Value Bending

At the same time, outside of the bend, where the wall tension of the metal, there is an increased yield strength. In practice, it is necessary to bend the pipe with the smallest possible radius of a bend. Smallest bending radius depends on the mechanical properties of pipe material, pipe wall thickness ratio to the value of the diameter, the way the fold. The most important physical-mechanical factor in determining the smallest possible bending radius, is the plastic properties of metal. Plastic properties of metal pipe to be fold, estimated by residual elongation in the gauge length under tension.

Therefore, in each case is recommended to check and set the value of the elongation of fibers stretched to the outer part of the fold. Check can be made by testing samples of pipes or by calculation. Test tubes in tension produced by GOST 1497-61 on a longitudinal sample (in the form of a strip cut from a pipe) – normal or proportionately, long or short, at the discretion of the manufacturer, in the form of nevypravlennom. There are many ways to bend pipes. In foreign practice, there are machines for cold bending of pipes stretching. The advantage of this method is that the presence of strain leads to a shift of the neutral axis to the axis of the fold. Such a shift leads to a decrease in compressive stress fibers and thereby reduces the possibility of Education corrugation. Bending process is that the tube is captured on the edges, stretch and bend at the same time by putting forward bending template.

The most expedient way to this flexible thin-walled pipes, especially for thin-walled tubes of rectangular cross section, and in cases where the pipe must be bent in one plane with a variable radius of curvature and when the tolerance on the outside diameter is large. To avoid loss stability of the wall on the inside of the fold, there is a flexible pipe under internal hydrostatic pressure. This is achieved by the fact that the pipe ends are inserted into the stub. One of which is provided with a connection for feeding into the fluid. By pumping liquid into the pipe wall having voltage dovodyaschie metal to a state close to the plastic. Upon reaching the middle of such stresses to the tube bending pattern which bring pressure pipe. Sometimes it is necessary to reduce the roundness in the bend. And this case, we introduce an additional operation changes (sized) tubes. To edit a pipe fixed in a certain most suitable for the curved pipe place and the cable extends through the ball with her. It is most convenient to perform calibration of broaching machines. Edit produce a composite mandrel, which has two to four balls of various diameters. Initially, through the tube stretch bead of smaller diameter, followed by the others. The last ball has the size, which should correspond to the inner diameter of the pipe. Calibration is used to obtain the desired size up to 0,025 mm.