Numerical simulation of human blunt trauma based on bilinear constitutive

In modern warfare, body armor has greatly reduced soldier casualties, yet back-face deformation from high-velocity bullets can still cause severe blunt trauma. Current studies mainly rely on numerical simulations, where accurately defining soft-tissue mechanical properties and constitutive models remains a key challenge. This study fitted a rate-dependent bilinear constitutive model for soft tissue using Hopkinson bar test data and implemented it in ABAQUS through a VUMAT subroutine. A protected human blunt-impact model was then established by combining a validated body-armor model with the Toyota THUMS human model. The model was used to simulate the impact of a 5.8 mm rifle bullet on an armored human thorax. Results show that the proposed constitutive model effectively captures the dynamic mechanical behavior of the heart and liver. Under impact, peak pressures reached 11.2 MPa in the ribs, 0.1 MPa in the lungs, 0.06 MPa in the heart, and 0.23 MPa in the liver, indicating the need for improved torso protection.