Research On Evaluation Method And Standard Of Wire Rope Magnetic Testing Technology

Wire rope non-destructive testing (NDT) instrument is the vital device in mine, tourism, construction, etc. where the damage of wire rope imperils operators, passengers and other important devices. The capability of wire rope NDT instrument should be evaluated rigorously, so that the customer knows how reliable the instrument and its test result are. In this dissertation, the theory of wire rope NDT is analyzed deeply and key issues relevant to evaluation, such as flaw mode description, standard sample configuration, are researched.Flaw description is the fundamental to configure the test standard. In this dissertation, a novel description mode rooted in the structure character of wire rope is presented. Wire rope can be described as a vector defined by 6 parameters, which are the number of strand layer, the number of strand, the rotation angle of strand, the number of wire layer, the number of wire and the rotation angle of wire. Wire can be expressed by a vector defined with 8 parameters including the former 6 parameters. The additional two are the change of wire rotation angle and the diameter of wire. Wire rope can be expressed as wire set. Broken wire in wire rope can be expressed by a vector defined with 8 parameters including the former 6 parameters. The additional two are the width of broken wire and the diameter of broken wire. Abrasion in wire rope can be expressed by a vector defined by 8 parameters including the former 6 parameters. The additional two are the change of wire rotation angle and the wear rate. With the novel method, cable telemetry, locked coil wire rope, 6 strands rope and multi-strand rope and their flaw are described.Based on the finite element model (FEM), relation between the magnetic flux leakage (MFL) and typical Local Flaw (LF), the broken wire, is researched. Research result indicates that the lift-off distance plays the most important pole among all the analyzed facts; the second fact is the diameter of wire rope; the next is the width of broken wire. These results redound to assort the test standard. Based on the theory of magnetic charge, a MFL model of 6 strands rope is created to investigate the influence of different gather of broken wire on MFL. Research result shows that vicinal broken wire effects not only on its neighbor's amplitude of signal, but also on its phase; therefore, the position performance is one most important part of wire rope NDT instruments. The configuration space of wire rope standard sample of broken wire is presented, and then the width configuration method, distribution configuration method, quantity configuration method and the measurement of broken wire set are researched.Based on magnetic resistant model, the theory of loss of metal cross-sectional area (LMA) testing and the influence facts are analyzed. 3-D FEM of steel strand and 3-D FEM of steel pipe are created, through which, differences in magnetization character, electro-magnetic testing (EMT) character and the sensitivity in abrasion position between the steel strand and steel pipe are researched. Research result shows that the magnetization character and EMT character between strand and pipe are quite similar, and the pipe is far more sensitive in the distribution of abrasion than the wire rope; therefore, steel pipe standard can be look upon a substitute of wire rope standard in evaluation on concentrating abrasion, and can not be used in the evaluation on distributed abrasion. The configuration of abrasion standard and the evaluation procedure are presented.For the sake of the requirement of standardization, testing accessibility of wire rope NDT is presented. And then, an evaluation method is presented after discarding standards of wire rope are analyzed. Based on the essence of EMT, the feasibility of EMT data modeling using the grey system theory is researched. The structure of wire rope is too complex to make some littlie scale flaw, because of which, the smallest size of flaw in wire rope standard is limited. So the instrument testing performance below the smallest size of flaw set can not be evaluated. A resolution prediction method is presented. At last, a wire rope NDT instrument for elevator is evaluated as an example.