calculating bending stress in round tubing

To calculate the exact length of the bend, the product of the above formula must therefore be divided by another coefficient – known as the coefficient of elongation.

This elongation can have the following consequences: To verify the feasibility of bending round steel tubes, the ratio between the average bending radius, diameter and thickness of the tube concerned is considered. In this case, tests must be run in order to evaluate whether the K-factor can be reduced and if special bending jigs need to be constructed.

K < 0.05 – The tube cannot be bent under normal conditions.

0.08 > K > 0.05 – Tube bending is possible only when using a movable, internal mandrel in conjunction with a wiper die.

0.10 > K > 0.08 – A fixed bending mandrel with a wiper die – a special tool to restrict tube deformation – will be needed for bending the tube.

0.30 > K > 0.10 – The bending process is of normal difficulty: using only an internal, fixed bending mandrel will be sufficient.

K > 0.30 – Bending the tube is more ‘straightforward’ and there is now need to use special support jigs that would need to be manufactured ad hoc.The difficulty of the tubing bending is inversely proportional to its value: the difficulty increases with a low K-factor and decreases with a high K-factor. This formula produces the value for the K-factor.

Calculating bending stress in round tubing