SHAFT ENLARGING METHOD AND SHAFT ENLARGING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a shaft-enlarging method which prevents permanent plastic deformation from generating on a workpiece by axial compressive stress, and to provide a device therefor.

SOLUTION: In the shaft enlarging method by which an enlarged part 8 is formed in the center of bending by arranging the workpiece 3 of a metallic bar on the reference line 2, inserting the both ends of the workpiece into a pair of holder units 4 which covers the workpiece from both ends by making a clearance 9 respectively, pressurizing the holder units 4 along the reference line 2 in the direction in which they come close to each other, rotating the holder units 4 and tilting the holder units 4, when pressurizing the holder units 4, a buckling mode n which is the number by which the workpiece 3 is deflected by the axial compressive force along the reference line 2 is determined on the basis of the clearance 9 and also bending stress in the clearance at the vertex part of the bending of the workpiece 3 is generated superposedly on a critical buckling stress, determining the maximum standardized critical buckling stress which is an index for preventing permanent plastic deformation of the workpiece 3 is determined by formula (4) and the pressurization is performed so that the maximum standardized buckling stress is≤1. The p(l/k) is expressed by formula (5) (whereinσyis an yield strength; l is the length of a workpiece which is housed in the holder unit; k is the radius of rotation of the cross section of the workpiece; and E is Young's modulus).

COPYRIGHT: (C)2011,JPO&INPIT