せん断帯形成による変形限界の数値的研究 : 第1報,板材の成形限界ひずみの板厚依存性と傾斜材料の変形限界

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By introducing a concept of extended plane strain, the dependence of the forming limit strain of sheet metals on their thickness is investigated numerically over the range of in-plane strain ratio α, 0 ≤ α ≤ 1, i.e., the biaxial tension range, using the elastic-plastic finite-element method (E. -P. FEM) whose code's name is GOLDA which was previously developed by one of the authors (Gotoh). The forming limit strain is estimated based on the evolution of the shear band. J2G (J_2-Gotoh's corner theory), which was previously proposed by Gotoh and applied successfully to problems of strain localization such as in the case of shear band, is adopted as the plasticity constitutive equation. It is confirmed that thicker sheets show higher limiting strain, and that such thickness effect becomes weaker for larger α and thicker sheets. Moreover, the forming limit of gradient material sheets (whose mechanical properties vary continuously along the thickness direction of the sheet) is investigated with respect to plane strain tension (α=0) by a similar method to the one above, in which only the distribution of the n-value (the strain-hardening exponent) is varied. Dependence of the shear-band evolution pattern on the n-value distribution pattern is clearly demonstrated. It is concluded that, for the same variation range of n-values, the forming limit increases in the order of ∨-type, simple linear type and ∧-type of n-value distribution through thickness.
一般社団法人日本機械学会の論文
1995-12-25

せん断帯形成による変形限界の数値的研究 : 第1報,板材の成形限界ひずみの板厚依存性と傾斜材料の変形限界

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