Abstract: The stress concentration in the imbalanced section of plastically imbalanced casing resulted from uniform load can easily make the casing bending,deforming or breaking out.The metal magnetic memory technique is an effective method for searching the stress concentration zone.For analyzing the unsteady leakage magnetic signals containing noise,the wavelet exponential denoising method and Hilbert transformation were applied to signal analysis of metal magnetic memory.As a result,the available signal can be reserved,and the characteristic quantity of magnetic signals can be obtained.

Key words: casing damage, stress concentration, metal magnetic memory technique, wavelet analysis, signal analysis

摘要： 套管受到非均匀载荷的作用易产生塑性变形,在应力集中区,易造成套管弯曲、变形或错断,用金属磁记忆技术可有效判断套管应力集中区域.对于含有噪声非平稳性的井下磁记忆信号,把指数小波去噪技术和希尔伯特(Hilbert)变换应用到了磁记忆的信号分析中.基于信号与噪声在小波分析中不同尺度的传播特性,利用小波非线性滤波方法消除了噪声、提高了信噪比.同时利用Hilbert变换得到磁记忆信号的包络线,从而有效提取了特征量.

关键词: 套管损害, 应力集中, 金属磁记忆技术, 小波分析法, 信号分析