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TECHNICAL PAPERS

Preform Design of Powder Metallurgy Turbine Disks Using Equi-Potential Line Method

[+] Author and Article Information
Yuhong Liu, Shuxin Wang

School of Mechanical Engineering, Tianjin University, Tianjin 300072, China

Fuguo Li

School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China

S. Jack Hu

Department of Mechanical Engineering, University of Michigan, 2250 G. G. Brown Building, Ann Arbor, MI 48145

J. Manuf. Sci. Eng 128(3), 677-682 (Feb 22, 2006) (6 pages) doi:10.1115/1.2194066 History: Received June 20, 2005; Revised February 22, 2006

In a material hot forging process, rational preform design not only ensures that metal flows properly in die cavity and that final products have excellent quality, but also reduces tooling cost. In the present work, it is proved in theory that the differential equation of electric potential (2ϕ=0) in the electrostatic field is similar to the differential equations of velocity potential function (2φ=0) and velocity stream function (2ψ=0) in velocity field during the material forming process, with all three represented in the form of the Laplace equation. Moreover, the material flow in the plastic stage and the energy in electrostatic field all meet the least-energy principle. Therefore, according to the similarity criteria, an equi-potential line (EPL) method is proposed for the design of the preform shape in material hot forging. Different voltages are applied to the billet shape and the final product shape to generate a proper electrostatic field. One optimal equi-potential line is selected among the innumerable equi-potential lines as the basic shape of the preform shape and is processed into the preform shape following a three-step procedure. The preform design by the EPL method is compared with that by the traditional industrial method. The results show that the proposed method for preform design is feasible and reliable for practical applications.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 8

Distribution of equivalent stress at the end of finish forging for different preform design (MPa): (a) preform design by TI method and (b) preform design by EPL method

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Figure 7

Distribution of equivalent strain at the end of finish forging for different preform designs: (a) preform design by TI method and (b) preform design by EPL method

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Figure 6

Load-displacement curves of upper die under different forming processes:—preform design by TI method; ----preform design by EPL method

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Figure 5

Comparison of preform design between EPL method and TI method

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Figure 4

Deformation degree at preforging and finish forging

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Figure 3

Equi-potential lines between the enlarged billet shape and the final shape

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Figure 2

Distribution of equi-potential lines under different enlargement factor; 0:0V, 1:0.1V, 2:0.2V, 3:0.3V, 4:0.4V, 5:0.5V, 6:0.6V, 7:0.7V, 8:0.8V, 9:0.9V, 10:1V

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Figure 1

Schematic illustration of the equi-potential line method

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