.
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  • Jarfors, A. E. W., et al. (författare)
  • Preface
  • 2010
  • Ingår i: Materials & Design. - : Elsevier BV. - 0261-3069. ; 31:SUPPL. 1, s. S1-
  • Tidskriftsartikel (populärvet., debatt m.m.)
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7.
  • Liu, J., et al. (författare)
  • Investigation of process parameters in superplastic forming of mechanical pre-formed sheet by FEM
  • 2010
  • Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 447-448, s. 437-441
  • Tidskriftsartikel (refereegranskat)abstract
    • Conventional superplastic forming has been applied in automotive and aerospace industries for a few decades. Recently, superplastic forming combined with mechanical pre-forming process has been reported to be capable of forming non-superplastic AA5083 at 400°C to a surface expansion of 200 % [1]. In this paper, finite element modeling (FEM) was used to develop the combined forming process by using the non-superplastic material AA5083-O. The simulation follows the experimental sequence and was divided into two phases (mechanical pre-forming and superplastic forming). A conventional creep equation based on tensile test data was adopted as a material model for the simulation. The pressure cycle and forming time was simulated according to the actual process route. The thickness distributions obtained from simulation validated the capability of the model to be used for this case. The influence of different parameters, such as holder force, friction, and punch depth was investigated by comparing the final sheet thickness and level of material draw-in. It was found that the punch depth played a significant effect on the uniformity of thickness distribution, from which a more uniform formed part can be obtained by using the punch with higher depth during mechanical pre-forming phase. © (2010) Trans Tech Publications.
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8.
  • Liu, J., et al. (författare)
  • Superplastic-like forming of non-superplastic AA5083 combined with mechanical pre-forming
  • 2011
  • Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 52:1-4, s. 123-129
  • Tidskriftsartikel (refereegranskat)abstract
    • Superplastic forming has been considered as an attractive process in the automotive and aerospace industries. However, the disadvantages of slow forming rate, high-temperature requirement, poor thickness distribution, and expensive base material have hindered its widespread use for high production volume. In this paper, the non-superplastic grade of 5083 aluminum alloy (AA5083) sheets with thickness of 3 mm was employed in a superplastic-like forming process, which is a combination of drawing (mechanical pre-forming) and superplastic forming (blow forming). Experimental trials were conducted to verify the possibility of improving the forming rate and lowering the process temperature. The blank was firstly pre-formed during the mechanical pre-forming phase. As a result, some part of material along the flange area was introduced inside the deformation cavity in advance of the blow forming phase. Secondly, argon gas was applied on the sheet, which would be deformed to come into contact with the inner die surface at the end of pressure cycle. It took only 8 min for the blow forming phase, and the process achieved an almost fully formed part at 400°C. The minimum thickness occurred at the inward corners, and the maximum thinning of the formed part was 54%. Grain growth and cavitation were found from the microstructure observations.
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  • Resultat 1-8 av 8

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