Research On Drilling Pipe Defect Detection Technology Based On Piezoelectric Ultrasound

As an important tool of oil drilling,the drill pipe has been widely used in oil exploitation.When using the drill by bending,torsion and other external forces as well as the working environment,the drill pipe surface will produce cracks and corrosion defects.Therefore,the detection of drill pipe defects is of great significance.In view of the single ultrasonic transducer cannot simultaneously detect the corrosion defects and axial cracks,the multi-channel water immersion piezoelectric ultrasonic transducer detection system was designed.In this thesis,the detection principle of water immersion piezoelectric ultrasonic detection of corrosion and crack defects,the propagation characteristics of vertical incidence,waveform conversion and the critical angle calculation of oblique incident of ultrasonic wave in different media.In order to obtain the optimal incidence angle of the ultrasonic wave during crack detection,the length of the near-field area,the acoustic wave propagation length in the drill pipe and the incidence angle curve were simulated.And the number of piezoelectric ultrasonic transducers was calculated based on the size value of the drill pipe.The arrangement mode of multi-channel piezoelectric ultrasonic transducer was designed to realize the detection of corrosion,circumferential crack and axial crack defects of the drill pipe.In view of the problem of inaccurate defect detection due to small pipe diameter and deviation of ultrasonic incidence angle during water immersion piezoelectric transducer detection the nonlinear probability model of angular error and nonlinear probability model of water immersion ultrasonic crack detection were constructed.The nonlinear correlation between the ultrasonic incidence angle and the defect detection error was studied.The least squares curve was fitted based on the function relationship between the ultrasonic incidence angle,the two parameters of acoustic range in the water layer and the normalized value of the error of the examined drill rod.The angular error model was constructed.To further improve the accuracy of model estimation,the weighted combination of basis functions and third-order Lagrangian interpolation was adopted to realize the complementary information between single models and reduce the model error.Regarding the unknown angle of ultrasonic incidence in the actual detection,an algorithm for error compensation of ultrasonic incident angle was proposed.Combined with the function approximation theory,the nonlinear probability model was applied to the error compensation algorithm.According to Snell’s law,the incidence angle was solved in reverse by using the refraction angle.The iterative operation between the ultrasonic incident angle and the thickness of the drill pipe can compensate for the error introduced by the angle of ultrasonic incidence.The ultrasonic incident angle was calculated by using the triangle tangent value.Through the iterative operation of the ultrasonic incident angle and the ultrasonic acoustic range in the drill pipe,the error introduced by the ultrasonic incident angle in the detection of the drill pipe crack defects was compensated,and the detection efficiency of drill rod defects was improved.Build an experimental platform to detect sample tubes of different water layer thickness and different types of defects.The results of the experiments show that,in the range of 25～40mm,ultrasonic wave incident at 0°～8° angles,after the model compensation treatment,the corrosion detection accuracy of the drill pipe is 0.89%.The ultrasonic wave is incident at 15°～26° angles,after the model compensation treatment,the circumferential crack detection accuracy of the drill rod is1.12%,and the axial crack detection accuracy of the drill rod is 2.34%,which effectively improves the detection accuracy of the corrosion and crack defects of the drill pipe.