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To solve the problems of poor high temperature resistance of conventional screw pump stator and difficult machining of screw pump stator with equal wall thickness, this paper created a finite element model of equal wall thickness metal spiral pipe for single screw sump with 42CrMo based on tube hydroforming (THF). In this paper, the forming effects of different processes were evaluated by analysing the average pitch, wall thickness thinning rate and inner contour accuracy. Due to the particularity of design section and irregular plastic flow of material, the wall thickness of internal high pressure forming decreases seriously; on the other hand, because the diameter of the designed section is relatively large, the minimum ratio of D 2 to D min is 1.12, which shows that wrinkles appear in external high pressure forming. As a result, based on the problems of internal and external high pressure forming, a coupling forming process was proposed. The results show that different parameters of coupling forming have little effect on the average pitch of metal spiral tube, and its maximum deviation is 1.08%; while thickness reduction ratio is proportional to initial diameter and thickness. Besides, when the liquid pressure is 350 MPa, the diameter is 60 mm and the wall thickness is 7.5 mm, the contour matching degree is higher; but the material accumulation and wrinkling will happen when the pipe diameter greater than 60 mm. [ABSTRACT FROM AUTHOR]

The sealing of the drive shaft assembly of the impact screw drilling tool is very easy to fail under the coupling of high temperature and 3-D compound motion, which limits the popularization and application of the impact screw drilling tool. In order to study the sealing characteristics and parameter sensitivity of the drive shaft assembly under the coupling effect of high temperature, high speed and reciprocating motion, the contact surface formed by the shaft and the slip ring was defined as the main sealing surface, and the contact surface formed by the O-ring and the groove bottom was defined as the secondary sealing surface. Based on the contact pressure of the main sealing surface, numerical simulation was performed on the relevant parameters that affect the sealing characteristics of the combined ring, and the influence of friction coefficient, O-ring diameter, carbon fiber content and reciprocating speed on the sealing performance of the combined ring was studied. Studies have shown that with the increase of friction coefficient, the contact pressure and Mises stress of the primary and secondary sealing surfaces in the pre-compression state increase, the contact pressure of the primary and secondary sealing surfaces in the static seal state decreases,and the Mises stress of the slip ring increases. In the dynamic seal state,when the friction coefficient of left and right stroke is 0. 01, 0.02, 0.03,the contact pressure fluctuation range is small. When the friction coefficient is 0.04,the contact pressure fluctuation range is larger. It is reasonable to recommend that the friction coefficient is less than 0.04. As the diameter of the O-ring and the carbon fiber content increase, the contact pressure of the primary and secondary sealing surfaces and the Mises stress of the O-ring and slip ring in the precompression state increase, and the contact pressure and Mises stress of the primary and secondary sealing surfaces in the static and dynamic sealing states increase. With the increase of reciprocating speed, the average contact pressure of the primary and secondary sealing surfaces in the right stroke is larger than that in the left stroke. The contact pressure of the left stroke shows a decreasing trend; on the contrary, the average value of the contact pressure and the stress difference between the left and right strokes increase. The research results provide guidance and reference for the selection and use of sealing rings of impact screw drilling tools in the future. [ABSTRACT FROM AUTHOR]