Creep Age Forming of 2024A, 8090 and 7449 Alloys

Pitcher, P.D.; Styles, C. M.

doi:10.4028/www.scientific.net/msf.331-337.455

Cited by 27 publications

(25 citation statements)

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“…Furthermore the alloys studied were in the solid solution condition or in the initial stage of the ageing. Spring back values around 80% were found for 7055 alloy 11 and around 70% for 7449 alloy 9 . Another work 6 that evaluates the CAF of an integrated panel machined from a 7475 alloy, report spring back values varying from 55% to 87%, depending on the section observed.…”

Section: Introductionmentioning

confidence: 94%

“…Spring back occurs because the holding (ageing) time, which is required to achieve proper mechanical properties, is not sufficient to fully fix the shape of the component. However, the final aged component has lower residual stresses 4,8,9 compared to structures formed by conventional forming processes such as roll forming, brake forming, shot peening or stretch forming.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of a 7050-TAF aluminum alloy submitted to creep age forming

2014

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CAF process combines creep and precipitation hardening which are highly dependent on time and temperature. The aging cycle relax the stresses induced during the loading phase. At the end of the process stress relaxation induces shape changes in the part but significant spring back is observed (about 70%). Usually CAF cycles for 7XXX alloys use times around 20 h and temperatures in the range of 120°C to 190°C. In the present work CAF tests were performed using the alloy 7050 in an intermediate condition named Temper to Age Forming (TAF). Using the alloy 7050-TAF resulted in significant process time reduction. From TAF temper, only 8 hours are necessary to achieve properties comparable to T74. Coupons were submitted to CAF in two levels of initial stress, 190 MPa and 290 MPa, resulting in spring back values of 70% and 60 % respectively. In addition, constant load creep tests were performed in the same stress levels and time of CAF tests to find the creep strain values. Creep tests performed under 190 MPa resulted in strain values around 0,1% after 8 h. On the other hand creep tests performed under 290 MPa failed after 7 h with creep strain values of 1,7%. Results obtained are close to that found in previous studies and it is possible to conclude that the use of alloy 7050 in TAF condition allows CAF to be done in 8 hours, since the initial stress is lower than 290 MPa.

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Evaluation of a 7050-TAF aluminum alloy submitted to creep age forming

2014

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“…The main challenge for application in these and other damage tolerant parts lies in obtaining the best balance between the often conflicting sets of requirements such as creep rate during age forming and fatigue crack growth resistance of the age formed product. A limited number of works have been published which focus on the principles of this relatively new processing technique [1,2] and on application to selected standard aerospace Al based alloys [3,4]. However, no reports on the main mechanisms responsible for the relations between composition, formability and resulting properties have been published, and no methodologies for optimising the combination of alloys and process with respect to damage tolerant properties have been published.…”

Section: Introductionmentioning

confidence: 99%

“…The process offers considerable design and manufacturing benefits over conventional forming operations such as peen forming, bump pressing and roll forming, through high potential of automation, potential of increased component accuracy and reduced residual stress levels. The process is directly amenable to higher strength 7xxx alloy components, as these are already optimised for use in artificially aged tempers [2,3], and the process is becoming established in airplane upper wing applications where 7xxx alloys are typically employed. However, incumbent lower wing skin alloys, such the 2024 Al-Cu-Mg-Mn based alloys in the damage tolerant T351 condition, lose their critical damage tolerant properties upon ageing.…”

Section: Introductionmentioning

confidence: 99%

Relations between microstructure, precipitation, age-formability and damage tolerance of Al–Cu–Mg–Li (Mn, Zr, Sc) alloys for age forming

Starink

Gao

Kamp³

et al. 2006

Materials Science and Engineering: A

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Age forming of Al based alloys for damage tolerant applications requires an alloy with good age formability and good post-forming mechanical properties. To investigate optimisation of this balance, several newly designed Al-Cu-Mg-Li (Mn,Zr,Sc) alloys were subjected to artificial ageing representative of age-forming. It was seen that combinations of yield strength and fatigue crack growth resistance could be achieved that are at least comparable to the incumbent damage tolerant material for such applications, whilst creep rates at the ageing temperatures applied were better than those achieved in commercially applied age forming processes of heat treatable Al based alloys. Coarse grain structure and high Li content are associated with good fatigue crack growth resistance but reduce age formability. The underlying physical aspects responsible for the balance between creep rates and resulting properties are discussed. The metallurgical and micromechanical mechanisms analysed and discussed provide a framework for optimisation of composition and forming conditions for age forming of damage tolerant parts.

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“…According to the figures provided by General Motors (Michigan, USA), the economic impact of delayed production and tooling revision costs due to springback alone was estimated to be over US$50m a year in the automotive industry [8]. This is an even bigger problem when translated to CAF as springback of CA-formed parts can reach up to 80 %, and the abruptly changing thicknesses of wing panels also further complicates the mechanism of springback in practical operations [4,[9][10][11].…”

mentioning

confidence: 99%

A method for designing lightweight and flexible creep-age forming tools using mechanical splines and sparse controlling points

Lam

Shi

Lin

et al. 2015

Int J Adv Manuf Technol

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Creep-age forming (CAF) is a proven forming technique in the aerospace industry for the production of large integrally stiffened panels. One of the most urgent issues to be addressed in CAF is the development of flexible tooling. Flexible tools already have a long-standing reputation for the economic impact they have brought to the aircraft industry. However, with the rising need to establish comprehensive springback prediction models for CAF, the need for flexible CAF tools is now stronger than ever. In this article, an existing state-of-the-art CAF tool is described followed by the introduction of a novel design concept for flexible tooling. Based on the proposed design method, which utilises mechanical splines and sparsely spaced controlling points, a proof-of-concept prototype is built and characterised using corresponding analytical and finite element models that have been developed. Three parameters that can influence forming surface error: (i) the number of control points, (ii) spaces between control points and (iii) spline thickness are identified and optimised. Finally, an integrated optimisation process for tool offsetting is introduced, and its use is demonstrated. It is confirmed that this design method can be used to make flexible CAF tools with less than ± 1 mm error (defined as vertical difference from prediction) in the forming surface. In addition, this error can eventually be compensated and thus eliminated from CA-formed parts by using the developed optimisation technique. This article provides CAF tool designers confirmed advices for making new flexible CAF tools. Lightweight and flexible CAF tools can now be constructed through the use of mechanical splines and sparse controlling points.

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Creep Age Forming of 2024A, 8090 and 7449 Alloys

Cited by 27 publications

References 0 publications

Evaluation of a 7050-TAF aluminum alloy submitted to creep age forming

Evaluation of a 7050-TAF aluminum alloy submitted to creep age forming

Relations between microstructure, precipitation, age-formability and damage tolerance of Al–Cu–Mg–Li (Mn, Zr, Sc) alloys for age forming

A method for designing lightweight and flexible creep-age forming tools using mechanical splines and sparse controlling points

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