構造設計による金属積層造形の熱変形低減

The reduction of thermal strain generated in the manufacturing process of metal additive manufacturing is an important issue. This review considers the problem of forming an object with an internal lattice structure to reduce the thermal strain and presents the author's research on the optimization of the lattice density distribution and its experimental verification. The base lattice geometry is assumed to be a cube with spherical voids, and the optimization problem is constructed based on the recurrent equation of the inherent strain model, sensitivity analysis, and gradient method. The design variable is the representative size of the internal lattice geometry. The effective stiffness tensor of the lattice is derived using the homogenization method, and the approximation function between the design variables and the effective properties is derived. The values of the inherent strain are calibrated using several specimens with uniform lattice density. Optimization is also performed for a quasi-two-dimensional example. Experimental verification is performed by laser powder bed fusion fabrication and warp deformation measurements.