Car occupant response: finite element analysis of knee-thigh-hip complex under frontal impact

Knee-thigh-hip complex (KTH) was simulated under automobile frontal impact with variation of energy and impactor mass to locate the high stress-strain zones within the model. Finite element model of KTH in seating posture was developed with computed tomography scan based material properties. Material properties (modulus of elasticity) of pelvis, left and right femur were 4072.8 MPa, 17,605 MPa and 16,099 MPa respectively. Impactor velocities of 4.58 m/s, 5.80 m/s and 7.10 m/s were considered for 250 J, 400 J and 600 J with 23.8 kg impactor mass and 3.24 m/s, 2.65 m/s for 250 J with 47.6 kg and 71.4 kg impactor mass respectively. Five zones were identified which showed maximum von-Mises stress and strain for all the three energy variations. High mass (71.4 kg) impactor with low velocity was safer than low mass (47.6 kg, 23.8 kg) with high velocity for the same 250 J impact energy. This model may be helpful during vehicle design for injury protection to the car occupant's lower extremity.