| 摘要 |
PROBLEM TO BE SOLVED: To provide an evaluation method of bending inside crack generated on the bending inside upon unbending deformation after bending deformation of metallic plate material such as thin steel plate.SOLUTION: An evaluation method of bending inside crack is characterized in that a bending test of subjecting metallic plate material to bending deformation is performed by variously changing a bending radius; an actual bending radius on the bending inside of the plate material upon the bending completion is measured; and thereafter, such an unbending test as to subject the plate material upon the bending completion to unbending deformation to at most 180° is performed; a critical bending radius of the actual bending radius at which the crack is generated on the bending inside of the plate material is determined; and a value provided by dividing the critical bending radius by a plate thickness of the plate material is defined as a bending inside crack limit of the plate material. |
