Compressive properties of imperfect Ti-6Al-4V lattice structure fabricated by electron beam powder bed fusion under static and dynamic loadings

Abstract

Mechanical response and deformation behavior of Ti-6Al-4V lattice structure are investigated by quasi-static and low-speed impact compression experiments. The lattice specimens with SC-BCC-FCC cells are designed and fabricated by electron beam powder bed fusion (EB-PBF). The nominal stress-strain and stress-time histories of the printed lattice structures under different loading speeds are determined by an electronic universal testing machine and a drop hammer system, respectively. The corresponding global collapse evolution of the specimens is recorded and analyzed. Meanwhile, the high-resolution scanning electron microscope (SEM) and X-ray computed tomography (CT) are adopted to capture the morphology, occurrences, and distributions of the geometric defects induced by the printing process. Based on the distribution characteristics of the defects, a novel statistical finite element model is proposed by considering the strut waviness and thickness variation to predict the mechanical performance and reveal the detailed deformation mechanism of the lattice. A good agreement is obtained between the statistical model predictions and experimental results. Furthermore, the role of each geometric defect on the initial peak stress of the lattice is investigated. The results demonstrate that the strut thickness variation in the lattice structure presents a more significant influence on initial peak stress than the strut waviness under quasi-static and low-speed impact loadings.