| 摘要 |
A PIPE (P) HAVING A SUBSTANTIALLY SQUARE CROSS SECTION PORTION (2) AND A SUBSTANTIALLY CIRCULAR CROSS SECTION PORTION(3) ARE DISPOSED ALTERNATELY IN THE AXIAL DIRECTION OF THE PIPE(P). THE THICKNESS OF THE CIRCULAR PORTION IS SET UNEVEN IN THE CIRCUMFERENTIAL DIRECTION. IN PARTICULAR, THE THICKNESS OF THE PORTIONS OF THE CIRCULAR PORTION THAT CORRESPOND TO THE CORNER PORTIONS(2A) OF THE SQUARE PORTION(2) IS SET LARGER THAN THE THICKNESS OF THE PORTIONS THAT CORRESPOND TO THE CENTRAL PORTIONS OF THE RESPECTIVE SIDES OF THE SQUARE PORTIONS. ACCORDINGLY, A PIPE (P)HAVING CORNER PORTIONS(2A) WITH INCREASED PRESSURE DEFORMATION RESISTANCE IS OBTAINED. ALSO, THE PIPE (P) IS CAPABLE OF BEING MANUFACTURED IN A HIGH EFFICIENCY MANNER.FIG.1
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