Mechanical, biological and tribological behaviour of fixation plates 3D printed by electron beam and selective laser melting

Abstract

Commercially available fixation plates are built using metallic biocompatible materials such as titanium and its alloys and stainless steel. However, these plates show a stiffness mismatch comparing to bone, leading to stress shielding and bone loss. In this paper, we investigate the combined use of topology optimisation and additive manufacturing to print fixation plates with reduced stiffness and improved biological performance. Ti-6Al-4 V plates were topology optimised considering different loading conditions and volume reductions and printed using electron beam melting and selective laser melting. The effect of processing conditions on the mechanical properties, microhardness, wear resistance and surface roughness was analysed. Results show acceptable wear resistance values for a medical device and a reduction of stress shielding by increasing volume reduction. It is also shown that no polishing is required as 3D printed plates are able to support cell attachment and proliferation. In comparison to commercial plates, 3D printed ones show significantly better biological performance. For the same design, SLM plates present higher mechanical properties, while EBM plates present better cell attachment and proliferation.

3D Topology Optimization and Mesh Dependency for Redesigning Locking Compression Plates Aiming to Reduce Stress Shielding

“…Researchers previously reported the successful combination of TO, electron beam melting, and selective laser melting, considering different conditions (i.e. low mesh density)[ 29 ], and similar conclusions were also obtained by other researchers[ 19 ].…”

Copper additive manufacturing using MIM feedstock: adjustment of printing, debinding, and sintering parameters for processing dense and defectless parts

“…The rapidly growing additive manufacturing (AM) processing has simplified the fabrication of complex and customized shapes with different metals [1][2][3][4]. The standard AM route involves layer-by-layer consolidation of a metal powder using different energy sources such as laser or electron beam [5][6][7]. The most popular metal AM techniques are laser beam melting (LBM), electron beam melting (EBM) and direct energy deposition (DED).…”

Optimization of a Patient-Specific External Fixation Device for Lower Limb Injuries

“…Topology optimization is a mathematical approach that allows us to obtain the best material distribution within a given design domain according to a set of loading and boundary conditions [ 33 , 34 ]. Therefore, topology optimization allows us to design lightweight objects with an optimal mechanical performance.…”

“…However, the optimized structure is often complex and requires refinement and simplifications using computer-aided techniques to allow the manufacturing of the part [ 35 ]. Topology optimization is widely used to solve a geometrical optimizing problem of minimizing the design compliance (i.e., strain energy), considering a specified volume/mass reduction value (design constraint), and can be mathematically formulated as follows [ 34 ]: where is the objective function, is the density of each element, p is the penalization factor, f is the volume fraction, V is the user-defined volume, Vi is the initial design volume and and are the element stiffness matrix and displacement vector, respectively. is the the relative density of the element and is the minimum relative densities (non-zero for FEA stability).…”

“…This method is controlled through the penalization factor. The governing equation that describes the SIMP process is given by the following equation [ 34 ]: where is the Young’s modulus, and is the initial elastic modulus of the material (where ).…”