Tensile Response Characterization and Constitutive Modeling of LPBF Ti6Al4V Thin Struts

• Published in: Advanced engineering materials Vol. 25; no. 4
• Main Authors: Hosseini, Ehsan, Robmann, Serjosha, Lüthi, Thomas, Affolter, Christian, Mazza, Edoardo
• Format: Journal Article
• Language: English
• Published: 01-02-2023
• Subjects: additive manufacturing; constitutive modeling; FE analyses; miniaturized mechanical experiment; Ti6Al4V lattices
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.202201135

Additive manufacturing enables the fabrication of orthopedic implants with lattice materials whose topology is tailored to mimic the mechanical response of native bone. Detailed analysis of such lattice structures for optimizing their mechanical biocompatibility requires an understanding of the mechanical response of their constituent components, that is, “struts”. The present study conducts a series of miniature‐specimen mechanical experiments to analyze the apparent stress–strain response of additive manufacturing Ti6Al4V struts. The “true” geometries of the struts are then derived based on observations from microcomputed tomography to discuss the size and orientation dependence of the “geometrical mismatch” as well as the “true” stress–strain response of the struts. It is however argued that considering the “true” mechanical response of struts in the design and topology optimization of lattice‐based implants is not practically feasible, since it requires information regarding the “true” geometry of each strut within the implant that is not accessible at the design stage. As an alternative, consideration of a representative “apparent” constitutive model in finite‐element simulations representing the “nominal” geometry of the lattices provides acceptable approximations of their experimentally observed mechanical response and, therefore might be employed for design analysis and topology optimization of lattice‐based implants.
This study reports the results of a series of miniature‐specimen mechanical experiments to derive constitutive models for representing the stress–strain response of LPBF Ti6Al4V struts with nominal diameters in the range of 200–500 μm. It is shown that the derived constitutive models are effective for approximating the mechanical response of lattice structures, typically considered for orthopedic implants.