Influence of Kind and Orientation of Surface Defect on Tensile Behavior of Aluminum Sheet Metal

摘要

Tensile behavior of specimens of both as-received and annealed pure aluminum sheet metal with three kinds of a single surface defect which is a thin groove at right angles to the tensile direction, is investigated experimentally. Tensile testing of the materials with the defect inclined in the tensile direction is also conducted. It is observed that the influence of the kind and orientation of the defect on the load-elongation curve is not manifested until rupture occurs. The existence of a limiting nondimensional defect depth (#alpha#_e=h/t) is observed in all cases; rupture elongation does not decrease in the region shallower than #alpha#_e. #alpha#_e of the annealed material with an indented defect was 1-2 percent greater than that of the annealed material with all other kinds of defects, because the work-hardened area around the defect affects the load-bearing capacity. The indented defect in the as-received material, in contrast, decreases #alpha#_e because work-hardening decreases the material's ductility. #alpha#_e for a ductile material depends only weakly on defect orientation, whereas #alpha#_e for a less ductile material is influenced strongly. As a result, mechanical properties can be measured when defect depth is less than 2 percent of the thickness of the sheet.