[Document Type] CLAIMS
1. A breaking prediction method of predicting a breaking portion of a
component obtained by forming a metal sheet, the method comprising:
a first step of performing forming analysis by using a finite element method in each of a case where the metal sheet is divided on the basis of a first mesh coarseness and a case where the metal sheet is divided on the basis of a second mesh coarseness which is coarser than the first mesh coarseness;
a second step of obtaining a maximum main stress for each mesh in each of the case of the first mesh coarseness and the case of the second mesh coarseness; and
a third step of obtaining a difference value between the maximum main stress in the case of the first mesh coarseness and the maximum main stress in the case of the second mesh coarseness in each portion of the component, and extracting a portion in the case of the first mesh coarseness, which corresponds to a portion in which the difference value is larger than a predetermined value, as the breaking portion.
2. The breaking prediction method according to claim 1, further comprising:
a 0-th step of determining the first mesh coarseness and the second mesh
coarseness on the basis of an n value indicating a work hardening property of the metal
sheet.
3. The breaking prediction method according to claim 1 or 2,
wherein in a case where the breaking portion is not extracted in the third step, the first step to the third step are performed again after resetting at least the first mesh coarseness, out of the first mesh coarseness and the second mesh coarseness, to a

coarseness coarser than at least the first mesh coarseness or resetting the predetermined value to a smaller value, or a combination thereof.
4. The breaking prediction method according to any one of claims 1 to 3,
wherein an adaptive mesh is used when division based on the first mesh
coarseness is performed.
5. The breaking prediction method according to any one of claims 1 to 4,
wherein the forming analysis in the first step is terminated in the middle of
forming of the component.
6. The breaking prediction method according to any one of claims 1 to 5,
wherein the second step further includes obtaining a shape index value, which
is at least one of a maximum main strain and a ratio of a reduction in a sheet thickness, for each mesh with respect to a case of division based on the first mesh coarseness and a case of division based on the second mesh coarseness,
wherein the third step further includes obtaining a difference value between the shape index value in the case of the first mesh coarseness and the shape index value in the case of the second mesh coarseness in each portion of the component, and
wherein a portion in the case of the first mesh coarseness, which corresponds to a portion satisfying the difference value in the shape index value being larger than a predetermined value or the difference value in the maximum main stress being larger than the predetermined value, or a combination thereof, is extracted as the breaking portion.

7. A breaking prediction method of predicting a breaking portion of a
component obtained by forming a metal sheet, the method comprising:
a first step of dividing the metal sheet into meshes on the basis of a predetermined mesh coarseness to perform forming analysis by using a finite element method;
a second step of obtaining a maximum main stress for each mesh;
a third step of obtaining a maximum main stress for each coupled mesh obtained by coupling two or more meshes adjacent to each other; and
a fourth step of obtaining a difference value between the maximum main stress obtained in the second step and the maximum main stress obtained in the third step for each portion of the component, and extracting a portion in the second step, which corresponds to a portion in which the difference value is larger than a predetermined value, as the breaking portion.
8. The breaking prediction method according to claim 7,
wherein an adaptive mesh is used when division based on the predetermined mesh coarseness is performed.
9. The breaking prediction method according to claim 7 or 8,
wherein the forming analysis in the first step is terminated in the middle of forming of the component.
10. The breaking prediction method according to any one of claims 7 to 9,
wherein the second step further includes obtaining a shape index value, which
is at least one of a maximum main strain and ratio of a reduction in a sheet thickness,

for each mesh,
wherein the third step further includes obtaining the shape index value for each coupled mesh, and
wherein the fourth step further includes obtaining a difference value between the shape index value obtained in the second step and the shape index value obtained in the third step for each portion of the component, and extracting a portion in the second step, which corresponds to a portion satisfying the difference value in the shape index value being larger than a predetermined value or the difference value in the maximum main stress being larger than the predetermined value, or a combination thereof, as the breaking portion.
11. The breaking prediction method according to any one of claims 1 to 10,
wherein an occurrence portion of a stretch flange crack is predicted as the
breaking portion.
12. The breaking prediction method according to any one of claims 1 to 11,
wherein the breaking portion at an end portion of the component is extracted.
13. The breaking prediction method according to any one of claims 1 to 12,
wherein the metal sheet is a steel sheet having a tensile strength of equal to or
greater than 980 MPa.
14. A program for executing the breaking prediction method according to
any one of claims 1 to 13.

15. A computer-readable recording medium that records the program according to claim 14.
16. An arithmetic processing device that executes the program according to claim. 14.