The Crack Detection For Ferrite Workpieces Based On Initial Permeability

Crack defects of ferrite affect its electrical properties seriously; traditionalmanual testing methods have been difficult to meet the demand for product testing.This paper presents a new crack detection method of the ferrite based on the initialpermeability, detection model and detect conditions is designed; For the faint pulse ofcracks is often flooded by disturbance, dual probe sensor is designed. Considering theunique characteristics of the autocorrelation function of double pulse signal, cracksare identified by multiple characteristic recognitions. Groups of experimental datashow that the method of multiple characteristic recognitions can accurately andqualitatively distinguish whether the object exist cracks.The main research of this paper contents include:1. Building detection model. In order to transform physical property of cracksinto electrical characterization, detection model is built. According to Ohm’s law formagnetism and Maxwell’s second equation, the relationship between Permeabilityand the voltage detected can be got.2. Sensor probe designing. Based on the magnetic circuit analysis, the smallermagnetic resistance sensor case, the higher detection sensitivity. Different sizes of theprobes are designed, for the different detection of different size and shape of parts.3. Signal acquisition and processing. For detection the natural forming cracksbelow20μm width, Signal analysis Based on the correlation analysis is designed,achieving identification of cracks below10μm.4. Application and promotion. Defect detection method based on the initialpermeability can not only detect the fine defects, but also other material defectdetection.After a large number of experimental methods, Defect detection method Basedon the initial permeability can be used in a variety of materials detection. Detectionaccuracy is not less than20μm, its automated detection greatly improve the detectionefficiency and reliability.