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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Simulation and Experiments for Hot Forming of Rectangular Pans in Fine-Grained Aluminum Alloy AA5083

    Paul A. SherekLouis G. Hector Jr.John R. BradleyPaul E. Krajewski...
    p.185-195页
    查看更多>>摘要：Accurate numerical simulation capability is critical to the development and implementation of hot forming technologies. Numerical simulations were developed for gas-pressure forming of commercial, fine-grained aluminum-magnesium (AA5083) material into deep pan shapes at 450℃. These simulations utilize a material constitutive model recently developed for fine-grained AA5083 materials as a user-defined routine in commercial Finite Element Method (FEM) software. Results from simulations are compared against data from gas-pressure forming experiments, which used the same forming conditions and die geometries. Specifically, local sheet thinning and radius of curvature in edges and corners are compared between simulation and experiment. Numerical simulations are in good agreement with experiments for local sheet thinning of up to 50%. For locations where sheet thinning exceeds 50%, simulations predict less thinning and larger formed radii than observed in experiments. It is likely that cavitation, which is not accounted for in simulations, plays a significant role in causing a decrease in simulation prediction accuracy for thinning values greater than 50%. This study demonstrates a simulation capability that is potentially of significant practical use for predicting the hot gas-pressure forming of fine-grained AA5083 material.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    High-Temperature Forming of a Vehicle Closure Component in Fine-Grained Aluminum Alloy AA5083: Finite Element Simulations and Experiments

    Louis G. Hector Jr.Paul E. KrajewskiEric M. TaleffJon T. Carter...
    p.197-209页
    查看更多>>摘要：Fine-grained AA5083 aluminum-magnesium alloy sheet can be formed into complex closure components with the Quick Plastic Forming process at high temperature (450℃). Material models that account for both the deformation mechanisms active during forming and the effect of stress state on material response are required to accurately predict final sheet thickness profiles, the locations of potential forming defects and forming cycle time. This study compares Finite Element (FE) predictions for forming of an automobile decklid inner panel in fine-grained AA5083 using two different material models. These are: the no-threshold, two-mechanism (NTTM) model and the Zhao. The effect of sheet/die friction is evaluated with five different sheet/die friction coefficients. Comparisons of predicted sheet thickness profiles with those obtained from a formed AA5083 panel shows that the NTTM model provides the most accurate predictions.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    New Developments in Superplastic Forming Simulation and Industrial Applications

    Shunping LiMathilde ChabinAndrew Heath
    p.211-217页
    查看更多>>摘要：In this paper, the authors presented the material models and numerical algorithms adopted in PAMSTAMP 2G for superplastic forming simulation. The improvements in strain rate control, automatic stop criteria, velocity scaling and shell element formulation to include normal stress can improve the accuracy and efficiency of superplastic forming simulation.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Finite Element Simulation on Superplastic Forming of Outer Jacket of Combustion Chamber

    Jong-Hoon YoonYeng-Moo YiHo-Sung Lee
    p.219-224页
    查看更多>>摘要：In this paper, mould configurations are studied by finite element simulation for superplastic blow forming of combustion chamber outer jacket. One concave and two convex mould configurations are basically considered to determine which type would be advantageous in terms of forming time and thickness distribution. For the simulation, the flow stress equation of duplex stainless steel was determined from free bulging test. The simulation results showed that the concave type was quit a bit different from the other two cases. The concave mould configuration produced shorter forming time and thicker thickness distribution than the others, and it seems to be more effective for superplastic forming of outer jacket. The obtained pressure profile for the concave mould configuration was employed in actual forming and the thickness distribution was compared for the verification.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    The role of the numerical simulation in superplastic forming process analysis and optimization

    Donato SorgenteLuigi Tricarico
    p.225-234页
    查看更多>>摘要：Numerical simulation took root in the last few decades in the superplastic forming field as one of the most dominant tools for process analysis and optimization. The big role of the simulation can be found in many areas concerning the study and the implementation of the forming process. The purpose of this paper is to outline some of the main applications of the numerical simulation in superplastic forming that can be found in the material characterization phase, in the simulation of forming tests and in the optimization of the process. A brief overview of results that can be found in literature is given with special regard to Finite Element numerical simulation of metal sheet Superplastic Forming.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Constitutive Modeling of Low-Temperature Superplastic Flow of Ultrafine Ti-6Al-4V Sheet Material

