Strain rate effect on dynamic responses of additively manufactured lattice structures

Lattice structures are promising energy-absorbing materials against dynamic impact. However, there is a lack of quantified study of the respective contributions of parent material’s strain-rate sensitivity and structural inertia to the dynamic strengthening of lattice structures. Therefore, to assess the contributions of these two mechanisms, BCC lattice structures were fabricated using selective laser melting 316 L stainless steel and tested under quasi-static compression and SHPB impact loading in this study. A finite element (FE) model based on the Johnson–Cook (J-C) constitutive law was developed and validated against experimental results. The influence of strain-rate sensitivity was then quantified by varying the strain-rate parameter in the FE model, and an analytical model incorporating both strain-rate and inertia effects was developed based on shock-wave theory. The results show that the strain-rate contribution can reach approximately 20% of the dynamic plateau stress at low impact velocities and remains about 5% even at 200 m/s. Below the critical velocity, the strain-rate effect dominates the dynamic strengthening, whereas inertia becomes dominant at higher velocities. The proposed model provides a calibrated predictive framework for evaluating the dynamic plateau stress of lattice structures.