Additive manufacturing (AM) is employed for fabricating industrial products with complex geometries. As topological optimization is suitable for designing complex geometries, studies have combined AM and topological optimization, evaluating the density optimization of lattice structures as a variant of topological optimization. The lattice structures of components fabricated via AM comprise voids. Models designed using topological optimization should be modified to ensure structures suitable for AM. As the lattice unit can be easily fabricated using AM with fewer design modifications, this study uses lattice density optimization for an industrial AM product. We propose a method of optimizing the lattice distribution for controlling the surface temperature uniformity of industrial products, such as molds. The effective thermal conductivity of the lattice is calculated using the homogenization and finite element methods. The effective thermal conductivity changes depending on the internal pore sizes. The proposed methodology is validated using a 3D example; the minimization problem of surface temperature variations in the target domain is considered. The variable density of the embedded lattice in the target domain is optimized, and we experimentally validated the performance of the lattice unit cell and optimal 3D structure using metal powder bed fusion AM.

Fabrication of steel materials using high heat processes, such as welding, for building structures may lead to unexpected complex distortion. Thus, the optimisation of the assembly sequence to obtain the lowest deformation for huge steel structures, such as ships and offshore structures, is crucial. The objective of this study is to introduce an efficient method to systemically determine the optimal welding sequence for the lowest deformation of a general ship side panel, which is widely employed to design vessels and offshore structures. In this study, numerical simulation with a finite element method based on the inherent strain, interface element and multipoint constraint function is used as a precise computational approach to analyse the welding deformation. The employed numerical simulation obviously validated proposed systemic method to efficiently decide the optimal welding sequence for minimising welding displacement.

When the Reynolds number exceeds approximately 10, drag from porous media becomes nonlinear and cannot be handled by Darcy's theory. The Darcy–Forchheimer law, which considers drag through porous media as a quadratic function, covers this region up to the Reynolds number of the order ${10}^2$. In this research, we study the optimal shape of a porous unit cell based on this law and topology optimisation. Darcy's permeability and Forchheimer's quadratic drag term are calculated based on the averaging theorem and finite element method. The topology optimisation method is based on classical flow channel optimisation. The pressure drop is considered as the objective function of topology optimisation. By changing the input flow velocity in cell model analysis, the optimal shape becomes accustomed to the specified flow speed. We derive 2D and 3D optimal cell shapes for both low and high velocity regions.