No abstract

Uneven distribution of stresses in the thread can cause fatigue failure of the joint, usually in the area of the first roots of the thread. This problem is very relevant for shouldered threaded joints of oil and gas equipment, which operate under conditions of significant cyclic loads. One of the ways to equalize the stresses in the thread is plastic deformation of the thread with a high load before make-up. The influence of various methods of such pre-deformation of the tool joint of drill pipes and the connection of sucker rods on the fatigue life in the thread roots of the pin and box has been studied. A method for optimizing the load for pre-deformation was proposed and it was found that the optimal load can increase the fatigue life by 5 times. The study was carried out by finite element analysis of the axisymmetric model in Abaqus/CAE and calculation of the fatigue life from the Brown-Miller dependence using fe-safe.

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The performance of the machines part reinforcement using surface plastic deformation shall be considered as formation of the whole complex of surface parameters and quality and their impact on the operational properties of these parts. The main surface quality parameters, affecting the performance of machine parts are geometric (microgeometry, wavelength, roughness, shape of inequalities, the size of the supporting surface, the direction of the traces of processing); physical parameters (structure, degree and slander depth, residual stresses in the surface layer). In the machine building, many methods of superficial plastic deformation are used for part reinforcement; these methods essentially differ in the scheme of impact of the surface deforming part to be treated. After analyzing the results obtained by scientists, involved in research on surface plastic deformation of surface layers and surfaces of parts, it was found that after hardening, practically all structural changes contribute to reinforcement of the surface layer material and increase the plastic deformation resistance. Increasing the density of dislocations and the separation of carbides, which block the shear slides and create obstacles to the movement of dislocations. Due to these changes, resistance to formation and spread of fatigue cracks have increased. The treatment depth, magnitude of residual stresses and increase in hardness depends on the original structure and chemical composition of the material. Reinforcement regimes have significant effects on the wear resistance. Use  of diamond smoothing, vibration processing, combined methods (surface plastic deformation in combination with other reinforcement methods, as well as the use of a combined tool) opens up new possibilities for increasing the quality characteristics of the surface and the surface layer of parts, and accordingly, increasing their operational properties with all the diversity and complexity of used processes. Based on the results of the studies, practical recommendations on the application of methods of hardening by surface plastic deformation of machine parts and a methodology for designing technological processes for their manufacture considering manufacturing capabilities are proposed.