Springback-amount-discrepancy-causing-portion specifying method and device

1 . A method for specifying a portion of a formed product shape that causes a first difference between a first springback amount occurring in a press-formed product obtained by press-forming an actual panel and a second springback amount obtained by conducting springback analysis on an analysis model of a same shape as the press-formed product, the method comprising:

creating a press-formed product model from three-dimensional shape measurement data acquired by measuring a surface shape of the analysis model of the same shape as the press-formed product after release of the analysis model of the same shape as the press-formed product from a die and conducting mechanical analysis in a state where the press-formed product model is held by a forming die model to a bottom dead center to acquire a stress distribution at a forming bottom dead center as a formed product driving stress distribution that contributes to springback of the analysis model of the same shape as the press-formed product;

acquiring a bottom dead center stress distribution and a remaining stress distribution after the release of the analysis model of the same shape as the press-formed product from the die in the springback analysis and acquiring a second difference between the bottom dead center stress distribution and the remaining stress distribution after the release of the analysis model of the same shape as the press-formed product from the die as an analysis driving stress distribution in the springback analysis;

setting the formed product driving stress distribution in the formed product shape at the bottom dead center in the springback analysis and acquiring a formed-product springback amount by performing springback analysis based on the formed product driving stress distribution set;

setting the analysis driving stress distribution in the formed product shape at the bottom dead center, substituting a value of analysis driving stress in a region of the analysis driving stress distribution set with a value of formed product driving stress in a region of the formed product driving stress distribution corresponding to the region, and acquiring a stress-substituted springback amount by conducting springback analysis based on a stress substituted distribution obtained by the substitution; and

finding a third difference between the stress-substituted springback amount and the formed-product springback amount and specifying, based on the third difference found, the portion of the formed product shape that causes the first difference, wherein

the die is adjusted based on the specified portion of the formed product shape that causes the first difference.

2 . The method according to claim 1 , further comprising acquiring a stress difference distribution from a fourth difference between the analysis driving stress distribution and the formed product driving stress distribution and selecting, from the stress difference distribution, a region having a larger stress difference than a second region as the region in which stress substitution is to be performed.

3 . A device for specifying a portion of a formed product shape that causes a first difference between a first springback amount occurring in a press-formed product obtained by press-forming an actual panel and a second springback amount obtained by conducting springback analysis on an analysis model of a same shape as the press-formed product, the device comprising:

a processor programmed to:

create a press-formed product model from three-dimensional shape measurement data acquired by measuring a surface shape of the analysis model of the same shape as the press-formed product after release of the analysis model of the same shape as the press-formed product from a die and conduct mechanical analysis in a state where the press-formed product model is held by a forming die model to a bottom dead center to acquire a stress distribution at a forming bottom dead center as a formed product driving stress distribution that contributes to springback of the analysis model of the same shape as the press-formed product;

acquire a bottom dead center stress distribution and a remaining stress distribution after the release of the analysis model of the same shape as the press-formed product from the die in the springback analysis and acquire a second difference between the bottom dead center stress distribution and the remaining stress distribution after the release of the analysis model of the same shape as the press-formed product from the die as an analysis driving stress distribution in the springback analysis;

set the formed product driving stress distribution in the formed product shape at the bottom dead center in the springback analysis and acquire a formed-product springback amount by performing springback analysis based on the formed product driving stress distribution set;

set the analysis driving stress distribution in the formed product shape at the bottom dead center, substitute a value of analysis driving stress in a region of the analysis driving stress distribution set with a value of formed product driving stress in a region of the formed product driving stress distribution corresponding to the region, and acquire a stress-substituted springback amount by conducting springback analysis based on a stress substituted distribution obtained by the substitution; and

find a third difference between the stress-substituted springback amount and the formed-product springback amount and specify, based on the third difference found, the portion of the formed product shape that causes the first difference in springback amount between the press-formed product and the springback analysis, wherein

the die is adjusted based on the specified portion of the formed product shape that causes the first difference.

4 . The device according to claim 3 , wherein the processor is further programmed to acquire a stress difference distribution from a fourth difference between the analysis driving stress distribution and the formed product driving stress distribution and select, from the stress difference distribution, a region having a larger stress difference than a second region as the region in which stress substitution is to be performed.

5 . A non-transitory computer readable medium storing a program for specifying a portion of a formed product shape that causes a first difference between a first springback amount occurring in a press-formed product obtained by press-forming an actual panel and a second springback amount obtained by conducting springback analysis on an analysis model of a same shape as the press-formed product, the program causing a processor to execute:

creating a press-formed product model from three-dimensional shape measurement data acquired by measuring a surface shape of the analysis model of the same shape as the press-formed product after release of the analysis model of the same shape as the press-formed product from a die and conducting mechanical analysis in a state where the press-formed product model is held by a forming die model to a bottom dead center to acquire a stress distribution at a forming bottom dead center as a formed product driving stress distribution that contributes to springback of the analysis model of the same shape as the press-formed product;

acquiring a bottom dead center stress distribution and a remaining stress distribution after the release of the analysis model of the same shape as the press-formed product from the die in the springback analysis and acquiring a second difference between the bottom dead center stress distribution and the remaining stress distribution after the release of the analysis model of the same shape as the press-formed product from the die as an analysis driving stress distribution in the springback analysis;

setting the formed product driving stress distribution in the formed product shape at the bottom dead center in the springback analysis and acquiring a formed-product springback amount by performing springback analysis based on the formed product driving stress distribution set;

setting the analysis driving stress distribution in the formed product shape at the bottom dead center, substituting a value of analysis driving stress in a region of the analysis driving stress distribution set with a value of formed product driving stress in a region of the formed product driving stress distribution corresponding to the region, and acquiring a stress-substituted springback amount by conducting springback analysis based on a stress substituted distribution obtained by the substitution; and

finding a third difference between the stress-substituted springback amount and the formed-product springback amount and specifying, based on the third difference found, the portion of the formed product shape that causes the first difference, wherein

the die is adjusted based on the specified portion of the formed product shape that causes the first difference.

6 . The non-transitory computer readable medium according to claim 5 , wherein the program causes the processor to further execute acquiring a stress difference distribution from a fourth difference between the analysis driving stress distribution and the formed product driving stress distribution and selecting, from the stress difference distribution, a region having a larger stress difference than a second region as the region in which stress substitution is to be performed.