    S.L. SemiatinG.A. Sargent
    p.235-240页
    查看更多>>摘要：The low-temperature superplastic flow behavior of two lots of Ti-6Al-4V sheet with an ultrafine microstructure was modeled. One lot (Sheet A) had an equiaxed-alpha starting microstructure; the flow stress/flow hardening exhibited by this material was explained on the basis of the Bird-Mukherjee-Dorn constitutive equation. The other material (Sheet B), having a mixed equiaxed- and remnant-lamellar alpha microstructure, underwent flow softening, flow hardening, or steady-state flow depending on test temperature and strain rate. These behaviors were interpreted in the context of a dynamic spheroidization model. The apparent flow softening at the end of all of the flow curves was explained using a simple flow-localization model.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Superplasticity in Friction Stir Processed AZ80 Magnesium Alloy

    Yoshimasa TakayamaItsuki TakedaToshiya ShibayanagiHajime Kato...
    p.241-246页
    查看更多>>摘要：Superplasticity in an AZ80 magnesium alloy subjected to friction stir processing (FSP) has been investigated. FSP was carried out at two traveling speeds of 150mm/min and 300mm/min for grain refinement. Optical microscopy on cross section to processing direction revealed obvious differences in size and feature between the stir zones at the two traveling speeds. The hardness of FSPed sample at the room temperature was about 30HV higher than that of as-received one. The maximum stress of the FSPed sample was reduced remarkably at lower strain rates compared with those of the as-received one at 573K and 673K. On the other hand, the elongation to failure of the FSPed sample showed ten to thirteen times larger than that of the as-received one at 573K and low strain rates. Further surface morphology near the fracture tip was observed by scanning electron microscopy to discuss deformation mechanism at high temperatures.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Finite element modelling and experimental testing of thermo-mechanical behaviour and failure of titanium superplastic forming dies

    Sean B LeenAditya A DeshpandeThomas H Hyde
    p.247-256页
    查看更多>>摘要：This paper describes high temperature cyclic and creep relaxation testing and modelling of a high nickel-chromium material (XN40F) for application to life prediction of superplastic forming (SPF) tools. An experimental test programme to (ⅰ) characterise the high temperature cyclic elastic-plastic-creep behaviour of the material over a range of temperatures between 20℃ and 900℃, including cyclic controlled strain-range tests at different strain-rates and creep relaxation tests, and (ⅱ) identify the material constants relevant to thermo-mechanical fatigue (TMF) life prediction, is described. The objective of the material testing is the development of high temperature material and failure models for cyclic analyses and life prediction of SPF and diffusion bonding (DB) dies for titanium aerospace components.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    An Overview of Hot- and Warm-Forming of Al-Mg Alloys

    Eric M. Taleff
    p.259-265页
    查看更多>>摘要：Al-Mg alloys exhibit remarkable hot and warm ductilities, which have made the 5000-series alloys a critical part of commercial hot gas-pressure forming operations for the transportation industry. A review of the metallurgical and practical engineering reasons for this success is presented, and new understanding for behaviors in these materials, expected to impact future advances in hot- and warm-forming technology, are described. The excellent formabilities in this material class are fundamentally attributable to two deformation mechanisms, grain-boundary-sliding and solute-drag creep. However, a number of failure mechanisms ultimately limit final ductility and formability. These include cavitation, flow localization and microstructure evolution. The interplay of these mechanisms is discussed in terms of the potential to improve processing windows in forming operations.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Large Deformability of Wrought Magnesium Alloys: Is Superplasticity Needed?

    R. BoissiereJ.J. BlandinL. Salvo
    p.267-272页
    查看更多>>摘要：The deformability of wrought magnesium alloys at room temperature is limited and a way to overcome this limit is to carry out forming operations in warm or hot conditions. In the case of fine grained alloys, superplastic properties can be generally achieved but in this regime, the Mg alloys are sensitive to strain induced cavitation. However, large grained alloys can also exhibit quite large deformabilities when they are deformed at high temperature. This can be due to the fact that on one hand, the Mg alloys may quite easily dynamically recrystallize and on the other hand, that dislocation movements may be controlled by a solute drag effect leading to significant strain rate sensitivity parameters. These various mechanisms of deformation will depend on the composition, the mean grain size and the conditions of deformation (i.e. temperature and strain rate). In this work, the high temperature deformation mechanisms as well as the associated damage mechanisms of two wrought magnesium alloys are discussed.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd