Study On Real-time And High Precision Monitoring System For Crack Status Based On ACFM Technology

This paper designs an automatic online monitoring and early warning system for defects of mechanical structures based on ACFM nondestructive detection principle.Through the real-time monitoring of the key parts of equipment during the period of service,the monitoring system can automatic diagnose on-line defect state and give early warning instructions with size quantification of defects and assessment of expanding defects’ state.Besides,it will provide the basic indexes of early repair or modification,life extension program and corresponding optimization for mechanical equipment to ensure the safe operation of offshore oil engineering,aerospace and other industrial production equipment.At the same time,the real-time and high precision ACFM crack monitoring system will fill in the blank of domestic ACFM online monitoring filed and promote ACFM monitoring technology to the development direction of automation,visualization and nondestructive evaluation.This paper’s main content and results of study are as follows:(1)Design of monitoring system strategy mechanismAccording to the requirements of real-time and high precision monitoring system for crack status based on ACFM technology this paper sets up monitoring system network frame.It designs monitoring system strategy mechanism based on that the life cycle of machinery and equipment products have the characteristic of bathtub curve.According to the real-time recognition of crack module and system risk assessment model to realize monitoring system’s adaptive cycle operation.It also designs the structure and layout of the sensor arrays to determine two types of monitoring,such as fixed monitoring and scanning monitoring.At the same time,it presents how to deal with the combination of the sampled data algorithm based on LABVIEW.(2)Design of defect recognition and early warning modelUsing circuit and magnetic field coupling probe motion model based on ANSYS to get the voltage simulation database of detection coil X and Z,changing coil X’s voltage curve into energy spectrum curve to get location threshold of the monitoring system,combining the characteristic of that coil Z’s phase difference is180 degrees at defect’s edge,this paperdesigns a automatic diagnosis algorithm for cracks.Besides,it establishes BP-GA model to caculate defect size and location threshold.In addition,this paper study on the risk assessment of the pipeline monitoring system model in detail.(3)Design of high precision automation system’s hardware and softwareThe system put mobile monitoring platform and guyed displacement sensors into existing ACFM detection system.This paper modularized designs system control subsystem and defect recognition subsystem based on LABVIEW software which includes a “one step of one get” model algorithm for magnetic field distortion signal acquisition based on DAQmax function and VISA to realize space synchronous acquisition of crack location information and signal information automatically.Finally,it uses the monitoring system to detect the surface crack of low carbon steel plate and pipe,the results verify the performance of the real-time ACFM crack monitoring system of high precision,real time,automation,early warning and adaptively adjusting monitoring equipment’s motion model.