Calculation method, calculation device, and calculation program of residual stress distribution

A calculation device of a residual stress distribution for calculating a distribution of residual stress generated in a metal sheet subjected to plastic deformation, the calculation device comprising:

• a deformation history acquiring unit;
• a sequential stress updating unit;
• and
• a residual stress distribution calculating unit,
• wherein the deformation history acquiring unit includes:
• a surface deformation history acquiring unit configured to acquire, as a deformation history on a surface from a start to an end of deformation of a deformable portion, three-dimensional coordinations measured in a deformation process of plastically deforming the metal sheet, the three-dimensional coordinations measured for a plurality of measurement points set to the deformable portion of the metal sheet;
• a strain history acquiring unit configured to acquire a strain history of the deformable portion in the deformation process from the acquired deformation history on the surface of the deformable portion;
• and
• a spin history acquiring unit configured to acquire a spin history of the deformable portion in the deformation process from the acquired deformation history on the surface of the deformable portion,
• the sequential stress updating unit includes:
• an acquired incremental strain calculating unit configured to calculate acquired incremental strain from the strain history acquired by the strain history acquiring unit;
• an assumptive incremental strain calculating unit configured to calculate an assumptive incremental strain by presuming a deformation state of the deformable portion, the assumptive incremental strain being an increment of strain other than strain for which the strain history has been acquired by the strain history acquiring unit;
• an acquired incremental spin calculating unit configured to calculate an acquired incremental spin from the spin history acquired by the spin history acquiring unit;
• an incremental stress calculating unit configured to calculate incremental stress at each of the measurement points in accordance with a material constitutive law using the acquired incremental strain, the assumptive incremental strain, and the acquired incremental spin;
• and
• a sequential stress updating unit configured to sequentially update stress in a material coordinate system of each of the measurement points from the start to the end of deformation in the deformation process using the incremental stress calculated for each of the measurement points, and
• the residual stress distribution calculating unit includes:
• a stress coordinate system converting unit configured to convert the stress in the material coordinate system of each of the measurement points at the end of deformation in the deformation process obtained by sequential update by the sequential stress updating unit into a global stress value in a predetermined direction in a global coordinate system and obtains the converted global stress value of each of the measurement points as a residual stress distribution of the deformable portion.

A non-transitory computer-readable recording medium recording a calculation program of a residual stress distribution for calculating a distribution of residual stress generated in a metal sheet subjected to plastic deformation, the calculation program causing a computer to function as:

• a deformation history acquiring unit, a sequential stress updating unit, and a residual stress distribution calculating unit,
• wherein the deformation history acquiring unit includes:
• a surface deformation history acquiring unit configured to acquire, as a deformation history on a surface from a start to an end of deformation of a deformable portion, three-dimensional coordinations measured in a deformation process of plastically deforming the metal sheet, the three-dimensional coordinations measured for a plurality of measurement points set to the deformable portion of the metal sheet;
• a strain history acquiring unit configured to acquire a strain history of the deformable portion in the deformation process from the acquired deformation history on the surface of the deformable portion;
• and
• a spin history acquiring unit configured to acquire a spin history of the deformable portion in the deformation process from the acquired deformation history on the surface of the deformable portion,
• the sequential stress updating unit includes:
• an acquired incremental strain calculating unit configured to calculate acquired incremental strain from the strain history acquired by the strain history acquiring unit;
• an assumptive incremental strain calculating unit configured to calculate an assumptive incremental strain by presuming a deformation state of the deformable portion, the assumptive incremental strain being an increment of strain other than strain for which the strain history has been acquired by the strain history acquiring unit;
• an acquired incremental spin calculating unit configured to calculate an acquired incremental spin from the spin history acquired by the spin history acquiring unit;
• an incremental stress calculating unit configured to calculate incremental stress at each of the measurement points in accordance with a material constitutive law using the acquired incremental strain, the assumptive incremental strain, and the acquired incremental spin;
• and
• a sequential stress updating unit configured to sequentially update stress in a material coordinate system of each of the measurement points from the start to the end of deformation in the deformation process using the incremental stress calculated for each of the measurement points, and
• the residual stress distribution calculating unit includes:
• a stress coordinate system converting unit configured to convert the stress in the material coordinate system of each of the measurement points at the end of deformation in the deformation process obtained by sequential update by the sequential stress updating unit into a global stress value in a predetermined direction in a global coordinate system and obtains the converted global stress value of each of the measurement points as a residual stress distribution of the deformable portion.