Numerical investigation on a key factor in superior stretchability of face-centered cubic polycrystalline sheets

Plastic deformation characteristics and limit strains are simulated for textured face-centered cubic polycrystalline sheets using a generalized Taylor-type crystal plasticity model. The r-values are predicted to be 1.04, 7.74, and 0.17 for the pseudo-random, {1 1 1}〈uvw〉, and {0 0 1}〈uvw〉 textures, respectively. The {1 1 1}〈uvw〉 texture gives limit strains as large as the random texture, whereas the {0 0 1}〈uvw〉 texture yields limit strains apparently higher than the other two, even though its r-value is extremely low. Thus, the r-value cannot act as an indicator of the stretchability of sheet metals. For the {0 0 1}〈uvw〉 texture, a superior strain-hardening ability under the plane-strain stretching mode is found to be responsible for the increase in the limit strains under plane strain and equi-biaxial stretching modes. It is concluded that the enhancement of the strain hardening ability for the plane-strain stretching mode is one of the key factors of high stretchability sheets.

► Using a generalized Taylor-type crystal plasticity model, we analyzed the r-value of three textured sheets. ► The predicted r-values are 1.04, 7.74, and 0.17 for the pseudo-random, {1 1 1}〈uvw〉, and {0 0 1}〈uvw〉 textures, respectively. ► Limit strains are simulated by M–K-type model. ► We found that the r-value cannot act as an indicator of the stretchability of sheet metals. ► A superior strain-hardening ability in the plane-strain stretching mode is able of rising the limit strain in the plane strain.