Research On Electromagnetic Nondestructive Testing Technology For Fatigue And Damage Of Elevator Steel Strip

The elevator steel strip is a new transmission and load-bearing carrier developed from the traditional steel wire rope.The core of the heavy load is the steel wire rope which is equally spaced inside the steel strip.Compared with the traditional elevator wire rope,the elevator steel belt has the advantages of high traction,strong and durable,can effectively reduce the vibration and noise during the operation of the elevator,and reduce the size of the traction sheave of the elevator.During the use of the elevator steel strip,the long-term stress-bearing effect will change the microstructure and residual stress of the steel wire ropes inside the steel strip,and eventually damage such as fatigue,structural deformation and broken wire.At present,the non-destructive testing technology for steel strips is still not perfect.Therefore,a high-reliability steel strip non-destructive testing flaw detector has been developed to timely and accurately detect the fatigue condition and macroscopic damage of the elevator steel strip,and the replacement time can be determined to avoid economic damage or safety accidents.In order to solve the problems of non-destructive testing of steel strips,the research on the non-destructive testing technology of Barkhausen noise and the non-destructive testing of magnetic flux leakage are carried out.The magnetization process and magnetization curve of the inner steel wire rope of the elevator steel strip are expounded.The Barkhausen noise detection principle and magnetic flux leakage detection principle are expounded according to the magnetization process.The principle of electromagnetic field finite element analysis is introduced,which lays a theoretical foundation for subsequent simulation and experiment.Aiming at the problem that the magnetic circuit of the Barkhausen noise excitation device is relatively simple,an excitation device without a yoke is designed.The relationship between the stress on the inner wire rope of the steel strip and the characteristic value of the MBN signal is detected,and the difference in the characteristic value of the MBN signal in the presence or absence of the defect is detected,and the residual st ress level of the steel strip can be estimated,which provide a reliable basis for the life prediction of steel strips.According to the principle of magnetic flux leakage detection and the characteristics of the elevator steel strip,the multi-yoke excitation device is designed for the problem that the magnetic circuit of the magnetic flux leakage non-destructive testing is relatively simple and the radial excitation is difficult.Combined with finite element simulation,the multi-yoke and multi-magnetic excitation device are compared,which lays a theoretical foundation for detecting the macro defects of elevator steel strip.According to the experimental data,the position and size of the steel strip defect appearing on the steel strip are reversed.It is verified that the newly designed excitation device with very small volume can detect and accurately locate the wire rope defect.The Barkhausen noise and magnetic flux leakage non-destructive testing are combined to realize the accurate comprehensive detection of residual stress,the size and the location of defects,and the fatigue damage in elevator steel strip,which can provide a basis for the replacement of the elevator steel strips.