Prediction of Bend Allowance and Springback in Air Bending

[+] Author and Article Information
Hyunok Kim, Ninad Nargundkar

Engineering Research Center for Net Shape Manufacturing (ERC/NSM), The Ohio State University, Columbus, OH 43210

Taylan Altan1

Engineering Research Center for Net Shape Manufacturing (ERC/NSM), The Ohio State University, Columbus, OH 43210Altan.1@osu.edu


Corresponding author.

J. Manuf. Sci. Eng 129(2), 342-351 (Nov 20, 2006) (10 pages) doi:10.1115/1.2673527 History: Received March 08, 2006; Revised November 20, 2006

In the fabrication industry, one of the critical challenges is to maintain close geometric tolerances in finished products, particularly in the air bending process. In many cases, this problem is related to springback and plastic elongation/compression of the sheet, as it undergoes deformation in bending. Springback refers to the elastic recovery of the bent sheet after unloading, whereas bend allowance refers to the elongation of the sheet during bending. Both factors, if not predicted properly, may lead to dimensional inaccuracies in the finished product and cause difficulties in the assembly. Therefore, it is essential to predict springback and bend allowance in order to obtain the final desired geometry. A new analytical model was developed to predict springback and bend allowance simultaneously in air bending, and a user-friendly computer program, BEND (Version 3.0), was developed. Results obtained from the BEND program were compared to other analytical predictions and experimental results available in the literature. It was concluded that the proposed analytical model and the computer program predicted bend allowance and springback within acceptable accuracy.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Schematic of air bending

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Figure 2

Springback in sheet bending

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Figure 3

Bend allowance and bend deduction

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Figure 4

Deformation zone along the sheet length

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Figure 5

Deformation zones along the sheet thickness

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Figure 6

Zone I (tensile strain) and zone II (compressive strain) in plastic zone

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Figure 7

Final dimensions of the bent sheet

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Figure 8

Calculation of bend allowance in elastoplastic zone

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Figure 14

Geometrical changes during an infinitesimal interval of bending

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Figure 13

Required punch stroke versus springback angle—comparison of predictions with experiments

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Figure 12

Prediction of sheet thickness in air bending [note: Radius of punch=2mm, initial sheet thickness=1mm]

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Figure 11

Algorithm of BEND (Version 3.0) program

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Figure 10

Bend angles and springback angle in air bending

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Figure 9

Moment distribution in bent sheet




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