Open AccessThe experience of operating oil wells showed that the weak point of tubing is a connecting thread.
Currently, the pipe thread of the specified class is made using the technology of cutting. The process of cutting a thread leads to waste metal chips and cutting fibers. Therefore the idea arose to make a thread by the method of pressure shaping.
The aim was to study the possibility for full filling of the threaded matrix profile.
The study was conducted by means of mathematical modeling in the software complex DEFORM. The impact of technological and geometrical factors on the process of form change was in detail analyzed. Thus, a work-piece material was specified to be continuous, isotropic, homogeneous, viscous-plastic and a tool material was set as a hard one. The friction was speci-fied according to Prandtl-Siebel law with the friction factor of 0.3. The thread profile has been replaced by the annular grooves of the similar profile. The task was considered to be axisymmetric.
Scientific novelty of received results consists in revealed regularities of the plastic de-formation process of the work-piece when forming a profile of the conical thread on the pipe in the process of its expansion with a conical punch.
The simulation allowed us to obtain information about the stress-strain state of the work-piece and tool, about the nature of the metal flow during deformation, and about the strength parameters of the process.
In particular, it was found that the work-piece metal is displaced along the pipe axis both in punch movement direction and in the opposite one. Thus, a mechanical end burr is formed. The article shows that to remove a mechanical end burr requires insertion of extra limit stop housing. The article also analyses distribution of stresses arising in the matrix at the final moment of deformation. It was proved that the highest stresses occur in the hollows of the threaded part of matrix. Thus, their absolute value does not exceed 470 MPa that is quite acceptable for the materials used in the production of stamps.
Research has been proven a principle possibility to have the external conical pipe thread by expansion with a conical punch.