A Study On Bionic Thread Compared To The Surface Of Shells

Gluing is one of the main reasons that causes malfunction of tubing thread, however, all types of pipe fittings(tubing, casing, pipelines, etc.) used in the process of oil production required threaded connection; therefore, how to solve the problem of gluing has always been a hot issue in the manufacturing of oil pipe. This paper starts from the mechanism of tubing thread, applied the trench-shaped structure of the shell surface into thread, in order to achieve the purpose of the antigalling.Given the limitation of simulation method, simulation is conducted on loads distribution of ordinary tubing thread and tubing thread with unsmoothed trench structure under the action of tightening torque force and axial force. The results show that the overall contacts stress on the tooth surface of bionic tubing thread is lower than that of an ordinary thread; therefore, it can effectively reduce the concentration force on thread.In order to obtain a desired anti-galling bionic thread, laser processing is used on the surface of the shell, processing trench structure on the surface of tubing thread. Unprocessed bionic thread, "0.5mm × 0.4mm bionic trench unit" threaded pipe specimens, and "0.5mm × 0.8mm bionic trench unit" threaded tubing were tested under actual working conditions. The results showed that, "0.5mm× 0.4mm bionic trench structure unit" threaded pipe specimens required less tightening force than common thread by 5.15%, with twice more screwing; "0.5mm × 0.8mm bionic structure unit" requires lower screwing force than common thread by 9.06%, but three times more screwing.Bionic trench structure significantly improves the anti-galling properties of a threaded pipe.Compared to bionic thread with smaller surface area, the tightening torque of thread with larger surface decreases by 4.03%, with once more screwing, but better anti-galling properties.