Development of the crack detection system of the steel structures by using magnetic properties

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For safe use of a steel structure thing, soundness inspection is required. It inquired for the purpose of development of the "crack detection system" by the non-destructive test using magnetic property which can be used for soundness inspection, and the following results were obtained.1) In order to consider component degradation, the magnetic property calculation program based on a Landau-Lifshiz-Gilbert equation was developed.2) While proposing the fatigue damage appraisal method by the non-destructive test which used magnetic property based on the consideration using the developed program, the magnetic property measuring device was developed.3) Using the developed magnetic property measuring device, static tensile load and the measurement examination of the degree of component damage according to load repeatedly were done, it checked that detection of component damage was possible, and the magnetic property parameter which can be used for damage evaluation was found out.4) While developing the small sensor for magnetic property measurement for the "crack detection system", for signal processing, the program was newly developed and it built as a "crack detection system".5) Using the developed "crack detection system", for the plain, butt welded joint and fillet welding joint specimens, the crack detection examination was carried out and the effective magnetic property parameter was found out. With this parameter, it was not concerned with the existence of paint, and the back and front of the plate, but checked that detection of a crack was possible.6) The check of the usefulness of the measuring device analyzed and developed about crack damage using the commercial magnetic field analysis program and the method of building a database required for crack form evaluation were clarified.The existence of the crack which exists in the weld joints of the steel structure is detectable by the "crack detection system" developed by this research.