Research On Detection Technology Of Drill Pipe Thread Defects Based On Alternating Current Field Measurement

Aiming at the detection requirement of special structural defects of drill pipe threads,the Alternating Current Field Measurement(ACFM)technology is introduced to establish the simulation model of drill pipe threads defects based on ACFM.The distortion rules of electromagnetic field around the transverse penetration defect,the longitudinal defect,the medial longitudinal defect,the root longitudinal defect and the natural pitting defect are simulated respectively.A threaded defect ACFM detection probe based on high sensitivity tunnel magnetoresistance(TMR)sensor is developed.With the help of MATLAB and Lab VIEW graphical programming software,a matching software system is developed.A hardware signal processing system is developed based on Compact RIO platform.Finally,a complete ACFM drill pipe thread defects detection system is built with software and hardware and crack detection experiments were carried out.The main contents of this paper are as follows:(1)Establishment and analysis of finite element simulation model for drill pipe thread defectsBased on the principle of ACFM detection technology and COMSOL finite element simulation software,a three-dimensional finite element theoretical simulation model of drill pipe thread defects is established.The finite element simulation was carried out for the transverse penetration defect,the longitudinal defect,the longitudinal defect inside the tooth,the longitudinal defect of the tooth root and the natural pitting defect of the threaded tooth top.The distortion law of electromagnetic field around various types of defects is analyzed,and the characteristic signal of drill pipe thread defects is determined.(2)Development of high sensitivity detection probe for drill dipe threadWith the help of finite element simulation model,the key parameters such as excitation frequency and lift-off height of drill pipe thread defect detection probe are optimized and analyzed.The internal signal processing circuit of the probe based on high-precision tunneling magnetoresistance(TMR)magnetic field sensor is developed,and the shell structure matching the drill pipe thread is designed.Finally,a high-sensitivity detection probe for drill pipe thread defects based on ACFM is developed.(3)Development of thread defects detection system for drill pipe based on ACFMWith the help of Compact RIO embedded real-time controller,a software system for thread defect detection is developed under Lab VIEW software programming environment,which includes core software modules such as incentive,acquisition and defect threshold alarm.Real-time communication between the core hardware of the FPGA(Field Programmable Gate Array)-RT(Real-Time)-host computer and data storage function of the characteristic signal are realized.Finally,a drill pipe thread defect detection system is built.(4)Testing experiment and result analysis of drill pipe thread defectsThe transverse penetration defect,longitudinal defect,inner longitudinal defect,root longitudinal defect and natural pitting defect of the top of the tooth were tested by the drill pipe thread defect detection system.The experimental results show that the system can realize high sensitivity detection and automatic determination of various types of defects in drill pipe threads.