Speaker
Description
Lattice structures are widespread in natural systems at the microscopic scale and are increasingly adopted in engineering applications at multiple scales due to their high strength-to-weight ratio and energy absorption capacity. The reliable assessment of their load-bearing capacity is therefore essential for safe design and must account for both geometrical and mechanical imperfections arising from natural variability or manufacturing processes.
In this contribution, the collapse strength of imperfect planar lattice structures is evaluated within an upper-bound limit analysis framework formulated as a limit programming problem. The failure load is obtained by solving a constrained optimisation problem in which kinematically admissible collapse mechanisms are imposed through linear programming. This approach provides an efficient alternative to nonlinear incremental micro-mechanical analyses, which become computationally demanding for large lattice systems.
Geometrical imperfections are introduced by perturbing the periodic cell configuration, thus affecting cell shape, while mechanical imperfections are modelled as random variations of material properties. Both randomly distributed and localised defects are considered. A Monte Carlo simulation strategy is coupled with the optimisation-based limit formulation to quantify the influence of imperfection intensity and relative density on the collapse load. The structural strength is characterised in terms of statistical moments and probability density functions.
Results show that the sensitivity to defects depends on the lattice geometry. Imperfections not only reduce the collapse load but also alter the governing failure mechanisms. The proposed optimisation-based upper-bound framework proves to be an effective and robust tool for the systematic assessment of strength variability in imperfect lattice structures.