Optimisation of Selective Laser Melted Ti6Al4V Functionally Graded Lattice Structures Accounting for Structural Safety

Abstract

This paper presents a new framework for lightweight optimisation of functionally graded lattice structures (FGLSs) with a particular focus on enhancing and guaranteeing structural safety through three main contributions. Firstly, a design strategy of adding fillets to the joints of body-centred cubic (BCC) type lattice cells was proposed to improve the effective yield stress of the lattices. Secondly, effective properties of lattice metamaterials were experimentally characterised by conducting quasi-static uniaxial compression tests on selective laser melted specimens of both Ti6Al4V BCC and filleted BCC (BCC-F) lattices with different relative densities. Thirdly, a yield stress constraint for optimising FGLSs was developed based on surrogate models quantifying the relationships between the relative density and the effective properties of BCC and BCC-F lattices developed using experimental results assisted by numerical homogenisation. This framework was tested with two case studies. Results showed that structural safety with respect to avoiding yield failure of the optimised FGLSs can be ensured and the introduction of fillets can effectively improve the strength-to-weight ratio of the optimised FGLSs composed of BCC type lattices. The BCC-F FGLS achieved 14.5% improvement in weight reduction compared with BCC FGLS for the Messerschmitt-Bölkow-Blohm beam optimisation case study.

Experimental Evaluation of the Effects of Discrete-Grading-Induced Discontinuities on the Material Properties of Functionally Graded Ti-6Al-4V Lattices

“…The mechanical testing results are consistent with previous studies using the same material (Ti64) with similar volume fractions [15,55,56]. When comparing the mechanical behavior of graded lattices, Xiao and Song also found in their study that step-wise grading is not significantly different from continuous grading [19], which supports the conclusion of this study.…”

Advancement in total hip implant: a comprehensive review of mechanics and performance parameters across diverse novelties

“…4 illustrates the unit cell and array structure of CAD and implicit-based porous unit cells utilized in the context of a hip implant stem application. 34,45,51,52,[73][74][75][76][77] To generate the image and topology based Gyroid and Schwarz Diamond porous and lattice structure, the formula stated in en ( 6) and ( 7) were followed by recent research. 42,65,78 f Gðx;y;zÞ ¼ sin…”

“…4 illustrates the unit cell and array structure of CAD and implicit-based porous unit cells utilized in the context of a hip implant stem application. 34,45,51,52,73–77 To generate the image and topology based Gyroid and Schwarz Diamond porous and lattice structure, the formula stated in en (6) and (7) were followed by recent research. 42,65,78 In this context, the Cartesian coordinate system is denoted by ( x , y , z ), while the lengths of the unit cell in the x , y , and z directions are represented by a , b , and c respectively.…”