In-situ observation of nonuniform deformation during tensile test of aluminum alloy sheet by means of screen-printed mechanoluminescence film

Nonuniform deformation in a tensile test of an aluminum alloy sheet was visualized by a coating of ∼ 5 μm thick mechanoluminescence (ML) material film (SrAl2O4:Eu2+) on the specimen. It is reported that ML material emits visible light under mechanical stress, and that the intensity increases with von Mises stress. Fine sized ML particles were used to form thin film on the specimen with a screen-printing technique. During the tensile test of A1050 aluminum sheets, it is observed that the Lüders bands initiated at the shoulders of the specimen, and the bands propagated to the center with tensile deformation. Meanwhile, the yield elongation appeared until a pair of bands initiated at either upper or lower shoulders show collision at the center of the parallel part. In addition, necking and fracture behaviors of the specimens during the tensile test are made clear.