Effects from different head models on dynamic response of the head impact using material point method / 医用生物力学

Objective To investigate the effects of muscles and boundary conditions on head impact response. Methods Three different 3D material point impact models of human head were constructed from the CT scanned images. The first model was the simple head model (SHFr) including skull, membrane and brain, in which the head was free. The second model was the simple head model with muscle (MHFr) including skull, membrane, brain and muscle of the head, in which the head was free. The third model was the MHFr model with shoulder, in which the bottom edge of the shoulder was fixed (MHSFi). The three models were under the impact of a cylindrical lead hammer projected at a speed of 6.4 m/s to simulate the dynamic response of the three models using 3D explicit material point method code. Results The peak values of acceleration of the head centroid for the SHFr, MHFr and MHSFi model were 6.018×103, 4.69×103 and 4.76×103 m/s2, respectively. Conclusions The muscle of the head can disperse distributions of the contact force, enlarge the damage area and relieve the damage of the head. In case of short-time impact, whether the boundary of the head is free or the shoulder is fixed does not affect the dynamic response of the head impact.

Numerical simulation on response of human spine with different bone mineral density to landing impact / 医用生物力学

Objective To study the effect of bone mineral density (BMD) change on response of human spine to landing impact by numerical simulation. Methods The three-dimensional material point model of human head skull, cervical vertebrae, thoracic, lumbar vertebra, pelvis, ligament and disc was constructed from the computed tomography (CT) scanned images, and they were attached together as a human spine model and placed on the backrest of the chair, which was constructed by the MPM3D program. The acceleration loading was applied on the back rest of the chair to simulate the landing impact loading when the human spine model was laid on the back of the chair. The different responses of human spine to landing impact were simulated by changing the BMD and the corresponding elastic modulus. Results The general risk of injury γ value of normal BMD was 1.589 3, and when the BMD was reduced by 2%, 4%, 6%, 8%, 10%, respectively, γ values were 1.608 6, 1.634 7, 1.641 0, 1.662 5, 1.680 5, correspondingly. Conclusions Under the same landing impact loading, the smaller the bone mineral density, the larger the response of human spine to landing impact loading, and human body is more vulnerable to injuries.