Computational study on subsonic impact resistance of lattice structures in 3D printed thin Ti6Al4V parts

Abstract

Additive manufacturing (AM) is a set of digital manufacturing processes which is gaining momentum in the industries for its flexibility, versatility and ability to manufacture complex geometries with limited human interaction. It has enabled relatively fast materialization of a conceptualized design for testing, inspecting and examining the components. AM is highly suitable for fabricating functional gas turbine components owing to its low volume production requirements, lightweight components and geometrical complexity requirements. Laser powder bed fusion (LPBF), is the most common form of metal AM method used. The shape complexity attribute of LPBF can be taken advantage of to fabricate lattice-induced gas turbine inlet components prone to hail or bird impact. In this study, a computational approach was implemented to assess the behaviour of thin Ti6Al4V parts induced with a single-layer lattice subjected to projectile impact. Homogenization of lattice structures was carried out in nTopology to shortlist them for impact studies based on Young’s modulus distribution. The impact analysis was performed on eight lattice structures, two of which were derived from topology optimization, along with a solid plate and hollow plate acting as benchmarks for comparison. The high-velocity impact (250 m/s) was simulated using the “Explicit Dynamics” module in Ansys. It was observed that the lattice geometry directly below the impact site influenced the deformation, stress and energy values. It was concluded that lattices such as isotruss, kelvin cell and FCC, which have more struts interfacing with the impact region, tend to show deformation comparable to solid plates (4.89E-04 m). The equivalent stress values were within the material's elastic limit, indicating elastic deformation. The reduction in kinetic energy of the projectile for lattice-induced plates was also comparable with the values for solid plates (68 %). A correlation coefficient of −0.807 was obtained between packing factor and minimum kinetic energy, indicating denser lattices resulted in higher deceleration.