COLD PLASTIC DEFORMATION OF PROCESSES IN CONDITIONS OF BORDER FORMATION

Abstract

The article considers the process of forming the inner slot profile on a pipe billet by the method of cold plastic deformation, by compressing them with a matrix on a profile slotted mandrel (by the method of "covering" drawing). A comprehensive study of the mechanics of shaping products to assess their quality and study the possibility of improving the process itself. In the case of three-dimensional molding, the surface of plasticity depends on the history of deformation, which is determined by the change in the stress state with increasing accumulated intensity of deformation. The surface of plasticity in this case is not fixed and can be constructed using the criterion of deformability, which provides the position of the point of the fracture surface, taking into account the history of deformation. The planes of deformation and boundary surfaces of plasticity are constructed, which showed a sufficient margin of plasticity for the process of forming the inner splined profile. It is substantiated that when constructing the load trajectory in the space of dimensionless indicators and its type is unambiguously determined by the conditions of formation characteristic of the studied process and practically does not depend on the mechanical properties of the deformed metal. The areas of deformation closest to the failure are determined by indicators that take into account the influence of the first and third invariants of the stress tensor (lateral region and area of depressions of the profile relative to the process of forming the internal splined profile), in which the used plasticity reaches values = 0,34 ... 0,4. From the point of view of providing a margin of safety, such calculations must be performed taking into account the indicator that takes into account the influence of the third invariant of the stress tensor.