Abstract: A method includes two or more reference strain gradient information being a relationship between the strain at the hole edge and a strain gradient along a radial direction. Hole expansion forming is performed on the evaluation metal sheet under the same forming conditions as respective forming conditions corresponding to at least two pieces of the reference strain gradient information to obtain at least two limit hole expansion ratios at a hole expansion limit of the evaluation metal sheet. A formable region of the evaluation metal sheet is obtained from the at least two pieces of the reference strain gradient information and the obtained at least two limit hole expansion ratios at the hole expansion limit. Stretch flange cracking at the sheared end face of the evaluation metal sheet is evaluated by the obtained formable region.

Abstract: There are provided an evaluation method and a prediction method for a technology to be reflected in a press die designing method. A deformation limit evaluation method includes evaluating the deformation limit on a sheared surface of a metal sheet in press-forming the sheared metal sheet. The deformation limit is evaluated and a crack in the sheared surface is predicted based on the relationship between an index value determined from two surface strain distribution gradients of a surface strain distribution gradient in a sheet thickness direction in the sheared surface and a surface strain distribution gradient in a bending ridge line direction by bending in a direction away from the sheared surface at an evaluation position among distributions of strains generated near the boundary between a bending outside surface and the sheared surface of the metal sheet to be bent and a tension generated in the sheared surface.

Abstract: To prevent a crack from occurring on a sheared end face due to press forming, a technology is provided for evaluating and predicting a crack limit of the sheared end face of a metal sheet and determining press forming conditions. In a deformation limit evaluation method for, when deforming by press forming a metal sheet subjected to shearing, evaluating a deformation limit of the sheared end face of the metal sheet, the deformation limit is evaluated by an index value obtained from two stress gradients at an evaluation position among stress distributions occurring in the vicinity of the sheared end face of the metal sheet due to the press forming, which gradients are a stress gradient in a sheet thickness direction and a stress gradient in a direction away from the sheared end face.

Abstract: A pressing technology for reducing tensile residual stress generated on a sheared edge face of a metal sheet after press forming in order to prevent occurrence of a delayed fracture on the sheared edge face. A pressed component manufacturing method for manufacturing a pressed component by press-forming a metal sheet having a sheared edge face includes a first press forming step in which it is estimated that tensile residual stress is generated in a direction along the sheared edge on a portion of the sheared edge face of the metal sheet after die release, in which the method includes, as a subsequent step to the first press forming step, a tensile residual stress relaxation step of bulging, in the sheet thickness direction, a region that includes at least a site on a sheared edge face where it is estimated that the tensile residual stress is generated.

Abstract: A method includes two or more reference strain gradient information being a relationship between the strain at the hole edge and a strain gradient along a radial direction. Hole expansion forming is performed on the evaluation metal sheet under the same forming conditions as respective forming conditions corresponding to at least two pieces of the reference strain gradient information to obtain at least two limit hole expansion ratios at a hole expansion limit of the evaluation metal sheet. A formable region of the evaluation metal sheet is obtained from the at least two pieces of the reference strain gradient information and the obtained at least two limit hole expansion ratios at the hole expansion limit. Stretch flange cracking at the sheared end face of the evaluation metal sheet is evaluated by the obtained formable region.

Abstract: A technology for evaluating forming allowance for a bending crack at a sheared end face of the press-formed component from shape information of an actual component. The method includes applying press forming including bending deformation to a metal sheet being sheared to manufacture a press-formed component, evaluating forming allowance for a bending crack at a sheared end face being an end face subjected to the shearing. A crack index value for evaluating the bending crack at the sheared end face of the press-formed component is obtained from a bend outer side strain at or near the sheared end face acquired on a basis of a component shape of the press-formed component and a press die bend radius at a portion forming the sheared end face in a press die used in the press forming, and the forming allowance for the bending crack is evaluated by the obtained crack index value.

Abstract: There are provided an evaluation method and a prediction method for a and a technology to be reflected in a press die designing method. A deformation limit evaluation method includes evaluating the deformation limit on a sheared surface of a metal sheet in press-forming the sheared metal sheet. The deformation limit is evaluated and a crack in the sheared surface is predicted based on the relationship between an index value determined from two surface strain distribution gradients of a surface strain distribution gradient in a sheet thickness direction in the sheared surface and a surface strain distribution gradient in a bending ridge line direction by bending in a direction away from the sheared surface at an evaluation position among distributions of strains generated near the boundary between a bending outside surface and the sheared surface of the metal sheet to be bent and a tension generated in the sheared surface.

Abstract: To prevent a crack from occurring on a sheared end face due to press forming, a technology is provided for evaluating and predicting a crack limit of the sheared end face of a metal sheet and determining press forming conditions. In a deformation limit evaluation method for, when deforming by press forming a metal sheet subjected to shearing, evaluating a deformation limit of the sheared end face of the metal sheet, the deformation limit is evaluated by an index value obtained from two stress gradients at an evaluation position among stress distributions occurring in the vicinity of the sheared end face of the metal sheet due to the press forming, which gradients are a stress gradient in a sheet thickness direction and a stress gradient in a direction away from the sheared end face.