| The shaft of the wind turbine is the core component of the wind turbine that connects the wind wheel and the gear box.The load is complex and variable,which is easy to cause cycle fatigue and lead to the formation of defects.Lateral fatigue cracks and internal expansion crack defects can cause major safety hazards..These crack defects will accelerate and expand under the action of stress,which can lead to the fracture of the main shaft and directly affect the safe use and life of the wind turbine.In order to realize the detection of crack defects in the in-service spindle,this paper studies the in-situ ultrasonic testing method of the in-service fan spindle.A shaft ultrasonic testing platform was built to study the multi-point ultrasonic detection signal imaging method for the spindle end face.The specific research content of this paper is divided into the following three parts:(1)For the problem that only the end face can be touched and detected after the fan spindle is installed,this paper designs a multi-point ultrasonic testing method for end face gridding.Aiming at the problem that small defects of large shaft cracks are difficult to detect,a shaft ultrasonic testing platform is built.Based on the conventional signal processing method,a signal processing method based on sound beam diffusion is proposed.The above two processing methods are used to process the detection signals.And compare the processing results.The results show that the superposition algorithm based on sound beam diffusion can improve the defect detection sensitivity by more than 12 d B.(2)In order to achieve accurate detection of internal lateral fatigue cracks and internal expansion defects,the single-probe method and double-probe method are used to test the shaft defects,and the spontaneous self-receiving and one-shot and onereceiving methods are designed.An ultrasonic signal processing method is compared with the processing results of the two processing methods on the experimental data.The results show that the one-shot-one-receive algorithm has higher accuracy and better stability in signal processing,and is more sensitive to defect detection.(3)For the end-grid multi-point detection method,this paper analyzes the signal of ultrasonic multi-point sampling detection signal,studies the imaging algorithm of multi-point ultrasonic detection signal,and establishes the tomographic ultrasound method.By normalizing the amplitude of the ultrasonic signal,the pseudo-color crosssectional image of each depth inside the workpiece is reconstructed,and the offline data analysis imaging software is developed to perform axial integration and axial display on the superimposed data.The imaging results show that the imaging method can quickly identify the location and extent of internal defects. |
