Superplastic forming of a spherical shell out a welded envelope

Hot isothermal/isostatic pressing machines are technically good candidates for superplastic forming (SPF) of otherwise hard-to-shape materials such as superalloys. These machines are, however, very expensive so that small or medium-size enterprises can not afford them. This has impeded widespread use of SPF processing. In an attempt to alleviate the problem, the authors have developed a laboratory model of an affordable hot isothermal pressing machine with differential gas pressure as the forming medium. Careful selection of process parameters such as temperature, gas pressure, strain rate, and process time as well as monitoring of thickness changes in a workpiece has a pivotal role in successful operation of such machine. It has been illustrated in this article that SPF can be successfully performed with this machine on the basis of process parameters estimated with existing analytical relations. The performance of this machine has been verified by several experiments on SPF of titanium-based sheets, as reported in this article.

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“…1, process time, T, forming pressure, P, and critical thickness, S n, for a spherical component are found as follows [38,42]:…”

Section: Appendixmentioning

confidence: 99%

“…Components with special configurations such as roll-formed disks, spherical shells, and thin circular diaphragms have already been developed ( Ref 33,38,39). Several lens-shaped components possessing numerous industrial applications were successfully formed from titanium blanks using the developed machine.…”

Section: Introductionmentioning

confidence: 99%

Experiments with a Low-Cost Hot Isothermal Pressing Machine Developed for Superplastic Forming

Nategh

Jafari

2008

J. of Materi Eng and Perform

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“…Atkinson [10] also tried to improve the accuracy of the analytical predictions referring to the polar thickness and dome radius. Kruglov [11] developed a formula for the calculation of the polar strains. Banabic [12] developed analytical models for the computation of the pressure-time relationship for the bulging of both strain hardening and superplastic materials trough elliptical dies and Vulcan [13] and Banabic [14] for superplastic forming of aluminium sheets for the cone-cup test.…”

Section: Introductionmentioning

confidence: 99%

Determination of Material Parameters of Sheet Metals Using the Hydraulic Bulge Test

Lăzărescu

Nicodim²,

Ciobanu³

et al. 2013

Acta Metall Slovaca

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Hydraulic bulging experiments are performed in order to evaluate the mechanical parameters of cold rolled steel (DC04) and aluminium alloy (EN AW 6016-T4) sheet materials. The biaxial yield stresses, and the biaxial anisotropy coefficients are derived from the biaxial stress-strain curves and the ratio between the strains in the transverse and in the rolling direction, respectively. The mechanical parameters resulted from the bulge test in combination with the results from the tensile tests are used to determine the yield loci of the two materials. The effect of the number of input parameters on the capability of the BBC 2008 yield criterion to predict the yield locus is also discussed in the paper. Keywords: hydraulic bulge test, mechanical properties, yield surface IntroductionThe most commonly used tests for the determination of the biaxial yield stress are the biaxial tensile test of cruciform specimens [1][2][3][4] and the hydraulic bulge test. A review of biaxial tensile tests using cruciform specimens is presented in the papers [5,6]. The disadvantages of this method are the complicated geometry of specimens as well as the complexity and high cost of the equipment. An alternative to this test is the hydraulic test. The most important advantage of the hydraulic bulge test is the absence of the contact (and therefore of the frictional interactions) between tools and specimen in the area of interest, which simplifies the analytical solutions for the calculation of stress and strain, but also ensures the repeatability of the test. The hydraulic bulge test is the subject of many scientific papers and has been investigated by other authors such as Hill [7], who developed analytical models for the calculation of polar thickness and curvature radius. He neglected the influence of the fillet radii of the die. The accuracy of the formulas proposed by Hill has been improved by Chakrabarty [8] by taking into account the hardening effects. Furthermore, Shang [9] extended the formulas proposed by Hill in order to take into account the fillet radius of the die insert. Atkinson [10] also tried to improve the accuracy of the analytical predictions referring to the polar thickness and dome radius. Kruglov [11] developed a formula for the calculation of the polar strains. Banabic [12] developed analytical models for the computation of the pressure-time relationship for the bulging of both strain hardening and superplastic materials trough elliptical dies and Vulcan [13] and Banabic [14] for superplastic forming of aluminium sheets for the cone-cup test. Lăzărescu [15][16][17] developed analytical models for the determination of stress-strain curves using dies with circular and elliptical apertures. Koç [18] performed experimental studies for the

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“…В лите-ратуре появились сведения об использовании СПФ при производстве вакуумных камер для ядерных исследова-ний, дверей для самолета Concorde размерами 400х350 мм, топливных баков диаметром 380 мм, сложных тон-костенных подпорок, деталей для катапультирующего сиденья, сосудов давления для космических спутников и др. [19][20][21][22][23][24].…”

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Stress analysis of the superplastic forming of circular membrane Part I. Problems of modeling of superplastic forming

Samoilova¹,

Ganieva²,

Enikeev³

et al. 2013

LoM

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Superplastic forming of a spherical shell out a welded envelope

Cited by 81 publications

References 28 publications

Experiments with a Low-Cost Hot Isothermal Pressing Machine Developed for Superplastic Forming

Experiments with a Low-Cost Hot Isothermal Pressing Machine Developed for Superplastic Forming

Determination of Material Parameters of Sheet Metals Using the Hydraulic Bulge Test

Stress analysis of the superplastic forming of circular membrane Part I. Problems of modeling of superplastic forming

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