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Technical Brief

Temperature Increase in Forming of Advanced High-Strength Steels Effect of Ram Speed Using a Servodrive Press

[+] Author and Article Information
Ali Fallahiarezoodar

Center for Precision Forming,
The Ohio State University,
339 Baker Systems,
9171 Neil Avenue,
Columbus, OH 43210
e-mail: fallahiarezoodar.1@osu.edu

Ruzgar Peker

Center for Precision Forming,
The Ohio State University,
339 Baker Systems,
9171 Neil Avenue,
Columbus, OH 43210
e-mail: peker.4@osu.edu

Taylan Altan

Center for Precision Forming,
The Ohio State University,
339 Baker Systems,
9171 Neil Avenue,
Columbus, OH 43210
e-mail: altan.1@osu.edu

Manuscript received January 15, 2016; final manuscript received June 21, 2016; published online July 19, 2016. Assoc. Editor: Matteo Strano.

J. Manuf. Sci. Eng 138(9), 094503 (Jul 19, 2016) (7 pages) Paper No: MANU-16-1040; doi: 10.1115/1.4033996 History: Received January 15, 2016; Revised June 21, 2016

In forming of advanced high-strength steel (AHSS), the temperature increase at die/sheet interface affects the performance of lubricants and die wear. This study demonstrates that finite-element (FE) analysis, using commercially available software, can be used to estimate temperature increase in single as well as in multiple stroke operations. To obtain a reliable numerical process design, the knowledge of the thermal and mechanical properties of the sheet as well as the tools is essential. Using U-channel drawing the thermomechanical FE model has been validated by comparing predictions with experimental results. The effect of ram speed and stroking rate (stroke per minute (SPM)) upon temperature increase in real productionlike operation have been investigated. Deep drawing of CP800 and DP590 sheets in a servodrive press, using an industrial scale die, has been studied. Thinning distribution and temperatures in the drawn part have been investigated in single and multiple forming operations. It is found that temperatures may reach several 100 deg and affect the coefficient of friction (COF). The values of COF under productionlike conditions were compared to that obtained from laboratory experiments. This study illustrates that in forming AHSS, (a) the temperature increase at the die/sheet interface is relatively high and should be considered in process design stage, and (b) the lubricant performance is significantly affected by the ram speed and sheet/die interface temperature during deformation.

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References

Figures

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Fig. 2

Schematic cross section of the simulation setup and the geometrical parameters used for simulation of U-channel forming [4]

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Fig. 1

Flow stress data for 1.4 mm CP800 and DP590 obtained from the VPB test

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Fig. 3

Max. temperature predicted by FE simulation and measured experimentally at die/sheet interface during the U-channel drawing of 2 mm DP780. The experimental results are from Ref.[4].

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Fig. 4

Schematic of the nonsymmetric industrial scale die used in this study for deep drawing process (die set built by Shiloh Industries)

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Fig. 5

Measurement of the thinning distribution along a curvilinear length of 1.4 mm CP800 panel formed up to 48 mm. Thickness of the six locations along the cutting line are measured in experimental sample and the thinning values are compared with simulation results for approximately the same locations (a) simulation prediction and (b) the formed panel and the locations of measurements.

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Fig. 8

Max. temperature rise at die/sheet interface for two values of COF, during the deep drawing of 1.4 CP800 with 250 kN blankholder force and 75 mm/s ram speed. (Die geometry is shown in Fig. 4).

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Fig. 12

Temperature rise at die/sheet interface at deep drawing of 1.4 mm CP800 in consecutive multiple forming, F: forming stage; T: transfer stage

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Fig. 9

Temperature predicted at panels formed up to 48 mm depth with 250 kN blankholder force and 75 mm/s ram speed; (top) 1.4 mm CP800, (bottom) 1.4 mm DP590

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Fig. 6

Thinning percentage versus curvilinear length at the corner of the formed panel, shown in Fig. 5, material CP800, initial thickness 1.4 mm, Drawing depth 48 mm, and blankholder force 250 kN

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Fig. 7

Thinning percentage versus curvilinear length at the corner of the formed panel, Fig. 5, material DP590, initial thickness 1.4 mm, drawing depth 70 mm, and blankholder force 200 kN

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Fig. 10

Ram speed versus stroke curve used in 48 mm deep drawing of CP800 with Aida 300-ton servodrive press and 25-ton servocushion, (crank diameter = 400 mm), stroke = 0 is the top dead center and stroke = 400 is when the ram is at bottom dead center

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Fig. 11

Calculated temperature rise at die/sheet interface in U-channel drawing with: (a) 5 SPM and (b) 30 SPM forming speed, F: forming stage; T: transfer stage

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