Application Research On Metal Magnetic Memory Technology On Weld Testing

The formation of weld is an extremely complicated metallurgical operation, where inevitably exist different variety of defects and stress concentration, which will reduce the strength and service life of equipment, lead to serious consequences of equipment failure and huge economic loss.The quality of welding joints are relevant to the components, safety service life and performance.Metal magnetic memory technology is one of the most promising new nondestructive testing method, can not only discover the formed macro defect, also can find the high level of stress concentration of micro defect and early damage, which makes it good prospects in the field of weld joint detection.Combining the characteristic value of metal magnetic memory signals of defective weld joints, and getting the normal component of MMM signals using the TSC-1M-4produced by Energodiagnostika Co. Ltd. The characteristic value can accurately determine the position of defects. The MMM signal belongs to a weak magnetic field, so it is susceptible to surrounding environment and human factors. To get accurate signals for further analysis through denoising. Wavelet packet analysis is an ideal method of signal processing, not only decompose the low frequency part of signal, also the high ones, which is beyond wavelet analysis. The wavelet packet denoising ensure the authenticity of MMM signal, at the same time, exclude the interference of noise in the maximum extend. Based on the distortion value of denoising signal is higher than Kmed to determine the position of defects on respective side. Then the overlapping area of adjacent side is defective area. Compared with Ultrasonic Testing results, metal magnetic memory technology can accurately determine the position of defects. Testing the manufacture weld joints of wind power tower using metal magnetic memory technology and contrast to Radiographic Testing results, the defective area of MMM is bigger than R-testing. This is relate to the stress concentration, level of stress concentration.