Mechanical metamaterials (MMs) are microstructured systems that can possess exceptional energy absorption and wave controlling capabilities. This work investigates the ballistic impact performance of mechanical metamaterials and focuses on developing low cost reduced order modeling (ROM) approaches for such problems. Extensive past work focused on and succeeded primarily at the control of and design for linear response of such media. Additionally, preliminary nonlinear analysis provided observations of great potential even when considering contact and fracture in such systems. The present work seeks to expand towards the design, analysis, and optimization for such large displacement, high impact energy, and nonlinear mechanics of ballistic and impact events. The proposed ROM approach employs generalized beam elements to reduce the computational cost in the explicit dynamic simulations. Additionally, the occurrence of contact and nonlinear material behavior is included through efficient and specialized computational algorithms. Iterative numerical solvers are used to update the deformation at each time step. Under high stress loading, the envelopes of axial force, bending moments, and other resultant forces that result in local failure in the ROM elements can be obtained using element-specific analysis. Additionally, under high amplitude loading, the internal resonators can undergo large displacements relative to the cell walls that result in local contact and friction events. Compared to full-scale finite element approach with higher fidelity, the ROM shows decent computational accuracy while demanding significantly fewer model parameters and degrees of freedoms. It has been shown previously that the speed up in the linear analysis case can be as high as 4 orders of magnitude. An estimate of speed up in the nonlinear case may be case specific and is quite significant for design and optimization process, especially considering the cost of full FE analysis.
2025-04-09 09:00:00
