Hybrid parameter identification of a Modified Nonlinear Lobdell Thorax Model for blunt ballistic impacts.

Kinetic energy non-lethal projectiles (KENLPs) can cause significant thoracic injuries, highlighting the need for computationally efficient tools in impact biomechanics. This study presents the Modified Nonlinear Lobdell Thorax Model (MNLTM), extending the original Lobdell architecture with nonlinear Hunt-Crossley contact and a progressive structural spring. A hybrid global-local strategy combining Latin Hypercube Sampling, Genetic Algorithm, and Sequential Quadratic Programming identifies a single parameter set across three experimental impact cases. The MNLTM reproduces displacement and force responses with improved agreement, achieving 77.0-85.4% displacement and 55.0-97.0% force corridor compliance. The model enables rapid thoracic simulations while reducing reliance on extensive physical testing.