Adjustable Elasticity of Anatomically Shaped Lattice Bone Scaffold Built by Electron Beam Melting Ti6Al4V Powder

Abstract

This study investigates the elasticity of specific lattice structures made from titanium alloy (Ti6Al4V), namely, anatomically shaped lattice scaffolds (ASLS) aimed for reinforcement of the bone tissue graft that substitute a missing piece of the previously injured bone during its recovery. ASLSs that were used for testing were fabricated using the Electron Beam Melting (EBM) method. The mechanical properties of the ASLS were examined through uniaxial compression tests. Compression testing revealed the complex non-linear behavior of the scaffold structure’s elasticity, with distinct compression stages and deformation dependencies. The ASLS structures exhibited quasi-elastic deformation followed by the rupture of individual struts. Results demonstrate that the ASLSs can be stiffened by applying appropriate compression load and accordingly achieve the target elasticity of the structure for the specific load range. The modulus of elasticity was determined for different compression stages of ASLS, allowing interpolation of the functional relation between the modulus of elasticity and compressive force that is used for stiffening the ASLS. This study enhances the understanding of the mechanical behavior of the specific lattice structures made of Ti6Al4V and provides insights for the development of mechanically optimized anatomically shaped lattice scaffolds.

Stiffness of Anatomically Shaped Lattice Scaffolds Made by Direct Metal Laser Sintering of Ti-6Al-4V Powder: A Comparison of Two Different Design Variants

“…After the second stage of compression, the third stage of compression began, which exhibited a quasi-linear relationship between the reactive force and the deformation of the scaffold. In addition, the same "elastic creeping" phenomenon (as explained in [28]) was also evident here. A series of compression and decompressions cycles of the ASLS models were completed, and each increase in compression force caused a further increase in permanent deformation of the ASLS (Figures 10 and 11).…”

“…The characteristic stages of deformation under the quasi-uniaxial compression load (force-stroke diagram F(x)) which were noticed during the same measurements where similar ASLSs (ASLS×60 • ) manufactured with EBM technology were subjected to the same compression force [28] were also noticed here for both strut orientations (Figure 9). As all stages of the ASLS force-stroke (force-displacement) diagram have already been explained in detail in the authors' previous paper [28], only a brief overview will be presented here. The first zone exhibited quasi-elastic deformation, and in the second zone, the rupture of scaffold struts occurred.…”

“…In the first compression stage, an almost linear relationship between the compression stroke and the reactive force of the scaffold was evident. The second stage of compression was characterized by an almost constant reactive force of the scaffold ("force plateau"), and this stage can be named as "elastic creeping" [28]. In this stage of compression, the reactive force of ASLS×90 • increased from 34 N to 44 N, and from 36 N to 49 N for ASLS×60 • .…”

“…Considering the complexity of the ASLS geometry, it was decided to manufacture the ASLS models with two additive manufacturing technologies: Electron Beam Melting (EBM) [28] and direct metal laser sintering (DMLS). This paper reports on the measurements of the deformation of ASLSs made by DMLS that were exposed to quasi-uniaxial compression load (in the direction of the mechanical axis of the bone).…”

“…The real load for such cases cannot be considered as an ideal uniaxial compression, but the dominant portion of the load can be considered almost uniaxial (that is why the designation of quasi-uniaxial will be used in the study). This research represents a logical extension of the prior work undertaken by the authors of [28] which predominantly centered on the quasi-elastic characteristics of the ASLS model manufactured via Electron Beam Melting (EBM) technology. However, it is relevant to note that the earlier study extensively explored the quasi-elastic attributes of the ASLS model.…”