Future vehicle design for integrated safety requires an accurate assessment of
occupants’ realistic behavior. Active muscle, one of the key reflexive actions
engaged by vehicle occupants, is a paucity of research data in the conventional
safety assessment program due to muscle absence in mechanical crash dummies.
This study seeks to explore how muscle activation level affects the neck
kinematics and injury risks in frontal collisions with various impact severities
via numerical analysis. A validated Finite Element (FE) vehicle model was
employed to generate the crash pulse. A MADYMO baseline model interior space was
imported from the FE model. A validated vehicle- driver model, including a
driver-side interior compartment and a multi-body active human model, was
numerically constructed under the MADYMO environment. A full-factorial matrix,
including 102 simulations, was designed. Two influencing parameters, including
the whole-body muscle activation level (0-1 with a gradient of 0.2) and the
crash velocity (30-70 km/h with a gradient of 2.5 km/h), were selected. The
driver neck kinematics, kinetics, and injury risks from various activation
levels and collision speed were compared and analyzed. An exponential fitting
model was performed to assess factors effect on the neck injury. The results
show that the activation of muscles could decrease the head pitch angle. The
active muscle response contributed to decreased neck injury risk in the low
severity frontal collisions while potentially increasing the neck injury risk in
the high severity collisions. With the increase of crash speed, the occurrence
of the peak value of the neck injury criterion (Nij)
would be delayed. The effect of muscle activation level on neck injury was
greater in high-speed collisions (ΔΝij =
29.5%, ΔP(AIS 3+) = 28.4 % for 70 km/h) than in low-speed
collisions (ΔΝij = −
22.0%, ΔP(AIS 3+) = − 5.6 % for 30 km/h). This study
demonstrates the importance of accounting for muscle activation in assessing
driver impact response. Therefore, muscle activation should be considered for
vehicle safety system design.