Enhanced flexural strength-to-weight ratio of Inconel718 lattice structure parts made of powder bed fusion process

Abstract

The present work investigates the enhancement of the flexural strength-to-weight ratio on the lattice structure of additively manufactured Inconel-718 parts made using the powder bed fusion (PBF) process. ASTM-E290 standard three-point bending experiments and finite element modeling were conducted on solid and lattice structure parts. Four novel lattice structure unit cells with positive Maxwell’s number for stretch-dominant mechanical behavior were designed and used in the three-point bending specimens. The different lattice structure types investigated are strengthened-cubic (named Model_1), strengthened-cubic + kagome (named Model_2), strengthened-cubic + octet truss (named Model_3), and strengthened-cubic + kagome+octet truss (named as Model_4). Results obtained for the lattice structure specimens were compared with those obtained for solid specimens. The study revealed significant differences in strength-to-weight ratio among them, proving the tremendous potential of lattice structures in flexural loading applications by giving higher strength-to-weight ratios than solid specimens. Out of the four lattice structures and one solid structure investigated, Model_2 with only angular beams and Model_3 with only interior beams gave a better strength-to-weight ratio than solid specimens. Model_2 and Model_3 have beams along the unit cell’s body diagonal, leading to better performance. Out of all the lattice-structured specimens, Model_2 showed the highest strength-to-weight ratio. In the finite element model, the maximum equivalent strain was used as the criterion for failure. The failure sites found by finite element simulation coincided with those in the experiments.