| 摘要 |
A long-member bending method and apparatus, and a door frame bending method are achieved, each of which makes it possible to perform a favorable bending process on long members which vary widely in tensile strength, especially long members which are low in tensile strength. A method of bending a long member, according to the present invention includes a step of applying a tensile force, which increases from an initial tensile force, to the long member to draw out the long member in a lengthwise direction thereof; a step of measuring a displacement of the long member after commencement of the application of the initial tensile force; and a step of bending the long member by applying a correction tensile force and a bending pressure for bending the long member into a curved shape in the lengthwise direction simultaneously to the long member upon the displacement exceeding a predetermined tensile fracture threshold value within a predetermined period of time or after a lapse of the predetermined period of time without the displacement exceeding the tensile fracture threshold value, wherein the correction tensile force is smaller than the tensile force at the time the displacement exceeds the tensile fracture threshold value or the tensile force at the lapse of the predetermined period of time. |
