SPECIAL ISSUE ‐ ENGINEERING AGAINST FAILURE Multifield modelling and failure prediction of cellular cores produced by selective laser melting George Lampeas | Ioannis Diamantakos | Evaggelos Ptochos Laboratory of Technology and Strength of Materials, Department of Mechanical Engineering and Aeronautics, University of Patras, 26500 Rion, Greece Correspondence G. Lampeas, Laboratory of Technology and Strength of Materials, Department of Mechanical Engineering and Aeronautics, University of Patras, 26500 Rion, Greece. Email: labeas@mech.upatras.gr Abstract A multifield simulation approach of cellular cores produced by additive manufacturing is presented. The analysis is aiming to derive the relation between the manufacturing process parameters and the resulting material failure behaviour. To this purpose, the selective laser melting manufacturing process is initially thermo‐mechanically simulated, followed by the mechanical analysis of the nonlinear core behaviour. The methodology is demonstrated in the case of open‐lattice body‐centred‐cubic (BCC) cellular cores. KEYWORDS body‐centred‐cubic, cellular cores, failure prediction, numerical simulation, selective laser melting 1 | INTRODUCTION Cellular materials are an attractive material category, as they can be designed to have higher specific mechanical properties compared with respective solid materials. Some of their key advantages are their high energy absorbing capability and their good thermal and acoustic insulation properties, which make them privileged mate- rials to be used in transportation and medical applications. Cellular materials are commonly applied as a core material in sandwich type of structures that present advantages, when compared with conventional monolithic stiffened structures, with respect to their com- pression and impact behaviour. A special type of cellular materials is the open lattice cellular materials that is composed of a number of beams connected to each other. 1 The open lattice cellular materials offer improved ventilation, compared with honeycombs or foams that are conventionally used as cores in sandwich materials, something that prevents moisture absorption, structural weight increase, and degradation of material properties. Conventional manufacturing processes can be used for the production of open lattice structures with rela- tively simple geometry. 2,3 On the other hand, additive manufacturing (AM) processes offer significant advan- tages for producing open‐lattice cellular materials and structures. AM has been developed and industrially applied since the 1980s in different sectors, such as aero- space, marine, automotive, and medical. 4-6 The most common AM processes used for the manufacturing of metal parts are electron beam melting (EBM), selective laser melting (SLM), and selective laser sintering (SLS). In the above processes, the final part is composed by fus- ing consecutive layers of powder material. Manufacturing of open lattice structures has been achieved by the Nomenclature: A, material absorptivity; a, b and d, unit‐cell dimensions; C(T), temperature‐dependent damping matrix; C p , specific heat capacity; E, strut bulk material elastic modulus; e, element edge size; F , view factor; F (t), external load vector; F th (t), temperature load vector; F x’ , F y’ , strut loading forces; k, powder material thermal conductivity; K(T), temperature‐dependent stiffness matrix; k f , thermal conductivity of the fluid surrounding the powder particles; k s , thermal conductivity of the solid material; L, is beam length; M(T), temperature‐dependent mass matrix; M p , bending moment required for the formation of a plastic hinge; M (x ′ = 0) , maximum bending moment at the unit cell centre; n, number of elements covered by the laser beam spot; P, laser power; _ q, supplied heat rate; r, strut radius; Q CD , conduction losses; Q CV , convection losses; Q L , laser beam heat input; Q R , radiation losses; Q S , energy related to phase transformations; T, powder particles temperature; t, time; u(t), displacement vector; _ ut ðÞ, velocity vector; € ut ðÞ, acceleration vector; x r , powder particles diameter; ρ, material density; σ, the Stefan– Boltzmann constant; σ a , strut axial stress; σ fs , strut tensile fracture stress; φ, powder porosity Received: 31 October 2018 Revised: 19 February 2019 Accepted: 23 February 2019 DOI: 10.1111/ffe.13008 Fatigue Fract Eng Mater Struct. 2019;1–14. © 2019 Wiley Publishing Ltd. wileyonlinelibrary.com/journal/ffe 1