Application Of Metal Magnetic Memory Testing Technology On Pipeline And Preliminary Investigation Into Comparable Quantitive Analysis

Metal magnetic memory(MMM) is a new branch of nondestructive testing. It isdistinct from other traditional methods that it can make a diagnosis in advance to avoidunplanned fatigue failure of components. Being one of basic and applied projects, ourtask is the quantification of the MMM signal detected which is expected to improve thespeed and efficiency of nondestructive testing in defects. Based on the testing scheme designed, artificial cracks are made on the pipelinewith diameter of 286 and signal detection is performed, which is followed by denoisingsignal. It is showed in the study of the signal denoised that the existence of cracks isdetermined by stress concentration detected with MMM equipment and most zeropoints indicate where the cracks are present, which proves that MMM is reliable notonly in theory also in practice. However, in some cases the cracks may appear innon-zero points if the stress concentration is not great enough. Moreover, the theory ofzero points can't realize the quantification between the signal and factors of cracks(depth, length, angle). To cover the shortage, the continuous wavelet transformationenergy is introduced. It can be seen from the fitting curve that the energy is related withthe length, the depth and the angle of the cracks. The energy decreases with the depth ofcracks increasing and in the study 6mm is the limit. The energy goes up with the lengthof cracks increasing when the length is lower than 20mm. When the length is beyond20mm, the energy falls down quickly with the length of cracks increasing. The energyincrease with the angle of cracks increasing and reaches the max when the angle is 90o.The results of the study lay the necessary found for the quantification of MMM signaland have the great value on theory and practice.