Abstract: An opening radial dimension is set as a radial direction permissible dimension K of the metal coil as expressed by the following equation or lower. K = Yp × Z 2 ? EI ? R 2 ? ( ? - sin ? ? ? ? ? cos ? ? ? ) Wherein: K is a radial direction permissible dimension at the load action point position in mm; Yp is a yield stress of the metal sheet, in kgf/mm2; Z is a section modulus of the metal sheet, in mm3; R=(a metal coil radius r)?½(the plate thickness t of the metal sheet), in mm; E is a Young's modulus of the metal sheet, in kgf/mm2; I is a second moment of area of the metal sheet in mm4; and ? is an angle in radians about the axis of the metal coil from the load action point to the nearest restraining roll along a rewind direction of the metal coil.

Abstract: An opening radial dimension is set as a radial direction permissible dimension K of the metal coil as expressed by the following equation or lower. K = Yp × Z 2 ? EI ? R 2 ? ( ? - sin ? ? ? ? ? cos ? ? ? ) Wherein: K is a radial direction permissible dimension at the load action point position in mm; Yp is a yield stress of the metal sheet, in kgf/mm2; Z is a section modulus of the metal sheet, in mm3; R=(a metal coil radius r)?½(the plate thickness t of the metal sheet), in mm; E is a Young's modulus of the metal sheet, in kgf/mm2; I is a second moment of area of the metal sheet in mm4; and ? is an angle in radians about the axis of the metal coil from the load action point to the nearest restraining roll along a rewind direction of the metal coil.