Research On The Structural Design And Experiment Of Connected Performance Of ZSB Thread Casing

At present, special oil casing thread cannot completely meet the need of modernpetroleum industry development, the stress distribution on the casing thread joint is notuniform, the teeth of screw thread are easily sticky and broken. To deal with this situation,this paper makes a systematic research of ZSB oil thread casing(“Z” is tapered thread,“S” is quadruple thread,“B” is variable pitch of screw), studying its structural design,theoretical analysis and calculation, three-dimensional finite element modeling,simulation and semi-physical physical model experiment. In detail, it includes thefollowing:(1) The structure design of ZSB thread casingBased on the extensive collection and analysis of related information of oil threadcasing both domestic and foreign, its characteristics (i.e. strengths and weaknesses, usingof occasion, the difficulty and cost of manufacturing) are studied. And an optimalstructure of ZSB thread casing is proposed, including the connection structure betweencoupling and tube, the structure of thread teeth, the variable pitch program, sealed form,the structure of proof loose and etc. the corresponding two-dimensional assemblydrawing and all parts diagram of ZSB thread casing is completed.(2) Theoretical calculation of the connection properties of ZSB thread casingIn this part, by doing fundamental technology researches on the self-locking,connection strength, the contained deformation under load, the ability to yield toresistance and destruction of ZSB thread casing, a related mechanical model isestablished and completes theoretical calculations. On this basis, the relevant data ofperformance is obtained, also the design principle and quantity of variable pitch structureis theoretically analyzed.(3) Three-dimensional modeling and simulation of ZSB thread casingAfter completing structural design and theoretical calculation, a three-dimensionalfinite element model is built, a more excellent grid unit is divided in this part, by usingthe finite element analysis software ANSYS Workbench. Moreover, according to themain conditions of the oil thread casing, the reasonable load simulation way of thethree-dimensional finite element model is explored, the contact type of both inside and outside of the teeth between coupling and tube is set up. By analyzing and comparing thestress field of thread casing with different variable pitch structure in the same condition,the best scheme of variable pitch is derived. Thus, the structure form of the casing isimproved and optimized, by adjusting the preliminary structure design and the sizeparameters of calculation process.(4) The research on semi-physical physical model experiment of ZSB thread casingA semi-physical physical model experiment of the ZSB thread casing is done in thispart. The deformated law of the screw thread teeth is analysed when the oil casing threadin low load, full load and over load, also the law of stress distribution in the thread jointis inferred. Moreover, the original pictures about the failure of ZSB thread casing can beconveniently observed in the course of the experiment and the failure reasons can beanalyzed in time. After determining the principle and method of the experiment, theprocess of design, manufacture, assembly, and commissioning of the experimental deviceis completed in this part. Through the systematic and complete experiment, the relatedexperimental data and pictures are obtained, the data collation and analysis is completed.Further, the experimental results are compared with the finite element simulation results,and it finally reaches the verification results.