The Characteristics Of The Bending Process Of The Pipe Bending Machine

The bending of pipes by a pipe bending machine is the same as the bending of sheet metal. In the case of pure bending, when a pipe with outer diameter D and wall thickness t is bent under the action of an external force moment M, the outer wall of the neutral layer is subjected to tensile stress σ 1. The effect is to thin the pipe wall; Tensile stress on the inner wall of the neutral layer σ 1. The action thickens the pipe wall. Moreover, the shape of the cross-section changes from circular to approximately elliptical due to the combined forces F1 and F2. When the deformation is too large, cracks will appear on the outer pipe wall and wrinkles will appear on the inner pipe wall.
The degree of deformation of pipes depends on the relative bending radius R/D and the relative thickness t/D values. The smaller the R/D and t/D values, the greater the degree of deformation. To ensure the quality of pipe forming, it is necessary to control the degree of deformation within the allowable range. The bending forming limit of pipes not only depends on the mechanical properties and bending methods of the material, but also considers the usage requirements of the pipe fittings. The forming limit of pipe fittings should include the following contents:
1) The maximum elongation deformation within the tensile deformation zone on the outer side of the neutral layer does not exceed the allowable plastic value of the material, resulting in fracture;
2) Within the compression deformation zone on the inner side of the neutral layer, the thin-walled structural parts subjected to tangential compressive stress shall not exceed instability and wrinkle;
3) If there is a requirement for ellipticity in the pipe fittings, control the distortion of their cross-section;
4) If the pipe fittings have strength requirements to withstand internal pressure, control the forming limit of wall thickness reduction.