| 摘要 |
<p>A complex Fourier transform is performed on measured values of wall thickness at a plurality of points in a cross section of a pipe in an axial direction, the types of thickness deviation is classified, a thickness deviation amount is calculated from the absolute value of the complex Fourier component, the position of a thick portion or thin portion of thickness deviation is calculated from the phase of the complex Fourier component, and manufacturing conditions of the pipe are adjusted based on the type of thickness deviation, the thickness deviation amount, and the position of the thick portion or thin portion. The relationship r €¢ exp (j¸) between the thickness deviation amount r and phase ¸ of a first-order thickness deviation obtained for a plurality of cross sections in the axial direction is subjected to a complex Fourier transform as a function of a longitudinal direction of the pipe, the thickness deviation is further classified by the frequency of twist of the thickness deviation, and an appropriate action is taken to prevent the thickness deviation according to the classified thickness deviation.</p> |
