MULTI-NODE DETECTION TECHNIQUE OF THREADED DRILL PIPE COMPOUND LOADS BASED ON FIBER BRAGG GRATING SENSING

Based on the separation theory of compound loads (axial force, bending moment and torque), the multi-node compound loads of a threaded drill pipe are separated and detected online in a drilling process by using fiber Bragg grating (FBG) strain sensors and temperature sensors. Temperature compensation is realized synchronously. Compared the measured value with the applied axial force and torque, the transfer losses in the front end of the threaded drill pipe (close to drill bit) is considered being greatly influenced by the lateral squeezing force and frictional resistance. The bigger value makes this part of the drill pipe easy wear and deformation. The middle and terminal end of the drill pipe are greatly influenced by bending moment. The former enters the object with short time. And the latter does not enter. It leads to low transfer losses. The detection technique provides a technical support for material selection, structural optimization, and drilling parameter selection of a drill pipe.