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K Factor Development

The document describes a method for determining the K-factor of sheet metal when bent. K-factor is a ratio related to the distance from the neutral axis to the inside and outside surfaces when bent. The method involves measuring a flat piece of sheet metal and the same piece after bending it 90 degrees. Calculations using these measurements and the inside bend radius allow solving for the K-factor. A table of K-factors for different material thicknesses and bend radii should be created and shared with sheet metal designers and fabricators.

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Ahmad Shuja
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191 views1 page

K Factor Development

The document describes a method for determining the K-factor of sheet metal when bent. K-factor is a ratio related to the distance from the neutral axis to the inside and outside surfaces when bent. The method involves measuring a flat piece of sheet metal and the same piece after bending it 90 degrees. Calculations using these measurements and the inside bend radius allow solving for the K-factor. A table of K-factors for different material thicknesses and bend radii should be created and shared with sheet metal designers and fabricators.

Uploaded by

Ahmad Shuja
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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8 7 6 5 4 3 2 1

REVISIONS
4.817
(Flat_Length) ZONE REV. DESCRIPTION DATE APPROVED

UP 90.0° R .125
D D
K-Factor is the ratio of the distance from the inside surface to the neutral
axis to the material thickness. In bending the material at the bend is
compressed on the inside and stretched on the outside. It is neither
stretched nor compressed at the neutral axis.
To determine K-factors for combinations of material thicknesses (t) and
inside bend radius (IBR) simply measure the thickness (t) and flat length
(Flat) of a suitable piece of material prior to bending and then the two
lengths L1 and L2 after bending the part 90 . Calculate K-factor as
below. Populate a table for the combinations of thicknesses and bend
radii and publish it to the sheet metal designers and fabricators.
Equation Development (Note: L1', L2' and S are along neutral axis)
Flat = L1' +S +L2'
L1' = L1 - (IBR + t)
C L2' = L2 - (IBR + t) C
S = S/2 * (IBR + K*t)
Solving for K in terms of measured values Flat, t, L1, L2 and known IBR:
K = 2/S/t * (Flat - L1 - L2 + 2*(IBR + t)) - IBR/t
Example shown:
K = 2/S/.094 * (4.817 - 3.0 - 2.0 +2*(.125 + .094)) - .125/.094
Therefore K=.40

R.125
R.163 (IBR)
(R)
1.781
(L2') 2.000
B (L2) B
.038
(K*t)

2.781 .255
(L1') (S)
.094
(t) UNLESS OTHERWISE SPECIFIED:
DIMENSIONS ARE IN INCHES [mm] PROPRIETARY AND CONFIDENTIAL
TOLERANCES:
X/X : 0.03125
X.XX : 0.015 THE INFORMATION CONTAINED IN THIS
X.XXX : 0.005 DRAWING IS THE SOLE PROPERTY OF SANDAR
3.000 X.XXXX : 0.0005
ANGULAR : 0.5
INDUSTRIES, INC. ANY REPRODUCTION IN
PART OR AS A WHOLE WITHOUT THE WRITTEN
(L1) 64 PERMISSION OF XXXXX INDUSTRIES, INC. IS
SURFACE FINISH : PROHIBITED.
TITLE:
K-Factor
BREAK CORNERS TO R.01
A XXXXX INDUSTRIES, INC. MAY REQUEST THE A
MATERIAL RETURN OF THIS DOCUMENT AT ANY TIME.
--
MADE FROM STOCK
-- Configuration: Default Development
FINISH
DRAWN 12/3/2010 SIZE DWG. NO. REV

B
--
HEAT TREAT CHECKED 12/3/2010
K-Factor Development
-- ENG APPR. 12/3/2010
WEIGHT: - - MODELED 12/3/2010 SCALE: 1:1 DO NOT SCALE DRAWING SHEET 1 OF 1
8 7 6 5 4 3 2 1

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