2015 年 56 巻 648 号 p. 47-52
In this study, numerical and multivariate statistical analyses are performed for the re-evaluation of each individual factor reported to have an effect on the estimation of the void closure behavior by FEM analysis in past studies. The following results were obtained. 1) True strain in the stroke direction and hydrostatic stress ratio are the most effective factors for evaluating the void closure behavior. Void closure can be predicted using true strain alone with R2 = 88% accuracy regardless of void position, and the accuracy can be raised by adding the hydrostatic stress ratio factor to the calculation. 2) A regression equation is obtained from the closure behavior at various positions in a cylinder model under the condition of one stroke upsetting, but the equation can also be applied to other cases such as side upsettings and V-die coggings with high accuracy. 3) With the use of the hydrostatic stress ratio, consideration of the difference in deformation resistance is not required for the evaluation of void closure.