Thinning rate of bending pipe

Pipe bending process will appear deformation, in addition to wrinkling and fracture is also thinning, then what is the thinning rate? Simply speaking, the thinning rate is a step before fracture, and when the thinning reaches a certain level, fracture will occur.

As shown in figure 1

Figure 1  Bending Thinning

The shadow will be stretched by bending, and the thickness of the pipe bending machine wall will become thinner, a phenomenon known as thinning. The difference between the thickness of the reduced pipe and the original pipe is called the thinning rate

Generally, when the user needs to pass gas or liquid in the bending machines for pipe and tube pipeline, the thinning rate will be required, because the liquid gas pipeline flow will have pressure. The thickness of this kind of pipeline is selected according to the pressure calculation, if the thinning is too much, the internal pressure is too high, the pipeline will burst.

As shown in figure 2

Figure 2  Pipe bending rupture

Therefore, the general value of thinning rate is about 15%, and the thickness of 3mm can only allow the thinnest thickness of 2.55mm.

So how do you meet this requirements? The most obvious way is to use mandrel and wiper die to constrain the deformation of the pipe, which can effectively ensure the wall thickness of the problem.