Research On Thread Structure Of Drill Pipe Connection

In the oil drilling and geological drilling construction,drill string as the main transmission part of drilling,bear transmission force and as a drilling mud channel and other important role.The actual production situation shows that composition of drill string as a drill pipe as the main force in drilling process and force components,the dangerous section is often in connection thread.By studying the form and specific parts of thread failure,thread structure is optimized to a certain extent reduce damage at thread.According to the existing two types of thread drilling31/2REG(normal type)and geological core drilling joint thread: nominal diameter 59,the model is modeled by SolidWorks software and simulated by ANSYS Workbench finite element software.Analysis of taper thread and pipe thread structure characteristics.The simulation results show that the two threads have the following common points:(1)Thread stress(strain)concentrated part is at the root of external thread to the third circle.(2)The main failure forms are root fracture and longitudinal cracking.(3)In starting part of the external thread,due to emergence of stress and strain concentration,in the processing need to be cutting,that is,the location of small teeth height.The difference between the two threads is(1)Under the action of torque,stress of the first and second laps of taper thread is obviously opposite to that of third lap,and the 3-lap of pipe thread is distributed evenly.(2)Under the action of torque,the taper thread at shoulder than pipe thread shoulder stress concentration.Based on study of the two kinds of threads in standard,force response is more sensitive and optimized by using flat tooth bottom cylindrical thread with the prospect.To maximize stress will be transferred to the bottom of carcass on principle of thread to optimize pitch,and then optimize the other parameters.Main dimensions of the non-standard system pipe thread are: pitch 6.5mm,tooth height 1mm,tooth type half angle 7mm,external thread tooth width 3.117 mm,internal thread tooth width 3.127 mm,external thread diameter(internal thread Large diameter)21mm,external thread diameter(internal thread diameter)19mm and so on.Through modeling and simulation of optimized thread,optimized non-standard small-caliber joint thread can reduce the stress-strain of 28.6% under the pressure,reduce the stress and strain of thread under the action of bending force and bending force by 15.92%.Under the action of torque and pressure.the stress strain increased by about 8%.Optimized overall performance of thread is better.