Cold bending DIN 6935 (Eng)

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General
This method of calculation applies to bent parts of flat steel products for use
in steel construction and in general mechanical engineering.
When bending flat rolled steel, such as sheets, strips, wide flat steels, etc. is considered
to take the rolling direction, because of better suitability for bending as possible transverse to the 
rolling direction
to be bent.
Bending radius
r bending radius 
a bending angle
b opening angle 
The bending angle a can be between 0 ° and 180 °. 
The Thickness is in the rounding up about 20% lower.
To achieve uniform curves on bending rails, it is recommended that only bending radius be 
used for bending
to choose from the following series. The bold values are to be preferred.
Table 1 gives the smallest permissible bending radius, which at certain sheet thicknesses 
and
Materials for the applicable bending machines can be selected. The specified values
apply to bending angle a £ 120 °. For bending angles a> 120 ° insert the next higher table 
value,
e.g. would be when bending transverse to the rolling direction of sheets of QSt 42-2 with 
the thickness s = 6
mm the smallest permissible bending radius r = 10 mm for a £ 120 ° and r = 12 mm for a 
<120 °.
Table 1: Smallest allowable bending radius r
Calculation of the stretched lengths 
Cold bending DIN 6935
of flat steel products
30 April 2018 15:57
 DIN 6935 Cold bending Page 1 
Elongated length = a + b + u. Depending on the value of the bending angle, u is different and 
represents one
Compensation value that is negative or positive at opening angle b from 0 ° to 65 ° (exact 
value 65 ° 24'30 ")
and at opening angles over 65 ° can only be negative.
Stretched lengths should be rounded to the nearest millimeter.
Opening angle b 0 ° to 90 °: Compensation value u:
Opening angle b> 90 ° to 165 °: Compensation value u:
 
Opening angle b> 165 ° to 180 °: Compensation value u = 0 The values for u are negligibly small, the 
Accuracy is sufficient for the practice.
K Factor 
Correction factor k for determining the cutting lengths of bent workpieces
The correction factor k indicates the deviation of the position of the neutral fiber s / 2 and is 
calculated
 DIN 6935 Cold bending Page 2 
For r: s> 5 the equation is no longer valid, then k = 1 has to be set.
example
Material: Q St 37-2 (steel grade up to 390 N / mm² tensile strength)
Completion:
Sum of leg lengths 50 + 170 + 256 + 50 = 516
For b = 90 °, r = 20, s = 12, u = - 25.41
for b = 45 °, r = 20, s = 12, u = - 6,12
for b = 135 °, r = 20, s = 12, u = - 7.25
- 38.78
Total leg length 516.00
- Sum of compensation values - 38.78
stretched length 477.22
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 DIN 6935 Cold bending Page 3