| The metal magnetic memory testing technology,as a new-brand nondestructivetesting technology, compare with the other tradional nondestructive testing methods,ittakes the advantages of early diagnosis to ferromagnetic material,can preventferromagnetic components in service from accident fracture failure and avoidunnecessary loss.This topic mainly research the change laws of the metal magneticmemory signal in the whole process of fatigue loading,then put forward thecorrelation coefficient and curved surface similarity coefficient,which canquantitatively evaluate the degree of fatigue.Firstly,research the change laws of the traditional metal magnetic memory singalcharacteristic quantity,such asHp (y)max、Hp (y)min、 Hp (y)suband magnetic fieldgrads,they would change as the fatigue load,reflect the fatigue loading well,butincompetently assess the degree of fatigue.According to the metal magnetic memorysignal change laws under the fatigue loading,base on the traditional characteristicquantity,several new characteristic quantity are founded to depict the loadingprocess,such as short-period second-order central moment ratio、peak-to-peak valueratio and correlation coefficient.the correlation coefficient, which depict thetwo-dimension leaky magnetic signal graph similarity, is proven feasible to evaluatethe degree of fatigue damage.Base on the evaluating method of two-dimension leaky magnetic graphsimilarity,the three-dimention leaky magnetic curved surface is constructed,thendefine the curved surface similarity coefficient η by curved surface normal vector.Thecurved surface similarity coefficient η well respond the change of the three-dimentionleaky magnetic curved surface,indirectly respond the laws of the metal magneticmemory signal during the macrocrake spread period.The result shows thatthree-dimention curved surface similarity coefficient η take the more advantages thancorrelation coefficient,well evaluate the ferromagnetic material degree of fatiguedamage. |
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