Research On Hydroforming Method Of Stator Bushing Of Screw Drilling Tool

With the development of exploration technology in oil and gas industry,oil and gas exploration development has been stridden forward from shallow layer into deep well and ultra-deep well in current China.Screw drill has been applied widely with the increase of drilling depth in adverse industrial environment surrounded by high temperature and pressure.However,conventional screw drill can't be adapted to deep well and ultra-deep well excellently because of inhomogeneous formation and inferior high temperature resistance of motor.Therefore,high performance equal wall thickness screw drill has been come up and applied in oil drilling development.High performance equal wall thickness screw drill stator is designed combining hydroforming and conventional stator to solve the problems with difficult manufacturing,low efficiency and low precision of large length-to-diameter ratio internal spiral surface screw drill stator.Hydroforming of equal wall thickness metal bushing is classed as elastoplastic problem with large deformation relating to geometry,material,boundary of non-linearity and mechanical characteristic,geometry size,load path of tube material,which is a complicated forming process.The numerical simulation method has been used to analyze the whole forming process,the research works are listed below:(1)Based on hydroforming fundamental theories,hydro forming principle of equal wall thickness metal bushing is introduced to analyze the forming parameters,collapsing pressure,forming pressure and maximum load pressure of metal tube.No.304 stainless steel is selected to be forming materials because of fair extensibility.The finite element theory and meshing technology of shell element are presented.(2)Based on conventional hydroforming method,the finite element model of equal wall thickness metal bushing is established to analyze the influence of geometry size,axial feeding parameters,load path match and friction factor for forming quality.The analysis results show that both sealing and material compensation are provided by axial feeding in conventional hydroforming method.Whereas,equal wall thickness metal bushing material compensation can't be offered by axial feeding since the metal bushing belongs to large length-to-diameter ratio internal spiral surface structure.(3)Inside and outside pressure composite forming method is used for equal wall thickness metal bushing forming manufacturing to overcome the drawback of poor adaptability in conventional loading method.Machine tools,geometry size and load path of inside and outside pressure composite forming are both designed and finite element simulated to gain the selection criterions.The results show that inside and outside pressure composite forming can be applied in equal wall thickness metal bushing because of high forming precise.The forming method of equal wall thickness metal bushing is analyzed by both theoretical derivation and numerical simulation to investigate the insufficiency in conventional forming method and bring up inside and outside pressure composite forming method,which can improve the manufacturing precise.Theoretical basis is provided in high performance equal wall thickness screw drill stator with high precision and low cost.