Influence of orientation of surface defects on breaking elongation of aluminum sheet metal

摘要

The influence of the initial orientation of a single surface defect on breaking elongation was experimentally studied using an aluminum sheet. Breaking elongation does not decrease in the region where the defect is shallower than a critical defect depth, α{sub}e, when the initial orientation of the defect, Φ, is inclined from 0 degrees to 35 degrees in the tensile direction. α{sub}e shows the minimum value, which is greater than zero, at the initial orientation, Φ{sub}(min). The value of Φ{sub}(min) is different from the theoretical value calculated under Hrll's anisotropic local-necking condition. Furthermore, we showed a method of predicting Φ{sub}(min), and that α{sub}e, is greater than zero because the increase of such factors as strain inclination and surface roughness restricts the fracture portion more than the initial single surface defect for defect depths less than α{sub}e.