Fatigue and biological properties of Ti-6Al-4V ELI cellular structures with variously arranged cubic cells made by selective laser melting

Hot isostatic pressure treatment of 3D printed Ti6Al4V alters surface modifications and cellular response

“…AM fabrication of Ti6Al4V can result in stress concentrations within the implant due to thermal discrepancies during manufacturing and the existence of imperfections on the exterior of the bulk material that collectively can impair its fatigue characteristics (Benedetti et al, ; Dallago et al, ). The Standardization Roadmap for Additive Manufacturing Version 2.0 points out that this is also the case for additively manufactured medical implants (America Makes & Collaborative AAMS, ).…”

“…The resulting constructs have a reduced microporosity within the solid sintered geometry due to a combination of plastic deformation, creep, and diffusion bonding. The heat treatment relaxes stress concentrations by removing intrinsic stresses created during the fusion process and improves the fatigue properties of the finished construct (America Makes & Collaborative AAMS, ; Benedetti et al, ; Dallago et al, ; Xu, Guo, Bai, Lei, & Yang, ; Zhang, Mei, Wain, & Wu, ). Previous studies have focused and validated the effect of HIP treatment and grit‐blasting on solid testing specimens produced by AM by decreasing crack initiation sites through pore removal throughout the cross‐section or near the surface, respectively (Benedetti et al, ).…”

Stress concentration factors for planar square cell lattices with filleted junctions

“…Such problem could be encountered, for instance, in the design of fatigue resistant load bearing orthopaedic implants: the cellular lattice should have low stresses and an elastic modulus close to that of the human bone. 12 Let us also assume that the lattice principal directions 1-2 can have an inclination θ to the load direction, as shown in Figure 4a. The elastic constants of regular square cell lattices with filleted junctions of the same type discussed in this work can be easily calculated using semianalytical functions developed by Dallago et al.…”

“…Let us consider a regular square cell lattice of finite size with filleted junctions loaded by a monoaxial distributed load (Figure a) and assume that we are interested in finding the geometrical parameters that minimize the stress concentration at the junctions while satisfying constraints on the elastic constants and on the geometrical parameters. Such problem could be encountered, for instance, in the design of fatigue resistant load bearing orthopaedic implants: the cellular lattice should have low stresses and an elastic modulus close to that of the human bone . Let us also assume that the lattice principal directions 1–2 can have an inclination θ to the load direction, as shown in Figure a.…”

“…Indeed, it is interesting to note that the fillet radius tends to be always the maximum allowed size, indicating a very strong influence of the fillet on the stresses. Therefore, to achieve low values of the elastic modulus but retain good fatigue resistance (as required, for instance, by biomedical lattices) it is convenient to incline the material principal directions to the load so that bending actions are introduced into the lattice. On the other hand, if the requested elastic modulus is higher (as in other engineering applications, such as the automotive or the aeronautic sectors), aligning the load with the material principal directions seems the best solution to minimize the stresses.…”