PROPERTIES OF STRUCTURE WITH NEGATIVE POISSON'S RATIO BUILT BY METAL POWDER BED FUSION ADDITIVE MANUFACTURING

Abstract

In this study, the two-dimensional structure with negative Poisson's ratio was built using the powder bed fusion (PBF) process which was one of the additive manufacturing method, and its mechanical characteristics were investigated. The unit cell was designed based on the topology optimization and the homogenization method. The bead model including the unit cell size of 20 × 20 mm was built, and the tensile test was performed by a universal tensing equipment. The bead model during the tensile test was captured by the digital camera, and the Poisson's ratio was evaluated by the digital image correlation method. The metal powder used was a mixture of chromium molybdenum steel, copper alloy and nickel. As results, the width of the bead model was increased as the bead model was extended by the tensile test. The Poisson's ratio calculated was -0.55. The difference of the Poisson's ratio between the target value and the calculated value was due to the limitation of the PBF processes. The micro structure in the designed model was filled by the partially melted powder which was formed around the built structure, and resulted in the decrease of the Poisson's ratio.