Numerical simulation of helmet through interaction of 2D and 3D elements

Abstract

Head injuries resulting from motorcycle accidents are a leading cause of severe mortality, with the most common injuries being traumatic brain injury, brain lesions, spinal cord injuries, facial injuries, and neck injuries. The helmet is a critical component for protecting the head during a motorcycle accident. A modern helmet typically features a rigid outer shell made from thermoplastic or fiberglass, designed to reduce the initial impact energy. 3D CAD modeling allows for the design of the helmet shell, creating a controlled discretization with hexahedral elements for 3D and quadratic elements for 2D to perform numerical simulations under the boundary conditions specified by the PROY-NOM-206-SCFI/SSA2-2016 standard. Each simulation is conducted with the same boundary conditions and mechanical properties for both the ABS helmet and the A36 steel block, with only the 2D and 3D elements of each piece (helmet and block) varying. The simulations, performed over 20 ms, provide unit deformations, stresses, and internal energy. The results show that, when using a rigid material, the computation time is similar regardless of the element type (2D or 3D). However, when 2D elements are used for deformable materials, the computation time is reduced by 88.4% compared to 3D elements. The observed variations mainly reflect differences in material rigidity and internal energy, due to the higher number of elements in the material thickness when using 3D elements. Nevertheless, the maximum stress and maximum unit deformation are the same, regardless of the element type used. The interaction between 2D and 3D elements does not result in significant variations, except in the iteration time, which increases by 0.05 ms. This is due to 2D elements, having fewer elements in the material thickness, requiring more time to generate interaction. However, this increase is insignificant.