| 摘要 |
<p>In a method of producing a pipe, the producing condition of the pipe is regulated as follows: complex Fourier transform is performed on measured values of thickness at different portions in an axial cross section of a pipe, kinds of wall thickness variations are classified, amounts of the variations are calculated from absolute values of complex Fourier components, positions of thick wall portions or thin wall portions are calculated from phases of the complex Fourier components, and the producing condition of the pipe is regulated based on the kinds of wall thickness variations, the amounts of the variations, and the positions of thick wall portions or thin wall portions. Relationship between an amount (r) of wall thickness variation of a primary wall thickness variation obtained for the axial cross section and a phase (theta), which is represented by r.exp (jtheta), is subjected to complex Fourier transform as a function in the length direction of the pipe. Wall thickness variations are further classified by frequency of torsion of the variations, and appropriate processing is performed in accordance with the classified variations so as to prevent the variations.</p> |
