Experiment research on the Metal Magnetic Memory in gear micro crack detection

Based on the magnetic flux leakage detection principle of magnetic dipole, a model of magnetic flux leakage signal of gear's early local micro crack is derived. The characters of the crack area that include the peak in the tangential component of magnetic flux leakage signal, pass zero point in normal component and the peak in the gradient of it are analyzed. The analysis results provide the basic theoretical foundation of the Metal Magnetic Memory application. Then based on the theory above, the detection of micro crack on the side of an actual gear is applied which includes static testing and dynamic detection with load. The detection position and load effect on detection results is analyzed. The detection results show the effectiveness of the peak in the gradient of normal component magnetic flux leakage signal normal component in the gear magnetic flux leakage signal model and the feasibility of the magnetic memory testing on gear fault.