| The security problem of marine diesel engine shafting is a systems engineering. To avoid or reduce occurrence of shafting accidents, detect the operating situation of shafts accurately and maintain diesel reliable operation, it is one of the fundamental ways to forecast shafts cracks tendency of marine diesel engine.Crank shaft of marine diesel engine was taken as research object in the task and it was discussed that principle and method of metal magnetic memory testing (MMMT) of cracks for shafts crack qualitatively testing. Based on the study on the principle of metal magnetic memory, magnetic memory detector of crack with PIC processor was developed.In the aspect of theory research it was analyzed that the principle, development and characters of MMMT, and it were compared the application of MMMT in different fields. Advantage and disadvantage of application were pointed out. Finally, theory of MMMT was discussed primarily in both macroscopic and microcosmic aspects.In the aspect of hardware designation, it was developed magnetoresistive sensor using magnetoresistive transduction chip HMC1001. It was designed analog signal processing circuit such as weak signal amplification, filtering and data processing circuit with PIC processor as center unit. Finally, the schematic circuit diagram and printed circuit board (PCB) drawing was designed by PROTEL software.In the aspect of software designation, it was compiled subprogram such as display, signal collection, communication and printing with assemble language. The main program was compiled to transfer subprogram. At the same time, programmer was used to debug the program to complete data procession of MMM signal.Finally, program instrument was used to debug both software and hardware on the PCB. After several times of debugging, the magnetic memory detector of crack was completed. After comparison experiment with production of other company, it was proved that the instrument has high precision and value in application.
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